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OUR treatise proposes to find a line of inquiry whereby we shall be able to reason from opinions that are

generally accepted about every problem propounded to us, and also shall ourselves, when standing up to an

argument, avoid saying anything that will obstruct us. First, then, we must say what reasoning is, and what its

varieties are, in order to grasp dialectical reasoning: for this is the object of our search in the treatise before

Now reasoning is an argument in which, certain things being laid down, something other than these

necessarily comes about through them. (a) It is a 'demonstration', when the premisses from which the

reasoning starts are true and primary, or are such that our knowledge of them has originally come through

premisses which are primary and true: (b) reasoning, on the other hand, is 'dialectical', if it reasons from

opinions that are generally accepted. Things are 'true' and 'primary' which are believed on the strength not of

anything else but of themselves: for in regard to the first principles of science it is improper to ask any further

for the why and wherefore of them; each of the first principles should command belief in and by itself. On the

other hand, those opinions are 'generally accepted' which are accepted by every one or by the majority or by

the philosophersi.e. by all, or by the majority, or by the most notable and illustrious of them. Again (c),

reasoning is 'contentious' if it starts from opinions that seem to be generally accepted, but are not really such,

or again if it merely seems to reason from opinions that are or seem to be generally accepted. For not every

opinion that seems to be generally accepted actually is generally accepted. For in none of the opinions which

we call generally accepted is the illusion entirely on the surface, as happens in the case of the principles of

contentious arguments; for the nature of the fallacy in these is obvious immediately, and as a rule even to

persons with little power of comprehension. So then, of the contentious reasonings mentioned, the former

really deserves to be called 'reasoning' as well, but the other should be called 'contentious reasoning', but not

'reasoning', since it appears to reason, but does not really do so. Further (d), besides all the reasonings we

have mentioned there are the misreasonings that start from the premisses peculiar to the special sciences, as

happens (for example) in the case of geometry and her sister sciences. For this form of reasoning appears to

differ from the reasonings mentioned above; the man who draws a false figure reasons from things that are

neither true and primary, nor yet generally accepted. For he does not fall within the definition; he does not

assume opinions that are received either by every one or by the majority or by philosophersthat is to say, by

all, or by most, or by the most illustrious of thembut he conducts his reasoning upon assumptions which,

though appropriate to the science in question, are not true; for he effects his misreasoning either by

describing the semicircles wrongly or by drawing certain lines in a way in which they could not be drawn.

The foregoing must stand for an outline survey of the species of reasoning. In general, in regard both to all

that we have already discussed and to those which we shall discuss later, we may remark that that amount of

distinction between them may serve, because it is not our purpose to give the exact definition of any of them;

we merely want to describe them in outline; we consider it quite enough from the point of view of the line of

Next in order after the foregoing, we must say for how many and for what purposes the treatise is useful.

They are threeintellectual training, casual encounters, and the philosophical sciences. That it is useful as a

training is obvious on the face of it. The possession of a plan of inquiry will enable us more easily to argue

about the subject proposed. For purposes of casual encounters, it is useful because when we have counted up

the opinions held by most people, we shall meet them on the ground not of other people's convictions but of

their own, while we shift the ground of any argument that they appear to us to state unsoundly. For the study

of the philosophical sciences it is useful, because the ability to raise searching difficulties on both sides of a

subject will make us detect more easily the truth and error about the several points that arise. It has a further

use in relation to the ultimate bases of the principles used in the several sciences. For it is impossible to

discuss them at all from the principles proper to the particular science in hand, seeing that the principles are

the prius of everything else: it is through the opinions generally held on the particular points that these have

to be discussed, and this task belongs properly, or most appropriately, to dialectic: for dialectic is a process of

We shall be in perfect possession of the way to proceed when we are in a position like that which we occupy

in regard to rhetoric and medicine and faculties of that kind: this means the doing of that which we choose

with the materials that are available. For it is not every method that the rhetorician will employ to persuade,

or the doctor to heal; still, if he omits none of the available means, we shall say that his grasp of the science is

First, then, we must see of what parts our inquiry consists. Now if we were to grasp (a) with reference to how

many, and what kind of, things arguments take place, and with what materials they start, and (h) how we are

to become well supplied with these, we should have sufficiently won our goal. Now the materials with which

arguments start are equal in number, and are identical, with the subjects on which reasonings take place. For

arguments start with 'propositions', while the subjects on which reasonings take place are 'problems'. Now

every proposition and every problem indicates either a genus or a peculiarity or an accidentfor the

differentia too, applying as it does to a class (or genus), should be ranked together with the genus. Since,

however, of what is peculiar to anything part signifies its essence, while part does not, let us divide the

'peculiar' into both the aforesaid parts, and call that part which indicates the essence a 'definition', while of the

remainder let us adopt the terminology which is generally current about these things, and speak of it as a

'property'. What we have said, then, makes it clear that according to our present division, the elements turn

out to be four, all told, namely either property or definition or genus or accident. Do not let any one suppose

us to mean that each of these enunciated by itself constitutes a proposition or problem, but only that it is from

these that both problems and propositions are formed. The difference between a problem and a proposition is

a difference in the turn of the phrase. For if it be put in this way, "'An animal that walks on two feet" is the

definition of man, is it not?' or '"Animal" is the genus of man, is it not?' the result is a proposition: but if thus,

'Is "an animal that walks on two feet" a definition of man or no?' [or 'Is "animal" his genus or no?'] the result

is a problem. Similarly too in other cases. Naturally, then, problems and propositions are equal in number: for

out of every proposition you will make a problem if you change the turn of the phrase.

We must now say what are 'definition', 'property', 'genus', and 'accident'. A 'definition' is a phrase signifying a

thing's essence. It is rendered in the form either of a phrase in lieu of a term, or of a phrase in lieu of another

phrase; for it is sometimes possible to define the meaning of a phrase as well. People whose rendering

consists of a term only, try it as they may, clearly do not render the definition of the thing in question,

because a definition is always a phrase of a certain kind. One may, however, use the word 'definitory' also of

such a remark as 'The "becoming" is "beautiful"', and likewise also of the question, 'Are sensation and

knowledge the same or different?', for argument about definitions is mostly concerned with questions of

sameness and difference. In a word we may call 'definitory' everything that falls under the same branch of

inquiry as definitions; and that all the abovementioned examples are of this character is clear on the face of

them. For if we are able to argue that two things are the same or are different, we shall be well supplied by

the same turn of argument with lines of attack upon their definitions as well: for when we have shown that

they are not the same we shall have demolished the definition. Observe, please, that the converse of this last

statement does not hold: for to show that they are the same is not enough to establish a definition. To show,

A 'property' is a predicate which does not indicate the essence of a thing, but yet belongs to that thing alone,

and is predicated convertibly of it. Thus it is a property of man tobecapable of learning grammar: for if A

be a man, then he is capable of learning grammar, and if he be capable of learning grammar, he is a man. For

no one calls anything a 'property' which may possibly belong to something else, e.g. 'sleep' in the case of

man, even though at a certain time it may happen to belong to him alone. That is to say, if any such thing

were actually to be called a property, it will be called not a 'property' absolutely, but a 'temporary' or a

'relative' property: for 'being on the right hand side' is a temporary property, while 'twofooted' is in point of

fact ascribed as a property in certain relations; e.g. it is a property of man relatively to a horse and a dog. That

nothing which may belong to anything else than A is a convertible predicate of A is clear: for it does not

A 'genus' is what is predicated in the category of essence of a number of things exhibiting differences in kind.

We should treat as predicates in the category of essence all such things as it would be appropriate to mention

in reply to the question, 'What is the object before you?'; as, for example, in the case of man, if asked that

question, it is appropriate to say 'He is an animal'. The question, 'Is one thing in the same genus as another or

in a different one?' is also a 'generic' question; for a question of that kind as well falls under the same branch

of inquiry as the genus: for having argued that 'animal' is the genus of man, and likewise also of ox, we shall

have argued that they are in the same genus; whereas if we show that it is the genus of the one but not of the

An 'accident' is (i) something which, though it is none of the foregoingi.e. neither a definition nor a property

nor a genus yet belongs to the thing: (something which may possibly either belong or not belong to any one

and the selfsame thing, as (e.g.) the 'sitting posture' may belong or not belong to some selfsame thing.

Likewise also 'whiteness', for there is nothing to prevent the same thing being at one time white, and at

another not white. Of the definitions of accident the second is the better: for if he adopts the first, any one is

bound, if he is to understand it, to know already what 'definition' and 'genus' and 'property' are, whereas the

second is sufficient of itself to tell us the essential meaning of the term in question. To Accident are to be

attached also all comparisons of things together, when expressed in language that is drawn in any kind of way

from what happens (accidit) to be true of them; such as, for example, the question, 'Is the honourable or the

expedient preferable?' and 'Is the life of virtue or the life of selfindulgence the pleasanter?', and any other

problem which may happen to be phrased in terms like these. For in all such cases the question is 'to which of

the two does the predicate in question happen (accidit) to belong more closely?' It is clear on the face of it

that there is nothing to prevent an accident from becoming a temporary or relative property. Thus the sitting

posture is an accident, but will be a temporary property, whenever a man is the only person sitting, while if he

be not the only one sitting, it is still a property relatively to those who are not sitting. So then, there is nothing

to prevent an accident from becoming both a relative and a temporary property; but a property absolutely it

We must not fail to observe that all remarks made in criticism of a 'property' and 'genus' and 'accident' will be

applicable to 'definitions' as well. For when we have shown that the attribute in question fails to belong only

to the term defined, as we do also in the case of a property, or that the genus rendered in the definition is not

the true genus, or that any of the things mentioned in the phrase used does not belong, as would be remarked

also in the case of an accident, we shall have demolished the definition; so that, to use the phrase previously

employed,' all the points we have enumerated might in a certain sense be called 'definitory'. But we must not

on this account expect to find a single line of inquiry which will apply universally to them all: for this is not

an easy thing to find, and, even were one found, it would be very obscure indeed, and of little service for the

treatise before us. Rather, a special plan of inquiry must be laid down for each of the classes we have

distinguished, and then, starting from the rules that are appropriate in each case, it will probably be easier to

make our way right through the task before us. So then, as was said before,' we must outline a division of our

subject, and other questions we must relegate each to the particular branch to which it most naturally belongs,

speaking of them as 'definitory' and 'generic' questions. The questions I mean have practically been already

First of all we must define the number of senses borne by the term 'Sameness'. Sameness would be generally

regarded as falling, roughly speaking, into three divisions. We generally apply the term numerically or

specifically or genericallynumerically in cases where there is more than one name but only one thing, e.g.

'doublet' and 'cloak'; specifically, where there is more than one thing, but they present no differences in

respect of their species, as one man and another, or one horse and another: for things like this that fall under

the same species are said to be 'specifically the same'. Similarly, too, those things are called generically the

same which fall under the same genus, such as a horse and a man. It might appear that the sense in which

water from the same spring is called 'the same water' is somehow different and unlike the senses mentioned

above: but really such a case as this ought to be ranked in the same class with the things that in one way or

another are called 'the same' in view of unity of species. For all such things seem to be of one family and to

resemble one another. For the reaon why all water is said to be specifically the same as all other water is

because of a certain likeness it bears to it, and the only difference in the case of water drawn from the same

spring is this, that the likeness is more emphatic: that is why we do not distinguish it from the things that in

one way or another are called 'the same' in view of unity of species. It is generally supposed that the term 'the

same' is most used in a sense agreed on by every one when applied to what is numerically one. But even so, it

is apt to be rendered in more than one sense; its most literal and primary use is found whenever the sameness

is rendered in reference to an alternative name or definition, as when a cloak is said to be the same as a

doublet, or an animal that walks on two feet is said to be the same as a man: a second sense is when it is

rendered in reference to a property, as when what can acquire knowledge is called the same as a man, and

what naturally travels upward the same as fire: while a third use is found when it is rendered in reference to

some term drawn from Accident, as when the creature who is sitting, or who is musical, is called the same as

Socrates. For all these uses mean to signify numerical unity. That what I have just said is true may be best

seen where one form of appellation is substituted for another. For often when we give the order to call one of

the people who are sitting down, indicating him by name, we change our description, whenever the person to

whom we give the order happens not to understand us; he will, we think, understand better from some

accidental feature; so we bid him call to us 'the man who is sitting' or 'who is conversing over there'clearly

supposing ourselves to be indicating the same object by its name and by its accident.

Of 'sameness' then, as has been said,' three senses are to be distinguished. Now one way to confirm that the

elements mentioned above are those out of which and through which and to which arguments proceed, is by

induction: for if any one were to survey propositions and problems one by one, it would be seen that each was

formed either from the definition of something or from its property or from its genus or from its accident.

Another way to confirm it is through reasoning. For every predicate of a subject must of necessity be either

convertible with its subject or not: and if it is convertible, it would be its definition or property, for if it

signifies the essence, it is the definition; if not, it is a property: for this was what a property is, viz. what is

predicated convertibly, but does not signify the essence. If, on the other hand, it is not predicated convertibly

of the thing, it either is or is not one of the terms contained in the definition of the subject: and if it be one of

those terms, then it will be the genus or the differentia, inasmuch as the definition consists of genus and

differentiae; whereas, if it be not one of those terms, clearly it would be an accident, for accident was said' to

be what belongs as an attribute to a subject without being either its definition or its genus or a property.

Next, then, we must distinguish between the classes of predicates in which the four orders in question are

found. These are ten in number: Essence, Quantity, Quality, Relation, Place, Time, Position, State, Activity,

Passivity. For the accident and genus and property and definition of anything will always be in one of these

categories: for all the propositions found through these signify either something's essence or its quality or

quantity or some one of the other types of predicate. It is clear, too, on the face of it that the man who

signifies something's essence signifies sometimes a substance, sometimes a quality, sometimes some one of

the other types of predicate. For when man is set before him and he says that what is set there is 'a man' or 'an

animal', he states its essence and signifies a substance; but when a white colour is set before him and he says

that what is set there is 'white' or is 'a colour', he states its essence and signifies a quality. Likewise, also, if a

magnitude of a cubit be set before him and he says that what is set there is a magnitude of a cubit, he will be

describing its essence and signifying a quantity. Likewise, also, in the other cases: for each of these kinds of

predicate, if either it be asserted of itself, or its genus be asserted of it, signifies an essence: if, on the other

hand, one kind of predicate is asserted of another kind, it does not signify an essence, but a quantity or a

quality or one of the other kinds of predicate. Such, then, and so many, are the subjects on which arguments

take place, and the materials with which they start. How we are to acquire them, and by what means we are to

First, then, a definition must be given of a 'dialectical proposition' and a 'dialectical problem'. For it is not

every proposition nor yet every problem that is to be set down as dialectical: for no one in his senses would

make a proposition of what no one holds, nor yet make a problem of what is obvious to everybody or to most

people: for the latter admits of no doubt, while to the former no one would assent. Now a dialectical

proposition consists in asking something that is held by all men or by most men or by the philosophers, i.e.

either by all, or by most, or by the most notable of these, provided it be not contrary to the general opinion;

for a man would probably assent to the view of the philosophers, if it be not contrary to the opinions of most

men. Dialectical propositions also include views which are like those generally accepted; also propositions

which contradict the contraries of opinions that are taken to be generally accepted, and also all opinions that

are in accordance with the recognized arts. Thus, supposing it to be a general opinion that the knowledge of

contraries is the same, it might probably pass for a general opinion also that the perception of contraries is the

same: also, supposing it to be a general opinion that there is but one single science of grammar, it might pass

for a general opinion that there is but one science of fluteplaying as well, whereas, if it be a general opinion

that there is more than one science of grammar, it might pass for a general opinion that there is more than one

science of fluteplaying as well: for all these seem to be alike and akin. Likewise, also, propositions

contradicting the contraries of general opinions will pass as general opinions: for if it be a general opinion

that one ought to do good to one's friends, it will also be a general opinion that one ought not to do them

harm. Here, that one ought to do harm to one's friends is contrary to the general view, and that one ought not

to do them harm is the contradictory of that contrary. Likewise also, if one ought to do good to one's friends,

one ought not to do good to one's enemies: this too is the contradictory of the view contrary to the general

view; the contrary being that one ought to do good to one's enemies. Likewise, also, in other cases. Also, on

comparison, it will look like a general opinion that the contrary predicate belongs to the contrary subject: e.g.

if one ought to do good to one's friends, one ought also to do evil to one's enemies. it might appear also as if

doing good to one's friends were a contrary to doing evil to one's enemies: but whether this is or is not so in

reality as well will be stated in the course of the discussion upon contraries. Clearly also, all opinions that are

in accordance with the arts are dialectical propositions; for people are likely to assent to the views held by

those who have made a study of these things, e.g. on a question of medicine they will agree with the doctor,

and on a question of geometry with the geometrician; and likewise also in other cases.

A dialectical problem is a subject of inquiry that contributes either to choice and avoidance, or to truth and

knowledge, and that either by itself, or as a help to the solution of some other such problem. It must,

moreover, be something on which either people hold no opinion either way, or the masses hold a contrary

opinion to the philosophers, or the philosophers to the masses, or each of them among themselves. For some

problems it is useful to know with a view to choice or avoidance, e.g. whether pleasure is to be chosen or not,

while some it is useful to know merely with a view to knowledge, e.g. whether the universe is eternal or not:

others, again, are not useful in and by themselves for either of these purposes, but yet help us in regard to

some such problems; for there are many things which we do not wish to know in and by themselves, but for

the sake of other things, in order that through them we may come to know something else. Problems also

include questions in regard to which reasonings conflict (the difficulty then being whether soand so is so or

not, there being convincing arguments for both views); others also in regard to which we have no argument

because they are so vast, and we find it difficult to give our reasons, e.g. the question whether the universe is

Problems, then, and propositions are to be defined as aforesaid. A 'thesis' is a supposition of some eminent

philosopher that conflicts with the general opinion; e.g. the view that contradiction is impossible, as

Antisthenes said; or the view of Heraclitus that all things are in motion; or that Being is one, as Melissus

says: for to take notice when any ordinary person expresses views contrary to men's usual opinions would be

silly. Or it may be a view about which we have a reasoned theory contrary to men's usual opinions, e.g. the

view maintained by the sophists that what is need not in every case either have come to be or be eternal: for a

musician who is a grammarian 'is' so without ever having 'come to be' so, or being so eternally. For even if a

man does not accept this view, he might do so on the ground that it is reasonable.

Now a 'thesis' also is a problem, though a problem is not always a thesis, inasmuch as some problems are

such that we have no opinion about them either way. That a thesis, however, also forms a problem, is clear:

for it follows of necessity from what has been said that either the mass of men disagree with the philosophers

about the thesis, or that the one or the other class disagree among themselves, seeing that the thesis is a

supposition in conflict with general opinion. Practically all dialectical problems indeed are now called

'theses'. But it should make no difference whichever description is used; for our object in thus distinguishing

them has not been to create a terminology, but to recognize what differences happen to be found between

Not every problem, nor every thesis, should be examined, but only one which might puzzle one of those who

need argument, not punishment or perception. For people who are puzzled to know whether one ought to

honour the gods and love one's parents or not need punishment, while those who are puzzled to know

whether snow is white or not need perception. The subjects should not border too closely upon the sphere of

demonstration, nor yet be too far removed from it: for the former cases admit of no doubt, while the latter

Having drawn these definitions, we must distinguish how many species there are of dialectical arguments.

There is on the one hand Induction, on the other Reasoning. Now what reasoning is has been said before:

induction is a passage from individuals to universals, e.g. the argument that supposing the skilled pilot is the

most effective, and likewise the skilled charioteer, then in general the skilled man is the best at his particular

task. Induction is the more convincing and clear: it is more readily learnt by the use of the senses, and is

applicable generally to the mass of men, though reasoning is more forcible and effective against

The classes, then, of things about which, and of things out of which, arguments are constructed, are to be

distinguished in the way we have said before. The means whereby we are to become well supplied with

reasonings are four: (1) the securing of propositions; (2) the power to distinguish in how many senses

particular expression is used; (3) the discovery of the differences of things; (4) the investigation of likeness.

The last three, as well, are in a certain sense propositions: for it is possible to make a proposition

corresponding to each of them, e.g. (1) 'The desirable may mean either the honourable or the pleasant or the

expedient'; and (2) Sensation differs from knowledge in that the latter may be recovered again after it has

been lost, while the former cannot'; and (3) The relation of the healthy to health is like that of the vigorous to

vigour'. The first proposition depends upon the use of one term in several senses, the second upon the

Propositions should be selected in a number of ways corresponding to the number of distinctions drawn in

regard to the proposition: thus one may first take in hand the opinions held by all or by most men or by the

philosophers, i.e. by all, or most, or the most notable of them; or opinions contrary to those that seem to be

generally held; and, again, all opinions that are in accordance with the arts. We must make propositions also

of the contradictories of opinions contrary to those that seem to be generally held, as was laid down before. It

is useful also to make them by selecting not only those opinions that actually are accepted, but also those that

are like these, e.g. 'The perception of contraries is the same'the knowledge of them being soand 'we see by

admission of something into ourselves, not by an emission'; for so it is, too, in the case of the other senses; for

in hearing we admit something into ourselves; we do not emit; and we taste in the same way. Likewise also in

the other cases. Moreover, all statements that seem to be true in all or in most cases, should be taken as a

principle or accepted position; for they are posited by those who do not also see what exception there may be.

We should select also from the written handbooks of argument, and should draw up sketchlists of them

upon each several kind of subject, putting them down under separate headings, e.g. 'On Good', or 'On

Life'and that 'On Good' should deal with every form of good, beginning with the category of essence. In the

margin, too, one should indicate also the opinions of individual thinkers, e.g. 'Empedocles said that the

elements of bodies were four': for any one might assent to the saying of some generally accepted authority.

Of propositions and problems there areto comprehend the matter in outlinethree divisions: for some are

ethical propositions, some are on natural philosophy, while some are logical. Propositions such as the

following are ethical, e.g. 'Ought one rather to obey one's parents or the laws, if they disagree?'; such as this

are logical, e.g. 'Is the knowledge of opposites the same or not?'; while such as this are on natural philosophy,

e.g. 'Is the universe eternal or not?' Likewise also with problems. The nature of each of the aforesaid kinds of

proposition is not easily rendered in a definition, but we have to try to recognize each of them by means of

the familiarity attained through induction, examining them in the light of the illustrations given above.

For purposes of philosophy we must treat of these things according to their truth, but for dialectic only with

an eye to general opinion. All propositions should be taken in their most universal form; then, the one should

be made into many. E.g. 'The knowledge of opposites is the same'; next, 'The knowledge of contraries is the

same', and that 'of relative terms'. In the same way these two should again be divided, as long as division is

possible, e.g. the knowledge of 'good and evil', of 'white and black', or 'cold and hot'. Likewise also in other

On the formation, then, of propositions, the above remarks are enough. As regards the number of senses a

term bears, we must not only treat of those terms which bear different senses, but we must also try to render

their definitions; e.g. we must not merely say that justice and courage are called 'good' in one sense, and that

what conduces to vigour and what conduces to health are called so in another, but also that the former are so

called because of a certain intrinsic quality they themselves have, the latter because they are productive of a

certain result and not because of any intrinsic quality in themselves. Similarly also in other cases.

Whether a term bears a number of specific meanings or one only, may be considered by the following means.

First, look and see if its contrary bears a number of meanings, whether the discrepancy between them be one

of kind or one of names. For in some cases a difference is at once displayed even in the names; e.g. the

contrary of 'sharp' in the case of a note is 'flat', while in the case of a solid edge it is 'dull'. Clearly, then, the

contrary of 'sharp' bears several meanings, and if so, also does 'sharp'; for corresponding to each of the former

terms the meaning of its contrary will be different. For 'sharp' will not be the same when contrary to 'dull' and

to 'flat', though 'sharp' is the contrary of each. Again Barhu ('flat', 'heavy') in the case of a note has 'sharp' as

its contrary, but in the case of a solid mass 'light', so that Barhu is used with a number of meanings, inasmuch

as its contrary also is so used. Likewise, also, 'fine' as applied to a picture has 'ugly' as its contrary, but, as

In some cases there is no discrepancy of any sort in the names used, but a difference of kind between the

meanings is at once obvious: e.g. in the case of 'clear' and 'obscure': for sound is called 'clear' and 'obscure',

just as 'colour' is too. As regards the names, then, there is no discrepancy, but the difference in kind between

the meanings is at once obvious: for colour is not called 'clear' in a like sense to sound. This is plain also

through sensation: for of things that are the same in kind we have the same sensation, whereas we do not

judge clearness by the same sensation in the case of sound and of colour, but in the latter case we judge by

sight, in the former by hearing. Likewise also with 'sharp' and 'dull' in regard to flavours and solid edges: here

in the latter case we judge by touch, but in the former by taste. For here again there is no discrepancy in the

names used, in the case either of the original terms or of their contraries: for the contrary also of sharp in

Moreover, see if one sense of a term has a contrary, while another has absolutely none; e.g. the pleasure of

drinking has a contrary in the pain of thirst, whereas the pleasure of seeing that the diagonal is

incommensurate with the side has none, so that 'pleasure' is used in more than one sense. To 'love' also, used

of the frame of mind, has to 'hate' as its contrary, while as used of the physical activity (kissing) it has none:

clearly, therefore, to 'love' is an ambiguous term. Further, see in regard to their intermediates, if some

meanings and their contraries have an intermediate, others have none, or if both have one but not the same

one, e.g. 'clear' and 'obscure' in the case of colours have 'grey' as an intermediate, whereas in the case of

sound they have none, or, if they have, it is 'harsh', as some people say that a harsh sound is intermediate.

'Clear', then, is an ambiguous term, and likewise also 'obscure'. See, moreover, if some of them have more

than one intermediate, while others have but one, as is the case with 'clear' and 'obscure', for in the case of

colours there are numbers of intermediates, whereas in regard to sound there is but one, viz. 'harsh'.

Again, in the case of the contradictory opposite, look and see if it bears more than one meaning. For if this

bears more than one meaning, then the opposite of it also will be used in more than one meaning; e.g. 'to fail

to see' a phrase with more than one meaning, viz. (1) to fail to possess the power of sight, (2) to fail to put

that power to active use. But if this has more than one meaning, it follows necessarily that 'to see' also has

more than one meaning: for there will be an opposite to each sense of 'to fail to see'; e.g. the opposite of 'not

to possess the power of sight' is to possess it, while of 'not to put the power of sight to active use', the

Moreover, examine the case of terms that denote the privation or presence of a certain state: for if the one

term bears more than one meaning, then so will the remaining term: e.g. if 'to have sense' be used with more

than one meaning, as applied to the soul and to the body, then 'to be wanting in sense' too will be used with

more than one meaning, as applied to the soul and to the body. That the opposition between the terms now in

question depends upon the privation or presence of a certain state is clear, since animals naturally possess

Moreover, examine the inflected forms. For if 'justly' has more than one meaning, then 'just', also, will be

used with more than one meaning; for there will be a meaning of 'just' to each of the meanings of 'justly'; e.g.

if the word 'justly' be used of judging according to one's own opinion, and also of judging as one ought, then

'just' also will be used in like manner. In the same way also, if 'healthy' has more than one meaning, then

'healthily' also will be used with more than one meaning: e.g. if 'healthy' describes both what produces health

and what preserves health and what betokens health, then 'healthily' also will be used to mean 'in such a way

as to produce' or 'preserve' or 'betoken' health. Likewise also in other cases, whenever the original term bears

more than one meaning, the inflexion also that is formed from it will be used with more than one meaning,

Look also at the classes of the predicates signified by the term, and see if they are the same in all cases. For if

they are not the same, then clearly the term is ambiguous: e.g. 'good' in the case of food means 'productive of

pleasure', and in the case of medicine 'productive of health', whereas as applied to the soul it means to be of a

certain quality, e.g. temperate or courageous or just: and likewise also, as applied to 'man'. Sometimes it

signifies what happens at a certain time, as (e.g.) the good that happens at the right time: for what happens at

the right time is called good. Often it signifies what is of certain quantity, e.g. as applied to the proper

amount: for the proper amount too is called good. So then the term 'good' is ambiguous. In the same way also

'clear', as applied to a body, signifies a colour, but in regard to a note it denotes what is 'easy to hear'. 'Sharp',

too, is in a closely similar case: for the same term does not bear the same meaning in all its applications: for a

sharp note is a swift note, as the mathematical theorists of harmony tell us, whereas a sharp (acute) angle is

one that is less than a right angle, while a sharp dagger is one containing a sharp angle (point).

Look also at the genera of the objects denoted by the same term, and see if they are different without being

subaltern, as (e.g.) 'donkey', which denotes both the animal and the engine. For the definition of them that

corresponds to the name is different: for the one will be declared to be an animal of a certain kind, and the

other to be an engine of a certain kind. If, however, the genera be subaltern, there is no necessity for the

definitions to be different. Thus (e.g.) 'animal' is the genus of 'raven', and so is 'bird'. Whenever therefore we

say that the raven is a bird, we also say that it is a certain kind of animal, so that both the genera are

predicated of it. Likewise also whenever we call the raven a 'flying biped animal', we declare it to be a bird:

in this way, then, as well, both the genera are predicated of raven, and also their definition. But in the case of

genera that are not subaltern this does not happen, for whenever we call a thing an 'engine', we do not call it

Look also and see not only if the genera of the term before you are different without being subaltern, but also

in the case of its contrary: for if its contrary bears several senses, clearly the term before you does so as well.

It is useful also to look at the definition that arises from the use of the term in combination, e.g. of a 'clear (lit.

white) body' of a 'clear note'. For then if what is peculiar in each case be abstracted, the same expression

ought to remain over. This does not happen in the case of ambiguous terms, e.g. in the cases just mentioned.

For the former will be body possessing such and such a colour', while the latter will be 'a note easy to hear'.

Abstract, then, 'a body 'and' a note', and the remainder in each case is not the same. It should, however, have

Often in the actual definitions as well ambiguity creeps in unawares, and for this reason the definitions also

should be examined. If (e.g.) any one describes what betokens and what produces health as 'related

commensurably to health', we must not desist but go on to examine in what sense he has used the term

'commensurably' in each case, e.g. if in the latter case it means that 'it is of the right amount to produce

health', whereas in the for it means that 'it is such as to betoken what kind of state prevails'.

Moreover, see if the terms cannot be compared as 'more or less' or as 'in like manner', as is the case (e.g.)

with a 'clear' (lit. white) sound and a 'clear' garment, and a 'sharp' flavour and a 'sharp' note. For neither are

these things said to be clear or sharp 'in a like degree', nor yet is the one said to be clearer or sharper than the

other. 'Clear', then, and 'sharp' are ambiguous. For synonyms are always comparable; for they will always be

Now since of genera that are different without being subaltern the differentiae also are different in kind, e.g.

those of 'animal' and 'knowledge' (for the differentiae of these are different), look and see if the meanings

comprised under the same term are differentiae of genera that are different without being subaltern, as e.g.

'sharp' is of a 'note' and a 'solid'. For being 'sharp' differentiates note from note, and likewise also one solid

from another. 'Sharp', then, is an ambiguous term: for it forms differentiae of genera that are different without

Again, see if the actual meanings included under the same term themselves have different differentiae, e.g.

'colour' in bodies and 'colour' in tunes: for the differentiae of 'colour' in bodies are 'sightpiercing' and 'sight

compressing', whereas 'colour' in melodies has not the same differentiae. Colour, then, is an ambiguous term;

Moreover, since the species is never the differentia of anything, look and see if one of the meanings included

under the same term be a species and another a differentia, as (e.g.) clear' (lit. white) as applied to a body is a

species of colour, whereas in the case of a note it is a differentia; for one note is differentiated from another

The presence, then, of a number of meanings in a term may be investigated by these and like means. The

differences which things present to each other should be examined within the same genera, e.g. 'Wherein

does justice differ from courage, and wisdom from temperance?'for all these belong to the same genus; and

also from one genus to another, provided they be not very much too far apart, e.g. 'Wherein does sensation

differ from knowledge?: for in the case of genera that are very far apart, the differences are entirely obvious.

Likeness should be studied, first, in the case of things belonging to different genera, the formulae being 'A:B

= C:D' (e.g. as knowledge stands to the object of knowledge, so is sensation related to the object of

sensation), and 'As A is in B, so is C in D' (e.g. as sight is in the eye, so is reason in the soul, and as is a calm

in the sea, so is windlessness in the air). Practice is more especially needed in regard to terms that are far

apart; for in the case of the rest, we shall be more easily able to see in one glance the points of likeness. We

should also look at things which belong to the same genus, to see if any identical attribute belongs to them

all, e.g. to a man and a horse and a dog; for in so far as they have any identical attribute, in so far they are

It is useful to have examined the number of meanings of a term both for clearness' sake (for a man is more

likely to know what it is he asserts, if it bas been made clear to him how many meanings it may have), and

also with a view to ensuring that our reasonings shall be in accordance with the actual facts and not addressed

merely to the term used. For as long as it is not clear in how many senses a term is used, it is possible that the

answerer and the questioner are not directing their minds upon the same thing: whereas when once it has been

made clear how many meanings there are, and also upon which of them the former directs his mind when he

makes his assertion, the questioner would then look ridiculous if he failed to address his argument to this. It

helps us also both to avoid being misled and to mislead by false reasoning: for if we know the number of

meanings of a term, we shall certainly never be misled by false reasoning, but shall know if the questioner

fails to address his argument to the same point; and when we ourselves put the questions we shall be able to

mislead him, if our answerer happens not to know the number of meanings of our terms. This, however, is not

possible in all cases, but only when of the many senses some are true and others are false. This manner of

argument, however, does not belong properly to dialectic; dialecticians should therefore by all means beware

of this kind of verbal discussion, unless any one is absolutely unable to discuss the subject before him in any

The discovery of the differences of things helps us both in reasonings about sameness and difference, and

also in recognizing what any particular thing is. That it helps us in reasoning about sameness and difference is

clear: for when we have discovered a difference of any kind whatever between the objects before us, we shall

already have shown that they are not the same: while it helps us in recognizing what a thing is, because we

usually distinguish the expression that is proper to the essence of each particular thing by means of the

The examination of likeness is useful with a view both to inductive arguments and to hypothetical reasonings,

and also with a view to the rendering of definitions. It is useful for inductive arguments, because it is by

means of an induction of individuals in cases that are alike that we claim to bring the universal in evidence:

for it is not easy to do this if we do not know the points of likeness. It is useful for hypothetical reasonings

because it is a general opinion that among similars what is true of one is true also of the rest. If, then, with

regard to any of them we are well supplied with matter for a discussion, we shall secure a preliminary

admission that however it is in these cases, so it is also in the case before us: then when we have shown the

former we shall have shown, on the strength of the hypothesis, the matter before us as well: for we have first

made the hypothesis that however it is in these cases, so it is also in the case before us, and have then proved

the point as regards these cases. It is useful for the rendering of definitions because, if we are able to see in

one glance what is the same in each individual case of it, we shall be at no loss into what genus we ought to

put the object before us when we define it: for of the common predicates that which is most definitely in the

category of essence is likely to be the genus. Likewise, also, in the case of objects widely divergent, the

examination of likeness is useful for purposes of definition, e.g. the sameness of a calm at sea, and

windlessness in the air (each being a form of rest), and of a point on a line and the unit in numbereach being

a starting point. If, then, we render as the genus what is common to all the cases, we shall get the credit of

defining not inappropriately. Definitionmongers too nearly always render them in this way: they declare the

unit to be the startingpoint of number, and the point the startingpoint of a line. It is clear, then, that they place

The means, then, whereby reasonings are effected, are these: the commonplace rules, for the observance of

Of problems some are universal, others particular. Universal problems are such as 'Every pleasure is good'

and 'No pleasure is good'; particular problems are such as 'Some pleasure is good' and 'Some pleasure is not

good'. The methods of establishing and overthrowing a view universally are common to both kinds of

problems; for when we have shown that a predicate belongs in every case, we shall also have shown that it

belongs in some cases. Likewise, also, if we show that it does not belong in any case, we shall also have

shown that it does not belong in every case. First, then, we must speak of the methods of overthrowing a view

universally, because such are common to both universal and particular problems, and because people more

usually introduce theses asserting a predicate than denying it, while those who argue with them overthrow it.

The conversion of an appropriate name which is drawn from the element 'accident' is an extremely precarious

thing; for in the case of accidents and in no other it is possible for something to be true conditionally and not

universally. Names drawn from the elements 'definition' and 'property' and 'genus' are bound to be

convertible; e.g. if 'to be an animal that walks on two feet is an attribute of S', then it will be true by

conversion to say that 'S is an animal that walks on two feet'. Likewise, also, if drawn from the genus; for if

'to be an animal is an attribute of S', then 'S is an animal'. The same is true also in the case of a property; for if

'to be capable of learning grammar is an attribute of S', then 'S will be capable of learning grammar'. For none

of these attributes can possibly belong or not belong in part; they must either belong or not belong absolutely.

In the case of accidents, on the other hand, there is nothing to prevent an attribute (e.g. whiteness or justice)

belonging in part, so that it is not enough to show that whiteness or justice is an attribute of a man in order to

show that he is white or just; for it is open to dispute it and say that he is white or just in part only.

We must also define the errors that occur in problems. They are of two kinds, caused either by false statement

or by transgression of the established diction. For those who make false statements, and say that an attribute

belongs to thing which does not belong to it, commit error; and those who call objects by the names of other

objects (e.g. calling a planetree a 'man') transgress the established terminology.

Now one commonplace rule is to look and see if a man has ascribed as an accident what belongs in some

other way. This mistake is most commonly made in regard to the genera of things, e.g. if one were to say that

white happens (accidit) to be a colourfor being a colour does not happen by accident to white, but colour is

its genus. The assertor may of course define it so in so many words, saying (e.g.) that 'Justice happens

(accidit) to be a virtue'; but often even without such definition it is obvious that he has rendered the genus as

an accident; e.g. suppose that one were to say that whiteness is coloured or that walking is in motion. For a

predicate drawn from the genus is never ascribed to the species in an inflected form, but always the genera

are predicated of their species literally; for the species take on both the name and the definition of their

genera. A man therefore who says that white is 'coloured' has not rendered 'coloured' as its genus, seeing that

he has used an inflected form, nor yet as its property or as its definition: for the definition and property of a

thing belong to it and to nothing else, whereas many things besides white are coloured, e.g. a log, a stone, a

Another rule is to examine all cases where a predicate has been either asserted or denied universally to belong

to something. Look at them species by species, and not in their infinite multitude: for then the inquiry will

proceed more directly and in fewer steps. You should look and begin with the most primary groups, and then

proceed in order down to those that are not further divisible: e.g. if a man has said that the knowledge of

opposites is the same, you should look and see whether it be so of relative opposites and of contraries and of

terms signifying the privation or presence of certain states, and of contradictory terms. Then, if no clear result

be reached so far in these cases, you should again divide these until you come to those that are not further

divisible, and see (e.g.) whether it be so of just deeds and unjust, or of the double and the half, or of blindness

and sight, or of being and notbeing: for if in any case it be shown that the knowledge of them is not the

same we shall have demolished the problem. Likewise, also, if the predicate belongs in no case. This rule is

convertible for both destructive and constructive purposes: for if, when we have suggested a division, the

predicate appears to hold in all or in a large number of cases, we may then claim that the other should

actually assert it universally, or else bring a negative instance to show in what case it is not so: for if he does

Another rule is to make definitions both of an accident and of its subject, either of both separately or else of

one of them, and then look and see if anything untrue has been assumed as true in the definitions. Thus (e.g.)

to see if it is possible to wrong a god, ask what is 'to wrong'? For if it be 'to injure deliberately', clearly it is

not possible for a god to be wronged: for it is impossible that God should be injured. Again, to see if the good

man is jealous, ask who is the 'jealous' man and what is 'jealousy'. For if 'jealousy' is pain at the apparent

success of some wellbehaved person, clearly the good man is not jealous: for then he would be bad. Again,

to see if the indignant man is jealous, ask who each of them is: for then it will be obvious whether the

statement is true or false; e.g. if he is 'jealous' who grieves at the successes of the good, and he is 'indignant'

who grieves at the successes of the evil, then clearly the indignant man would not be jealous. A man should

substitute definitions also for the terms contained in his definitions, and not stop until he comes to a familiar

term: for often if the definition be rendered whole, the point at issue is not cleared up, whereas if for one of

Moreover, a man should make the problem into a proposition for himself, and then bring a negative instance

against it: for the negative instance will be a ground of attack upon the assertion. This rule is very nearly the

same as the rule to look into cases where a predicate has been attributed or denied universally: but it differs in

Moreover, you should define what kind of things should be called as most men call them, and what should

not. For this is useful both for establishing and for overthrowing a view: e.g. you should say that we ought to

use our terms to mean the same things as most people mean by them, but when we ask what kind of things

are or are not of such and such a kind, we should not here go with the multitude: e.g. it is right to call 'healthy'

whatever tends to produce health, as do most men: but in saying whether the object before us tends to

produce health or not, we should adopt the language no longer of the multitude but of the doctor.

Moreover, if a term be used in several senses, and it has been laid down that it is or that it is not an attribute

of S, you should show your case of one of its several senses, if you cannot show it of both. This rule is to be

observed in cases where the difference of meaning is undetected; for supposing this to be obvious, then the

other man will object that the point which he himself questioned has not been discussed, but only the other

point. This commonplace rule is convertible for purposes both of establishing and of overthrowing a view.

For if we want to establish a statement, we shall show that in one sense the attribute belongs, if we cannot

show it of both senses: whereas if we are overthrowing a statement, we shall show that in one sense the

attribute does not belong, if we cannot show it of both senses. Of course, in overthrowing a statement there is

no need to start the discussion by securing any admission, either when the statement asserts or when it denies

the attribute universally: for if we show that in any case whatever the attribute does not belong, we shall have

demolished the universal assertion of it, and likewise also if we show that it belongs in a single case, we shall

demolish the universal denial of it. Whereas in establishing a statement we ought to secure a preliminary

admission that if it belongs in any case whatever, it belongs universally, supposing this claim to be a

plausible one. For it is not enough to discuss a single instance in order to show that an attribute belongs

universally; e.g. to argue that if the soul of man be immortal, then every soul is immortal, so that a previous

admission must be secured that if any soul whatever be immortal, then every soul is immortal. This is not to

be done in every case, but only whenever we are not easily able to quote any single argument applying to all

cases in common, as (e.g.) the geometrician can argue that the triangle has its angles equal to two right

If, again, the variety of meanings of a term be obvious, distinguish how many meanings it has before

proceeding either to demolish or to establish it: e.g. supposing 'the right' to mean 'the expedient' or 'the

honourable', you should try either to establish or to demolish both descriptions of the subject in question; e.g.

by showing that it is honourable and expedient, or that it is neither honourable nor expedient. Supposing,

however, that it is impossible to show both, you should show the one, adding an indication that it is true in

the one sense and not in the other. The same rule applies also when the number of senses into which it is

Again, consider those expressions whose meanings are many, but differ not by way of ambiguity of a term,

but in some other way: e.g. 'The science of many things is one': here 'many things' may mean the end and the

means to that end, as (e.g.) medicine is the science both of producing health and of dieting; or they may be

both of them ends, as the science of contraries is said to be the same (for of contraries the one is no more an

end than the other); or again they may be an essential and an accidental attribute, as (e.g.) the essential fact

that the triangle has its angles equal to two right angles, and the accidental fact that the equilateral figure has

them so: for it is because of the accident of the equilateral triangle happening to be a triangle that we know

that it has its angles equal to two right angles. If, then, it is not possible in any sense of the term that the

science of many things should be the same, it clearly is altogether impossible that it should be so; or, if it is

possible in some sense, then clearly it is possible. Distinguish as many meanings as are required: e.g. if we

want to establish a view, we should bring forward all such meanings as admit that view and should divide

them only into those meanings which also are required for the establishment of our case: whereas if we want

to overthrow a view, we should bring forward all that do not admit that view, and leave the rest aside. We

must deal also in these cases as well with any uncertainty about the number of meanings involved. Further,

that one thing is, or is not, 'of' another should be established by means of the same commonplace rules; e.g.

that a particular science is of a particular thing, treated either as an end or as a means to its end, or as

accidentally connected with it; or again that it is not 'of' it in any of the aforesaid ways. The same rule holds

true also of desire and all other terms that have more than one object. For the 'desire of X' may mean the

desire of it as an end (e.g. the desire of health) or as a means to an end (e.g. the desire of being doctored), or

as a thing desired accidentally, as, in the case of wine, the sweettoothed person desires it not because it is

wine but because it is sweet. For essentially he desires the sweet, and only accidentally the wine: for if it be

dry, he no longer desires it. His desire for it is therefore accidental. This rule is useful in dealing with relative

Moreover, it is well to alter a term into one more familiar, e.g. to substitute 'clear' for 'exact' in describing a

conception, and 'being fussy' for 'being busy': for when the expression is made more familiar, the thesis

becomes easier to attack. This commonplace rule also is available for both purposes alike, both for

In order to show that contrary attributes belong to the same thing, look at its genus; e.g. if we want to show

that rightness and wrongness are possible in regard to perception, and to perceive is to judge, while it is

possible to judge rightly or wrongly, then in regard to perception as well rightness and wrongness must be

possible. In the present instance the proof proceeds from the genus and relates to the species: for 'to judge' is

the genus of 'to perceive'; for the man who perceives judges in a certain way. But per contra it may proceed

from the species to the genus: for all the attributes that belong to the species belong to the genus as well; e.g.

if there is a bad and a good knowledge there is also a bad and a good disposition: for 'disposition' is the genus

of knowledge. Now the former commonplace argument is fallacious for purposes of establishing a view,

while the second is true. For there is no necessity that all the attributes that belong to the genus should belong

also to the species; for 'animal' is flying and quadruped, but not so 'man'. All the attributes, on the other hand,

that belong to the species must of necessity belong also to the genus; for if 'man' is good, then animal also is

good. On the other hand, for purposes of overthrowing a view, the former argument is true while the latter is

fallacious; for all the attributes which do not belong to the genus do not belong to the species either; whereas

all those that are wanting to the species are not of necessity wanting to the genus.

Since those things of which the genus is predicated must also of necessity have one of its species predicated

of them, and since those things that are possessed of the genus in question, or are described by terms derived

from that genus, must also of necessity be possessed of one of its species or be described by terms derived

from one of its species (e.g. if to anything the term 'scientific knowledge' be applied, then also there will be

applied to it the term 'grammatical' or 'musical' knowledge, or knowledge of one of the other sciences; and if

any one possesses scientific knowledge or is described by a term derived from 'science', then he will also

possess grammatical or musical knowledge or knowledge of one of the other sciences, or will be described by

a term derived from one of them, e.g. as a 'grammarian' or a 'musician')therefore if any expression be

asserted that is in any way derived from the genus (e.g. that the soul is in motion), look and see whether it be

possible for the soul to be moved with any of the species of motion; whether (e.g.) it can grow or be

destroyed or come to be, and so forth with all the other species of motion. For if it be not moved in any of

these ways, clearly it does not move at all. This commonplace rule is common for both purposes, both for

overthrowing and for establishing a view: for if the soul moves with one of the species of motion, clearly it

does move; while if it does not move with any of the species of motion, clearly it does not move.

If you are not well equipped with an argument against the assertion, look among the definitions, real or

apparent, of the thing before you, and if one is not enough, draw upon several. For it will be easier to attack

people when committed to a definition: for an attack is always more easily made on definitions.

Moreover, look and see in regard to the thing in question, what it is whose reality conditions the reality of the

thing in question, or what it is whose reality necessarily follows if the thing in question be real: if you wish to

establish a view inquire what there is on whose reality the reality of the thing in question will follow (for if

the former be shown to be real, then the thing in question will also have been shown to be real); while if you

want to overthrow a view, ask what it is that is real if the thing in question be real, for if we show that what

follows from the thing in question is unreal, we shall have demolished the thing in question.

Moreover, look at the time involved, to see if there be any discrepancy anywhere: e.g. suppose a man to have

stated that what is being nourished of necessity grows: for animals are always of necessity being nourished,

but they do not always grow. Likewise, also, if he has said that knowing is remembering: for the one is

concerned with past time, whereas the other has to do also with the present and the future. For we are said to

know things present and future (e.g. that there will be an eclipse), whereas it is impossible to remember

Moreover, there is the sophistic turn of argument, whereby we draw our opponent into the kind of statement

against which we shall be well supplied with lines of argument. This process is sometimes a real necessity,

sometimes an apparent necessity, sometimes neither an apparent nor a real necessity. It is really necessary

whenever the answerer has denied any view that would be useful in attacking the thesis, and the questioner

thereupon addresses his arguments to the support of this view, and when moreover the view in question

happens to be one of a kind on which he has a good stock of lines of argument. Likewise, also, it is really

necessary whenever he (the questioner) first, by an induction made by means of the view laid down, arrives at

a certain statement and then tries to demolish that statement: for when once this has been demolished, the

view originally laid down is demolished as well. It is an apparent necessity, when the point to which the

discussion comes to be directed appears to be useful, and relevant to the thesis, without being really so;

whether it be that the man who is standing up to the argument has refused to concede something, or whether

he (the questioner) has first reached it by a plausible induction based upon the thesis and then tries to

demolish it. The remaining case is when the point to which the discussion comes to be directed is neither

really nor apparently necessary, and it is the answerer's luck to be confuted on a mere side issue You should

beware of the last of the aforesaid methods; for it appears to be wholly disconnected from, and foreign to, the

art of dialectic. For this reason, moreover, the answerer should not lose his temper, but assent to those

statements that are of no use in attacking the thesis, adding an indication whenever he assents although he

does not agree with the view. For, as a rule, it increases the confusion of questioners if, after all propositions

Moreover, any one who has made any statement whatever has in a certain sense made several statements,

inasmuch as each statement has a number of necessary consequences: e.g. the man who said 'X is a man' has

also said that it is an animal and that it is animate and a biped and capable of acquiring reason and

knowledge, so that by the demolition of any single one of these consequences, of whatever kind, the original

statement is demolished as well. But you should beware here too of making a change to a more difficult

subject: for sometimes the consequence, and sometimes the original thesis, is the easier to demolish.

In regard to subjects which must have one and one only of two predicates, as (e.g.) a man must have either a

disease or health, supposing we are well supplied as regards the one for arguing its presence or absence, we

shall be well equipped as regards the remaining one as well. This rule is convertible for both purposes: for

when we have shown that the one attribute belongs, we shall have shown that the remaining one does not

belong; while if we show that the one does not belong, we shall have shown that the remaining one does

Moreover, you may devise a line of attack by reinterpreting a term in its literal meaning, with the implication

that it is most fitting so to take it rather than in its established meaning: e.g. the expression 'strong at heart'

will suggest not the courageous man, according to the use now established, but the man the state of whose

heart is strong; just as also the expression 'of a good hope' may be taken to mean the man who hopes for good

things. Likewise also 'wellstarred' may be taken to mean the man whose star is good, as Xenocrates says

Some things occur of necessity, others usually, others however it may chance; if therefore a necessary event

has been asserted to occur usually, or if a usual event (or, failing such an event itself, its contrary) has been

stated to occur of necessity, it always gives an opportunity for attack. For if a necessary event has been

asserted to occur usually, clearly the speaker has denied an attribute to be universal which is universal, and so

has made a mistake: and so he has if he has declared the usual attribute to be necessary: for then he declares it

to belong universally when it does not so belong. Likewise also if he has declared the contrary of what is

usual to be necessary. For the contrary of a usual attribute is always a comparatively rare attribute: e.g. if men

are usually bad, they are comparatively seldom good, so that his mistake is even worse if he has declared

them to be good of necessity. The same is true also if he has declared a mere matter of chance to happen of

necessity or usually; for a chance event happens neither of necessity nor usually. If the thing happens usually,

then even supposing his statement does not distinguish whether he meant that it happens usually or that it

happens necessarily, it is open to you to discuss it on the assumption that he meant that it happens

necessarily: e.g. if he has stated without any distinction that disinherited persons are bad, you may assume in

Moreover, look and see also if he has stated a thing to be an accident of itself, taking it to be a different thing

because it has a different name, as Prodicus used to divide pleasures into joy and delight and good cheer: for

all these are names of the same thing, to wit, Pleasure. If then any one says that joyfulness is an accidental

attribute of cheerfulness, he would be declaring it to be an accidental attribute of itself.

Inasmuch as contraries can be conjoined with each other in six ways, and four of these conjunctions

constitute a contrariety, we must grasp the subject of contraries, in order that it may help us both in

demolishing and in establishing a view. Well then, that the modes of conjunction are six is clear: for either (1)

each of the contrary verbs will be conjoined to each of the contrary objects; and this gives two modes: e.g. to

do good to friends and to do evil to enemies, or per contra to do evil to friends and to do good to enemies. Or

else (2) both verbs may be attached to one object; and this too gives two modes, e.g. to do good to friends and

to do evil to friends, or to do good to enemies and to do evil to enemies. Or (3) a single verb may be attached

to both objects: and this also gives two modes; e.g. to do good to friends and to do good to enemies, or to do

The first two then of the aforesaid conjunctions do not constitute any contrariety; for the doing of good to

friends is not contrary to the doing of evil to enemies: for both courses are desirable and belong to the same

disposition. Nor is the doing of evil to friends contrary to the doing of good to enemies: for both of these are

objectionable and belong to the same disposition: and one objectionable thing is not generally thought to be

the contrary of another, unless the one be an expression denoting an excess, and the other an expression

denoting a defect: for an excess is generally thought to belong to the class of objectionable things, and

likewise also a defect. But the other four all constitute a contrariety. For to do good to friends is contrary to

the doing of evil to friends: for it proceeds from the contrary disposition, and the one is desirable, and the

other objectionable. The case is the same also in regard to the other conjunctions: for in each combination the

one course is desirable, and the other objectionable, and the one belongs to a reasonable disposition and the

other to a bad. Clearly, then, from what has been said, the same course has more than one contrary. For the

doing of good to friends has as its contrary both the doing of good to enemies and the doing of evil to friends.

Likewise, if we examine them in the same way, we shall find that the contraries of each of the others also are

two in number. Select therefore whichever of the two contraries is useful in attacking the thesis.

Moreover, if the accident of a thing have a contrary, see whether it belongs to the subject to which the

accident in question has been declared to belong: for if the latter belongs the former could not belong; for it is

impossible that contrary predicates should belong at the same time to the same thing.

Or again, look and see if anything has been said about something, of such a kind that if it be true, contrary

predicates must necessarily belong to the thing: e.g. if he has said that the 'Ideas' exist in us. For then the

result will be that they are both in motion and at rest, and moreover that they are objects both of sensation and

of thought. For according to the views of those who posit the existence of Ideas, those Ideas are at rest and

are objects of thought; while if they exist in us, it is impossible that they should be unmoved: for when we

move, it follows necessarily that all that is in us moves with us as well. Clearly also they are objects of

sensation, if they exist in us: for it is through the sensation of sight that we recognize the Form present in

Again, if there be posited an accident which has a contrary, look and see if that which admits of the accident

will admit of its contrary as well: for the same thing admits of contraries. Thus (e.g.) if he has asserted that

hatred follows anger, hatred would in that case be in the 'spirited faculty': for that is where anger is. You

should therefore look and see if its contrary, to wit, friendship, be also in the 'spirited faculty': for if notif

friendship is in the faculty of desirethen hatred could not follow anger. Likewise also if he has asserted that

the faculty of desire is ignorant. For if it were capable of ignorance, it would be capable of knowledge as

well: and this is not generally heldI mean that the faculty of desire is capable of knowledge. For purposes,

then, of overthrowing a view, as has been said, this rule should be observed: but for purposes of establishing

one, though the rule will not help you to assert that the accident actually belongs, it will help you to assert

that it may possibly belong. For having shown that the thing in question will not admit of the contrary of the

accident asserted, we shall have shown that the accident neither belongs nor can possibly belong; while on

the other hand, if we show that the contrary belongs, or that the thing is capable of the contrary, we shall not

indeed as yet have shown that the accident asserted does belong as well; our proof will merely have gone to

Seeing that the modes of opposition are four in number, you should look for arguments among the

contradictories of your terms, converting the order of their sequence, both when demolishing and when

establishing a view, and you should secure them by means of inductionsuch arguments (e.g.) as that man be

an animal, what is not an animal is not a man': and likewise also in other instances of contradictories. For in

those cases the sequence is converse: for 'animal' follows upon 'man but 'notanimal' does not follow upon

'notman', but conversely 'notman' upon 'notanimal'. In all cases, therefore, a postulate of this sort should

be made, (e.g.) that 'If the honourable is pleasant, what is not pleasant is not honourable, while if the latter be

untrue, so is the former'. Likewise, also, 'If what is not pleasant be not honourable, then what is honourable is

pleasant'. Clearly, then, the conversion of the sequence formed by contradiction of the terms of the thesis is a

Then look also at the case of the contraries of S and P in the thesis, and see if the contrary of the one follows

upon the contrary of the other, either directly or conversely, both when you are demolishing and when you

are establishing a view: secure arguments of this kind as well by means of induction, so far as may be

required. Now the sequence is direct in a case such as that of courage and cowardice: for upon the one of

them virtue follows, and vice upon the other; and upon the one it follows that it is desirable, while upon the

other it follows that it is objectionable. The sequence, therefore, in the latter case also is direct; for the

desirable is the contrary of the objectionable. Likewise also in other cases. The sequence is, on the other

hand, converse in such a case as this: Health follows upon vigour, but disease does not follow upon debility;

rather debility follows upon disease. In this case, then, clearly the sequence is converse. Converse sequence

is, however, rare in the case of contraries; usually the sequence is direct. If, therefore, the contrary of the one

term does not follow upon the contrary of the other either directly or conversely, clearly neither does the one

term follow upon the other in the statement made: whereas if the one followed the other in the case of the

You should look also into cases of the privation or presence of a state in like manner to the case of contraries.

Only, in the case of such privations the converse sequence does not occur: the sequence is always bound to be

direct: e.g. as sensation follows sight, while absence of sensation follows blindness. For the opposition of

sensation to absence of sensation is an opposition of the presence to the privation of a state: for the one of

The case of relative terms should also be studied in like manner to that of a state and its privation: for the

sequence of these as well is direct; e.g. if 3/1 is a multiple, then 1/3 is a fraction: for 3/1 is relative to 1/3, and

so is a multiple to a fraction. Again, if knowledge be a conceiving, then also the object of knowledge is an

object of conception; and if sight be a sensation, then also the object of sight is an object of sensation. An

objection may be made that there is no necessity for the sequence to take place, in the case of relative terms,

in the way described: for the object of sensation is an object of knowledge, whereas sensation is not

knowledge. The objection is, however, not generally received as really true; for many people deny that there

is knowledge of objects of sensation. Moreover, the principle stated is just as useful for the contrary purpose,

e.g. to show that the object of sensation is not an object of knowledge, on the ground that neither is sensation

Again look at the case of the coordinates and inflected forms of the terms in the thesis, both in demolishing

and in establishing it. By coordinates' are meant terms such as the following: 'Just deeds' and the 'just man'

are coordinates of 'justice', and 'courageous deeds' and the 'courageous man' are coordinates of courage.

Likewise also things that tend to produce and to preserve anything are called coordinates of that which they

tend to produce and to preserve, as e.g. 'healthy habits' are coordinates of 'health' and a 'vigorous

constitutional' of a 'vigorous constitution' and so forth also in other cases. 'Coordinate', then, usually

describes cases such as these, whereas 'inflected forms' are such as the following: 'justly', 'courageously',

'healthily', and such as are formed in this way. It is usually held that words when used in their inflected forms

as well are coordinates, as (e.g.) 'justly' in relation to justice, and 'courageously' to courage; and then

'coordinate' describes all the members of the same kindred series, e.g. 'justice', 'just', of a man or an act,

'justly'. Clearly, then, when any one member, whatever its kind, of the same kindred series is shown to be

good or praiseworthy, then all the rest as well come to be shown to be so: e.g. if 'justice' be something

praiseworthy, then so will 'just', of a man or thing, and 'justly' connote something praiseworthy. Then 'justly'

will be rendered also 'praiseworthily', derived will by the same inflexion from 'the praiseworthy' whereby

Look not only in the case of the subject mentioned, but also in the case of its contrary, for the contrary

predicate: e.g. argue that good is not necessarily pleasant; for neither is evil painful: or that, if the latter be the

case, so is the former. Also, if justice be knowledge, then injustice is ignorance: and if 'justly' means

'knowingly' and 'skilfully', then 'unjustly' means 'ignorantly' and 'unskilfully': whereas if the latter be not true,

neither is the former, as in the instance given just now: for 'unjustly' is more likely to seem equivalent to

'skilfully' than to 'unskilfully'. This commonplace rule has been stated before in dealing with the sequence of

contraries; for all we are claiming now is that the contrary of P shall follow the contrary of S.

Moreover, look at the modes of generation and destruction of a thing, and at the things which tend to produce

or to destroy it, both in demolishing and in establishing a view. For those things whose modes of generation

rank among good things, are themselves also good; and if they themselves be good, so also are their modes of

generation. If, on the other hand, their modes of generation be evil, then they themselves also are evil. In

regard to modes of destruction the converse is true: for if the modes of destruction rank as good things, then

they themselves rank as evil things; whereas if the modes of destruction count as evil, they themselves count

as good. The same argument applies also to things tending to produce and destroy: for things whose

productive causes are good, themselves also rank as good; whereas if causes destructive of them are good,

Again, look at things which are like the subject in question, and see if they are in like case; e.g. if one branch

of knowledge has more than one object, so also will one opinion; and if to possess sight be to see, then also to

possess hearing will be to hear. Likewise also in the case of other things, both those which are and those

which are generally held to be like. The rule in question is useful for both purposes; for if it be as stated in the

case of some one like thing, it is so with the other like things as well, whereas if it be not so in the case of

some one of them, neither is it so in the case of the others. Look and see also whether the cases are alike as

regards a single thing and a number of things: for sometimes there is a discrepancy. Thus, if to 'know' a thing

be to 'think of' it, then also to 'know many things' is to 'be thinking of many things'; whereas this is not true;

for it is possible to know many things but not to be thinking of them. If, then, the latter proposition be not

true, neither was the former that dealt with a single thing, viz. that to 'know' a thing is to 'think of' it.

Moreover, argue from greater and less degrees. In regard to greater degrees there are four commonplace

rules. One is: See whether a greater degree of the predicate follows a greater degree of the subject: e.g. if

pleasure be good, see whether also a greater pleasure be a greater good: and if to do a wrong be evil, see

whether also to do a greater wrong is a greater evil. Now this rule is of use for both purposes: for if an

increase of the accident follows an increase of the subject, as we have said, clearly the accident belongs;

while if it does not follow, the accident does not belong. You should establish this by induction. Another rule

is: If one predicate be attributed to two subjects; then supposing it does not belong to the subject to which it is

the more likely to belong, neither does it belong where it is less likely to belong; while if it does belong

where it is less likely to belong, then it belongs as well where it is more likely. Again: If two predicates be

attributed to one subject, then if the one which is more generally thought to belong does not belong, neither

does the one that is less generally thought to belong; or, if the one that is less generally thought to belong

does belong, so also does the other. Moreover: If two predicates be attributed to two subjects, then if the one

which is more usually thought to belong to the one subject does not belong, neither does the remaining

predicate belong to the remaining subject; or, if the one which is less usually thought to belong to the one

subject does belong, so too does the remaining predicate to the remaining subject.

Moreover, you can argue from the fact that an attribute belongs, or is generally supposed to belong, in a like

degree, in three ways, viz. those described in the last three rules given in regard to a greater degree.' For

supposing that one predicate belongs, or is supposed to belong, to two subjects in a like degree, then if it does

not belong to the one, neither does it belong to the other; while if it belongs to the one, it belongs to the

remaining one as well. Or, supposing two predicates to belong in a like degree to the same subject, then, if

the one does not belong, neither does the remaining one; while if the one does belong, the remaining one

belongs as well. The case is the same also if two predicates belong in a like degree to two subjects; for if the

one predicate does not belong to the one subject, neither does the remaining predicate belong to the

remaining subject, while if the one predicate does belong to the one subject, the remaining predicate belongs

You can argue, then, from greater or less or like degrees of truth in the aforesaid number of ways. Moreover,

you should argue from the addition of one thing to another. If the addition of one thing to another makes that

other good or white, whereas formerly it was not white or good, then the thing added will be white or goodit

will possess the character it imparts to the whole as well. Moreover, if an addition of something to a given

object intensifies the character which it had as given, then the thing added will itself as well be of that

character. Likewise, also, in the case of other attributes. The rule is not applicable in all cases, but only in

those in which the excess described as an 'increased intensity' is found to take place. The above rule is,

however, not convertible for overthrowing a view. For if the thing added does not make the other good, it is

not thereby made clear whether in itself it may not be good: for the addition of good to evil does not

necessarily make the whole good, any more than the addition of white to black makes the whole white.

Again, any predicate of which we can speak of greater or less degrees belongs also absolutely: for greater or

less degrees of good or of white will not be attributed to what is not good or white: for a bad thing will never

be said to have a greater or less degree of goodness than another, but always of badness. This rule is not

convertible, either, for the purpose of overthrowing a predication: for several predicates of which we cannot

speak of a greater degree belong absolutely: for the term 'man' is not attributed in greater and less degrees, but

You should examine in the same way predicates attributed in a given respect, and at a given time and place:

for if the predicate be possible in some respect, it is possible also absolutely. Likewise, also, is what is

predicated at a given time or place: for what is absolutely impossible is not possible either in any respect or at

any place or time. An objection may be raised that in a given respect people may be good by nature, e.g. they

may be generous or temperately inclined, while absolutely they are not good by nature, because no one is

prudent by nature. Likewise, also, it is possible for a destructible thing to escape destruction at a given time,

whereas it is not possible for it to escape absolutely. In the same way also it is a good thing at certain places

to follow see and such a diet, e.g. in infected areas, though it is not a good thing absolutely. Moreover, in

certain places it is possible to live singly and alone, but absolutely it is not possible to exist singly and alone.

In the same way also it is in certain places honourable to sacrifice one's father, e.g. among the Triballi,

whereas, absolutely, it is not honourable. Or possibly this may indicate a relativity not to places but to

persons: for it is all the same wherever they may be: for everywhere it will be held honourable among the

Triballi themselves, just because they are Triballi. Again, at certain times it is a good thing to take medicines,

e.g. when one is ill, but it is not so absolutely. Or possibly this again may indicate a relativity not to a certain

time, but to a certain state of health: for it is all the same whenever it occurs, if only one be in that state. A

thing is 'absolutely' so which without any addition you are prepared to say is honourable or the contrary. Thus

(e.g.) you will deny that to sacrifice one's father is honourable: it is honourable only to certain persons: it is

not therefore honourable absolutely. On the other hand, to honour the gods you will declare to be honourable

without adding anything, because that is honourable absolutely. So that whatever without any addition is

generally accounted to be honourable or dishonourable or anything else of that kind, will be said to be so

THE question which is the more desirable, or the better, of two or more things, should be examined upon the

following lines: only first of all it must be clearly laid down that the inquiry we are making concerns not

things that are widely divergent and that exhibit great differences from one another (for nobody raises any

doubt whether happiness or wealth is more desirable), but things that are nearly related and about which we

commonly discuss for which of the two we ought rather to vote, because we do not see any advantage on

either side as compared with the other. Clearly, in such cases if we can show a single advantage, or more than

one, our judgement will record our assent that whichever side happens to have the advantage is the more

First, then, that which is more lasting or secure is more desirable than that which is less so: and so is that

which is more likely to be chosen by the prudent or by the good man or by the right law, or by men who are

good in any particular line, when they make their choice as such, or by the experts in regard to any particular

class of things; i.e. either whatever most of them or what all of them would choose; e.g. in medicine or in

carpentry those things are more desirable which most, or all, doctors would choose; or, in general, whatever

most men or all men or all things would choose, e.g. the good: for everything aims at the good. You should

direct the argument you intend to employ to whatever purpose you require. Of what is 'better' or 'more

desirable' the absolute standard is the verdict of the better science, though relatively to a given individual the

In the second place, that which is known as 'an x' is more desirable than that which does not come within the

genus 'x'e.g. justice than a just man; for the former falls within the genus 'good', whereas the other does not,

and the former is called 'a good', whereas the latter is not: for nothing which does not happen to belong to the

genus in question is called by the generic name; e.g. a 'white man' is not 'a colour'. Likewise also in other

Also, that which is desired for itself is more desirable than that which is desired for something else; e.g.

health is more desirable than gymnastics: for the former is desired for itself, the latter for something else.

Also, that which is desirable in itself is more desirable than what is desirable per accidens; e.g. justice in our

friends than justice in our enemies: for the former is desirable in itself, the latter per accidens: for we desire

that our enemies should be just per accidens, in order that they may do us no harm. This last principle is the

same as the one that precedes it, with, however, a different turn of expression. For we desire justice in our

friends for itself, even though it will make no difference to us, and even though they be in India; whereas in

our enemies we desire it for something else, in order that they may do us no harm.

Also, that which is in itself the cause of good is more desirable than what is so per accidens, e.g. virtue than

luck (for the former in itself, and the latter per accidens, the cause of good things), and so in other cases of the

same kind. Likewise also in the case of the contrary; for what is in itself the cause of evil is more

objectionable than what is so per accidens, e.g. vice and chance: for the one is bad in itself, whereas chance is

Also, what is good absolutely is more desirable than what is good for a particular person, e.g. recovery of

health than a surgical operation; for the former is good absolutely, the latter only for a particular person, viz.

the man who needs an operation. So too what is good by nature is more desirable than the good that is not so

by nature, e.g. justice than the just man; for the one is good by nature, whereas in the other case the goodness

is acquired. Also the attribute is more desirable which belongs to the better and more honourable subject, e.g.

to a god rather than to a man, and to the soul rather than to the body. So too the property of the better thing is

better than the property of the worse; e.g. the property of God than the property of man: for whereas in

respect of what is common in both of them they do not differ at all from each other, in respect of their

properties the one surpasses the other. Also that is better which is inherent in things better or prior or more

honourable: thus (e.g.) health is better than strength and beauty: for the former is inherent in the moist and the

dry, and the hot and the cold, in fact in all the primary constituents of an animal, whereas the others are

inherent in what is secondary, strength being a feature of the sinews and bones, while beauty is generally

supposed to consist in a certain symmetry of the limbs. Also the end is generally supposed to be more

desirable than the means, and of two means, that which lies nearer the end. In general, too, a means directed

towards the end of life is more desirable than a means to anything else, e.g. that which contributes to

happiness than that which contributes to prudence. Also the competent is more desirable than the

incompetent. Moreover, of two productive agents that one is more desirable whose end is better; while

between a productive agent and an end we can decide by a proportional sum whenever the excess of the one

end over the other is greater than that of the latter over its own productive means: e.g. supposing the excess of

happiness over health to be greater than that of health over what produces health, then what produces

happiness is better than health. For what produces happiness exceeds what produces health just as much as

happiness exceeds health. But health exceeds what produces health by a smaller amount; ergo, the excess of

what produces happiness over what produces health is greater than that of health over what produces health.

Clearly, therefore, what produces happiness is more desirable than health: for it exceeds the same standard by

a greater amount. Moreover, what is in itself nobler and more precious and praiseworthy is more desirable

than what is less so, e.g. friendship than wealth, and justice than strength. For the former belong in

themselves to the class of things precious and praiseworthy, while the latter do so not in themselves but for

something else: for no one prizes wealth for itself but always for something else, whereas we prize friendship

Moreover, whenever two things are very much like one another, and we cannot see any superiority in the one

over the other of them, we should look at them from the standpoint of their consequences. For the one which

is followed by the greater good is the more desirable: or, if the consequences be evil, that is more desirable

which is followed by the less evil. For though both may be desirable, yet there may possibly be some

unpleasant consequence involved to turn the scale. Our survey from the point of view of consequences lies in

two directions, for there are prior consequences and later consequences: e.g. if a man learns, it follows that he

was ignorant before and knows afterwards. As a rule, the later consequence is the better to consider. You

Moreover, a greater number of good things is more desirable than a smaller, either absolutely or when the one

is included in the other, viz. the smaller number in the greater. An objection may be raised suppose in some

particular case the one is valued for the sake of the other; for then the two together are not more desirable

than the one; e.g. recovery of health and health, than health alone, inasmuch as we desire recovery of health

for the sake of health. Also it is quite possible for what is not good, together with what is, to be more

desirable than a greater number of good things, e.g. the combination of happiness and something else which

is not good may be more desirable than the combination of justice and courage. Also, the same things are

more valuable if accompanied than if unaccompanied by pleasure, and likewise when free from pain than

Also, everything is more desirable at the season when it is of greater consequence; e.g. freedom from pain in

old age more than in youth: for it is of greater consequence in old age. On the same principle also, prudence

is more desirable in old age; for no man chooses the young to guide him, because he does not expect them to

be prudent. With courage, the converse is the case, for it is in youth that the active exercise of courage is

more imperatively required. Likewise also with temperance; for the young are more troubled by their

Also, that is more desirable which is more useful at every season or at most seasons, e.g. justice and

temperance rather than courage: for they are always useful, while courage is only useful at times. Also, that

one of two things which if all possess, we do not need the other thing, is more desirable than that which all

may possess and still we want the other one as well. Take the case of justice and courage; if everybody were

just, there would be no use for courage, whereas all might be courageous, and still justice would be of use.

Moreover, judge by the destructions and losses and generations and acquisitions and contraries of things: for

things whose destruction is more objectionable are themselves more desirable. Likewise also with the losses

and contraries of things; for a thing whose loss or whose contrary is more objectionable is itself more

desirable. With the generations or acquisitions of things the opposite is the case: for things whose acquisition

or generation is more desirable are themselves also desirable. Another commonplace rule is that what is

nearer to the good is better and more desirable, i.e. what more nearly resembles the good: thus justice is better

than a just man. Also, that which is more like than another thing to something better than itself, as e.g. some

say that Ajax was a better man than Odysseus because he was more like Achilles. An objection may be raised

to this that it is not true: for it is quite possible that Ajax did not resemble Achilles more nearly than

Odysseus in the points which made Achilles the best of them, and that Odysseus was a good man, though

unlike Achilles. Look also to see whether the resemblance be that of a caricature, like the resemblance of a

monkey to a man, whereas a horse bears none: for the monkey is not the more handsome creature, despite its

nearer resemblance to a man. Again, in the case of two things, if one is more like the better thing while

another is more like the worse, then that is likely to be better which is more like the better. This too, however,

admits of an objection: for quite possibly the one only slightly resembles the better, while the other strongly

resembles the worse, e.g. supposing the resemblance of Ajax to Achilles to be slight, while that of Odysseus

to Nestor is strong. Also it may be that the one which is like the better type shows a degrading likeness,

whereas the one which is like the worse type improves upon it: witness the likeness of a horse to a donkey,

Another rule is that the more conspicuous good is more desirable than the less conspicuous, and the more

difficult than the easier: for we appreciate better the possession of things that cannot be easily acquired. Also

the more personal possession is more desirable than the more widely shared. Also, that which is more free

from connexion with evil: for what is not attended by any unpleasantness is more desirable than what is so

Moreover, if A be without qualification better than B, then also the best of the members of A is better than

the best of the members of B; e.g. if Man be better than Horse, then also the best man is better than the best

horse. Also, if the best in A be better than the best in B, then also A is better than B without qualification; e.g.

if the best man be better than the best horse, then also Man is better than Horse without qualification.

Moreover, things which our friends can share are more desirable than those they cannot. Also, things which

we like rather to do to our friend are more desirable than those we like to do to the man in the street, e.g. just

dealing and the doing of good rather than the semblance of them: for we would rather really do good to our

friends than seem to do so, whereas towards the man in the street the converse is the case.

Also, superfluities are better than necessities, and are sometimes more desirable as well: for the good life is

better than mere life, and good life is a superfluity, whereas mere life itself is a necessity. Sometimes, though,

what is better is not also more desirable: for there is no necessity that because it is better it should also be

more desirable: at least to be a philosopher is better than to make money, but it is not more desirable for a

man who lacks the necessities of life. The expression 'superfluity' applies whenever a man possesses the

necessities of life and sets to work to secure as well other noble acquisitions. Roughly speaking, perhaps,

Also, what cannot be got from another is more desirable than what can be got from another as well, as (e.g.)

is the case of justice compared with courage. Also, A is more desirable if A is desirable without B, but not B

without A: power (e.g.) is not desirable without prudence, but prudence is desirable without power. Also, if

of two things we repudiate the one in order to be thought to possess the other, then that one is more desirable

which we wish to be thought to possess; thus (e.g.) we repudiate the love of hard work in order that people

Moreover, that is more desirable in whose absence it is less blameworthy for people to be vexed; and that is

more desirable in whose absence it is more blameworthy for a man not to be vexed.

Moreover, of things that belong to the same species one which possesses the peculiar virtue of the species is

more desirable than one which does not. If both possess it, then the one which possesses it in a greater degree

Moreover, if one thing makes good whatever it touches, while another does not, the former is more desirable,

just as also what makes things warm is warmer than what does not. If both do so, then that one is more

desirable which does so in a greater degree, or if it render good the better and more important objectif (e.g.),

Moreover, judge things by their inflexions and uses and actions and works, and judge these by them: for they

go with each other: e.g. if 'justly' means something more desirable than 'courageously', then also justice

means something more desirable than courage; and if justice be more desirable than courage, then also 'justly'

means something more desirable than 'courageously'. Similarly also in the other cases.

Moreover, if one thing exceeds while the other falls short of the same standard of good, the one which

exceeds is the more desirable; or if the one exceeds an even higher standard. Nay more, if there be two things

both preferable to something, the one which is more highly preferable to it is more desirable than the less

highly preferable. Moreover, when the excess of a thing is more desirable than the excess of something else,

that thing is itself also more desirable than the other, as (e.g.) friendship than money: for an excess of

friendship is more desirable than an excess of money. So also that of which a man would rather that it were

his by his own doing is more desirable than what he would rather get by another's doing, e.g. friends than

money. Moreover, judge by means of an addition, and see if the addition of A to the same thing as B makes

the whole more desirable than does the addition of B. You must, however, beware of adducing a case in

which the common term uses, or in some other way helps the case of, one of the things added to it, but not the

other, as (e.g.) if you took a saw and a sickle in combination with the art of carpentry: for in the combination

the saw is a more desirable thing, but it is not a more desirable thing without qualification. Again, a thing is

more desirable if, when added to a lesser good, it makes the whole greater good. Likewise, also, you should

judge by means of subtraction: for the thing upon whose subtraction the remainder is a lesser good may be

taken to be a greater good, whichever it be whose subtraction makes the remainder a lesser good.

Also, if one thing be desirable for itself, and the other for the look of it, the former is more desirable, as (e.g.)

health than beauty. A thing is defined as being desired for the look of it if, supposing no one knew of it, you

would not care to have it. Also, it is more desirable both for itself and for the look of it, while the other thing

is desirable on the one ground alone. Also, whichever is the more precious for itself, is also better and more

desirable. A thing may be taken to be more precious in itself which we choose rather for itself, without

Moreover, you should distinguish in how many senses 'desirable' is used, and with a view to what ends, e.g.

expediency or honour or pleasure. For what is useful for all or most of them may be taken to be more

desirable than what is not useful in like manner. If the same characters belong to both things you should look

and see which possesses them more markedly, i.e. which of the two is the more pleasant or more honourable

or more expedient. Again, that is more desirable which serves the better purpose, e.g. that which serves to

promote virtue more than that which serves to promote pleasure. Likewise also in the case of objectionable

things; for that is more objectionable which stands more in the way of what is desirable, e.g. disease more

than ugliness: for disease is a greater hindrance both to pleasure and to being good.

Moreover, argue by showing that the thing in question is in like measure objectionable and desirable: for a

thing of such a character that a man might well desire and object to it alike is less desirable than the other

Comparisons of things together should therefore be conducted in the manner prescribed. The same

commonplace rules are useful also for showing that anything is simply desirable or objectionable: for we

have only to subtract the excess of one thing over another. For if what is more precious be more desirable,

then also what is precious is desirable; and if what is more useful be more desirable, then also what is useful

is desirable. Likewise, also, in the case of other things which admit of comparisons of that kind. For in some

cases in the very course of comparing the things together we at once assert also that each of them, or the one

of them, is desirable, e.g. whenever we call the one good 'by nature' and the other 'not by nature': for dearly

The commonplace rules relating to comparative degrees and amounts ought to be taken in the most general

possible form: for when so taken they are likely to be useful in a larger number of instances. It is possible to

render some of the actual rules given above more universal by a slight alteration of the expression, e.g. that

what by nature exhibits such and such a quality exhibits that quality in a greater degree than what exhibits it

not by nature. Also, if one thing does, and another does not, impart such and such a quality to that which

possesses it, or to which it belongs, then whichever does impart it is of that quality in greater degree than the

one which does not impart it; and if both impart it, then that one exhibits it in a greater degree which imparts

Moreover, if in any character one thing exceeds and another falls short of the same standard; also, if the one

exceeds something which exceeds a given standard, while the other does not reach that standard, then clearly

the firstnamed thing exhibits that character in a greater degree. Moreover, you should judge by means of

addition, and see if A when added to the same thing as B imparts to the whole such and such a character in a

more marked degree than B, or if, when added to a thing which exhibits that character in a less degree, it

imparts that character to the whole in a greater degree. Likewise, also, you may judge by means of

subtraction: for a thing upon whose subtraction the remainder exhibits such and such a character in a less

degree, itself exhibits that character in a greater degree. Also, things exhibit such and such a character in a

greater degree if more free from admixture with their contraries; e.g. that is whiter which is more free from

admixture with black. Moreover, apart from the rules given above, that has such and such a character in

greater degree which admits in a greater degree of the definition proper to the given character; e.g. if the

definition of 'white' be 'a colour which pierces the vision', then that is whiter which is in a greater degree a

If the question be put in a particular and not in a universal form, in the first place the universal constructive or

destructive commonplace rules that have been given may all be brought into use. For in demolishing or

establishing a thing universally we also show it in particular: for if it be true of all, it is true also of some, and

if untrue of all, it is untrue of some. Especially handy and of general application are the commonplace rules

that are drawn from the opposites and coordinates and inflexions of a thing: for public opinion grants alike

the claim that if all pleasure be good, then also all pain is evil, and the claim that if some pleasure be good,

then also some pain is evil. Moreover, if some form of sensation be not a capacity, then also some form of

failure of sensation is not a failure of capacity. Also, if the object of conception is in some cases an object of

knowledge, then also some form of conceiving is knowledge. Again, if what is unjust be in some cases good,

then also what is just is in some cases evil; and if what happens justly is in some cases evil, then also what

happens unjustly is in some cases good. Also, if what is pleasant is in some cases objectionable, then pleasure

is in some cases an objectionable thing. On the same principle, also, if what is pleasant is in some cases

beneficial, then pleasure is in some cases a beneficial thing. The case is the same also as regards the things

that destroy, and the processes of generation and destruction. For if anything that destroys pleasure or

knowledge be in some cases good, then we may take it that pleasure or knowledge is in some cases an evil

thing. Likewise, also, if the destruction of knowledge be in some cases a good thing or its production an evil

thing, then knowledge will be in some cases an evil thing; e.g. if for a man to forget his disgraceful conduct

be a good thing, and to remember it be an evil thing, then the knowledge of his disgraceful conduct may be

taken to be an evil thing. The same holds also in other cases: in all such cases the premiss and the conclusion

Moreover you should judge by means of greater or smaller or like degrees: for if some member of another

genus exhibit such and such a character in a more marked degree than your object, while no member of that

genus exhibits that character at all, then you may take it that neither does the object in question exhibit it; e.g.

if some form of knowledge be good in a greater degree than pleasure, while no form of knowledge is good,

then you may take it that pleasure is not good either. Also, you should judge by a smaller or like degree in the

same way: for so you will find it possible both to demolish and to establish a view, except that whereas both

are possible by means of like degrees, by means of a smaller degree it is possible only to establish, not to

overthrow. For if a certain form of capacity be good in a like degree to knowledge, and a certain form of

capacity be good, then so also is knowledge; while if no form of capacity be good, then neither is knowledge.

If, too, a certain form of capacity be good in a less degree than knowledge, and a certain form of capacity be

good, then so also is knowledge; but if no form of capacity be good, there is no necessity that no form of

knowledge either should be good. Clearly, then, it is only possible to establish a view by means of a less

Not only by means of another genus can you overthrow a view, but also by means of the same, if you take the

most marked instance of the character in question; e.g. if it be maintained that some form of knowledge is

good, then, suppose it to be shown that prudence is not good, neither will any other kind be good, seeing that

not even the kind upon which there is most general agreement is so. Moreover, you should go to work by

means of an hypothesis; you should claim that the attribute, if it belongs or does not belong in one case, does

so in a like degree in all, e.g. that if the soul of man be immortal, so are other souls as well, while if this one

be not so, neither are the others. If, then, it be maintained that in some instance the attribute belongs, you

must show that in some instance it does not belong: for then it will follow, by reason of the hypothesis, that it

does not belong to any instance at all. If, on the other hand, it be maintained that it does not belong in some

instance, you must show that it does belong in some instance, for in this way it will follow that it belongs to

all instances. It is clear that the maker of the hypothesis universalizes the question, whereas it was stated in a

particular form: for he claims that the maker of a particular admission should make a universal admission,

inasmuch as he claims that if the attribute belongs in one instance, it belongs also in all instances alike.

If the problem be indefinite, it is possible to overthrow a statement in only one way; e.g. if a man has asserted

that pleasure is good or is not good, without any further definition. For if he meant that a particular pleasure

is good, you must show universally that no pleasure is good, if the proposition in question is to be

demolished. And likewise, also, if he meant that some particular pleasure is not good you must show

universally that all pleasure is good: it is impossible to demolish it in any other way. For if we show that

some particular pleasure is not good or is good, the proposition in question is not yet demolished. It is clear,

then, that it is possible to demolish an indefinite statement in one way only, whereas it can be established in

two ways: for whether we show universally that all pleasure is good, or whether we show that a particular

pleasure is good, the proposition in question will have been proved. Likewise, also, supposing we are

required to argue that some particular pleasure is not good, if we show that no pleasure is good or that a

particular pleasure is not good, we shall have produced an argument in both ways, both universally and in

particular, to show that some particular pleasure is not good. If, on the other hand, the statement made be

definite, it will be possible to demolish it in two ways; e.g. if it be maintained that it is an attribute of some

particular pleasure to be good, while of some it is not: for whether it be shown that all pleasure, or that no

pleasure, is good, the proposition in question will have been demolished. If, however, he has stated that only

one single pleasure is good, it is possible to demolish it in three ways: for by showing that all pleasure, or that

no pleasure, or that more than one pleasure, is good, we shall have demolished the statement in question. If

the statement be made still more definite, e.g. that prudence alone of the virtues is knowledge, there are four

ways of demolishing it: for if it be shown that all virtue is knowledge, or that no virtue is so, or that some

other virtue (e.g. justice) is so, or that prudence itself is not knowledge, the proposition in question will have

It is useful also to take a look at individual instances, in cases where some attribute has been said to belong or

not to belong, as in the case of universal questions. Moreover, you should take a glance among genera,

dividing them by their species until you come to those that are not further divisible, as has been said before:'

for whether the attribute is found to belong in all cases or in none, you should, after adducing several

instances, claim that he should either admit your point universally, or else bring an objection showing in what

case it does not hold. Moreover, in cases where it is possible to make the accident definite either specifically

or numerically, you should look and see whether perhaps none of them belongs, showing e.g. that time is not

moved, nor yet a movement, by enumerating how many species there are of movement: for if none of these

belong to time, clearly it does not move, nor yet is a movement. Likewise, also, you can show that the soul is

not a number, by dividing all numbers into either odd or even: for then, if the soul be neither odd nor even,

In regard then to Accident, you should set to work by means like these, and in this manner.

NEXT we must go on to examine questions relating to Genus and Property. These are elements in the

questions that relate to definitions, but dialecticians seldom address their inquiries to these by themselves. If,

then, a genus be suggested for something that is, first take a look at all objects which belong to the same

genus as the thing mentioned, and see whether the genus suggested is not predicated of one of them, as

happens in the case of an accident: e.g. if 'good' be laid down to be the genus of 'pleasure', see whether some

particular pleasure be not good: for, if so, clearly good' is not the genus of pleasure: for the genus is

predicated of all the members of the same species. Secondly, see whether it be predicated not in the category

of essence, but as an accident, as 'white' is predicated of 'snow', or 'selfmoved' of the soul. For 'snow' is not a

kind of 'white', and therefore 'white' is not the genus of snow, nor is the soul a kind of 'moving object': its

motion is an accident of it, as it often is of an animal to walk or to be walking. Moreover, 'moving' does not

seem to indicate the essence, but rather a state of doing or of having something done to it. Likewise, also,

'white': for it indicates not the essence of snow, but a certain quality of it. So that neither of them is predicated

Especially you should take a look at the definition of Accident, and see whether it fits the genus mentioned,

as (e.g.) is also the case in the instances just given. For it is possible for a thing to be and not to be

selfmoved, and likewise, also, for it to be and not to be white. So that neither of these attributes is the genus

but an accident, since we were saying that an accident is an attribute which can belong to a thing and also not

Moreover, see whether the genus and the species be not found in the same division, but the one be a

substance while the other is a quality, or the one be a relative while the other is a quality, as (e.g.) 'slow' and

'swan' are each a substance, while 'white' is not a substance but a quality, so that 'white' is not the genus either

of 'snow' or of 'swan'. Again, knowledge' is a relative, while 'good' and 'noble' are each a quality, so that

good, or noble, is not the genus of knowledge. For the genera of relatives ought themselves also to be

relatives, as is the case with 'double': for multiple', which is the genus of 'double', is itself also a relative. To

speak generally, the genus ought to fall under the same division as the species: for if the species be a

substance, so too should be the genus, and if the species be a quality, so too the genus should be a quality;

e.g. if white be a quality, so too should colour be. Likewise, also, in other cases.

Again, see whether it be necessary or possible for the genus to partake of the object which has been placed in

the genus. 'To partake' is defined as 'to admit the definition of that which is partaken. Clearly, therefore, the

species partake of the genera, but not the genera of the species: for the species admits the definition of the

genus, whereas the genus does not admit that of the species. You must look, therefore, and see whether the

genus rendered partakes or can possibly partake of the species, e.g. if any one were to render anything as

genus of 'being' or of 'unity': for then the result will be that the genus partakes of the species: for of

everything that is, 'being' and 'unity' are predicated, and therefore their definition as well.

Moreover, see if there be anything of which the species rendered is true, while the genus is not so, e.g.

supposing 'being' or 'object of knowledge' were stated to be the genus of 'object of opinion'. For 'object of

opinion' will be a predicate of what does not exist; for many things which do not exist are objects of opinion;

whereas that 'being' or 'object of knowledge' is not predicated of what does not exist is clear. So that neither

'being' nor 'object of knowledge' is the genus of 'object of opinion': for of the objects of which the species is

Again, see whether the object placed in the genus be quite unable to partake of any of its species: for it is

impossible that it should partake of the genus if it do not partake of any of its species, except it be one of the

species reached by the first division: these do partake of the genus alone. If, therefore, 'Motion' be stated as

the genus of pleasure, you should look and see if pleasure be neither locomotion nor alteration, nor any of the

rest of the given modes of motion: for clearly you may then take it that it does not partake of any of the

species, and therefore not of the genus either, since what partakes of the genus must necessarily partake of

one of the species as well: so that pleasure could not be a species of Motion, nor yet be one of the individual

phenomena comprised under the term 'motion'. For individuals as well partake in the genus and the species,

Moreover, see if the term placed in the genus has a wider denotation than the genus, as (e.g.) 'object of

opinion' has, as compared with 'being': for both what is and what is not are objects of opinion, so that 'object

of opinion' could not be a species of being: for the genus is always of wider denotation than the species.

Again, see if the species and its genus have an equal denotation; suppose, for instance, that of the attributes

which go with everything, one were to be stated as a species and the other as its genus, as for example Being

and Unity: for everything has being and unity, so that neither is the genus of the other, since their denotation

is equal. Likewise, also, if the 'first' of a series and the 'beginning' were to be placed one under the other: for

the beginning is first and the first is the beginning, so that either both expressions are identical or at any rate

neither is the genus of the other. The elementary principle in regard to all such cases is that the genus has a

wider denotation than the species and its differentia: for the differentia as well has a narrower denotation than

See also whether the genus mentioned fails, or might be generally thought to fail, to apply to some object

which is not specifically different from the thing in question; or, if your argument be constructive, whether it

does so apply. For all things that are not specifically different have the same genus. If, therefore, it be shown

to apply to one, then clearly it applies to all, and if it fails to apply to one, clearly it fails to apply to any; e.g.

if any one who assumes 'indivisible lines' were to say that the 'indivisible' is their genus. For the aforesaid

term is not the genus of divisible lines, and these do not differ as regards their species from indivisible: for

Look and see, also, if there be any other genus of the given species which neither embraces the genus

rendered nor yet falls under it, e.g. suppose any one were to lay down that 'knowledge' is the genus of justice.

For virtue is its genus as well, and neither of these genera embraces the remaining one, so that knowledge

could not be the genus of justice: for it is generally accepted that whenever one species falls under two

genera, the one is embraced by the other. Yet a principle of this kind gives rise to a difficulty in some cases.

For some people hold that prudence is both virtue and knowledge, and that neither of its genera is embraced

by the other: although certainly not everybody admits that prudence is knowledge. If, however, any one were

to admit the truth of this assertion, yet it would still be generally agreed to be necessary that the genera of the

same object must at any rate be subordinate either the one to the other or both to the same, as actually is the

case with virtue and knowledge. For both fall under the same genus; for each of them is a state and a

disposition. You should look, therefore, and see whether neither of these things is true of the genus rendered;

for if the genera be subordinate neither the one to the other nor both to the same, then what is rendered could

Look, also, at the genus of the genus rendered, and so continually at the next higher genus, and see whether

all are predicated of the species, and predicated in the category of essence: for all the higher genera should be

predicated of the species in the category of essence. If, then, there be anywhere a discrepancy, clearly what is

rendered is not the true genus. [Again, see whether either the genus itself, or one of its higher genera, partakes

of the species: for the higher genus does not partake of any of the lower.] If, then, you are overthrowing a

view, follow the rule as given: if establishing one, thensuppose that what has been named as genus be

admitted to belong to the species, only it be disputed whether it belongs as genusit is enough to show that

one of its higher genera is predicated of the species in the category of essence. For if one of them be

predicated in the category of essence, all of them, both higher and lower than this one, if predicated at all of

the species, will be predicated of it in the category of essence: so that what has been rendered as genus is also

predicated in the category of essence. The premiss that when one genus is predicated in the category of

essence, all the rest, if predicated at all, will be predicated in the category of essence, should be secured by

induction. Supposing, however, that it be disputed whether what has been rendered as genus belongs at all, it

is not enough to show that one of the higher genera is predicated of the species in the category of essence:

e.g. if any one has rendered 'locomotion' as the genus of walking, it is not enough to show that walking is

'motion' in order to show that it is 'locomotion', seeing that there are other forms of motion as well; but one

must show in addition that walking does not partake of any of the species of motion produced by the same

division except locomotion. For of necessity what partakes of the genus partakes also of one of the species

produced by the first division of the genus. If, therefore, walking does not partake either of increase or

decrease or of the other kinds of motion, clearly it would partake of locomotion, so that locomotion would be

Again, look among the things of which the given species is predicated as genus, and see if what is rendered as

its genus be also predicated in the category of essence of the very things of which the species is so predicated,

and likewise if all the genera higher than this genus are so predicated as well. For if there be anywhere a

discrepancy, clearly what has been rendered is not the true genus: for had it been the genus, then both the

genera higher than it, and it itself, would all have been predicated in the category of essence of those objects

of which the species too is predicated in the category of essence. If, then, you are overthrowing a view, it is

useful to see whether the genus fails to be predicated in the category of essence of those things of which the

species too is predicated. If establishing a view, it is useful to see whether it is predicated in the category of

essence: for if so, the result will be that the genus and the species will be predicated of the same object in the

category of essence, so that the same object falls under two genera: the genera must therefore of necessity be

subordinate one to the other, and therefore if it be shown that the one we wish to establish as genus is not

subordinate to the species, clearly the species would be subordinate to it, so that you may take it as shown

Look, also, at the definitions of the genera, and see whether they apply both to the given species and to the

objects which partake of the species. For of necessity the definitions of its genera must be predicated of the

species and of the objects which partake of the species: if, then, there be anywhere a discrepancy, clearly

Again, see if he has rendered the differentia as the genus, e.g. 'immortal' as the genus of 'God'. For 'immortal'

is a differentia of 'living being', seeing that of living beings some are mortal and others immortal. Clearly,

then, a bad mistake has been made; for the differentia of a thing is never its genus. And that this is true is

clear: for a thing's differentia never signifies its essence, but rather some quality, as do 'walking' and 'biped'.

Also, see whether he has placed the differentia inside the genus, e.g. by taking 'odd' as a number'. For 'odd' is

a differentia of number, not a species. Nor is the differentia generally thought to partake of the genus: for

what partakes of the genus is always either a species or an individual, whereas the differentia is neither a

species nor an individual. Clearly, therefore, the differentia does not partake of the genus, so that 'odd' too is

Moreover, see whether he has placed the genus inside the species, e.g. by taking 'contact' to be a 'juncture', or

'mixture' a 'fusion', or, as in Plato's definition,' 'locomotion' to be the same as 'carriage'. For there is no

necessity that contact should be juncture: rather, conversely, juncture must be contact: for what is in contact

is not always joined, though what is joined is always in contact. Likewise, also, in the remaining instances:

for mixture is not always a 'fusion' (for to mix dry things does not fuse them), nor is locomotion always

'carriage'. For walking is not generally thought to be carriage: for 'carriage' is mostly used of things that

change one place for another involuntarily, as happens in the case of inanimate things. Clearly, also, the

species, in the instances given, has a wider denotation than the genus, whereas it ought to be vice versa.

Again, see whether he has placed the differentia inside the species, by taking (e.g.) 'immortal' to be 'a god'.

For the result will be that the species has an equal or wider denotation: and this cannot be, for always the

differentia has an equal or a wider denotation than the species. Moreover, see whether he has placed the

genus inside the differentia, by making 'colour' (e.g.) to be a thing that 'pierces', or 'number' a thing that is

'odd'. Also, see if he has mentioned the genus as differentia: for it is possible for a man to bring forward a

statement of this kind as well, e.g. that 'mixture' is the differentia of 'fusion', or that change of place' is the

differentia of 'carriage'. All such cases should be examined by means of the same principles: for they depend

upon common rules: for the genus should have a wider denotation that its differentia, and also should not

partake of its differentia; whereas, if it be rendered in this manner, neither of the aforesaid requirements can

be satisfied: for the genus will both have a narrower denotation than its differentia, and will partake of it.

Again, if no differentia belonging to the genus be predicated of the given species, neither will the genus be

predicated of it; e.g. of 'soul' neither 'odd' nor 'even' is predicated: neither therefore is 'number'. Moreover, see

whether the species is naturally prior and abolishes the genus along with itself: for the contrary is the general

view. Moreover, if it be possible for the genus stated, or for its differentia, to be absent from the alleged

species, e.g. for 'movement' to be absent from the 'soul', or 'truth and falsehood' from 'opinion', then neither of

the terms stated could be its genus or its differentia: for the general view is that the genus and the differentia

Look and see, also, if what is placed in the genus partakes or could possibly partake of any contrary of the

genus: for in that case the same thing will at the same time partake of contrary things, seeing that the genus is

never absent from it, while it partakes, or can possibly partake, of the contrary genus as well. Moreover, see

whether the species shares in any character which it is utterly impossible for any member of the genus to

have. Thus (e.g.) if the soul has a share in life, while it is impossible for any number to live, then the soul

You should look and see, also, if the species be a homonym of the genus, and employ as your elementary

principles those already stated for dealing with homonymity: for the genus and the species are synonymous.

Seeing that of every genus there is more than one species, look and see if it be impossible that there should be

another species than the given one belonging to the genus stated: for if there should be none, then clearly

Look and see, also, if he has rendered as genus a metaphorical expression, describing (e.g. 'temperance' as a

'harmony': a 'harmony': for a genus is always predicated of its species in its literal sense, whereas 'harmony' is

predicated of temperance not in a literal sense but metaphorically: for a harmony always consists in notes.

Moreover, if there be any contrary of the species, examine it. The examination may take different forms; first

of all see if the contrary as well be found in the same genus as the species, supposing the genus to have no

contrary; for contraries ought to be found in the same genus, if there be no contrary to the genus. Supposing,

on the other hand, that there is a contrary to the genus, see if the contrary of the species be found in the

contrary genus: for of necessity the contrary species must be in the contrary genus, if there be any contrary to

the genus. Each of these points is made plain by means of induction. Again, see whether the contrary of the

species be not found in any genus at all, but be itself a genus, e.g. 'good': for if this be not found in any genus,

neither will its contrary be found in any genus, but will itself be a genus, as happens in the case of 'good' and

'evil': for neither of these is found in a genus, but each of them is a genus. Moreover, see if both genus and

species be contrary to something, and one pair of contraries have an intermediary, but not the other. For if the

genera have an intermediary, so should their species as well, and if the species have, so should their genera as

well, as is the case with (1) virtue and vice and (2) justice and injustice: for each pair has an intermediary. An

objection to this is that there is no intermediary between health and disease, although there is one between

evil and good. Or see whether, though there be indeed an intermediary between both pairs, i.e. both between

the species and between the genera, yet it be not similarly related, but in one case be a mere negation of the

extremes, whereas in the other case it is a subject. For the general view is that the relation should be similar in

both cases, as it is in the cases of virtue and vice and of justice and injustice: for the intermediaries between

both are mere negations. Moreover, whenever the genus has no contrary, look and see not merely whether the

contrary of the species be found in the same genus, but the intermediate as well: for the genus containing the

extremes contains the intermediates as well, as (e.g.) in the case of white and black: for 'colour' is the genus

both of these and of all the intermediate colours as well. An objection may be raised that 'defect' and 'excess'

are found in the same genus (for both are in the genus 'evil'), whereas moderate amount', the intermediate

between them, is found not in 'evil' but in 'good'. Look and see also whether, while the genus has a contrary,

the species has none; for if the genus be contrary to anything, so too is the species, as virtue to vice and

Likewise. also, if one were to look at other instances, one would come to see clearly a fact like this. An

objection may be raised in the case of health and disease: for health in general is the contrary of disease,

whereas a particular disease, being a species of disease, e.g. fever and ophthalmia and any other particular

If, therefore, you are demolishing a view, there are all these ways in which you should make your

examination: for if the aforesaid characters do not belong to it, clearly what has been rendered is not the

genus. If, on the other hand, you are establishing a view, there are three ways: in the first place, see whether

the contrary of the species be found in the genus stated, suppose the genus have no contrary: for if the

contrary be found in it, clearly the species in question is found in it as well. Moreover, see if the intermediate

species is found in the genus stated: for whatever genus contains the intermediate contains the extremes as

well. Again, if the genus have a contrary, look and see whether also the contrary species is found in the

contrary genus: for if so, clearly also the species in question is found in the genus in question.

Again, consider in the case of the inflexions and the coordinates of species and genus, and see whether they

follow likewise, both in demolishing and in establishing a view. For whatever attribute belongs or does not

belong to one belongs or does not belong at the same time to all; e.g. if justice be a particular form of

knowledge, then also 'justly' is 'knowingly' and the just man is a man of knowledge: whereas if any of these

Again, consider the case of things that bear a like relation to one another. Thus (e.g.) the relation of the

pleasant to pleasure is like that of the useful to the good: for in each case the one produces the other. If

therefore pleasure be a kind of 'good', then also the pleasant will be a kind of 'useful': for clearly it may be

taken to be productive of good, seeing that pleasure is good. In the same way also consider the case of

processes of generation and destruction; if (e.g.) to build be to be active, then to have built is to have been

active, and if to learn be to recollect, then also to have learnt is to have recollected, and if to be decomposed

be to be destroyed, then to have been decomposed is to have been destroyed, and decomposition is a kind of

destruction. Consider also in the same way the case of things that generate or destroy, and of the capacities

and uses of things; and in general, both in demolishing and in establishing an argument, you should examine

things in the light of any resemblance of whatever description, as we were saying in the case of generation

and destruction. For if what tends to destroy tends to decompose, then also to be destroyed is to be

decomposed: and if what tends to generate tends to produce, then to be generated is to be produced, and

generation is production. Likewise, also, in the case of the capacities and uses of things: for if a capacity be a

disposition, then also to be capable of something is to be disposed to it, and if the use of anything be an

activity, then to use it is to be active, and to have used it is to have been active.

If the opposite of the species be a privation, there are two ways of demolishing an argument, first of all by

looking to see if the opposite be found in the genus rendered: for either the privation is to be found absolutely

nowhere in the same genus, or at least not in the same ultimate genus: e.g. if the ultimate genus containing

sight be sensation, then blindness will not be a sensation. Secondly, if there be a sensation. Secondly, if there

be a privation opposed to both genus and species, but the opposite of the species be not found in the opposite

of the genus, then neither could the species rendered be in the genus rendered. If, then, you are demolishing a

view, you should follow the rule as stated; but if establishing one there is but one way: for if the opposite

species be found in the opposite genus, then also the species in question would be found in the genus in

question: e.g. if 'blindness' be a form of 'insensibility', then 'sight' is a form of 'sensation'.

Again, look at the negations of the genus and species and convert the order of terms, according to the method

described in the case of Accident: e.g. if the pleasant be a kind of good, what is not good is not pleasant. For

were this no something not good as well would then be pleasant. That, however, cannot be, for it is

impossible, if 'good' be the genus of pleasant, that anything not good should be pleasant: for of things of

which the genus is not predicated, none of the species is predicated either. Also, in establishing a view, you

should adopt the same method of examination: for if what is not good be not pleasant, then what is pleasant is

If the species be a relative term, see whether the genus be a relative term as well: for if the species be a

relative term, so too is the genus, as is the case with 'double' and 'multiple': for each is a relative term. If, on

the other hand, the genus be a relative term, there is no necessity that the species should be so as well: for

'knowledge'is a relative term, but not so 'grammar'. Or possibly not even the first statement would be

generally considered true: for virtue is a kind of 'noble' and a kind of 'good' thing, and yet, while 'virtue' is a

relative term, 'good' and 'noble' are not relatives but qualities. Again, see whether the species fails to be used

in the same relation when called by its own name, and when called by the name of its genus: e.g. if the term

'double' be used to mean the double of a 'half', then also the term 'multiple' ought to be used to mean multiple

Moreover, see whether the term fail to be used in the same relation both when called by the name of its

genus, and also when called by those of all the genera of its genus. For if the double be a multiple of a half,

then 'in excess of 'will also be used in relation to a 'half': and, in general, the double will be called by the

names of all the higher genera in relation to a 'half'. An objection may be raised that there is no necessity for a

term to be used in the same relation when called by its own name and when called by that of its genus: for

'knowledge' is called knowledge 'of an object', whereas it is called a 'state' and 'disposition' not of an 'object'

Again, see whether the genus and the species be used in the same way in respect of the inflexions they take,

e.g. datives and genitives and all the rest. For as the species is used, so should the genus be as well, as in the

case of 'double' and its higher genera: for we say both 'double of' and 'multiple of' a thing. Likewise, also, in

the case of 'knowledge': for both knowledge' itself and its genera, e.g. 'disposition' and 'state', are said to be

'of' something. An objection may be raised that in some cases it is not so: for we say 'superior to' and

'contrary to' so and so, whereas 'other', which is the genus of these terms, demands not 'to' but 'than': for the

Again, see whether terms used in like case relationships fail to yield a like construction when converted, as

do 'double' and 'multiple'. For each of these terms takes a genitive both in itself and in its converted form: for

we say both a half of' and 'a fraction of' something. The case is the same also as regards both 'knowledge' and

'conception': for these take a genitive, and by conversion an 'object of knowledge' and an 'object of

conception' are both alike used with a dative. If, then, in any cases the constructions after conversion be not

Again, see whether the species and the genus fail to be used in relation to an equal number of things: for the

general view is that the uses of both are alike and equal in number, as is the case with 'present' and 'grant'. For

a present' is of something or to some one, and also a 'grant' is of something and to some one: and 'grant' is the

genus of 'present', for a 'present' is a 'grant that need not be returned'. In some cases, however, the number of

relations in which the terms are used happens not to be equal, for while 'double' is double of something, we

speak of 'in excess' or 'greater' in something, as well as of or than something: for what is in excess or greater

is always in excess in something, as well as in excess of something. Hence the terms in question are not the

genera of 'double', inasmuch as they are not used in relation to an equal number of things with the species. Or

possibly it is not universally true that species and genus are used in relation to an equal number of things.

See, also, if the opposite of the species have the opposite of the genus as its genus, e.g. whether, if 'multiple'

be the genus of 'double', 'fraction' be also the genus of 'half'. For the opposite of the genus should always be

the genus of the opposite species. If, then, any one were to assert that knowledge is a kind of sensation, then

also the object of knowledge will have to be a kind of object of sensation, whereas it is not: for an object of

knowledge is not always an object of sensation: for objects of knowledge include some of the objects of

intuition as well. Hence 'object of sensation' is not the genus of 'object of knowledge': and if this be so,

Seeing that of relative terms some are of necessity found in, or used of, the things in relation to which they

happen at any time to be used (e.g. 'disposition' and 'state' and 'balance'; for in nothing else can the aforesaid

terms possibly be found except in the things in relation to which they are used), while others need not be

found in the things in relation to which they are used at any time, though they still may be (e.g. if the term

'object of knowledge' be applied to the soul: for it is quite possible that the knowledge of itself should be

possessed by the soul itself, but it is not necessary, for it is possible for this same knowledge to be found in

some one else), while for others, again, it is absolutely impossible that they should be found in the things in

relation to which they happen at any time to be used (as e.g. that the contrary should be found in the contrary

or knowledge in the object of knowledge, unless the object of knowledge happen to be a soul or a man)you

should look, therefore, and see whether he places a term of one kind inside a genus that is not of that kind,

e.g. suppose he has said that 'memory' is the 'abiding of knowledge'. For 'abiding' is always found in that

which abides, and is used of that, so that the abiding of knowledge also will be found in knowledge. Memory,

then, is found in knowledge, seeing that it is the abiding of knowledge. But this is impossible, for memory is

always found in the soul. The aforesaid commonplace rule is common to the subject of Accident as well: for

it is all the same to say that 'abiding' is the genus of memory, or to allege that it is an accident of it. For if in

any way whatever memory be the abiding of knowledge, the same argument in regard to it will apply.

Again, see if he has placed what is a 'state' inside the genus 'activity', or an activity inside the genus 'state',

e.g. by defining 'sensation' as 'movement communicated through the body': for sensation is a 'state', whereas

movement is an 'activity'. Likewise, also, if he has said that memory is a 'state that is retentive of a

They also make a bad mistake who rank a 'state' within the 'capacity' that attends it, e.g. by defining 'good

temper' as the 'control of anger', and 'courage' and 'justice' as 'control of fears' and of 'gains': for the terms

'courageous' and 'goodtempered' are applied to a man who is immune from passion, whereas

'selfcontrolled' describes the man who is exposed to passion and not led by it. Quite possibly, indeed, each

of the former is attended by a capacity such that, if he were exposed to passion, he would control it and not be

led by it: but, for all that, this is not what is meant by being 'courageous' in the one case, and 'good tempered'

in the other; what is meant is an absolute immunity from any passions of that kind at all.

Sometimes, also, people state any kind of attendant feature as the genus, e.g. 'pain' as the genus of 'anger' and

'conception' as that of conviction'. For both of the things in question follow in a certain sense upon the given

species, but neither of them is genus to it. For when the angry man feels pain, the pain bas appeared in him

earlier than the anger: for his anger is not the cause of his pain, but his pain of his anger, so that anger

emphatically is not pain. By the same reasoning, neither is conviction conception: for it is possible to have

the same conception even without being convinced of it, whereas this is impossible if conviction be a species

of conception: for it is impossible for a thing still to remain the same if it be entirely transferred out of its

species, just as neither could the same animal at one time be, and at another not be, a man. If, on the other

hand, any one says that a man who has a conception must of necessity be also convinced of it, then

'conception' and 'conviction' will be used with an equal denotation, so that not even so could the former be the

See, also, whether both naturally come to be anywhere in the same thing: for what contains the species

contains the genus as well: e.g. what contains 'white' contains 'colour' as well, and what contains 'knowledge

of grammar' contains 'knowledge' as well. If, therefore, any one says that 'shame' is 'fear', or that 'anger' is

'pain', the result will be that genus and species are not found in the same thing: for shame is found in the

'reasoning' faculty, whereas fear is in the 'spirited' faculty, and 'pain' is found in the faculty of 'desires'. (for in

this pleasure also is found), whereas 'anger' is found in the 'spirited' faculty. Hence the terms rendered are not

the genera, seeing that they do not naturally come to be in the same faculty as the species. Likewise, also, if

'friendship' be found in the faculty of desires, you may take it that it is not a form of 'wishing': for wishing is

always found in the 'reasoning' faculty. This commonplace rule is useful also in dealing with Accident: for

the accident and that of which it is an accident are both found in the same thing, so that if they do not appear

Again, see if the species partakes of the genus attributed only in some particular respect: for it is the general

view that the genus is not thus imparted only in some particular respect: for a man is not an animal in a

particular respect, nor is grammar knowledge in a particular respect only. Likewise also in other instances.

Look, therefore, and see if in the case of any of its species the genus be imparted only in a certain respect;

e.g. if 'animal' has been described as an 'object of perception' or of 'sight'. For an animal is an object of

perception or of sight in a particular respect only; for it is in respect of its body that it is perceived and seen,

not in respect of its soul, so that'object of sight' and 'object of perception' could not be the genus of 'animal'.

Sometimes also people place the whole inside the part without detection, defining (e.g.) 'animal' as an

'animate body'; whereas the part is not predicated in any sense of the whole, so that 'body' could not be the

See also if he has put anything that is blameworthy or objectionable into the class 'capacity' or 'capable', e.g.

by defining a 'sophist' or a 'slanderer', or a 'thief' as 'one who is capable of secretly thieving other people's

property'. For none of the aforesaid characters is so called because he is 'capable' in one of these respects: for

even God and the good man are capable of doing bad things, but that is not their character: for it is always in

respect of their choice that bad men are so called. Moreover, a capacity is always a desirable thing: for even

the capacities for doing bad things are desirable, and therefore it is we say that even God and the good man

possess them; for they are capable (we say) of doing evil. So then 'capacity' can never be the genus of

anything blameworthy. Else, the result will be that what is blameworthy is sometimes desirable: for there will

Also, see if he has put anything that is precious or desirable for its own sake into the class 'capacity' or

'capable' or 'productive' of anything. For capacity, and what is capable or productive of anything, is always

Or see if he has put anything that exists in two genera or more into one of them only. For some things it is

impossible to place in a single genus, e.g. the 'cheat' and the 'slanderer': for neither he who has the will

without the capacity, nor he who has the capacity without the will, is a slanderer or cheat, but he who has

both of them. Hence he must be put not into one genus, but into both the aforesaid genera.

Moreover, people sometimes in converse order render genus as differentia, and differentia as genus, defining

(e.g.) astonishment as 'excess of wonderment' and conviction as 'vehemence of conception'. For neither

'excess' nor 'vehemence' is the genus, but the differentia: for astonishment is usually taken to be an 'excessive

wonderment', and conviction to be a 'vehement conception', so that 'wonderment' and 'conception' are the

genus, while 'excess' and 'vehemence' are the differentia. Moreover, if any one renders 'excess' and

'vehemence' as genera, then inanimate things will be convinced and astonished. For 'vehemence' and 'excess'

of a thing are found in a thing which is thus vehement and in excess. If, therefore, astonishment be excess of

wonderment the astonishment will be found in the wonderment, so that 'wonderment' will be astonished!

Likewise, also, conviction will be found in the conception, if it be 'vehemence of conception', so that the

conception will be convinced. Moreover, a man who renders an answer in this style will in consequence find

himself calling vehemence vehement and excess excessive: for there is such a thing as a vehement

conviction: if then conviction be 'vehemence', there would be a 'vehement vehemence'. Likewise, also, there

is such a thing as excessive astonishment: if then astonishment be an excess, there would be an 'excessive

excess'. Whereas neither of these things is generally believed, any more than that knowledge is a knower or

Sometimes, too, people make the bad mistake of putting an affection into that which is affected, as its genus,

e.g. those who say that immortality is everlasting life: for immortality seems to be a certain affection or

accidental feature of life. That this saying is true would appear clear if any one were to admit that a man can

pass from being mortal and become immortal: for no one will assert that he takes another life, but that a

certain accidental feature or affection enters into this one as it is. So then 'life' is not the genus of immortality.

Again, see if to an affection he has ascribed as genus the object of which it is an affection, by defining (e.g.)

wind as 'air in motion'. Rather, wind is 'a movement of air': for the same air persists both when it is in motion

and when it is still. Hence wind is not 'air' at all: for then there would also have been wind when the air was

not in motion, seeing that the same air which formed the wind persists. Likewise, also, in other cases of the

kind. Even, then, if we ought in this instance to admit the point that wind is 'air in motion', yet we should

accept a definition of the kind, not about all those things of which the genus is not true, but only in cases

where the genus rendered is a true predicate. For in some cases, e.g. 'mud' or 'snow', it is not generally held to

be true. For people tell you that snow is 'frozen water' and mud is earth mixed with moisture', whereas snow

is not water, nor mud earth, so that neither of the terms rendered could be the genus: for the genus should be

true of all its species. Likewise neither is wine 'fermented water', as Empedocles speaks of 'water fermented

Moreover, see whether the term rendered fail to be the genus of anything at all; for then clearly it also fails to

be the genus of the species mentioned. Examine the point by seeing whether the objects that partake of the

genus fail to be specifically different from one another, e.g. white objects: for these do not differ specifically

from one another, whereas of a genus the species are always different, so that 'white' could not be the genus

Again, see whether he has named as genus or differentia some feature that goes with everything: for the

number of attributes that follow everything is comparatively large: thus (e.g.) 'Being' and 'Unity' are among

the number of attributes that follow everything. If, therefore, he has rendered 'Being' as a genus, clearly it

would be the genus of everything, seeing that it is predicated of everything; for the genus is never predicated

of anything except of its species. Hence Unity, inter alia, will be a species of Being. The result, therefore, is

that of all things of which the genus is predicated, the species is predicated as well, seeing that Being and

Unity are predicates of absolutely everything, whereas the predication of the species ought to be of narrower

range. If, on the other hand, he has named as differentia some attribute that follows everything, clearly the

denotation of the differentia will be equal to, or wider than, that of the genus. For if the genus, too, be some

attribute that follows everything, the denotation of the differentia will be equal to its denotation, while if the

Moreover, see if the description 'inherent in S' be used of the genus rendered in relation to its species, as it is

used of 'white' in the case of snow, thus showing clearly that it could not be the genus: for 'true of S' is the

only description used of the genus in relation to its species. Look and see also if the genus fails to be

synonymous with its species. For the genus is always predicated of its species synonymously.

Moreover, beware, whenever both species and genus have a contrary, and he places the better of the

contraries inside the worse genus: for the result will be that the remaining species will be found in the

remaining genus, seeing that contraries are found in contrary genera, so that the better species will be found

in the worse genus and the worse in the better: whereas the usual view is that of the better species the genus

too is better. Also see if he has placed the species inside the worse and not inside the better genus, when it is

at the same time related in like manner to both, as (e.g.) if he has defined the 'soul' as a 'form of motion' or 'a

form of moving thing'. For the same soul is usually thought to be a principle alike of rest and of motion, so

that, if rest is the better of the two, this is the genus into which the soul should have been put.

Moreover, judge by means of greater and less degrees: if overthrowing a view, see whether the genus admits

of a greater degree, whereas neither the species itself does so, nor any term that is called after it: e.g. if virtue

admits of a greater degree, so too does justice and the just man: for one man is called 'more just than another'.

If, therefore, the genus rendered admits of a greater degree, whereas neither the species does so itself nor yet

Again, if what is more generally, or as generally, thought to be the genus be not so, clearly neither is the

genus rendered. The commonplace rule in question is useful especially in cases where the species appears to

have several predicates in the category of essence, and where no distinction has been drawn between them,

and we cannot say which of them is genus; e.g. both 'pain' and the 'conception of a slight' are usually thought

to be predicates of 'anger in the category of essence: for the angry man is both in pain and also conceives that

he is slighted. The same mode of inquiry may be applied also to the case of the species, by comparing it with

some other species: for if the one which is more generally, or as generally, thought to be found in the genus

rendered be not found therein, then clearly neither could the species rendered be found therein.

In demolishing a view, therefore, you should follow the rule as stated. In establishing one, on the other hand,

the commonplace rule that you should see if both the genus rendered and the species admit of a greater

degree will not serve: for even though both admit it, it is still possible for one not to be the genus of the other.

For both 'beautiful' and 'white' admit of a greater degree, and neither is the genus of the other. On the other

hand, the comparison of the genera and of the species one with another is of use: e.g. supposing A and B to

have a like claim to be genus, then if one be a genus, so also is the other. Likewise, also, if what has less

claim be a genus, so also is what has more claim: e.g. if 'capacity' have more claim than 'virtue' to be the

genus of selfcontrol, and virtue be the genus, so also is capacity. The same observations will apply also in

the case of the species. For instance, supposing A and B to have a like claim to be a species of the genus in

question, then if the one be a species, so also is the other: and if that which is less generally thought to be so

Moreover, to establish a view, you should look and see if the genus is predicated in the category of essence of

those things of which it has been rendered as the genus, supposing the species rendered to be not one single

species but several different ones: for then clearly it will be the genus. If, on the other, the species rendered be

single, look and see whether the genus be predicated in the category of essence of other species as well: for

then, again, the result will be that it is predicated of several different species.

Since some people think that the differentia, too, is a predicate of the various species in the category of

essence, you should distinguish the genus from the differentia by employing the aforesaid elementary

principles(a) that the genus has a wider denotation than the differentia; (b) that in rendering the essence of a

thing it is more fitting to state the genus than the differentia: for any one who says that 'man' is an 'animal'

shows what man is better than he who describes him as 'walking'; also (c) that the differentia always signifies

a quality of the genus, whereas the genus does not do this of the differentia: for he who says 'walking'

describes an animal of a certain quality, whereas he who says 'animal' describes an animal of a certain

quality, whereas he who says 'animal' does not describe a walking thing of a certain quality.

The differentia, then, should be distinguished from the genus in this manner. Now seeing it is generally held

that if what is musical, in being musical, possesses knowledge in some respect, then also 'music' is a

particular kind of 'knowledge'; and also that if what walks is moved in walking, then 'walking' is a particular

kind of 'movement'; you should therefore examine in the aforesaid manner any genus in which you want to

establish the existence of something; e.g. if you wish to prove that 'knowledge' is a form of 'conviction', see

whether the knower in knowing is convinced: for then clearly knowledge would be a particular kind of

conviction. You should proceed in the same way also in regard to the other cases of this kind.

Moreover, seeing that it is difficult to distinguish whatever always follows along with a thing, and is not

convertible with it, from its genus, if A follows B universally, whereas B does not follow A universallyas

e.g. 'rest' always follows a 'calm' and 'divisibility' follows 'number', but not conversely (for the divisible is not

always a number, nor rest a calm)you may yourself assume in your treatment of them that the one which

always follows is the genus, whenever the other is not convertible with it: if, on the other hand, some one else

puts forward the proposition, do not accept it universally. An objection to it is that 'notbeing' always follows

what is 'coming to be' (for what is coming to be is not) and is not convertible with it (for what is not is not

always coming to be), and that still 'notbeing' is not the genus of 'coming to be': for 'notbeing' has not any

species at all. Questions, then, in regard to Genus should be investigated in the ways described.

THE question whether the attribute stated is or is not a property, should be examined by the following

Any 'property' rendered is always either essential and permanent or relative and temporary: e.g. it is an

'essential property' of man to be 'by nature a civilized animal': a 'relative property' is one like that of the soul

in relation to the body, viz. that the one is fitted to command, and the other to obey: a 'permanent property' is

one like the property which belongs to God, of being an 'immortal living being': a 'temporary property' is one

like the property which belongs to any particular man of walking in the gymnasium.

[The rendering of a property 'relatively' gives rise either to two problems or to four. For if he at the same time

render this property of one thing and deny it of another, only two problems arise, as in the case of a statement

that it is a property of a man, in relation to a horse, to be a biped. For one might try both to show that a man is

not a biped, and also that a horse is a biped: in both ways the property would be upset. If on the other hand he

render one apiece of two attributes to each of two things, and deny it in each case of the other, there will then

be four problems; as in the case of a statement that it is a property of a man in relation to a horse for the

former to be a biped and the latter a quadruped. For then it is possible to try to show both that a man is not

naturally a biped, and that he is a quadruped, and also that the horse both is a biped, and is not a quadruped. If

An 'essential' property is one which is rendered of a thing in comparison with everything else and

distinguishes the said thing from everything else, as does 'a mortal living being capable of receiving

knowledge' in the case of man. A 'relative' property is one which separates its subject off not from everything

else but only from a particular definite thing, as does the property which virtue possesses, in comparison with

knowledge, viz. that the former is naturally produced in more than one faculty, whereas the latter is produced

in that of reason alone, and in those who have a reasoning faculty. A 'permanent' property is one which is true

at every time, and never fails, like being' compounded of soul and body', in the case of a living creature. A

'temporary' property is one which is true at some particular time, and does not of necessity always follow; as,

To render a property 'relatively' to something else means to state the difference between them as it is found

either universally and always, or generally and in most cases: thus a difference that is found universally and

always, is one such as man possesses in comparison with a horse, viz. being a biped: for a man is always and

in every case a biped, whereas a horse is never a biped at any time. On the other hand, a difference that is

found generally and in most cases, is one such as the faculty of reason possesses in comparison with that of

desire and spirit, in that the former commands, while the latter obeys: for the reasoning faculty does not

always command, but sometimes also is under command, nor is that of desire and spirit always under

command, but also on occasion assumes the command, whenever the soul of a man is vicious.

Of 'properties' the most 'arguable' are the essential and permanent and the relative. For a relative property

gives rise, as we said before, to several questions: for of necessity the questions arising are either two or four,

or that arguments in regard to these are several. An essential and a permanent property you can discuss in

relation to many things, or can observe in relation to many periods of time: if essential', discuss it in

comparison with many things: for the property ought to belong to its subject in comparison with every single

thing that is, so that if the subject be not distinguished by it in comparison with everything else, the property

could not have been rendered correctly. So a permanent property you should observe in relation to many

periods of time; for if it does not or did not, or is not going to, belong, it will not be a property. On the other

hand, about a temporary property we do not inquire further than in regard to the time called 'the present'; and

so arguments in regard to it are not many; whereas an arguable' question is one in regard to which it is

The socalled 'relative' property, then, should be examined by means of the commonplace arguments relating

to Accident, to see whether it belongs to the one thing and not to the other: on the other hand, permanent and

First, see whether the property has or has not been rendered correctly. Of a rendering being incorrect or

correct, one test is to see whether the terms in which the property is stated are not or are more intelligiblefor

destructive purposes, whether they are not so, and for constructive purposes, whether they are so. Of the

terms not being more intelligible, one test is to see whether the property which he renders is altogether more

unintelligible than the subject whose property he has stated: for, if so, the property will not have been stated

correctly. For the object of getting a property constituted is to be intelligible: the terms therefore in which it is

rendered should be more intelligible: for in that case it will be possible to conceive it more adequately, e.g.

any one who has stated that it is a property of 'fire' to 'bear a very close resemblance to the soul', uses the term

'soul', which is less intelligible than 'fire'for we know better what fire is than what soul is, and therefore a

'very close resemblance to the soul' could not be correctly stated to be a property of fire. Another test is to see

whether the attribution of A (property) to B (subject) fails to be more intelligible. For not only should the

property be more intelligible than its subject, but also it should be something whose attribution to the

particular subject is a more intelligible attribution. For he who does not know whether it is an attribute of the

particular subject at all, will not know either whether it belongs to it alone, so that whichever of these results

happens, its character as a property becomes obscure. Thus (e.g.) a man who has stated that it is a property of

fire to be 'the primary element wherein the soul is naturally found', has introduced a subject which is less

intelligible than 'fire', viz. whether the soul is found in it, and whether it is found there primarily; and

therefore to be 'the primary element in which the soul is naturally found' could not be correctly stated to be a

property of 'fire'. On the other hand, for constructive purposes, see whether the terms in which the property is

stated are more intelligible, and if they are more intelligible in each of the aforesaid ways. For then the

property will have been correctly stated in this respect: for of constructive arguments, showing the

correctness of a rendering, some will show the correctness merely in this respect, while others will show it

without qualification. Thus (e.g.) a man who has said that the 'possession of sensation' is a property of

'animal' has both used more intelligible terms and has rendered the property more intelligible in each of the

aforesaid senses; so that to 'possess sensation' would in this respect have been correctly rendered as a

Next, for destructive purposes, see whether any of the terms rendered in the property is used in more than one

sense, or whether the whole expression too signifies more than one thing. For then the property will not have

been correctly stated. Thus (e.g.) seeing that to 'being natural sentient' signifies more than one thing, viz. (1)

to possess sensation, (2) to use one's sensation, being naturally sentient' could not be a correct statement of a

property of 'animal'. The reason why the term you use, or the whole expression signifying the property,

should not bear more than one meaning is this, that an expression bearing more than one meaning makes the

object described obscure, because the man who is about to attempt an argument is in doubt which of the

various senses the expression bears: and this will not do, for the object of rendering the property is that he

may understand. Moreover, in addition to this, it is inevitable that those who render a property after this

fashion should be somehow refuted whenever any one addresses his syllogism to that one of the term's

several meanings which does not agree. For constructive purposes, on the other hand, see whether both all the

terms and also the expression as a whole avoid bearing more than one sense: for then the property will have

been correctly stated in this respect. Thus (e.g.) seeing that 'body' does not bear several meanings, nor

quickest to move upwards in space', nor yet the whole expression made by putting them together, it would be

correct in this respect to say that it is a property of fire to be the 'body quickest to move upwards in space'.

Next, for destructive purposes, see if the term of which he renders the property is used in more than one

sense, and no distinction has been drawn as to which of them it is whose property he is stating: for then the

property will not have been correctly rendered. The reasons why this is so are quite clear from what has been

said above: for the same results are bound to follow. Thus (e.g.) seeing that 'the knowledge of this' signifies

many things for it means (1) the possession of knowledge by it, (2) the use of its knowledge by it, (3) the

existence of knowledge about it, (4) the use of knowledge about itno property of the 'knowledge of this'

could be rendered correctly unless he draw a distinction as to which of these it is whose property he is

rendering. For constructive purposes, a man should see if the term of which he is rendering the property

avoids bearing many senses and is one and simple: for then the property will have been correctly stated in this

respect. Thus (e.g.) seeing that 'man' is used in a single sense, 'naturally civilized animal' would be correctly

Next, for destructive purposes, see whether the same term has been repeated in the property. For people often

do this undetected in rendering 'properties' also, just as they do in their 'definitions' as well: but a property to

which this has happened will not have been correctly stated: for the repetition of it confuses the hearer; thus

inevitably the meaning becomes obscure, and further, such people are thought to babble. Repetition of the

same term is likely to happen in two ways; one is, when a man repeatedly uses the same word, as would

happen if any one were to render, as a property of fire, 'the body which is the most rarefied of bodies' (for he

has repeated the word 'body'); the second is, if a man replaces words by their definitions, as would happen if

any one were to render, as a property of earth, 'the substance which is by its nature most easily of all bodies

borne downwards in space', and were then to substitute 'substances of such and such a kind' for the word

'bodies': for 'body' and 'a substance of such and such a kind' mean one and the same thing. For he will have

repeated the word 'substance', and accordingly neither of the properties would be correctly stated. For

constructive purposes, on the other hand, see whether he avoids ever repeating the same term; for then the

property will in this respect have been correctly rendered. Thus (e.g.) seeing that he who has stated 'animal

capable of acquiring knowledge' as a property of man has avoided repeating the same term several times, the

Next, for destructive purposes, see whether he has rendered in the property any such term as is a universal

attribute. For one which does not distinguish its subject from other things is useless, and it is the business of

the language Of 'properties', as also of the language of definitions, to distinguish. In the case contemplated,

therefore, the property will not have been correctly rendered. Thus (e.g.) a man who has stated that it is a

property of knowledge to be a 'conception incontrovertible by argument, because of its unity', has used in the

property a term of that kind, viz. 'unity', which is a universal attribute; and therefore the property of

knowledge could not have been correctly stated. For constructive purposes, on the other hand, see whether he

has avoided all terms that are common to everything and used a term that distinguishes the subject from

something: for then the property will in this respect have been correctly stated. Thus (e.g.) inasmuch as he

who has said that it is a property of a 'living creature' to 'have a soul' has used no term that is common to

everything, it would in this respect have been correctly stated to be a property of a 'living creature' to 'have a

Next, for destructive purposes see whether he renders more than one property of the same thing, without a

definite proviso that he is stating more than one: for then the property will not have been correctly stated. For

just as in the case of definitions too there should be no further addition beside the expression which shows the

essence, so too in the case of properties nothing further should be rendered beside the expression that

constitutes the property mentioned: for such an addition is made to no purpose. Thus (e.g.) a man who has

said that it is a property of fire to be 'the most rarefied and lightest body' has rendered more than one property

(for each term is a true predicate of fire alone); and so it could not be a correctly stated property of fire to be

'the most rarefied and lightest body'. On the other hand, for constructive purposes, see whether he has avoided

rendering more than one property of the same thing, and has rendered one only: for then the property will in

this respect have been correctly stated. Thus (e.g.) a man who has said that it is a property of a liquid to be a

'body adaptable to every shape' has rendered as its property a single character and not several, and so the

Next, for destructive purposes, see whether he has employed either the actual subject whose property he is

rendering, or any of its species: for then the property will not have been correctly stated. For the object of

rendering the property is that people may understand: now the subject itself is just as unintelligible as it was

to start with, while any one of its species is posterior to it, and so is no more intelligible. Accordingly it is

impossible to understand anything further by the use of these terms. Thus (e.g.) any one who has said that it

is property of 'animal' to be 'the substance to which "man" belongs as a species' has employed one of its

species, and therefore the property could not have been correctly stated. For constructive purposes, on the

other hand, see whether he avoids introducing either the subject itself or any of its species: for then the

property will in this respect have been correctly stated. Thus (e.g.) a man who has stated that it is a property

of a living creature to be 'compounded of soul and body' has avoided introducing among the rest either the

subject itself or any of its species, and therefore in this respect the property of a 'living creature' would have

You should inquire in the same way also in the case of other terms that do or do not make the subject more

intelligible: thus, for destructive purposes, see whether he has employed anything either opposite to the

subject or, in general, anything simultaneous by nature with it or posterior to it: for then the property will not

have been correctly stated. For an opposite is simultaneous by nature with its opposite, and what is

simultaneous by nature or is posterior to it does not make its subject more intelligible. Thus (e.g.) any one

who has said that it is a property of good to be 'the most direct opposite of evil', has employed the opposite of

good, and so the property of good could not have been correctly rendered. For constructive purposes, on the

other hand, see whether he has avoided employing anything either opposite to, or, in general, simultaneous by

nature with the subject, or posterior to it: for then the property will in this respect have been correctly

rendered. Thus (e.g.) a man who has stated that it is a property of knowledge to be 'the most convincing

conception' has avoided employing anything either opposite to, or simultaneous by nature with, or posterior

to, the subject; and so the property of knowledge would in this respect have been correctly stated.

Next, for destructive purposes, see whether he has rendered as property something that does not always

follow the subject but sometimes ceases to be its property: for then the property will not have been correctly

described. For there is no necessity either that the name of the subject must also be true of anything to which

we find such an attribute belonging; nor yet that the name of the subject will be untrue of anything to which

such an attribute is found not to belong. Moreover, in addition to this, even after he has rendered the property

it will not be clear whether it belongs, seeing that it is the kind of attribute that may fall: and so the property

will not be clear. Thus (e.g.) a man who has stated that it is a property of animal 'sometimes to move and

sometimes to stand still' rendered the kind of property which sometimes is not a property, and so the property

could not have been correctly stated. For constructive purposes, on the other hand, see whether he has

rendered something that of necessity must always be a property: for then the property will have been in this

respect correctly stated. Thus (e.g.) a man who has stated that it is a property of virtue to be 'what makes its

possessor good' has rendered as property something that always follows, and so the property of virtue would

Next, for destructive purposes, see whether in rendering the property of the present time he has omitted to

make a definite proviso that it is the property of the present time which he is rendering: for else the property

will not have been correctly stated. For in the first place, any unusual procedure always needs a definite

proviso: and it is the usual procedure for everybody to render as property some attribute that always follows.

In the second place, a man who omits to provide definitely whether it was the property of the present time

which he intended to state, is obscure: and one should not give any occasion for adverse criticism. Thus (e.g.)

a man who has stated it as the property of a particular man 'to be sitting with a particular man', states the

property of the present time, and so he cannot have rendered the property correctly, seeing that he has

described it without any definite proviso. For constructive purposes, on the other hand, see whether, in

rendering the property of the present time, he has, in stating it, made a definite proviso that it is the property

of the present time that he is stating: for then the property will in this respect have been correctly stated. Thus

(e.g.) a man who has said that it is the property of a particular man 'to be walking now', has made this

distinction in his statement, and so the property would have been correctly stated.

Next, for destructive purposes, see whether he has rendered a property of the kind whose appropriateness is

not obvious except by sensation: for then the property will not have been correctly stated. For every sensible

attribute, once it is taken beyond the sphere of sensation, becomes uncertain. For it is not clear whether it still

belongs, because it is evidenced only by sensation. This principle will be true in the case of any attributes that

do not always and necessarily follow. Thus (e.g.) any one who has stated that it is a property of the sun to be

'the brightest star that moves over the earth', has used in describing the property an expression of that kind,

viz. 'to move over the earth', which is evidenced by sensation; and so the sun's property could not have been

correctly rendered: for it will be uncertain, whenever the sun sets, whether it continues to move over the

earth, because sensation then fails us. For constructive purposes, on the other hand, see whether he has

rendered the property of a kind that is not obvious to sensation, or, if it be sensible, must clearly belong of

necessity: for then the property will in this respect have been correctly stated. Thus (e.g.) a man who has

stated that it is a property of a surface to be 'the primary thing that is coloured', has introduced amongst the

rest a sensible quality, 'to be coloured', but still a quality such as manifestly always belongs, and so the

Next, for destructive purposes, see whether he has rendered the definition as a property: for then the property

will not have been correctly stated: for the property of a thing ought not to show its essence. Thus (e.g.) a

man who has said that it is the property of man to be 'a walking, biped animal' has rendered a property of man

so as to signify his essence, and so the property of man could not have been correctly rendered. For

constructive purposes, on the other hand, see whether the property which he has rendered forms a predicate

convertible with its subject, without, however, signifying its essence: for then the property will in this respect

have been correctly rendered. Thus (e.g.) he who has stated that it is a property of man to be a 'naturally

civilized animal' has rendered the property so as to be convertible with its subject, without, however, showing

its essence, and so the property of man' would in this respect have been correctly rendered.

Next, for destructive purposes, see whether he has rendered the property without having placed the subject

within its essence. For of properties, as also of definitions, the first term to be rendered should be the genus,

and then the rest of it should be appended immediately afterwards, and should distinguish its subject from

other things. Hence a property which is not stated in this way could not have been correctly rendered. Thus

(e.g.) a man who has said that it is a property of a living creature to 'have a soul' has not placed 'living

creature' within its essence, and so the property of a living creature could not have been correctly stated. For

constructive purposes, on the other hand, see whether a man first places within its essence the subject whose

property he is rendering, and then appends the rest: for then the property will in this respect have been

correctly rendered. Thus (e.g.) he who has stated that is a property of man to be an 'animal capable of

receiving knowledge', has rendered the property after placing the subject within its essence, and so the

The inquiry, then, whether the property has been correctly rendered or no, should be made by these means.

The question, on the other hand, whether what is stated is or is not a property at all, you should examine from

the following points of view. For the commonplace arguments which establish absolutely that the property is

accurately stated will be the same as those that constitute it a property at all: accordingly they will be

Firstly, then, for destructive purposes, take a look at each subject of which he has rendered the property, and

see (e.g.) if it fails to belong to any of them at all, or to be true of them in that particular respect, or to be a

property of each of them in respect of that character of which he has rendered the property: for then what is

stated to be a property will not be a property. Thus, for example, inasmuch as it is not true of the

geometrician that he 'cannot be deceived by an argument' (for a geometrician is deceived when his figure is

misdrawn), it could not be a property of the man of science that he is not deceived by an argument. For

constructive purposes, on the other hand, see whether the property rendered be true of every instance, and

true in that particular respect: for then what is stated not to be a property will be a property. Thus, for

example, in as much as the description 'an animal capable of receiving knowledge' is true of every man, and

true of him qua man, it would be a property of man to be 'an animal capable of receiving knowledge'.

commonplace rule meansfor destructive purposes, see if the description fails to be true of that of which the

name is true; and if the name fails to be true of that of which the description is true: for constructive purposes,

on the other hand, see if the description too is predicated of that of which the name is predicated, and if the

Next, for destructive purposes, see if the description fails to apply to that to which the name applies, and if

the name fails to apply to that to which the description applies: for then what is stated to be a property will

not be a property. Thus (e.g.) inasmuch as the description 'a living being that partakes of knowledge' is true of

God, while 'man' is not predicated of God, to be a living being that partakes of knowledge' could not be a

property of man. For constructive purposes, on the other hand, see if the name as well be predicated of that of

which the description is predicated, and if the description as well be predicated of that of which the name is

predicated. For then what is stated not to be a property will be a property. Thus (e.g.) the predicate 'living

creature' is true of that of which 'having a soul' is true, and 'having a soul' is true of that of which the predicate

'living creature' is true; and so 'having a soul would be a property of 'living creature'.

Next, for destructive purposes, see if he has rendered a subject as a property of that which is described as 'in

the subject': for then what has been stated to be a property will not be a property. Thus (e.g.) inasmuch as he

who has rendered 'fire' as the property of 'the body with the most rarefied particles', has rendered the subject

as the property of its predicate, 'fire' could not be a property of 'the body with the most rarefied particles'. The

reason why the subject will not be a property of that which is found in the subject is this, that then the same

thing will be the property of a number of things that are specifically different. For the same thing has quite a

number of specifically different predicates that belong to it alone, and the subject will be a property of all of

these, if any one states the property in this way. For constructive purposes, on the other hand, see if he has

rendered what is found in the subject as a property of the subject: for then what has been stated not to be a

property will be a property, if it be predicated only of the things of which it has been stated to be the property.

Thus (e.g.) he who has said that it is a property of 'earth' to be 'specifically the heaviest body' has rendered of

the subject as its property something that is said of the thing in question alone, and is said of it in the manner

in which a property is predicated, and so the property of earth would have been rightly stated.

Next, for destructive purposes, see if he has rendered the property as partaken of: for then what is stated to be

a property will not be a property. For an attribute of which the subject partakes is a constituent part of its

essence: and an attribute of that kind would be a differentia applying to some one species. E.g. inasmuch as

he who has said that 'walking on two feet' is property of man has rendered the property as partaken of,

'walking on two feet' could not be a property of 'man'. For constructive purposes, on the other hand, see if he

has avoided rendering the property as partaken of, or as showing the essence, though the subject is predicated

convertibly with it: for then what is stated not to be a property will be a property. Thus (e.g.) he who has

stated that to be 'naturally sentient' is a property of 'animal' has rendered the property neither as partaken of

nor as showing the essence, though the subject is predicated convertibly with it; and so to be 'naturally

Next, for destructive purposes, see if the property cannot possibly belong simultaneously, but must belong

either as posterior or as prior to the attribute described in the name: for then what is stated to be a property

will not be a property either never, or not always. Thus (e.g.) inasmuch as it is possible for the attribute

'walking through the marketplace' to belong to an object as prior and as posterior to the attribute 'man',

'walking through the marketplace' could not be a property of 'man' either never, or not always. For

constructive purposes, on the other hand, see if it always and of necessity belongs simultaneously, without

being either a definition or a differentia: for then what is stated not to be a property will be a property. Thus

(e.g.) the attribute 'an animal capable of receiving knowledge' always and of necessity belongs

simultaneously with the attribute 'man', and is neither differentia nor definition of its subject, and so 'an

Next, for destructive purposes, see if the same thing fails to be a property of things that are the same as the

subject, so far as they are the same: for then what is stated to be a property will not be a property. Thus, for

example, inasmuch as it is no property of a 'proper object of pursuit' to 'appear good to certain persons', it

could not be a property of the 'desirable' either to 'appear good to certain persons': for 'proper object of

pursuit' and 'desirable' mean the same. For constructive purposes, on the other hand, see if the same thing be a

property of something that is the same as the subject, in so far as it is the same. For then is stated not to be a

property will be a property. Thus (e.g.) inasmuch as it is called a property of a man, in so far as he is a man,

'to have a tripartite soul', it would also be a property of a mortal, in so far as he is a mortal, to have a tripartite

soul. This commonplace rule is useful also in dealing with Accident: for the same attributes ought either to

Next, for destructive purposes, see if the property of things that are the same in kind as the subject fails to be

always the same in kind as the alleged property: for then neither will what is stated to be the property of the

subject in question. Thus (e.g.) inasmuch as a man and a horse are the same in kind, and it is not always a

property of a horse to stand by its own initiative, it could not be a property of a man to move by his own

initiative; for to stand and to move by his own initiative are the same in kind, because they belong to each of

them in so far as each is an 'animal'. For constructive purposes, on the other hand, see if of things that are the

same in kind as the subject the property that is the same as the alleged property is always true: for then what

is stated not to be a property will be a property. Thus (e.g.) since it is a property of man to be a 'walking

biped,' it would also be a property of a bird to be a 'flying biped': for each of these is the same in kind, in so

far as the one pair have the sameness of species that fall under the same genus, being under the genus

'animal', while the other pair have that of differentiae of the genus, viz. of 'animal'. This commonplace rule is

deceptive whenever one of the properties mentioned belongs to some one species only while the other

Inasmuch as 'same' and 'different' are terms used in several senses, it is a job to render to a sophistical

questioner a property that belongs to one thing and that only. For an attribute that belongs to something

qualified by an accident will also belong to the accident taken along with the subject which it qualifies; e.g.

an attribute that belongs to 'man' will belong also to 'white man', if there be a white man, and one that belongs

to 'white man' will belong also to 'man'. One might, then, bring captious criticism against the majority of

properties, by representing the subject as being one thing in itself, and another thing when combined with its

accident, saying, for example, that 'man' is one thing, and white man' another, and moreover by representing

as different a certain state and what is called after that state. For an attribute that belongs to the state will

belong also to what is called after that state, and one that belongs to what is called after a state will belong

also to the state: e.g. inasmuch as the condition of the scientist is called after his science, it could not be a

property of 'science' that it is 'incontrovertible by argument'; for then the scientist also will be incontrovertible

by argument. For constructive purposes, however, you should say that the subject of an accident is not

absolutely different from the accident taken along with its subject; though it is called 'another' thing because

the mode of being of the two is different: for it is not the same thing for a man to be a man and for a white

man to be a white man. Moreover, you should take a look along at the inflections, and say that the description

of the man of science is wrong: one should say not 'it' but 'he is incontrovertible by argument'; while the

description of Science is wrong too: one should say not 'it' but 'she is incontrovertible by argument'. For

Next, for destructive purposes, see if, while intending to render an attribute that naturally belongs, he states it

in his language in such a way as to indicate one that invariably belongs: for then it would be generally agreed

that what has been stated to be a property is upset. Thus (e.g.) the man who has said that 'biped' is a property

of man intends to render the attribute that naturally belongs, but his expression actually indicates one that

invariably belongs: accordingly, 'biped' could not be a property of man: for not every man is possessed of two

feet. For constructive purposes, on the other hand, see if he intends to render the property that naturally

belongs, and indicates it in that way in his language: for then the property will not be upset in this respect.

Thus (e.g.) he who renders as a property of 'man' the phrase 'an animal capable of receiving knowledge' both

intends, and by his language indicates, the property that belongs by nature, and so 'an animal capable of

receiving knowledge' would not be upset or shown in that respect not to be a property of man.

Moreover, as regards all the things that are called as they are primarily after something else, or primarily in

themselves, it is a job to render the property of such things. For if you render a property as belonging to the

subject that is so called after something else, then it will be true of its primary subject as well; whereas if you

state it of its primary subject, then it will be predicated also of the thing that is so called after this other. Thus

(e.g.) if any one renders , coloured' as the property of 'surface', 'coloured' will be true of body as well;

whereas if he render it of 'body', it will be predicated also of 'surface'. Hence the name as well will not be true

In the case of some properties it mostly happens that some error is incurred because of a failure to define how

as well as to what things the property is stated to belong. For every one tries to render as the property of a

thing something that belongs to it either naturally, as 'biped' belongs to 'man', or actually, as 'having four

fingers' belongs to a particular man, or specifically, as 'consisting of most rarefied particles' belongs to 'fire',

or absolutely, as 'life' to 'living being', or one that belongs to a thing only as called after something else, as

'wisdom' to the 'soul', or on the other hand primarily, as 'wisdom' to the 'rational faculty', or because the thing

is in a certain state, as 'incontrovertible by argument' belongs to a 'scientist' (for simply and solely by reason

of his being in a certain state will he be 'incontrovertible by argument'), or because it is the state possessed by

something, as 'incontrovertible by argument' belongs to 'science', or because it is partaken of, as 'sensation'

belongs to 'animal' (for other things as well have sensation, e.g. man, but they have it because they already

partake of 'animal'), or because it partakes of something else, as 'life' belongs to a particular kind of 'living

being'. Accordingly he makes a mistake if he has failed to add the word 'naturally', because what belongs

naturally may fail to belong to the thing to which it naturally belongs, as (e.g.) it belongs to a man to have

two feet: so too he errs if he does not make a definite proviso that he is rendering what actually belongs,

because one day that attribute will not be what it now is, e.g. the man's possession of four fingers. So he errs

if he has not shown that he states a thing to be such and such primarily, or that he calls it so after something

else, because then its name too will not be true of that of which the description is true, as is the case with

'coloured', whether rendered as a property of 'surface' or of 'body'. So he errs if he has not said beforehand

that he has rendered a property to a thing either because that thing possesses a state, or because it is a state

possessed by something; because then it will not be a property. For, supposing he renders the property to

something as being a state possessed, it will belong to what possesses that state; while supposing he renders it

to what possesses the state, it will belong to the state possessed, as did 'incontrovertible by argument' when

stated as a property of 'science' or of the 'scientist'. So he errs if he has not indicated beforehand that the

property belongs because the thing partakes of, or is partaken of by, something; because then the property

will belong to certain other things as well. For if he renders it because its subject is partaken of, it will belong

to the things which partake of it; whereas if he renders it because its subject partakes of something else, it will

belong to the things partaken of, as (e.g.) if he were to state 'life' to be a property of a 'particular kind of living

being', or just of 'living being. So he errs if he has not expressly distinguished the property that belongs

specifically, because then it will belong only to one of the things that fall under the term of which he states

the property: for the superlative belongs only to one of them, e.g. 'lightest' as applied to 'fire'. Sometimes, too,

a man may even add the word 'specifically', and still make a mistake. For the things in question should all be

of one species, whenever the word 'specifically' is added: and in some cases this does not occur, as it does

not, in fact, in the case of fire. For fire is not all of one species; for live coals and flame and light are each of

them 'fire', but are of different species. The reason why, whenever 'specifically' is added, there should not be

any species other than the one mentioned, is this, that if there be, then the property in question will belong to

some of them in a greater and to others in a less degree, as happens with 'consisting of most rarefied particles'

in the case of fire: for 'light' consists of more rarefied particles than live coals and flame. And this should not

happen unless the name too be predicated in a greater degree of that of which the description is truer;

otherwise the rule that where the description is truer the name too should be truer is not fulfilled. Moreover,

in addition to this, the same attribute will be the property both of the term which has it absolutely and of that

element therein which has it in the highest degree, as is the condition of the property 'consisting of most

rarefied particles' in the case of 'fire': for this same attribute will be the property of 'light' as well: for it is

'light' that 'consists of the most rarefied particles'. If, then, any one else renders a property in this way one

should attack it; for oneself, one should not give occasion for this objection, but should define in what

Next, for destructive purposes, see if he has stated a thing as a property of itself: for then what has been stated

to be a property will not be a property. For a thing itself always shows its own essence, and what shows the

essence is not a property but a definition. Thus (e.g.) he who has said that 'becoming' is a property of

'beautiful' has rendered the term as a property of itself (for 'beautiful' and 'becoming' are the same); and so

'becoming' could not be a property of 'beautiful'. For constructive purposes, on the other hand, see if he has

avoided rendering a thing as a property of itself, but has yet stated a convertible predicate: for then what is

stated not to be a property will be a property. Thus he who has stated 'animate substance' as a property of

'livingcreature' has not stated 'livingcreature' as a property of itself, but has rendered a convertible

Next, in the case of things consisting of like parts, you should look and see, for destructive purposes, if the

property of the whole be not true of the part, or if that of the part be not predicated of the whole: for then

what has been stated to be the property will not be a property. In some cases it happens that this is so: for

sometimes in rendering a property in the case of things that consist of like parts a man may have his eye on

the whole, while sometimes he may address himself to what is predicated of the part: and then in neither case

will it have been rightly rendered. Take an instance referring to the whole: the man who has said that it is a

property of the 'sea' to be 'the largest volume of salt water', has stated the property of something that consists

of like parts, but has rendered an attribute of such a kind as is not true of the part (for a particular sea is not

'the largest volume of salt water'); and so the largest volume of salt water' could not be a property of the 'sea'.

Now take one referring to the part: the man who has stated that it is a property of 'air' to be 'breathable' has

stated the property of something that consists of like parts, but he has stated an attribute such as, though true

of some air, is still not predicable of the whole (for the whole of the air is not breathable); and so 'breathable'

could not be a property of 'air'. For constructive purposes, on the other hand, see whether, while it is true of

each of the things with similar parts, it is on the other hand a property of them taken as a collective whole: for

then what has been stated not to be a property will be a property. Thus (e.g.) while it is true of earth

everywhere that it naturally falls downwards, it is a property of the various particular pieces of earth taken as

'the Earth', so that it would be a property of 'earth' 'naturally to fall downwards'.

Next, look from the point of view of the respective opposites, and first (a) from that of the contraries, and see,

for destructive purposes, if the contrary of the term rendered fails to be a property of the contrary subject. For

then neither will the contrary of the first be a property of the contrary of the second. Thus (e.g.) inasmuch as

injustice is contrary to justice, and the lowest evil to the highest good, but 'to be the highest good' is not a

property of 'justice', therefore 'to be the lowest evil' could not be a property of 'injustice'. For constructive

purposes, on the other hand, see if the contrary is the property of the contrary: for then also the contrary of the

first will be the property of the contrary of the second. Thus (e.g.) inasmuch as evil is contrary to good, and

objectionable to desirable, and 'desirable' is a property of 'good', 'objectionable' would be a property of 'evil'.

Secondly (h) look from the point of view of relative opposites and see, for destructive purposes, if the

correlative of the term rendered fails to be a property of the correlative of the subject: for then neither will the

correlative of the first be a property of the correlative of the second. Thus (e.g.) inasmuch as 'double' is

relative to 'half', and 'in excess' to 'exceeded', while 'in excess' is not a property of 'double', exceeded' could

not be a property of 'half'. For constructive purposes, on the other hand, see if the correlative of the alleged

property is a property of the subject's correlative: for then also the correlative of the first will be a property of

the correlative of the second: e.g. inasmuch as 'double' is relative to 'half', and the proportion 1:2 is relative to

the proportion 2:1, while it is a property of 'double' to be 'in the proportion of 2 to 1', it would be a property of

Thirdly (c) for destructive purposes, see if an attribute described in terms of a state (X) fails to be a property

of the given state (Y): for then neither will the attribute described in terms of the privation (of X) be a

property of the privation (of Y). Also if, on the other hand, an attribute described in terms of the privation (of

X) be not a property of the given privation (of Y), neither will the attribute described in terms of the state (X)

be a property of the state (Y). Thus, for example, inasmuch as it is not predicated as a property of 'deafness' to

be a 'lack of sensation', neither could it be a property of 'hearing' to be a 'sensation'. For constructive

purposes, on the other hand, see if an attribute described in terms of a state (X) is a property of the given state

(Y): for then also the attribute that is described in terms of the privation (of X) will be a property of the

privation (of Y). Also, if an attribute described in terms of a privation (of X) be a property of the privation (of

Y), then also the attribute that is described in terms of the state (X) will be a property of the state (Y). Thus

(e.g.) inasmuch as 'to see' is a property of 'sight', inasmuch as we have sight, 'failure to see' would be a

property of 'blindness', inasmuch as we have not got the sight we should naturally have.

Next, look from the point of view of positive and negative terms; and first (a) from the point of view of the

predicates taken by themselves. This commonplace rule is useful only for a destructive purpose. Thus (e.g.)

see if the positive term or the attribute described in terms of it is a property of the subject: for then the

negative term or the attribute described in terms of it will not be a property of the subject. Also if, on the

other hand, the negative term or the attribute described in terms of it is a property of the subject, then the

positive term or the attribute described in terms of it will not be a property of the subject: e.g. inasmuch as

'animate' is a property of 'living creature', 'inanimate' could not be a property of 'living creature'.

Secondly (b) look from the point of view of the predicates, positive or negative, and their respective subjects;

and see, for destructive purposes, if the positive term falls to be a property of the positive subject: for then

neither will the negative term be a property of the negative subject. Also, if the negative term fails to be a

property of the negative subject, neither will the positive term be a property of the positive subject. Thus

(e.g.) inasmuch as 'animal' is not a property of 'man', neither could 'notanimal' be a property of 'notman'.

Also if 'notanimal' seems not to be a property of 'notman', neither will 'animal' be a property of 'man'. For

constructive purposes, on the other hand, see if the positive term is a property of the positive subject: for then

the negative term will be a property of the negative subject as well. Also if the negative term be a property of

the negative subject, the positive will be a property of the positive as well. Thus (e.g.) inasmuch as it is a

property of 'notliving being' 'not to live', it would be a property of 'living being' 'to live': also if it seems to

be a property of 'living being' 'to live', it will also seem to be a property of 'notliving being' 'not to live'.

Thirdly (c) look from the point of view of the subjects taken by themselves, and see, for destructive purposes,

if the property rendered is a property of the positive subject: for then the same term will not be a property of

the negative subject as well. Also, if the term rendered be a property of the negative subject, it will not be a

property of the positive. Thus (e.g.) inasmuch as 'animate' is a property of 'living creature', 'animate' could not

be a property of 'notliving creature'. For constructive purposes, on the other hand, if the term rendered fails

to be a property of the affirmative subject it would be a property of the negative. This commonplace rule is,

however, deceptive: for a positive term is not a property of a negative, or a negative of a positive. For a

positive term does not belong at all to a negative, while a negative term, though it belongs to a positive, does

Next, look from the point of view of the coordinate members of a division, and see, for destructive purposes,

if none of the coordinate members (parallel with the property rendered) be a property of any of the

remaining set of coordinate members (parallel with the subject): for then neither will the term stated be a

property of that of which it is stated to be a property. Thus (e.g.) inasmuch as 'sensible living being' is not a

property of any of the other living beings, 'intelligible living being' could not be a property of God. For

constructive purposes, on the other hand, see if some one or other of the remaining coordinate members

(parallel with the property rendered) be a property of each of these coordinate members (parallel with the

subject): for then the remaining one too will be a property of that of which it has been stated not to be a

property. Thus (e.g.) inasmuch as it is a property of 'wisdom' to be essentially 'the natural virtue of the

rational faculty', then, taking each of the other virtues as well in this way, it would be a property of

Next, look from the point of view of the inflexions, and see, for destructive purposes, if the inflexion of the

property rendered fails to be a property of the inflexion of the subject: for then neither will the other inflexion

be a property of the other inflexion. Thus (e.g.) inasmuch as 'beautifully' is not a property of 'justly', neither

could 'beautiful' be a property of 'just'. For constructive purposes, on the other hand, see if the inflexion of the

property rendered is a property of the inflexion of the subject: for then also the other inflexion will be a

property of the other inflexion. Thus (e.g.) inasmuch as 'walking biped' is a property of man, it would also be

any one's property 'as a man' to be described 'as a walking biped'. Not only in the case of the actual term

mentioned should one look at the inflexions, but also in the case of its opposites, just as has been laid down in

the case of the former commonplace rules as well.' Thus, for destructive purposes, see if the inflexion of the

opposite of the property rendered fails to be the property of the inflexion of the opposite of the subject: for

then neither will the inflexion of the other opposite be a property of the inflexion of the other opposite. Thus

(e.g.) inasmuch as 'well' is not a property of 'justly', neither could 'badly' be a property of 'unjustly'. For

constructive purposes, on the other hand, see if the inflexion of the opposite of the property originally

suggested is a property of the inflexion of the opposite of the original subject: for then also the inflexion of

the other opposite will be a property of the inflexion of the other opposite. Thus (e.g.) inasmuch as 'best' is a

Next, look from the point of view of things that are in a like relation, and see, for destructive purposes, if

what is in a relation like that of the property rendered fails to be a property of what is in a relation like that of

the subject: for then neither will what is in a relation like that of the first be a property of what is in a relation

like that of the second. Thus (e.g.) inasmuch as the relation of the builder towards the production of a house is

like that of the doctor towards the production of health, and it is not a property of a doctor to produce health,

it could not be a property of a builder to produce a house. For constructive purposes, on the other hand, see if

what is in a relation like that of the property rendered is a property of what is in a relation like that of the

subject: for then also what is in a relation like that of the first will be a property of what is in a relation like

that of the second. Thus (e.g.) inasmuch as the relation of a doctor towards the possession of ability to

produce health is like that of a trainer towards the possession of ability to produce vigour, and it is a property

of a trainer to possess the ability to produce vigour, it would be a property of a doctor to possess the ability to

Next look from the point of view of things that are identically related, and see, for destructive purposes, if the

predicate that is identically related towards two subjects fails to be a property of the subject which is

identically related to it as the subject in question; for then neither will the predicate that is identically related

to both subjects be a property of the subject which is identically related to it as the first. If, on the other hand,

the predicate which is identically related to two subjects is the property of the subject which is identically

related to it as the subject in question, then it will not be a property of that of which it has been stated to be a

property. (e.g.) inasmuch as prudence is identically related to both the noble and the base, since it is

knowledge of each of them, and it is not a property of prudence to be knowledge of the noble, it could not be

a property of prudence to be knowledge of the base. If, on the other hand, it is a property of prudence to be

the knowledge of the noble, it could not be a property of it to be the knowledge of the base.] For it is

impossible for the same thing to be a property of more than one subject. For constructive purposes, on the

other hand, this commonplace rule is of no use: for what is 'identically related' is a single predicate in process

Next, for destructive purposes, see if the predicate qualified by the verb 'to be' fails to be a property of the

subject qualified by the verb 'to be': for then neither will the destruction of the one be a property of the other

qualified by the verb 'to be destroyed', nor will the 'becoming'the one be a property of the other qualified by

the verb 'to become'. Thus (e.g.) inasmuch as it is not a property of 'man' to be an animal, neither could it be a

property of becoming a man to become an animal; nor could the destruction of an animal be a property of the

destruction of a man. In the same way one should derive arguments also from 'becoming' to 'being' and 'being

destroyed', and from 'being destroyed' to 'being' and to 'becoming' exactly as they have just been given from

'being' to 'becoming' and 'being destroyed'. For constructive purposes, on the other hand, see if the subject set

down as qualified by the verb 'to be' has the predicate set down as so qualified, as its property: for then also

the subject qualified by the very 'to become' will have the predicate qualified by 'to become' as its property,

and the subject qualified by the verb to be destroyed' will have as its property the predicate rendered with this

qualification. Thus, for example, inasmuch as it is a property of man to be a mortal, it would be a property of

becoming a man to become a mortal, and the destruction of a mortal would be a property of the destruction of

a man. In the same way one should derive arguments also from 'becoming' and 'being destroyed' both to

'being' and to the conclusions that follow from them, exactly as was directed also for the purpose of

Next take a look at the 'idea' of the subject stated, and see, for destructive purposes, if the suggested property

fails to belong to the 'idea' in question, or fails to belong to it in virtue of that character which causes it to bear

the description of which the property was rendered: for then what has been stated to be a property will not be

a property. Thus (e.g.) inasmuch as 'being motionless' does not belong to 'manhimself' qua 'man', but qua

'idea', it could not be a property of 'man' to be motionless. For constructive purposes, on the other hand, see if

the property in question belongs to the idea, and belongs to it in that respect in virtue of which there is

predicated of it that character of which the predicate in question has been stated not to be a property: for then

what has been stated not to be a property will be a property. Thus (e.g.) inasmuch as it belongs to

'livingcreatureitself' to be compounded of soul and body, and further this belongs to it qua

'livingcreature', it would be a property of 'livingcreature' to be compounded of soul and body.

Next look from the point of view of greater and less degrees, and first (a) for destructive purposes, see if what

is moreP fails to be a property of what is moreS: for then neither will what is lessP be a property of what

is lessS, nor leastP of leastS, nor mostP of mostS, nor P simply of S simply. Thus (e.g.) inasmuch as

being more highly coloured is not a property of what is more a body, neither could being less highly coloured

be a property of what is less a body, nor being coloured be a property of body at all. For constructive

purposes, on the other hand, see if what is moreP is a property of what is moreS: for then also what is

lessP will be a property of what is less S, and leastP of leastS, and mostP of mostS, and P simply of S

simply. Thus (e.g.) inasmuch as a higher degree of sensation is a property of a higher degree of life, a lower

degree of sensation also would be a property of a lower degree of life, and the highest of the highest and the

Also you should look at the argument from a simple predication to the same qualified types of predication,

and see, for destructive purposes, if P simply fails to be a property of S simply; for then neither will moreP

be a property of moreS, nor lessP of lessS, nor mostP of mostS, nor leastP of leastS. Thus (e.g.)

inasmuch as 'virtuous' is not a property of 'man', neither could 'more virtuous' be a property of what is 'more

human'. For constructive purposes, on the other hand, see if P simply is a property of S simply: for then more

P also will be a property of moreS, and lessP of lessS, and leastP of leastS, and mostP of mostS.

Thus (e.g.) a tendency to move upwards by nature is a property of fire, and so also a greater tendency to

move upwards by nature would be a property of what is more fiery. In the same way too one should look at

Secondly (b) for destructive purposes, see if the more likely property fails to be a property of the more likely

subject: for then neither will the less likely property be a property of the less likely subject. Thus (e.g.)

inasmuch as 'perceiving' is more likely to be a property of 'animal' than 'knowing' of 'man', and 'perceiving' is

not a property of 'animal', 'knowing' could not be a property of 'man'. For constructive purposes, on the other

hand, see if the less likely property is a property of the less likely subject; for then too the more likely

property will be a property of the more likely subject. Thus (e.g.) inasmuch as 'to be naturally civilized' is less

likely to be a property of man than 'to live' of an animal, and it is a property of man to be naturally civilized,

Thirdly (c) for destructive purposes, see if the predicate fails to be a property of that of which it is more likely

to be a property: for then neither will it be a property of that of which it is less likely to be a property: while if

it is a property of the former, it will not be a property of the latter. Thus (e.g.) inasmuch as 'to be coloured' is

more likely to be a property of a 'surface' than of a 'body', and it is not a property of a surface, 'to be coloured'

could not be a property of 'body'; while if it is a property of a 'surface', it could not be a property of a 'body'.

For constructive purposes, on the other hand, this commonplace rule is not of any use: for it is impossible for

Fourthly (d) for destructive purposes, see if what is more likely to be a property of a given subject fails to be

its property: for then neither will what is less likely to be a property of it be its property. Thus (e.g.) inasmuch

as 'sensible' is more likely than 'divisible' to be a property of 'animal', and 'sensible' is not a property of

animal, 'divisible' could not be a property of animal. For constructive purposes, on the other hand, see if what

is less likely to be a property of it is a property; for then what is more likely to be a property of it will be a

property as well. Thus, for example, inasmuch as 'sensation' is less likely to be a property of 'animal' than

life', and 'sensation' is a property of animal, 'life' would be a property of animal.

Next, look from the point of view of the attributes that belong in a like manner, and first (a) for destructive

purposes, see if what is as much a property fails to be a property of that of which it is as much a property: for

then neither will that which is as much a property as it be a property of that of which it is as much a property.

Thus (e.g.) inasmuch as 'desiring' is as much a property of the faculty of desire as reasoning' is a property of

the faculty of reason, and desiring is not a property of the faculty of desire, reasoning could not be a property

of the faculty of reason. For constructive purposes, on the other hand, see if what is as much a property is a

property of that of which it is as much a property: for then also what is as much a property as it will be a

property of that of which it is as much a property. Thus (e.g.) inasmuch as it is as much a property of 'the

faculty of reason' to be 'the primary seat of wisdom' as it is of 'the faculty of desire' to be 'the primary seat of

temperance', and it is a property of the faculty of reason to be the primary seat of wisdom, it would be a

Secondly (b) for destructive purposes, see if what is as much a property of anything fails to be a property of

it: for then neither will what is as much a property be a property of it. Thus (e.g.) inasmuch as 'seeing' is as

much a property of man as 'hearing', and 'seeing' is not a property of man, 'hearing' could not be a property of

man. For constructive purposes, on the other hand, see if what is as much a property of it is its property: for

then what is as much a property of it as the former will be its property as well. Thus (e.g.) it is as much a

property of the soul to be the primary possessor of a part that desires as of a part that reasons, and it is a

property of the soul to be the primary possessor of a part that desires, and so it be a property of the soul to be

Thirdly (c) for destructive purposes, see if it fails to be a property of that of which it is as much a property:

for then neither will it be a property of that of which it is as much a property as of the former, while if it be a

property of the former, it will not be a property of the other. Thus (e.g.) inasmuch as 'to burn' is as much a

property of 'flame' as of 'live coals', and 'to burn' is not a property of flame, 'to burn' could not be a property

of live coals: while if it is a property of flame, it could not be a property of live coals. For constructive

The rule based on things that are in a like relation' differs from the rule based on attributes that belong in a

like manner,' because the former point is secured by analogy, not from reflection on the belonging of any

attribute, while the latter is judged by a comparison based on the fact that an attribute belongs.

Next, for destructive purposes, see if in rendering the property potentially, he has also through that

potentiality rendered the property relatively to something that does not exist, when the potentiality in question

cannot belong to what does not exist: for then what is stated to be a property will not be a property. Thus

(e.g.) he who has said that 'breathable' is a property of 'air' has, on the one hand, rendered the property

potentially (for that is 'breathable' which is such as can be breathed), and on the other hand has also rendered

the property relatively to what does not exist:for while air may exist, even though there exist no animal so

constituted as to breathe the air, it is not possible to breathe it if no animal exist: so that it will not, either, be a

property of air to be such as can be breathed at a time when there exists no animal such as to breathe it and so

For constructive purposes, see if in rendering the property potentially he renders the property either relatively

to something that exists, or to something that does not exist, when the potentiality in question can belong to

what does not exist: for then what has been stated not to be a property will be a property. Thus e.g.) he who

renders it as a property of 'being' to be 'capable of being acted upon or of acting', in rendering the property

potentially, has rendered the property relatively to something that exists: for when 'being' exists, it will also

be capable of being acted upon or of acting in a certain way: so that to be 'capable of being acted upon or of

Next, for destructive purposes, see if he has stated the property in the superlative: for then what has been

stated to be a property will not be a property. For people who render the property in that way find that of the

object of which the description is true, the name is not true as well: for though the object perish the

description will continue in being none the less; for it belongs most nearly to something that is in being. An

example would be supposing any one were to render 'the lightest body' as a property of 'fire': for, though fire

perish, there eh re will still be some form of body that is the lightest, so that 'the lightest body' could not be a

property of fire. For constructive purposes, on the other hand, see if he has avoided rendering the property in

the superlative: for then the property will in this respect have been property of man has not rendered the

property correctly stated. Thus (e.g.) inasmuch as he in the superlative, the property would in who states 'a

THE discussion of Definitions falls into five parts. For you have to show either (1) that it is not true at all to

apply the expression as well to that to which the term is applied (for the definition of Man ought to be true of

every man); or (2) that though the object has a genus, he has failed to put the object defined into the genus, or

to put it into the appropriate genus (for the framer of a definition should first place the object in its genus, and

then append its differences: for of all the elements of the definition the genus is usually supposed to be the

principal mark of the essence of what is defined): or (3) that the expression is not peculiar to the object (for,

as we said above as well, a definition ought to be peculiar): or else (4) see if, though he has observed all the

aforesaid cautions, he has yet failed to define the object, that is, to express its essence. (5) It remains, apart

Whether, then, the expression be not also true of that of which the term is true you should proceed to examine

according to the commonplace rules that relate to Accident. For there too the question is always 'Is so and so

true or untrue?': for whenever we argue that an accident belongs, we declare it to be true, while whenever we

argue that it does not belong, we declare it to be untrue. If, again, he has failed to place the object in the

appropriate genus, or if the expression be not peculiar to the object, we must go on to examine the case

It remains, then, to prescribe how to investigate whether the object has been either not defined at all, or else

defined incorrectly. First, then, we must proceed to examine if it has been defined incorrectly: for with

anything it is easier to do it than to do it correctly. Clearly, then, more mistakes are made in the latter task on

account of its greater difficulty. Accordingly the attack becomes easier in the latter case than in the former.

Incorrectness falls into two branches: (1) first, the use of obscure language (for the language of a definition

ought to be the very clearest possible, seeing that the whole purpose of rendering it is to make something

known); (secondly, if the expression used be longer than is necessary: for all additional matter in a definition

is superfluous. Again, each of the aforesaid branches is divided into a number of others.

One commonplace rule, then, in regard to obscurity is, See if the meaning intended by the definition involves

an ambiguity with any other, e.g. 'Becoming is a passage into being', or 'Health is the balance of hot and cold

elements'. Here 'passage' and 'balance' are ambiguous terms: it is accordingly not clear which of the several

possible senses of the term he intends to convey. Likewise also, if the term defined be used in different senses

and he has spoken without distinguishing between them: for then it is not clear to which of them the

definition rendered applies, and one can then bring a captious objection on the ground that the definition does

not apply to all the things whose definition he has rendered: and this kind of thing is particularly easy in the

case where the definer does not see the ambiguity of his terms. Or, again, the questioner may himself

distinguish the various senses of the term rendered in the definition, and then institute his argument against

each: for if the expression used be not adequate to the subject in any of its senses, it is clear that he cannot

Another rule is, See if he has used a metaphorical expression, as, for instance, if he has defined knowledge as

'unsupplantable', or the earth as a 'nurse', or temperance as a 'harmony'. For a metaphorical expression is

always obscure. It is possible, also, to argue sophistically against the user of a metaphorical expression as

though he had used it in its literal sense: for the definition stated will not apply to the term defined, e.g. in the

case of temperance: for harmony is always found between notes. Moreover, if harmony be the genus of

temperance, then the same object will occur in two genera of which neither contains the other: for harmony

does not contain virtue, nor virtue harmony. Again, see if he uses terms that are unfamiliar, as when Plato

describes the eye as 'browshaded', or a certain spider as poisonfanged', or the marrow as 'boneformed'. For

Sometimes a phrase is used neither ambiguously, nor yet metaphorically, nor yet literally, as when the law is

said to be the 'measure' or 'image' of the things that are by nature just. Such phrases are worse than metaphor;

for the latter does make its meaning to some extent clear because of the likeness involved; for those who use

metaphors do so always in view of some likeness: whereas this kind of phrase makes nothing clear; for there

is no likeness to justify the description 'measure' or 'image', as applied to the law, nor is the law ordinarily so

called in a literal sense. So then, if a man says that the law is literally a 'measure' or an 'image', he speaks

falsely: for an image is something produced by imitation, and this is not found in the case of the law. If, on

the other hand, he does not mean the term literally, it is clear that he has used an unclear expression, and one

Moreover, see if from the expression used the definition of the contrary be not clear; for definitions that have

been correctly rendered also indicate their contraries as well. Or, again, see if, when it is merely stated by

itself, it is not evident what it defines: just as in the works of the old painters, unless there were an inscription,

If, then, the definition be not clear, you should proceed to examine on lines such as these. If, on the other

hand, he has phrased the definition redundantly, first of all look and see whether he has used any attribute that

belongs universally, either to real objects in general, or to all that fall under the same genus as the object

defined: for the mention of this is sure to be redundant. For the genus ought to divide the object from things

in general, and the differentia from any of the things contained in the same genus. Now any term that belongs

to everything separates off the given object from absolutely nothing, while any that belongs to all the things

that fall under the same genus does not separate it off from the things contained in the same genus. Any

Or see if, though the additional matter may be peculiar to the given term, yet even when it is struck out the

rest of the expression too is peculiar and makes clear the essence of the term. Thus, in the definition of man,

the addition 'capable of receiving knowledge' is superfluous; for strike it out, and still the expression is

peculiar and makes clear his essence. Speaking generally, everything is superfluous upon whose removal the

remainder still makes the term that is being defined clear. Such, for instance, would also be the definition of

the soul, assuming it to be stated as a 'selfmoving number'; for the soul is just 'the selfmoving', as Plato

defined it. Or perhaps the expression used, though appropriate, yet does not declare the essence, if the word

'number' be eliminated. Which of the two is the real state of the case it is difficult to determine clearly: the

right way to treat the matter in all cases is to be guided by convenience. Thus (e.g.) it is said that the

definition of phlegm is the 'undigested moisture that comes first off food'. Here the addition of the word

'undigested' is superfluous, seeing that 'the first' is one and not many, so that even when undigested' is left out

the definition will still be peculiar to the subject: for it is impossible that both phlegm and also something else

should both be the first to arise from the food. Or perhaps the phlegm is not absolutely the first thing to come

off the food, but only the first of the undigested matters, so that the addition 'undigested' is required; for

stated the other way the definition would not be true unless the phlegm comes first of all.

Moreover, see if anything contained in the definition fails to apply to everything that falls under the same

species: for this sort of definition is worse than those which include an attribute belonging to all things

universally. For in that case, if the remainder of the expression be peculiar, the whole too will be peculiar: for

absolutely always, if to something peculiar anything whatever that is true be added, the whole too becomes

peculiar. Whereas if any part of the expression do not apply to everything that falls under the same species, it

is impossible that the expression as a whole should be peculiar: for it will not be predicated convertibly with

the object; e.g. 'a walking biped animal six feet high': for an expression of that kind is not predicated

convertibly with the term, because the attribute 'six feet high' does not belong to everything that falls under

Again, see if he has said the same thing more than once, saying (e.g.) 'desire' is a 'conation for the pleasant'.

For 'desire' is always 'for the pleasant', so that what is the same as desire will also be 'for the pleasant'.

Accordingly our definition of desire becomes 'conationforthepleasant': for the word 'desire' is the exact

equivalent of the words 'conation forthepleasant', so that both alike will be 'for the pleasant'. Or perhaps

there is no absurdity in this; for consider this instance:Man is a biped': therefore, what is the same as man is

a biped: but 'a walking biped animal' is the same as man, and therefore walking biped animal is a biped'. But

this involves no real absurdity. For 'biped' is not a predicate of 'walking animal': if it were, then we should

certainly have 'biped' predicated twice of the same thing; but as a matter of fact the subject said to be a biped

is'a walking biped animal', so that the word 'biped' is only used as a predicate once. Likewise also in the case

of 'desire' as well: for it is not 'conation' that is said to be 'for the pleasant', but rather the whole idea, so that

there too the predication is only made once. Absurdity results, not when the same word is uttered twice, but

when the same thing is more than once predicated of a subject; e.g. if he says, like Xenocrates, that wisdom

defines and contemplates reality:' for definition is a certain type of contemplation, so that by adding the

words 'and contemplates' over again he says the same thing twice over. Likewise, too, those fail who say that

'cooling' is 'the privation of natural heat'. For all privation is a privation of some natural attribute, so that the

addition of the word 'natural' is superfluous: it would have been enough to say 'privation of heat', for the word

Again, see if a universal have been mentioned and then a particular case of it be added as well, e.g. 'Equity is

a remission of what is expedient and just'; for what is just is a branch of what is expedient and is therefore

included in the latter term: its mention is therefore redundant, an addition of the particular after the universal

has been already stated. So also, if he defines 'medicine' as 'knowledge of what makes for health in animals

and men', or 'the law' as 'the image of what is by nature noble and just'; for what is just is a branch of what is

Whether, then, a man defines a thing correctly or incorrectly you should proceed to examine on these and

similar lines. But whether he has mentioned and defined its essence or no, should be examined as follows:

First of all, see if he has failed to make the definition through terms that are prior and more intelligible. For

the reason why the definition is rendered is to make known the term stated, and we make things known by

taking not any random terms, but such as are prior and more intelligible, as is done in demonstrations (for so

it is with all teaching and learning); accordingly, it is clear that a man who does not define through terms of

this kind has not defined at all. Otherwise, there will be more than one definition of the same thing: for

clearly he who defines through terms that are prior and more intelligible has also framed a definition, and a

better one, so that both would then be definitions of the same object. This sort of view, however, does not

generally find acceptance: for of each real object the essence is single: if, then, there are to be a number of

definitions of the same thing, the essence of the object will be the same as it is represented to be in each of

the definitions, and these representations are not the same, inasmuch as the definitions are different. Clearly,

then, any one who has not defined a thing through terms that are prior and more intelligible has not defined it

The statement that a definition has not been made through more intelligible terms may be understood in two

senses, either supposing that its terms are absolutely less intelligible, or supposing that they are less

intelligible to us: for either sense is possible. Thus absolutely the prior is more intelligible than the posterior,

a point, for instance, than a line, a line than a plane, and a plane than a solid; just as also a unit is more

intelligible than a number; for it is the prius and startingpoint of all number. Likewise, also, a letter is more

intelligible than a syllable. Whereas to us it sometimes happens that the converse is the case: for the solid

falls under perception most of allmore than a planeand a plane more than a line, and a line more than a

point; for most people learn things like the former earlier than the latter; for any ordinary intelligence can

Absolutely, then, it is better to try to make what is posterior known through what is prior, inasmuch as such a

way of procedure is more scientific. Of course, in dealing with persons who cannot recognize things through

terms of that kind, it may perhaps be necessary to frame the expression through terms that are intelligible to

them. Among definitions of this kind are those of a point, a line, and a plane, all of which explain the prior by

the posterior; for they say that a point is the limit of a line, a line of a plane, a plane of a solid. One must,

however, not fail to observe that those who define in this way cannot show the essential nature of the term

they define, unless it so happens that the same thing is more intelligible both to us and also absolutely, since a

correct definition must define a thing through its genus and its differentiae, and these belong to the order of

things which are absolutely more intelligible than, and prior to, the species. For annul the genus and

differentia, and the species too is annulled, so that these are prior to the species. They are also more

intelligible; for if the species be known, the genus and differentia must of necessity be known as well (for any

one who knows what a man is knows also what 'animal' and 'walking' are), whereas if the genus or the

differentia be known it does not follow of necessity that the species is known as well: thus the species is less

intelligible. Moreover, those who say that such definitions, viz. those which proceed from what is intelligible

to this, that, or the other man, are really and truly definitions, will have to say that there are several

definitions of one and the same thing. For, as it happens, different things are more intelligible to different

people, not the same things to all; and so a different definition would have to be rendered to each several

person, if the definition is to be constructed from what is more intelligible to particular individuals.

Moreover, to the same people different things are more intelligible at different times; first of all the objects of

sense; then, as they become more sharpwitted, the converse; so that those who hold that a definition ought to

be rendered through what is more intelligible to particular individuals would not have to render the same

definition at all times even to the same person. It is clear, then, that the right way to define is not through

terms of that kind, but through what is absolutely more intelligible: for only in this way could the definition

come always to be one and the same. Perhaps, also, what is absolutely intelligible is what is intelligible, not

to all, but to those who are in a sound state of understanding, just as what is absolutely healthy is what is

healthy to those in a sound state of body. All such points as this ought to be made very precise, and made use

of in the course of discussion as occasion requires. The demolition of a definition will most surely win a

general approval if the definer happens to have framed his expression neither from what is absolutely more

One form, then, of the failure to work through more intelligible terms is the exhibition of the prior through

the posterior, as we remarked before.' Another form occurs if we find that the definition has been rendered of

what is at rest and definite through what is indefinite and in motion: for what is still and definite is prior to

(1) The first is when an opposite has been defined through its opposite, e.g.i. good through evil: for opposites

are always simultaneous by nature. Some people think, also, that both are objects of the same science, so that

the one is not even more intelligible than the other. One must, however, observe that it is perhaps not possible

to define some things in any other way, e.g. the double without the half, and all the terms that are essentially

relative: for in all such cases the essential being is the same as a certain relation to something, so that it is

impossible to understand the one term without the other, and accordingly in the definition of the one the other

too must be embraced. One ought to learn up all such points as these, and use them as occasion may seem to

(2) Another isif he has used the term defined itself. This passes unobserved when the actual name of the

object is not used, e.g. supposing any one had defined the sun as a star that appears by day'. For in bringing in

'day' he brings in the sun. To detect errors of this sort, exchange the word for its definition, e.g. the definition

of 'day' as the 'passage of the sun over the earth'. Clearly, whoever has said 'the passage of the sun over the

earth' has said 'the sun', so that in bringing in the 'day' he has brought in the sun.

(3) Again, see if he has defined one coordinate member of a division by another, e.g. 'an odd number' as 'that

which is greater by one than an even number'. For the coordinate members of a division that are derived

from the same genus are simultaneous by nature and 'odd' and 'even' are such terms: for both are differentiae

Likewise also, see if he has defined a superior through a subordinate term, e.g. 'An "even number" is "a

number divisible into halves"', or '"the good" is a "state of virtue" '. For 'half' is derived from 'two', and 'two'

is an even number: virtue also is a kind of good, so that the latter terms are subordinate to the former.

Moreover, in using the subordinate term one is bound to use the other as well: for whoever employs the term

'virtue' employs the term 'good', seeing that virtue is a certain kind of good: likewise, also, whoever employs

the term 'half' employs the term 'even', for to be 'divided in half' means to be divided into two, and two is

Generally speaking, then, one commonplace rule relates to the failure to frame the expression by means of

terms that are prior and more intelligible: and of this the subdivisions are those specified above. A second is,

see whether, though the object is in a genus, it has not been placed in a genus. This sort of error is always

found where the essence of the object does not stand first in the expression, e.g. the definition of 'body' as

'that which has three dimensions', or the definition of 'man', supposing any one to give it, as 'that which

knows how to count': for it is not stated what it is that has three dimensions, or what it is that knows how to

count: whereas the genus is meant to indicate just this, and is submitted first of the terms in the definition.

Moreover, see if, while the term to be defined is used in relation to many things, he has failed to render it in

relation to all of them; as (e.g.) if he define 'grammar' as the 'knowledge how to write from dictation': for he

ought also to say that it is a knowledge how to read as well. For in rendering it as 'knowledge of writing' has

no more defined it than by rendering it as 'knowledge of reading': neither in fact has succeeded, but only he

who mentions both these things, since it is impossible that there should be more than one definition of the

same thing. It is only, however, in some cases that what has been said corresponds to the actual state of

things: in some it does not, e.g. all those terms which are not used essentially in relation to both things: as

medicine is said to deal with the production of disease and health; for it is said essentially to do the latter, but

the former only by accident: for it is absolutely alien to medicine to produce disease. Here, then, the man who

renders medicine as relative to both of these things has not defined it any better than he who mentions the one

only. In fact he has done it perhaps worse, for any one else besides the doctor is capable of producing disease.

Moreover, in a case where the term to be defined is used in relation to several things, see if he has rendered it

as relative to the worse rather than to the better; for every form of knowledge and potentiality is generally

Again, if the thing in question be not placed in its own proper genus, one must examine it according to the

Moreover, see if he uses language which transgresses the genera of the things he defines, defining, e.g. justice

as a 'state that produces equality' or 'distributes what is equal': for by defining it so he passes outside the

sphere of virtue, and so by leaving out the genus of justice he fails to express its essence: for the essence of a

thing must in each case bring in its genus. It is the same thing if the object be not put into its nearest genus;

for the man who puts it into the nearest one has stated all the higher genera, seeing that all the higher genera

are predicated of the lower. Either, then, it ought to be put into its nearest genus, or else to the higher genus

all the differentiae ought to be appended whereby the nearest genus is defined. For then he would not have

left out anything: but would merely have mentioned the subordinate genus by an expression instead of by

name. On the other hand, he who mentions merely the higher genus by itself, does not state the subordinate

Again, in regard to the differentiae, we must examine in like manner whether the differentiae, too, that he has

stated be those of the genus. For if a man has not defined the object by the differentiae peculiar to it, or has

mentioned something such as is utterly incapable of being a differentia of anything, e.g. 'animal' or

'substance', clearly he has not defined it at all: for the aforesaid terms do not differentiate anything at all.

Further, we must see whether the differentia stated possesses anything that is coordinate with it in a

division; for, if not, clearly the one stated could not be a differentia of the genus. For a genus is always

divided by differentiae that are coordinate members of a division, as, for instance, by the terms 'walking',

'flying', 'aquatic', and 'biped'. Or see if, though the contrasted differentia exists, it yet is not true of the genus,

for then, clearly, neither of them could be a differentia of the genus; for differentiae that are coordinates in a

division with the differentia of a thing are all true of the genus to which the thing belongs. Likewise, also, see

if, though it be true, yet the addition of it to the genus fails to make a species. For then, clearly, this could not

be a specific differentia of the genus: for a specific differentia, if added to the genus, always makes a species.

If, however, this be no true differentia, no more is the one adduced, seeing that it is a coordinate member of

Moreover, see if he divides the genus by a negation, as those do who define line as 'length without breadth':

for this means simply that it has not any breadth. The genus will then be found to partake of its own species:

for, since of everything either an affirmation or its negation is true, length must always either lack breadth or

possess it, so that 'length' as well, i.e. the genus of 'line', will be either with or without breadth. But 'length

without breadth' is the definition of a species, as also is 'length with breadth': for 'without breadth' and 'with

breadth' are differentiae, and the genus and differentia constitute the definition of the species. Hence the

genus would admit of the definition of its species. Likewise, also, it will admit of the definition of the

differentia, seeing that one or the other of the aforesaid differentiae is of necessity predicated of the genus.

The usefulness of this principle is found in meeting those who assert the existence of 'Ideas': for if absolute

length exist, how will it be predicable of the genus that it has breadth or that it lacks it? For one assertion or

the other will have to be true of 'length' universally, if it is to be true of the genus at all: and this is contrary to

the fact: for there exist both lengths which have, and lengths which have not, breadth. Hence the only people

against whom the rule can be employed are those who assert that a genus is always numerically one; and this

is what is done by those who assert the real existence of the 'Ideas'; for they allege that absolute length and

It may be that in some cases the definer is obliged to employ a negation as well, e.g. in defining privations.

For 'blind' means a thing which cannot see when its nature is to see. There is no difference between dividing

the genus by a negation, and dividing it by such an affirmation as is bound to have a negation as its

coordinate in a division, e.g. supposing he had defined something as 'length possessed of breadth'; for

coordinate in the division with that which is possessed of breadth is that which possesses no breadth and

Again, see if he rendered the species as a differentia, as do those who define 'contumely' as 'insolence

accompanied by jeering'; for jeering is a kind of insolence, i.e. it is a species and not a differentia.

Moreover, see if he has stated the genus as the differentia, e.g. 'Virtue is a good or noble state: for 'good' is

the genus of 'virtue'. Or possibly 'good' here is not the genus but the differentia, on the principle that the same

thing cannot be in two genera of which neither contains the other: for 'good' does not include 'state', nor vice

versa: for not every state is good nor every good a 'state'. Both, then, could not be genera, and consequently,

if 'state' is the genus of virtue, clearly 'good' cannot be its genus: it must rather be the differentia'. Moreover,

'a state' indicates the essence of virtue, whereas 'good' indicates not the essence but a quality: and to indicate a

quality is generally held to be the function of the differentia. See, further, whether the differentia rendered

indicates an individual rather than a quality: for the general view is that the differentia always expresses a

Look and see, further, whether the differentia belongs only by accident to the object defined. For the

differentia is never an accidental attribute, any more than the genus is: for the differentia of a thing cannot

Moreover, if either the differentia or the species, or any of the things which are under the species, is

predicable of the genus, then he could not have defined the term. For none of the aforesaid can possibly be

predicated of the genus, seeing that the genus is the term with the widest range of all. Again, see if the genus

be predicated of the differentia; for the general view is that the genus is predicated, not of the differentia, but

of the objects of which the differentia is predicated. Animal (e.g.) is predicated of 'man' or 'ox' or other

walking animals, not of the actual differentia itself which we predicate of the species. For if 'animal' is to be

predicated of each of its differentiae, then 'animal' would be predicated of the species several times over; for

the differentiae are predicates of the species. Moreover, the differentiae will be all either species or

individuals, if they are animals; for every animal is either a species or an individual.

Likewise you must inquire also if the species or any of the objects that come under it is predicated of the

differentia: for this is impossible, seeing that the differentia is a term with a wider range than the various

species. Moreover, if any of the species be predicated of it, the result will be that the differentia is a species:

if, for instance, 'man' be predicated, the differentia is clearly the human race. Again, see if the differentia fails

to be prior to the species: for the differentia ought to be posterior to the genus, but prior to the species.

Look and see also if the differentia mentioned belongs to a different genus, neither contained in nor

containing the genus in question. For the general view is that the same differentia cannot be used of two

nonsubaltern genera. Else the result will be that the same species as well will be in two nonsubaltern

genera: for each of the differentiae imports its own genus, e.g. 'walking' and 'biped' import with them the

genus 'animal'. If, then, each of the genera as well is true of that of which the differentia is true, it clearly

follows that the species must be in two nonsubaltern genera. Or perhaps it is not impossible for the same

differentia to be used of two nonsubaltern genera, and we ought to add the words 'except they both be

subordinate members of the same genus'. Thus 'walking animal' and 'flying animal' are nonsubaltern genera,

and 'biped' is the differentia of both. The words 'except they both be subordinate members of the same genus'

ought therefore to be added; for both these are subordinate to 'animal'. From this possibility, that the same

differentia may be used of two nonsubaltern genera, it is clear also that there is no necessity for the

differentia to carry with it the whole of the genus to which it belongs, but only the one or the other of its

limbs together with the genera that are higher than this, as 'biped' carries with it either 'flying' or 'walking

See, too, if he has rendered 'existence in' something as the differentia of a thing's essence: for the general

view is that locality cannot differentiate between one essence and another. Hence, too, people condemn those

who divide animals by means of the terms 'walking' and 'aquatic', on the ground that 'walking' and 'aquatic'

indicate mere locality. Or possibly in this case the censure is undeserved; for 'aquatic' does not mean 'in'

anything; nor does it denote a locality, but a certain quality: for even if the thing be on the dry land, still it is

aquatic: and likewise a landanimal, even though it be in the water, will still be a and not an aquaticanimal.

But all the same, if ever the differentia does denote existence in something, clearly he will have made a bad

Again, see if he has rendered an affection as the differentia: for every affection, if intensified, subverts the

essence of the thing, while the differentia is not of that kind: for the differentia is generally considered rather

to preserve that which it differentiates; and it is absolutely impossible for a thing to exist without its own

special differentia: for if there be no 'walking', there will be no 'man'. In fact, we may lay down absolutely

that a thing cannot have as its differentia anything in respect of which it is subject to alteration: for all things

of that kind, if intensified, destroy its essence. If, then, a man has rendered any differentia of this kind, he has

made a mistake: for we undergo absolutely no alteration in respect of our differentiae.

Again, see if he has failed to render the differentia of a relative term relatively to something else; for the

differentiae of relative terms are themselves relative, as in the case also of knowledge. This is classed as

speculative, practical and productive; and each of these denotes a relation: for it speculates upon something,

Look and see also if the definer renders each relative term relatively to its natural purpose: for while in some

cases the particular relative term can be used in relation to its natural purpose only and to nothing else, some

can be used in relation to something else as well. Thus sight can only be used for seeing, but a strigil can also

be used to dip up water. Still, if any one were to define a strigil as an instrument for dipping water, he has

made a mistake: for that is not its natural function. The definition of a thing's natural function is 'that for

which it would be used by the prudent man, acting as such, and by the science that deals specially with that

Or see if, whenever a term happens to be used in a number of relations, he has failed to introduce it in its

primary relation: e.g. by defining 'wisdom' as the virtue of 'man' or of the 'soul,' rather than of the 'reasoning

faculty': for 'wisdom' is the virtue primarily of the reasoning faculty: for it is in virtue of this that both the

Moreover, if the thing of which the term defined has been stated to be an affection or disposition, or whatever

it may be, be unable to admit it, the definer has made a mistake. For every disposition and every affection is

formed naturally in that of which it is an affection or disposition, as knowledge, too, is formed in the soul,

being a disposition of soul. Sometimes, however, people make bad mistakes in matters of this sort, e.g. all

those who say that 'sleep' is a 'failure of sensation', or that 'perplexity' is a state of 'equality between contrary

reasonings', or that 'pain' is a 'violent disruption of parts that are naturally conjoined'. For sleep is not an

attribute of sensation, whereas it ought to be, if it is a failure of sensation. Likewise, perplexity is not an

attribute of opposite reasonings, nor pain of parts naturally conjoined: for then inanimate things will be in

pain, since pain will be present in them. Similar in character, too, is the definition of 'health', say, as a

'balance of hot and cold elements': for then health will be necessarily exhibited by the hot and cold elements:

for balance of anything is an attribute inherent in those things of which it is the balance, so that health would

be an attribute of them. Moreover, people who define in this way put effect for cause, or cause for effect. For

the disruption of parts naturally conjoined is not pain, but only a cause of pain: nor again is a failure of

sensation sleep, but the one is the cause of the other: for either we go to sleep because sensation fails, or

sensation fails because we go to sleep. Likewise also an equality between contrary reasonings would be

generally considered to be a cause of perplexity: for it is when we reflect on both sides of a question and find

everything alike to be in keeping with either course that we are perplexed which of the two we are to do.

Moreover, with regard to all periods of time look and see whether there be any discrepancy between the

differentia and the thing defined: e.g. supposing the 'immortal' to be defined as a 'living thing immune at

present from destruction'. For a living thing that is immune 'at present' from destruction will be immortal 'at

present'. Possibly, indeed, in this case this result does not follow, owing to the ambiguity of the words

'immune at present from destruction': for it may mean either that the thing has not been destroyed at present,

or that it cannot be destroyed at present, or that at present it is such that it never can be destroyed. Whenever,

then, we say that a living thing is at present immune from destruction, we mean that it is at present a living

thing of such a kind as never to be destroyed: and this is equivalent to saying that it is immortal, so that it is

not meant that it is immortal only at present. Still, if ever it does happen that what has been rendered

according to the definition belongs in the present only or past, whereas what is meant by the word does not so

belong, then the two could not be the same. So, then, this commonplace rule ought to be followed, as we have

You should look and see also whether the term being defined is applied in consideration of something other

than the definition rendered. Suppose (e.g.) a definition of 'justice' as the 'ability to distribute what is equal'.

This would not be right, for 'just' describes rather the man who chooses, than the man who is able to distribute

what is equal: so that justice could not be an ability to distribute what is equal: for then also the most just man

Moreover, see if the thing admits of degrees, whereas what is rendered according to the definition does not,

or, vice versa, what is rendered according to the definition admits of degrees while the thing does not. For

either both must admit them or else neither, if indeed what is rendered according to the definition is the same

as the thing. Moreover, see if, while both of them admit of degrees, they yet do not both become greater

together: e.g. suppose sexual love to be the desire for intercourse: for he who is more intensely in love has not

a more intense desire for intercourse, so that both do not become intensified at once: they certainly should,

Moreover, suppose two things to be before you, see if the term to be defined applies more particularly to the

one to which the content of the definition is less applicable. Take, for instance, the definition of 'fire' as the

'body that consists of the most rarefied particles'. For 'fire' denotes flame rather than light, but flame is less

the body that consists of the most rarefied particles than is light: whereas both ought to be more applicable to

the same thing, if they had been the same. Again, see if the one expression applies alike to both the objects

before you, while the other does not apply to both alike, but more particularly to one of them.

Moreover, see if he renders the definition relative to two things taken separately: thus, the beautiful' is 'what

is pleasant to the eyes or to the ears": or 'the real' is 'what is capable of being acted upon or of acting'. For

then the same thing will be both beautiful and not beautiful, and likewise will be both real and not real. For

'pleasant to the ears' will be the same as 'beautiful', so that 'not pleasant to the ears' will be the same as 'not

beautiful': for of identical things the opposites, too, are identical, and the opposite of 'beautiful' is 'not

beautiful', while of 'pleasant to the ears' the opposite is not pleasant to the cars': clearly, then, 'not pleasant to

the ears' is the same thing as 'not beautiful'. If, therefore, something be pleasant to the eyes but not to the ears,

it will be both beautiful and not beautiful. In like manner we shall show also that the same thing is both real

Moreover, of both genera and differentiae and all the other terms rendered in definitions you should frame

definitions in lieu of the terms, and then see if there be any discrepancy between them.

If the term defined be relative, either in itself or in respect of its genus, see whether the definition fails to

mention that to which the term, either in itself or in respect of its genus, is relative, e.g. if he has defined

'knowledge' as an 'incontrovertible conception' or 'wishing' as 'painless conation'. For of everything relative

the essence is relative to something else, seeing that the being of every relative term is identical with being in

a certain relation to something. He ought, therefore, to have said that knowledge is 'conception of a knowable'

and that wishing is 'conation for a good'. Likewise, also, if he has defined 'grammar' as 'knowledge of letters':

whereas in the definition there ought to be rendered either the thing to which the term itself is relative, or that,

whatever it is, to which its genus is relative. Or see if a relative term has been described not in relation to its

end, the end in anything being whatever is best in it or gives its purpose to the rest. Certainly it is what is best

or final that should be stated, e.g. that desire is not for the pleasant but for pleasure: for this is our purpose in

Look and see also if that in relation to which he has rendered the term be a process or an activity: for nothing

of that kind is an end, for the completion of the activity or process is the end rather than the process or

activity itself. Or perhaps this rule is not true in all cases, for almost everybody prefers the present experience

of pleasure to its cessation, so that they would count the activity as the end rather than its completion.

Again see in some cases if he has failed to distinguish the quantity or quality or place or other differentiae of

an object; e.g. the quality and quantity of the honour the striving for which makes a man ambitious: for all

men strive for honour, so that it is not enough to define the ambitious man as him who strives for honour, but

the aforesaid differentiae must be added. Likewise, also, in defining the covetous man the quantity of money

he aims at, or in the case of the incontinent man the quality of the pleasures, should be stated. For it is not the

man who gives way to any sort of pleasure whatever who is called incontinent, but only he who gives way to

a certain kind of pleasure. Or again, people sometimes define night as a 'shadow on the earth', or an

earthquake as a movement of the earth', or a cloud as 'condensation of the air', or a wind as a 'movement of

the air'; whereas they ought to specify as well quantity, quality, place, and cause. Likewise, also, in other

cases of the kind: for by omitting any differentiae whatever he fails to state the essence of the term. One

should always attack deficiency. For a movement of the earth does not constitute an earthquake, nor a

Moreover, in the case of conations, and in any other cases where it applies, see if the word 'apparent' is left

out, e.g. 'wishing is a conation after the good', or 'desire is a conation after the pleasant'instead of saying 'the

apparently good', or 'pleasant'. For often those who exhibit the conation do not perceive what is good or

pleasant, so that their aim need not be really good or pleasant, but only apparently so. They ought, therefore,

to have rendered the definition also accordingly. On the other hand, any one who maintains the existence of

Ideas ought to be brought face to face with his Ideas, even though he does render the word in question: for

there can be no Idea of anything merely apparent: the general view is that an Idea is always spoken of in

relation to an Idea: thus absolute desire is for the absolutely pleasant, and absolute wishing is for the

absolutely good; they therefore cannot be for an apparent good or an apparently pleasant: for the existence of

Moreover, if the definition be of the state of anything, look at what is in the state, while if it be of what is in

the state, look at the state: and likewise also in other cases of the kind. Thus if the pleasant be identical with

the beneficial, then, too, the man who is pleased is benefited. Speaking generally, in definitions of this sort it

happens that what the definer defines is in a sense more than one thing: for in defining knowledge, a man in a

sense defines ignorance as well, and likewise also what has knowledge and what lacks it, and what it is to

know and to be ignorant. For if the first be made clear, the others become in a certain sense clear as well. We

have, then, to be on our guard in all such cases against discrepancy, using the elementary principles drawn

Moreover, in the case of relative terms, see if the species is rendered as relative to a species of that to which

the genus is rendered as relative, e.g. supposing belief to be relative to some object of belief, see whether a

particular belief is made relative to some particular object of belief: and, if a multiple be relative to a fraction,

see whether a particular multiple be made relative to a particular fraction. For if it be not so rendered, clearly

See, also, if the opposite of the term has the opposite definition, whether (e.g.) the definition of 'half' is the

opposite of that of 'double': for if 'double' is 'that which exceeds another by an equal amount to that other',

'half' is 'that which is exceeded by an amount equal to itself'. In the same way, too, with contraries. For to the

contrary term will apply the definition that is contrary in some one of the ways in which contraries are

conjoined. Thus (e.g.) if 'useful'='productive of good', 'injurious'=productive of evil' or 'destructive of good',

for one or the other of thee is bound to be contrary to the term originally used. Suppose, then, neither of these

things to be the contrary of the term originally used, then clearly neither of the definitions rendered later

could be the definition of the contrary of the term originally defined: and therefore the definition originally

rendered of the original term has not been rightly rendered either. Seeing, moreover, that of contraries, the

one is sometimes a word forced to denote the privation of the other, as (e.g.) inequality is generally held to be

the privation of equality (for 'unequal' merely describes things that are not equal'), it is therefore clear that

that contrary whose form denotes the privation must of necessity be defined through the other; whereas the

other cannot then be defined through the one whose form denotes the privation; for else we should find that

each is being interpreted by the other. We must in the case of contrary terms keep an eye on this mistake, e.g.

supposing any one were to define equality as the contrary of inequality: for then he is defining it through the

term which denotes privation of it. Moreover, a man who so defines is bound to use in his definition the very

term he is defining; and this becomes clear, if for the word we substitute its definition. For to say 'inequality'

is the same as to say 'privation of equality'. Therefore equality so defined will be 'the contrary of the privation

of equality', so that he would have used the very word to be defined. Suppose, however, that neither of the

contraries be so formed as to denote privation, but yet the definition of it be rendered in a manner like the

above, e.g. suppose 'good' to be defined as 'the contrary of evil', then, since it is clear that 'evil' too will be 'the

contrary of good' (for the definition of things that are contrary in this must be rendered in a like manner), the

result again is that he uses the very term being defined: for 'good' is inherent in the definition of 'evil'. If, then,

'good' be the contrary of evil, and evil be nothing other than the 'contrary of good', then 'good' will be the

'contrary of the contrary of good'. Clearly, then, he has used the very word to be defined.

Moreover, see if in rendering a term formed to denote privation, he has failed to render the term of which it is

the privation, e.g. the state, or contrary, or whatever it may be whose privation it is: also if he has omitted to

add either any term at all in which the privation is naturally formed, or else that in which it is naturally

formed primarily, e.g. whether in defining 'ignorance' a privation he has failed to say that it is the privation of

'knowledge'; or has failed to add in what it is naturally formed, or, though he has added this, has failed to

render the thing in which it is primarily formed, placing it (e.g.) in 'man' or in 'the soul', and not in the

'reasoning faculty': for if in any of these respects he fails, he has made a mistake. Likewise, also, if he has

failed to say that 'blindness' is the 'privation of sight in an eye': for a proper rendering of its essence must state

Examine further whether he has defined by the expression 'a privation' a term that is not used to denote a

privation: thus a mistake of this sort also would be generally thought to be incurred in the case of 'error' by

any one who is not using it as a merely negative term. For what is generally thought to be in error is not that

which has no knowledge, but rather that which has been deceived, and for this reason we do not talk of

inanimate things or of children as 'erring'. 'Error', then, is not used to denote a mere privation of knowledge.

Moreover, see whether the like inflexions in the definition apply to the like inflexions of the term; e.g. if

'beneficial' means 'productive of health', does 'beneficially' mean productively of health' and a 'benefactor' a

Look too and see whether the definition given will apply to the Idea as well. For in some cases it will not do

so; e.g. in the Platonic definition where he adds the word 'mortal' in his definitions of living creatures: for the

Idea (e.g. the absolute Man) is not mortal, so that the definition will not fit the Idea. So always wherever the

words 'capable of acting on' or 'capable of being acted upon' are added, the definition and the Idea are

absolutely bound to be discrepant: for those who assert the existence of Ideas hold that they are incapable of

being acted upon, or of motion. In dealing with these people even arguments of this kind are useful.

Further, see if he has rendered a single common definition of terms that are used ambiguously. For terms

whose definition corresponding their common name is one and the same, are synonymous; if, then, the

definition applies in a like manner to the whole range of the ambiguous term, it is not true of any one of the

objects described by the term. This is, moreover, what happens to Dionysius' definition of 'life' when stated as

'a movement of a creature sustained by nutriment, congenitally present with it': for this is found in plants as

much as in animals, whereas 'life' is generally understood to mean not one kind of thing only, but to be one

thing in animals and another in plants. It is possible to hold the view that life is a synonymous term and is

always used to describe one thing only, and therefore to render the definition in this way on purpose: or it

may quite well happen that a man may see the ambiguous character of the word, and wish to render the

definition of the one sense only, and yet fail to see that he has rendered a definition common to both senses

instead of one peculiar to the sense he intends. In either case, whichever course he pursues, he is equally at

fault. Since ambiguous terms sometimes pass unobserved, it is best in questioning to treat such terms as

though they were synonymous (for the definition of the one sense will not apply to the other, so that the

answerer will be generally thought not to have defined it correctly, for to a synonymous term the definition

should apply in its full range), whereas in answering you should yourself distinguish between the senses.

Further, as some answerers call 'ambiguous' what is really synonymous, whenever the definition rendered

fails to apply universally, and, vice versa, call synonymous what is really ambiguous supposing their

definition applies to both senses of the term, one should secure a preliminary admission on such points, or

else prove beforehand that soandso is ambiguous or synonymous, as the case may be: for people are more

ready to agree when they do not foresee what the consequence will be. If, however, no admission has been

made, and the man asserts that what is really synonymous is ambiguous because the definition he has

rendered will not apply to the second sense as well, see if the definition of this second meaning applies also to

the other meanings: for if so, this meaning must clearly be synonymous with those others. Otherwise, there

will be more than one definition of those other meanings, for there are applicable to them two distinct

definitions in explanation of the term, viz. the one previously rendered and also the later one. Again, if any

one were to define a term used in several senses, and, finding that his definition does not apply to them all,

were to contend not that the term is ambiguous, but that even the term does not properly apply to all those

senses, just because his definition will not do so either, then one may retort to such a man that though in some

things one must not use the language of the people, yet in a question of terminology one is bound to employ

Suppose now that a definition has been rendered of some complex term, take away the definition of one of

the elements in the complex, and see if also the rest of the definition defines the rest of it: if not, it is clear

that neither does the whole definition define the whole complex. Suppose, e.g. that some one has defined a

'finite straight line' as 'the limit of a finite plane, such that its centre is in a line with its extremes'; if now the

definition of a finite line' be the 'limit of a finite plane', the rest (viz. 'such that its centre is in a line with its

extremes') ought to be a definition of straight'. But an infinite straight line has neither centre nor extremes and

yet is straight so that this remainder does not define the remainder of the term.

Moreover, if the term defined be a compound notion, see if the definition rendered be equimembral with the

term defined. A definition is said to be equimembral with the term defined when the number of the elements

compounded in the latter is the same as the number of nouns and verbs in the definition. For the exchange in

such cases is bound to be merely one of term for term, in the case of some if not of all, seeing that there are

no more terms used now than formerly; whereas in a definition terms ought to be rendered by phrases, if

possible in every case, or if not, in the majority. For at that rate, simple objects too could be defined by

The mistake is even worse, if actually a less well known term be substituted, e.g. 'pellucid mortal' for 'white

man': for it is no definition, and moreover is less intelligible when put in that form.

Look and see also whether, in the exchange of words, the sense fails still to be the same. Take, for instance,

the explanation of 'speculative knowledge' as 'speculative conception': for conception is not the same as

knowledgeas it certainly ought to be if the whole is to be the same too: for though the word 'speculative' is

Moreover, see if in replacing one of the terms by something else he has exchanged the genus and not the

differentia, as in the example just given: for 'speculative' is a less familiar term than knowledge; for the one is

the genus and the other the differentia, and the genus is always the most familiar term of all; so that it is not

this, but the differentia, that ought to have been changed, seeing that it is the less familiar. It might be held

that this criticism is ridiculous: because there is no reason why the most familiar term should not describe the

differentia, and not the genus; in which case, clearly, the term to be altered would also be that denoting the

genus and not the differentia. If, however, a man is substituting for a term not merely another term but a

phrase, clearly it is of the differentia rather than of the genus that a definition should be rendered, seeing that

the object of rendering the definition is to make the subject familiar; for the differentia is less familiar than

If he has rendered the definition of the differentia, see whether the definition rendered is common to it and

something else as well: e.g. whenever he says that an odd number is a 'number with a middle', further

definition is required of how it has a middle: for the word 'number' is common to both expressions, and it is

the word 'odd' for which the phrase has been substituted. Now both a line and a body have a middle, yet they

are not 'odd'; so that this could not be a definition of 'odd'. If, on the other hand, the phrase 'with a middle' be

used in several senses, the sense here intended requires to be defined. So that this will either discredit the

Again, see if the term of which he renders the definition is a reality, whereas what is contained in the

definition is not, e.g. Suppose 'white' to be defined as 'colour mingled with fire': for what is bodiless cannot

be mingled with body, so that 'colour' 'mingled with fire' could not exist, whereas 'white' does exist.

Moreover, those who in the case of relative terms do not distinguish to what the object is related, but have

described it only so as to include it among too large a number of things, are wrong either wholly or in part;

e.g. suppose some one to have defined 'medicine' as a science of Reality'. For if medicine be not a science of

anything that is real, the definition is clearly altogether false; while if it be a science of some real thing, but

not of another, it is partly false; for it ought to hold of all reality, if it is said to be of Reality essentially and

not accidentally: as is the case with other relative terms: for every object of knowledge is a term relative to

knowledge: likewise, also, with other relative terms, inasmuch as all such are convertible. Moreover, if the

right way to render account of a thing be to render it as it is not in itself but accidentally, then each and every

relative term would be used in relation not to one thing but to a number of things. For there is no reason why

the same thing should not be both real and white and good, so that it would be a correct rendering to render

the object in relation to any one whatsoever of these, if to render what it is accidentally be a correct way to

render it. It is, moreover, impossible that a definition of this sort should be peculiar to the term rendered: for

not only but the majority of the other sciences too, have for their object some real thing, so that each will be a

science of reality. Clearly, then, such a definition does not define any science at all; for a definition ought to

Sometimes, again, people define not the thing but only the thing in a good or perfect condition. Such is the

definition of a rhetorician as 'one who can always see what will persuade in the given circumstances, and

omit nothing'; or of a thief, as 'one who pilfers in secret': for clearly, if they each do this, then the one will be

a good rhetorician, and the other a good thief: whereas it is not the actual pilfering in secret, but the wish to

Again, see if he has rendered what is desirable for its own sake as desirable for what it produces or does, or as

in any way desirable because of something else, e.g. by saying that justice is 'what preserves the laws' or that

wisdom is 'what produces happiness'; for what produces or preserves something else is one of the things

desirable for something else. It might be said that it is possible for what is desirable in itself to be desirable

for something else as well: but still to define what is desirable in itself in such a way is none the less wrong:

for the essence contains par excellence what is best in anything, and it is better for a thing to be desirable in

itself than to be desirable for something else, so that this is rather what the definition too ought to have

See also whether in defining anything a man has defined it as an 'A and B', or as a 'product of A and B' or as

an 'A+B'. If he defines it as and B', the definition will be true of both and yet of neither of them; suppose, e.g.

justice to be defined as 'temperance and courage.' For if of two persons each has one of the two only, both

and yet neither will be just: for both together have justice, and yet each singly fails to have it. Even if the

situation here described does not so far appear very absurd because of the occurrence of this kind of thing in

other cases also (for it is quite possible for two men to have a mina between them, though neither of them has

it by himself), yet least that they should have contrary attributes surely seems quite absurd; and yet this will

follow if the one be temperate and yet a coward, and the other, though brave, be a profligate; for then both

will exhibit both justice and injustice: for if justice be temperance and bravery, then injustice will be

cowardice and profligacy. In general, too, all the ways of showing that the whole is not the same as the sum

of its parts are useful in meeting the type just described; for a man who defines in this way seems to assert

that the parts are the same as the whole. The arguments are particularly appropriate in cases where the

process of putting the parts together is obvious, as in a house and other things of that sort: for there, clearly,

you may have the parts and yet not have the whole, so that parts and whole cannot be the same.

If, however, he has said that the term being defined is not 'A and B' but the 'product of A and B', look and see

in the first place if A and B cannot in the nature of things have a single product: for some things are so related

to one another that nothing can come of them, e.g. a line and a number. Moreover, see if the term that has

been defined is in the nature of things found primarily in some single subject, whereas the things which he

has said produce it are not found primarily in any single subject, but each in a separate one. If so, clearly that

term could not be the product of these things: for the whole is bound to be in the same things wherein its parts

are, so that the whole will then be found primarily not in one subject only, but in a number of them. If, on the

other hand, both parts and whole are found primarily in some single subject, see if that medium is not the

same, but one thing in the case of the whole and another in that of the parts. Again, see whether the parts

perish together with the whole: for it ought to happen, vice versa, that the whole perishes when the parts

perish; when the whole perishes, there is no necessity that the parts should perish too. Or again, see if the

whole be good or evil, and the parts neither, or, vice versa, if the parts be good or evil and the whole neither.

For it is impossible either for a neutral thing to produce something good or bad, or for things good or bad to

produce a neutral thing. Or again, see if the one thing is more distinctly good than the other is evil, and yet

the product be no more good than evil, e.g. suppose shamelessness be defined as 'the product of courage and

false opinion': here the goodness of courage exceeds the evil of false opinion; accordingly the product of

these ought to have corresponded to this excess, and to be either good without qualification, or at least more

good than evil. Or it may be that this does not necessarily follow, unless each be in itself good or bad; for

many things that are productive are not good in themselves, but only in combination; or, per contra, they are

good taken singly, and bad or neutral in combination. What has just been said is most clearly illustrated in the

case of things that make for health or sickness; for some drugs are such that each taken alone is good, but if

Again, see whether the whole, as produced from a better and worse, fails to be worse than the better and

better than the worse element. This again, however, need not necessarily be the case, unless the elements

compounded be in themselves good; if they are not, the whole may very well not be good, as in the cases just

Moreover, see if the whole be synonymous with one of the elements: for it ought not to be, any more than in

the case of syllables: for the syllable is not synonymous with any of the letters of which it is made up.

Moreover, see if he has failed to state the manner of their composition: for the mere mention of its elements is

not enough to make the thing intelligible. For the essence of any compound thing is not merely that it is a

product of soandso, but that it is a product of them compounded in such and such a way, just as in the case

of a house: for here the materials do not make a house irrespective of the way they are put together.

If a man has defined an object as 'A+B', the first thing to be said is that 'A+B' means the same either as 'A and

B', or as the 'product of A and B.' for 'honey+water' means either the honey and the water, or the 'drink made

of honey and water'. If, then, he admits that 'A+B' is + B' is the same as either of these two things, the same

criticisms will apply as have already been given for meeting each of them. Moreover, distinguish between the

different senses in which one thing may be said to be '+' another, and see if there is none of them in which A

could be said to exist '+ B.' Thus e.g. supposing the expression to mean that they exist either in some identical

thing capable of containing them (as e.g. justice and courage are found in the soul), or else in the same place

or in the same time, and if this be in no way true of the A and B in question, clearly the definition rendered

could not hold of anything, as there is no possible way in which A can exist B'. If, however, among the

various senses above distinguished, it be true that A and B are each found in the same time as the other, look

and see if possibly the two are not used in the same relation. Thus e.g. suppose courage to have been defined

as 'daring with right reasoning': here it is possible that the person exhibits daring in robbery, and right

reasoning in regard to the means of health: but he may have 'the former quality+the latter' at the same time,

and not as yet be courageous! Moreover, even though both be used in the same relation as well, e.g. in

relation to medical treatment (for a man may exhibit both daring and right reasoning in respect of medical

treatment), still, none the less, not even this combination of 'the one+the other 'makes him 'courageous'. For

the two must not relate to any casual object that is the same, any more than each to a different object; rather,

they must relate to the function of courage, e.g. meeting the perils of war, or whatever is more properly

Some definitions rendered in this form fail to come under the aforesaid division at all, e.g. a definition of

anger as 'pain with a consciousness of being slighted'. For what this means to say is that it is because of a

consciousness of this sort that the pain occurs; but to occur 'because of' a thing is not the same as to occur '+ a

Again, if he have described the whole compounded as the 'composition' of these things (e.g. 'a living creature'

as a 'composition of soul and body'), first of all see whether he has omitted to state the kind of composition,

as (e.g.) in a definition of 'flesh' or 'bone' as the 'composition of fire, earth, and air'. For it is not enough to say

it is a composition, but you should also go on to define the kind of composition: for these things do not form

flesh irrespective of the manner of their composition, but when compounded in one way they form flesh,

when in another, bone. It appears, moreover, that neither of the aforesaid substances is the same as a

'composition' at all: for a composition always has a decomposition as its contrary, whereas neither of the

aforesaid has any contrary. Moreover, if it is equally probable that every compound is a composition or else

that none is, and every kind of living creature, though a compound, is never a composition, then no other

Again, if in the nature of a thing two contraries are equally liable to occur, and the thing has been defined

through the one, clearly it has not been defined; else there will be more than one definition of the same thing;

for how is it any more a definition to define it through this one than through the other, seeing that both alike

are naturally liable to occur in it? Such is the definition of the soul, if defined as a substance capable of

Also, even when one cannot attack the definition as a whole for lack of acquaintance with the whole, one

should attack some part of it, if one knows that part and sees it to be incorrectly rendered: for if the part be

demolished, so too is the whole definition. Where, again, a definition is obscure, one should first of all correct

and reshape it in order to make some part of it clear and get a handle for attack, and then proceed to examine

it. For the answerer is bound either to accept the sense as taken by the questioner, or else himself to explain

clearly whatever it is that his definition means. Moreover, just as in the assemblies the ordinary practice is to

move an emendation of the existing law and, if the emendation is better, they repeal the existing law, so one

ought to do in the case of definitions as well: one ought oneself to propose a second definition: for if it is seen

to be better, and more indicative of the object defined, clearly the definition already laid down will have been

demolished, on the principle that there cannot be more than one definition of the same thing.

In combating definitions it is always one of the chief elementary principles to take by oneself a happy shot at

a definition of the object before one, or to adopt some correctly expressed definition. For one is bound, with

the model (as it were) before one's eyes, to discern both any shortcoming in any features that the definition

ought to have, and also any superfluous addition, so that one is better supplied with lines of attack.

WHETHER two things are 'the same' or 'different', in the most literal of the meanings ascribed to 'sameness'

(and we said' that 'the same' applies in the most literal sense to what is numerically one), may be examined in

the light of their inflexions and coordinates and opposites. For if justice be the same as courage, then too the

just man is the same as the brave man, and 'justly' is the same as 'bravely'. Likewise, too, in the case of their

opposites: for if two things be the same, their opposites also will be the same, in any of the recognized forms

of opposition. For it is the same thing to take the opposite of the one or that of the other, seeing that they are

the same. Again it may be examined in the light of those things which tend to produce or to destroy the things

in question of their formation and destruction, and in general of any thing that is related in like manner to

each. For where things are absolutely the same, their formations and destructions also are the same, and so

are the things that tend to produce or to destroy them. Look and see also, in a case where one of two things is

said to be something or other in a superlative degree, if the other of these alleged identical things can also be

described by a superlative in the same respect. Thus Xenocrates argues that the happy life and the good life

are the same, seeing that of all forms of life the good life is the most desirable and so also is the happy life:

for 'the most desirable' and the greatest' apply but to one thing.' Likewise also in other cases of the kind. Each,

however, of the two things termed 'greatest' or most desirable' must be numerically one: otherwise no proof

will have been given that they are the same; for it does not follow because Peloponnesians and Spartans are

the bravest of the Greeks, that Peloponnesians are the same as Spartans, seeing that 'Peloponnesian' is not any

one person nor yet 'Spartan'; it only follows that the one must be included under the other as 'Spartans' are

under 'Peloponnesians': for otherwise, if the one class be not included under the other, each will be better than

the other. For then the Peloponnesians are bound to be better than the Spartans, seeing that the one class is

not included under the other; for they are better than anybody else. Likewise also the Spartans must perforce

be better than the Peloponnesians; for they too are better than anybody else; each then is better than the other!

Clearly therefore what is styled 'best' and 'greatest' must be a single thing, if it is to be proved to be 'the same'

as another. This also is why Xenocrates fails to prove his case: for the happy life is not numerically single,

nor yet the good life, so that it does not follow that, because they are both the most desirable, they are

Again, look and see if, supposing the one to be the same as something, the other also is the same as it: for if

they be not both the same as the same thing, clearly neither are they the same as one another.

Moreover, examine them in the light of their accidents or of the things of which they are accidents: for any

accident belonging to the one must belong also to the other, and if the one belong to anything as an accident,

so must the other also. If in any of these respects there is a discrepancy, clearly they are not the same.

See further whether, instead of both being found in one class of predicates, the one signifies a quality and the

other a quantity or relation. Again, see if the genus of each be not the same, the one being 'good' and the other

evil', or the one being 'virtue' and the other 'knowledge': or see if, though the genus is the same, the

differentiae predicted of either be not the same, the one (e.g.) being distinguished as a 'speculative' science,

Moreover, from the point of view of 'degrees', see if the one admits an increase of degree but not the other, or

if though both admit it, they do not admit it at the same time; just as it is not the case that a man desires

intercourse more intensely, the more intensely he is in love, so that love and the desire for intercourse are not

Moreover, examine them by means of an addition, and see whether the addition of each to the same thing

fails to make the same whole; or if the subtraction of the same thing from each leaves a different remainder.

Suppose (e.g.) that he has declared 'double a half' to be the same as 'a multiple of a half': then, subtracting the

words 'a half' from each, the remainders ought to have signified the same thing: but they do not; for 'double'

Inquire also not only if some impossible consequence results directly from the statement made, that A and B

are the same, but also whether it is possible for a supposition to bring it about; as happens to those who assert

that 'empty' is the same as 'full of air': for clearly if the air be exhausted, the vessel will not be less but more

empty, though it will no longer be full of air. So that by a supposition, which may be true or may be false (it

makes no difference which), the one character is annulled and not the other, showing that they are not the

Speaking generally, one ought to be on the lookout for any discrepancy anywhere in any sort of predicate of

each term, and in the things of which they are predicated. For all that is predicated of the one should be

predicated also of the other, and of whatever the one is a predicate, the other should be a predicate of it as

Moreover, as 'sameness' is a term used in many senses, see whether things that are the same in one way are

the same also in a different way. For there is either no necessity or even no possibility that things that are the

same specifically or generically should be numerically the same, and it is with the question whether they are

Moreover, see whether the one can exist without the other; for, if so, they could not be the same.

Such is the number of the commonplace rules that relate to 'sameness'. It is clear from what has been said that

all the destructive commonplaces relating to sameness are useful also in questions of definition, as was said

before:' for if what is signified by the term and by the expression be not the same, clearly the expression

rendered could not be a definition. None of the constructive commonplaces, on the other hand, helps in the

matter of definition; for it is not enough to show the sameness of content between the expression and the

term, in order to establish that the former is a definition, but a definition must have also all the other

This then is the way, and these the arguments, whereby the attempt to demolish a definition should always be

made. If, on the other hand, we desire to establish one, the first thing to observe is that few if any who engage

in discussion arrive at a definition by reasoning: they always assume something of the kind as their starting

pointsboth in geometry and in arithmetic and the other studies of that kind. In the second place, to say

accurately what a definition is, and how it should be given, belongs to another inquiry. At present it concerns

us only so far as is required for our present purpose, and accordingly we need only make the bare statement

that to reason to a thing's definition and essence is quite possible. For if a definition is an expression

signifying the essence of the thing and the predicates contained therein ought also to be the only ones which

are predicated of the thing in the category of essence; and genera and differentiae are so predicated in that

category: it is obvious that if one were to get an admission that so and so are the only attributes predicated in

that category, the expression containing so and so would of necessity be a definition; for it is impossible that

anything else should be a definition, seeing that there is not anything else predicated of the thing in the

That a definition may thus be reached by a process of reasoning is obvious. The means whereby it should be

established have been more precisely defined elsewhere, but for the purposes of the inquiry now before us the

same commonplace rules serve. For we have to examine into the contraries and other opposites of the thing,

surveying the expressions used both as wholes and in detail: for if the opposite definition defines that

opposite term, the definition given must of necessity be that of the term before us. Seeing, however, that

contraries may be conjoined in more than one way, we have to select from those contraries the one whose

contrary definition seems most obvious. The expressions, then, have to be examined each as a whole in the

way we have said, and also in detail as follows. First of all, see that the genus rendered is correctly rendered;

for if the contrary thing be found in the contrary genus to that stated in the definition, and the thing before

you is not in that same genus, then it would clearly be in the contrary genus: for contraries must of necessity

be either in the same genus or in contrary genera. The differentiae, too, that are predicated of contraries we

expect to be contrary, e.g. those of white and black, for the one tends to pierce the vision, while the other

tends to compress it. So that if contrary differentiae to those in the definition are predicated of the contrary

term, then those rendered in the definition would be predicated of the term before us. Seeing, then, that both

the genus and the differentiae have been rightly rendered, clearly the expression given must be the right

definition. It might be replied that there is no necessity why contrary differentiae should be predicated of

contraries, unless the contraries be found within the same genus: of things whose genera are themselves

contraries it may very well be that the same differentia is used of both, e.g. of justice and injustice; for the

one is a virtue and the other a vice of the soul: 'of the soul', therefore, is the differentia in both cases, seeing

that the body as well has its virtue and vice. But this much at least is true, that the differentiae of contraries

are either contrary or else the same. If, then, the contrary differentia to that given be predicated of the

contrary term and not of the one in hand, clearly the differentia stated must be predicated of the latter.

Speaking generally, seeing that the definition consists of genus and differentiae, if the definition of the

contrary term be apparent, the definition of the term before you will be apparent also: for since its contrary is

found either in the same genus or in the contrary genus, and likewise also the differentiae predicated of

opposites are either contrary to, or the same as, each other, clearly of the term before you there will be

predicated either the same genus as of its contrary, while, of its differentiae, either all are contrary to those of

its contrary, or at least some of them are so while the rest remain the same; or, vice versa, the differentiae will

be the same and the genera contrary; or both genera and differentiae will be contrary. And that is all; for that

both should be the same is not possible; else contraries will have the same definition.

Moreover, look at it from the point of view of its inflexions and coordinates. For genera and definitions are

bound to correspond in either case. Thus if forgetfulness be the loss of knowledge, to forget is to lose

knowledge, and to have forgotten is to have lost knowledge. If, then, any one whatever of these is agreed to,

the others must of necessity be agreed to as well. Likewise, also, if destruction is the decomposition of the

thing's essence, then to be destroyed is to have its essence decomposed, and 'destructively' means 'in such a

way as to decompose its essence'; if again 'destructive' means 'apt to decompose something's essence', then

also 'destruction' means 'the decomposition of its essence'. Likewise also with the rest: an admission of any

Moreover, look at it from the point of view of things that stand in relations that are like each other. For if

'healthy' means 'productive of health', 'vigorous' too will mean 'productive of vigour', and 'useful' will mean

'productive of good.' For each of these things is related in like manner to its own peculiar end, so that if one

of them is defined as 'productive of' that end, this will also be the definition of each of the rest as well.

Moreover, look at it from the point of and like degrees, in all the ways in which it is possible to establish a

result by comparing two and two together. Thus if A defines a better than B defines and B is a definition of so

too is A of a. Further, if A's claim to define a is like B's to define B, and B defines B, then A too defines a.

This examination from the point of view of greater degrees is of no use when a single definition is compared

with two things, or two definitions with one thing; for there cannot possibly be one definition of two things or

The most handy of all the commonplace arguments are those just mentioned and those from coordinates and

inflexions, and these therefore are those which it is most important to master and to have ready to hand: for

they are the most useful on the greatest number of occasions. Of the rest, too, the most important are those of

most general application: for these are the most effective, e.g. that you should examine the individual cases,

and then look to see in the case of their various species whether the definition applies. For the species is

synonymous with its individuals. This sort of inquiry is of service against those who assume the existence of

Ideas, as has been said before.' Moreover see if a man has used a term metaphorically, or predicated it of

itself as though it were something different. So too if any other of the commonplace rules is of general

That it is more difficult to establish than to overthrow a definition, is obvious from considerations presently

to be urged. For to see for oneself, and to secure from those whom one is questioning, an admission of

premisses of this sort is no simple matter, e.g. that of the elements of the definition rendered the one is genus

and the other differentia, and that only the genus and differentiae are predicated in the category of essence.

Yet without these premisses it is impossible to reason to a definition; for if any other things as well are

predicated of the thing in the category of essence, there is no telling whether the formula stated or some other

one is its definition, for a definition is an expression indicating the essence of a thing. The point is clear also

from the following: It is easier to draw one conclusion than many. Now in demolishing a definition it is

sufficient to argue against one point only (for if we have overthrown any single point whatsoever, we shall

have demolished the definition); whereas in establishing a definition, one is bound to bring people to the view

that everything contained in the definition is attributable. Moreover, in establishing a case, the reasoning

brought forward must be universal: for the definition put forward must be predicated of everything of which

the term is predicated, and must moreover be convertible, if the definition rendered is to be peculiar to the

subject. In overthrowing a view, on the other hand, there is no longer any necessity to show one's point

universally: for it is enough to show that the formula is untrue of any one of the things embraced under the

Further, even supposing it should be necessary to overthrow something by a universal proposition, not even

so is there any need to prove the converse of the proposition in the process of overthrowing the definition.

For merely to show that the definition fails to be predicated of every one of the things of which the term is

predicated, is enough to overthrow it universally: and there is no need to prove the converse of this in order to

show that the term is predicated of things of which the expression is not predicated. Moreover, even if it

applies to everything embraced under the term, but not to it alone, the definition is thereby demolished.

The case stands likewise in regard to the property and genus of a term also. For in both cases it is easier to

overthrow than to establish. As regards the property this is clear from what has been said: for as a rule the

property is rendered in a complex phrase, so that to overthrow it, it is only necessary to demolish one of the

terms used, whereas to establish it is necessary to reason to them all. Then, too, nearly all the other rules that

apply to the definition will apply also to the property of a thing. For in establishing a property one has to

show that it is true of everything included under the term in question, whereas to overthrow one it is enough

to show in a single case only that it fails to belong: further, even if it belongs to everything falling under the

term, but not to that only, it is overthrown in this case as well, as was explained in the case of the definition.

In regard to the genus, it is clear that you are bound to establish it in one way only, viz. by showing that it

belongs in every case, while of overthrowing it there are two ways: for if it has been shown that it belongs

either never or not in a certain case, the original statement has been demolished. Moreover, in establishing a

genus it is not enough to show that it belongs, but also that it belongs as genus has to be shown; whereas in

overthrowing it, it is enough to show its failure to belong either in some particular case or in every case. It

appears, in fact, as though, just as in other things to destroy is easier than to create, so in these matters too to

In the case of an accidental attribute the universal proposition is easier to overthrow than to establish; for to

establish it, one has to show that it belongs in every case, whereas to overthrow it, it is enough to show that it

does not belong in one single case. The particular proposition is, on the contrary, easier to establish than to

overthrow: for to establish it, it is enough to show that it belongs in a particular instance, whereas to

It is clear also that the easiest thing of all is to overthrow a definition. For on account of the number of

statements involved we are presented in the definition with the greatest number of points for attack, and the

more plentiful the material, the quicker an argument comes: for there is more likelihood of a mistake

occurring in a large than in a small number of things. Moreover, the other rules too may be used as means for

attacking a definition: for if either the formula be not peculiar, or the genus rendered be the wrong one, or

something included in the formula fail to belong, the definition is thereby demolished. On the other hand,

against the others we cannot bring all of the arguments drawn from definitions, nor yet of the rest: for only

those relating to accidental attributes apply generally to all the aforesaid kinds of attribute. For while each of

the aforesaid kinds of attribute must belong to the thing in question, yet the genus may very well not belong

as a property without as yet being thereby demolished. Likewise also the property need not belong as a genus,

nor the accident as a genus or property, so long as they do belong. So that it is impossible to use one set as a

basis of attack upon the other except in the case of definition. Clearly, then, it is the easiest of all things to

demolish a definition, while to establish one is the hardest. For there one both has to establish all those other

points by reasoning (i.e. that the attributes stated belong, and that the genus rendered is the true genus, and

that the formula is peculiar to the term), and moreover, besides this, that the formula indicates the essence of

Of the rest, the property is most nearly of this kind: for it is easier to demolish, because as a rule it contains

several terms; while it is the hardest to establish, both because of the number of things that people must be

brought to accept, and, besides this, because it belongs to its subject alone and is predicated convertibly with

The easiest thing of all to establish is an accidental predicate: for in other cases one has to show not only that

the predicate belongs, but also that it belongs in such and such a particular way: whereas in the case of the

accident it is enough to show merely that it belongs. On the other hand, an accidental predicate is the hardest

thing to overthrow, because it affords the least material: for in stating accident a man does not add how the

predicate belongs; and accordingly, while in other cases it is possible to demolish what is said in two ways,

by showing either that the predicate does not belong, or that it does not belong in the particular way stated, in

the case of an accidental predicate the only way to demolish it is to show that it does not belong at all.

The commonplace arguments through which we shall be well supplied with lines of argument with regard to

NEXT there fall to be discussed the problems of arrangement and method in pitting questions. Any one who

intends to frame questions must, first of all, select the ground from which he should make his attack;

secondly, he must frame them and arrange them one by one to himself; thirdly and lastly, he must proceed

actually to put them to the other party. Now so far as the selection of his ground is concerned the problem is

one alike for the philosopher and the dialectician; but how to go on to arrange his points and frame his

questions concerns the dialectician only: for in every problem of that kind a reference to another party is

involved. Not so with the philosopher, and the man who is investigating by himself: the premisses of his

reasoning, although true and familiar, may be refused by the answerer because they lie too near the original

statement and so he foresees what will follow if he grants them: but for this the philosopher does not care.

Nay, he may possibly be even anxious to secure axioms as familiar and as near to the question in hand as

The sources from which one's commonplace arguments should be drawn have already been described:' we

have now to discuss the arrangement and formation of questions and first to distinguish the premisses, other

than the necessary premisses, which have to be adopted. By necessary premisses are meant those through

which the actual reasoning is constructed. Those which are secured other than these are of four kinds; they

serve either inductively to secure the universal premiss being granted, or to lend weight to the argument, or to

conceal the conclusion, or to render the argument more clear. Beside these there is no other premiss which

need be secured: these are the ones whereby you should try to multiply and formulate your questions. Those

which are used to conceal the conclusion serve a controversial purpose only; but inasmuch as an undertaking

of this sort is always conducted against another person, we are obliged to employ them as well.

The necessary premisses through which the reasoning is effected, ought not to be propounded directly in so

many words. Rather one should soar as far aloof from them as possible. Thus if one desires to secure an

admission that the knowledge of contraries is one, one should ask him to admit it not of contraries, but of

opposites: for, if he grants this, one will then argue that the knowledge of contraries is also the same, seeing

that contraries are opposites; if he does not, one should secure the admission by induction, by formulating a

proposition to that effect in the case of some particular pair of contraries. For one must secure the necessary

premisses either by reasoning or by induction, or else partly by one and partly by the other, although any

propositions which are too obvious to be denied may be formulated in so many words. This is because the

coming conclusion is less easily discerned at the greater distance and in the process of induction, while at the

same time, even if one cannot reach the required premisses in this way, it is still open to one to formulate

them in so many words. The premisses, other than these, that were mentioned above, must be secured with a

view to the latter. The way to employ them respectively is as follows: Induction should proceed from

individual cases to the universal and from the known to the unknown; and the objects of perception are better

known, to most people if not invariably. Concealment of one's plan is obtained by securing through

prosyllogisms the premisses through which the proof of the original proposition is going to be

constructedand as many of them as possible. This is likely to be effected by making syllogisms to prove not

only the necessary premisses but also some of those which are required to establish them. Moreover, do not

state the conclusions of these premisses but draw them later one after another; for this is likely to keep the

answerer at the greatest possible distance from the original proposition. Speaking generally, a man who

desires to get information by a concealed method should so put his questions that when he has put his whole

argument and has stated the conclusion, people still ask 'Well, but why is that?' This result will be secured

best of all by the method above described: for if one states only the final conclusion, it is unclear how it

comes about; for the answerer does not foresee on what grounds it is based, because the previous syllogisms

have not been made articulate to him: while the final syllogism, showing the conclusion, is likely to be kept

least articulate if we lay down not the secured propositions on which it is based, but only the grounds on

It is a useful rule, too, not to secure the admissions claimed as the bases of the syllogisms in their proper

order, but alternately those that conduce to one conclusion and those that conduce to another; for, if those

which go together are set side by side, the conclusion that will result from them is more obvious in advance.

One should also, wherever possible, secure the universal premiss by a definition relating not to the precise

terms themselves but to their coordinates; for people deceive themselves, whenever the definition is taken in

regard to a coordinate, into thinking that they are not making the admission universally. An instance would

be, supposing one had to secure the admission that the angry man desires vengeance on account of an

apparent slight, and were to secure this, that 'anger' is a desire for vengeance on account of an apparent slight:

for, clearly, if this were secured, we should have universally what we intend. If, on the other hand, people

formulate propositions relating to the actual terms themselves, they often find that the answerer refuses to

grant them because on the actual term itself he is readier with his objection, e.g. that the 'angry man' does not

desire vengeance, because we become angry with our parents, but we do not desire vengeance on them. Very

likely the objection is not valid; for upon some people it is vengeance enough to cause them pain and make

them sorry; but still it gives a certain plausibility and air of reasonableness to the denial of the proposition. In

the case, however, of the definition of 'anger' it is not so easy to find an objection.

Moreover, formulate your proposition as though you did so not for its own sake, but in order to get at

something else: for people are shy of granting what an opponent's case really requires. Speaking generally, a

questioner should leave it as far as possible doubtful whether he wishes to secure an admission of his

proposition or of its opposite: for if it be uncertain what their opponent's argument requires, people are more

Moreover, try to secure admissions by means of likeness: for such admissions are plausible, and the universal

involved is less patent; e.g. make the other person admit that as knowledge and ignorance of contraries is the

same, so too perception of contraries is the same; or vice versa, that since the perception is the same, so is the

knowledge also. This argument resembles induction, but is not the same thing; for in induction it is the

universal whose admission is secured from the particulars, whereas in arguments from likeness, what is

It is a good rule also, occasionally to bring an objection against oneself: for answerers are put off their guard

against those who appear to be arguing impartially. It is useful too, to add that 'So and so is generally held or

commonly said'; for people are shy of upsetting the received opinion unless they have some positive

objection to urge: and at the same time they are cautious about upsetting such things because they themselves

too find them useful. Moreover, do not be insistent, even though you really require the point: for insistence

always arouses the more opposition. Further, formulate your premiss as though it were a mere illustration: for

people admit the more readily a proposition made to serve some other purpose, and not required on its own

account. Moreover, do not formulate the very proposition you need to secure, but rather something from

which that necessarily follows: for people are more willing to admit the latter, because it is not so clear from

this what the result will be, and if the one has been secured, the other has been secured also. Again, one

should put last the point which one most wishes to have conceded; for people are specially inclined to deny

the first questions put to them, because most people in asking questions put first the points which they are

most eager to secure. On the other hand, in dealing with some people propositions of this sort should be put

forward first: for illtempered men admit most readily what comes first, unless the conclusion that will result

actually stares them in the face, while at the close of an argument they show their illtemper. Likewise also

with those who consider themselves smart at answering: for when they have admitted most of what you want

they finally talk claptrap to the effect that the conclusion does not follow from their admissions: yet they say

'Yes' readily, confident in their own character, and imagining that they cannot suffer any reverse. Moreover, it

is well to expand the argument and insert things that it does not require at all, as do those who draw false

geometrical figures: for in the multitude of details the whereabouts of the fallacy is obscured. For this reason

also a questioner sometimes evades observation as he adds in a corner what, if he formulated it by itself,

For concealment, then, the rules which should be followed are the above. Ornament is attained by induction

and distinction of things closely akin. What sort of process induction is obvious: as for distinction, an

instance of the kind of thing meant is the distinction of one form of knowledge as better than another by

being either more accurate, or concerned with better objects; or the distinction of sciences into speculative,

practical, and productive. For everything of this kind lends additional ornament to the argument, though there

For clearness, examples and comparisons should be adduced, and let the illustrations be relevant and drawn

from things that we know, as in Homer and not as in Choerilus; for then the proposition is likely to become

In dialectics, syllogism should be employed in reasoning against dialecticians rather than against the crowd:

induction, on the other hand, is most useful against the crowd. This point has been treated previously as well.'

In induction, it is possible in some cases to ask the question in its universal form, but in others this is not

easy, because there is no established general term that covers all the resemblances: in this case, when people

need to secure the universal, they use the phrase 'in all cases of this sort'. But it is one of the very hardest

things to distinguish which of the things adduced are 'of this sort', and which are not: and in this connexion

people often throw dust in each others' eyes in their discussion, the one party asserting the likeness of things

that are not alike, and the other disputing the likeness of things that are. One ought, therefore, to try oneself to

coin a word to cover all things of the given sort, so as to leave no opportunity either to the answerer to

dispute, and say that the thing advanced does not answer to a like description, or to the questioner to suggest

falsely that it does answer to a like description, for many things appear to answer to like descriptions that do

If one has made an induction on the strength of several cases and yet the answerer refuses to grant the

universal proposition, then it is fair to demand his objection. But until one has oneself stated in what cases it

is so, it is not fair to demand that he shall say in what cases it is not so: for one should make the induction

first, and then demand the objection. One ought, moreover, to claim that the objections should not be brought

in reference to the actual subject of the proposition, unless that subject happen to be the one and only thing of

the kind, as for instance two is the one prime number among the even numbers: for, unless he can say that

this subject is unique of its kind, the objector ought to make his objection in regard to some other. People

sometimes object to a universal proposition, and bring their objection not in regard to the thing itself, but in

regard to some homonym of it: thus they argue that a man can very well have a colour or a foot or a hand

other than his own, for a painter may have a colour that is not his own, and a cook may have a foot that is not

his own. To meet them, therefore, you should draw the distinction before putting your question in such cases:

for so long as the ambiguity remains undetected, so long will the objection to the proposition be deemed

valid. If, however, he checks the series of questions by an objection in regard not to some homonym, but to

the actual thing asserted, the questioner should withdraw the point objected to, and form the remainder into a

universal proposition, until he secures what he requires; e.g. in the case of forgetfulness and having forgotten:

for people refuse to admit that the man who has lost his knowledge of a thing has forgotten it, because if the

thing alters, he has lost knowledge of it, but he has not forgotten it. Accordingly the thing to do is to

withdraw the part objected to, and assert the remainder, e.g. that if a person have lost knowledge of a thing

while it still remains, he then has forgotten it. One should similarly treat those who object to the statement

that 'the greater the good, the greater the evil that is its opposite': for they allege that health, which is a less

good thing than vigour, has a greater evil as its opposite: for disease is a greater evil than debility. In this case

too, therefore, we have to withdraw the point objected to; for when it has been withdrawn, the man is more

likely to admit the proposition, e.g. that 'the greater good has the greater evil as its opposite, unless the one

good involves the other as well', as vigour involves health. This should be done not only when he formulates

an objection, but also if, without so doing, he refuses to admit the point because he foresees something of the

kind: for if the point objected to be withdrawn, he will be forced to admit the proposition because he cannot

foresee in the rest of it any case where it does not hold true: if he refuse to admit it, then when asked for an

objection he certainly will be unable to render one. Propositions that are partly false and partly true are of this

type: for in the case of these it is possible by withdrawing a part to leave the rest true. If, however, you

formulate the proposition on the strength of many cases and he has no objection to bring, you may claim that

he shall admit it: for a premiss is valid in dialectics which thus holds in several instances and to which no

Whenever it is possible to reason to the same conclusion either through or without a reduction per

impossibile, if one is demonstrating and not arguing dialectically it makes no difference which method of

reasoning be adopted, but in argument with another reasoning per impossibile should be avoided. For where

one has reasoned without the reduction per impossibile, no dispute can arise; if, on the other hand, one does

reason to an impossible conclusion, unless its falsehood is too plainly manifest, people deny that it is

One should put forward all propositions that hold true of several cases, and to which either no objection

whatever appears or at least not any on the surface: for when people cannot see any case in which it is not so,

The conclusion should not be put in the form of a question; if it be, and the man shakes his head, it looks as if

the reasoning had failed. For often, even if it be not put as a question but advanced as a consequence, people

deny it, and then those who do not see that it follows upon the previous admissions do not realize that those

who deny it have been refuted: when, then, the one man merely asks it as a question without even saying that

it so follows, and the other denies it, it looks altogether as if the reasoning had failed.

Not every universal question can form a dialectical proposition as ordinarily understood, e.g. 'What is man?'

or 'How many meanings has "the good"?' For a dialectical premiss must be of a form to which it is possible to

reply 'Yes' or 'No', whereas to the aforesaid it is not possible. For this reason questions of this kind are not

dialectical unless the questioner himself draws distinctions or divisions before expressing them, e.g. 'Good

means this, or this, does it not?' For questions of this sort are easily answered by a Yes or a No. Hence one

should endeavour to formulate propositions of this kind in this form. It is at the same time also perhaps fair to

ask the other man how many meanings of 'the good' there are, whenever you have yourself distinguished and

Any one who keeps on asking one thing for a long time is a bad inquirer. For if he does so though the person

questioned keeps on answering the questions, clearly he asks a large number of questions, or else asks the

same question a large number of times: in the one case he merely babbles, in the other he fails to reason: for

reasoning always consists of a small number of premisses. If, on the other hand, he does it because the person

questioned does not answer the questions, he is at fault in not taking him to task or breaking off the

There are certain hypotheses upon which it is at once difficult to bring, and easy to stand up to, an argument.

Such (e.g.) are those things which stand first and those which stand last in the order of nature. For the former

require definition, while the latter have to be arrived at through many steps if one wishes to secure a

continuous proof from first principles, or else all discussion about them wears the air of mere sophistry: for to

prove anything is impossible unless one begins with the appropriate principles, and connects inference with

inference till the last are reached. Now to define first principles is just what answerers do not care to do, nor

do they pay any attention if the questioner makes a definition: and yet until it is clear what it is that is

proposed, it is not easy to discuss it. This sort of thing happens particularly in the case of the first principles:

for while the other propositions are shown through these, these cannot be shown through anything else: we

are obliged to understand every item of that sort by a definition. The inferences, too, that lie too close to the

first principle are hard to treat in argument: for it is not possible to bring many arguments in regard to them,

because of the small number of those steps, between the conclusion and the principle, whereby the

succeeding propositions have to be shown. The hardest, however, of all definitions to treat in argument are

those that employ terms about which, in the first place, it is uncertain whether they are used in one sense or

several, and, further, whether they are used literally or metaphorically by the definer. For because of their

obscurity, it is impossible to argue upon such terms; and because of the impossibility of saying whether this

obscurity is due to their being used metaphorically, it is impossible to refute them.

In general, it is safe to suppose that, whenever any problem proves intractable, it either needs definition or

else bears either several senses, or a metaphorical sense, or it is not far removed from the first principles; or

else the reason is that we have yet to discover in the first place just thisin which of the aforesaid directions

the source of our difficulty lies: when we have made this clear, then obviously our business must be either to

define or to distinguish, or to supply the intermediate premisses: for it is through these that the final

It often happens that a difficulty is found in discussing or arguing a given position because the definition has

not been correctly rendered: e.g. 'Has one thing one contrary or many?': here when the term 'contraries' has

been properly defined, it is easy to bring people to see whether it is possible for the same thing to have

several contraries or not: in the same way also with other terms requiring definition. It appears also in

mathematics that the difficulty in using a figure is sometimes due to a defect in definition; e.g. in proving that

the line which cuts the plane parallel to one side divides similarly both the line which it cuts and the area;

whereas if the definition be given, the fact asserted becomes immediately clear: for the areas have the same

fraction subtracted from them as have the sides: and this is the definition of 'the same ratio'. The most primary

of the elementary principles are without exception very easy to show, if the definitions involved, e.g. the

nature of a line or of a circle, be laid down; only the arguments that can be brought in regard to each of them

are not many, because there are not many intermediate steps. If, on the other hand, the definition of the

startingpoints be not laid down, to show them is difficult and may even prove quite impossible. The case of

the significance of verbal expressions is like that of these mathematical conceptions.

One may be sure then, whenever a position is hard to discuss, that one or other of the aforesaid things has

happened to it. Whenever, on the other hand, it is a harder task to argue to the point claimed, i.e. the premiss,

than to the resulting position, a doubt may arise whether such claims should be admitted or not: for if a man

is going to refuse to admit it and claim that you shall argue to it as well, he will be giving the signal for a

harder undertaking than was originally proposed: if, on the other hand, he grants it, he will be giving the

original thesis credence on the strength of what is less credible than itself. If, then, it is essential not to

enhance the difficulty of the problem, he had better grant it; if, on the other hand, it be essential to reason

through premisses that are better assured, he had better refuse. In other words, in serious inquiry he ought not

to grant it, unless he be more sure about it than about the conclusion; whereas in a dialectical exercise he may

do so if he is merely satisfied of its truth. Clearly, then, the circumstances under which such admissions

should be claimed are different for a mere questioner and for a serious teacher.

As to the formulation, then, and arrangement of one's questions, about enough has been said.

With regard to the giving of answers, we must first define what is the business of a good answerer, as of a

good questioner. The business of the questioner is so to develop the argument as to make the answerer utter

the most extrvagant paradoxes that necessarily follow because of his position: while that of the answerer is to

make it appear that it is not he who is responsible for the absurdity or paradox, but only his position: for one

may, perhaps, distinguish between the mistake of taking up a wrong position to start with, and that of not

Inasmuch as no rules are laid down for those who argue for the sake of training and of examination:and the

aim of those engaged in teaching or learning is quite different from that of those engaged in a competition; as

is the latter from that of those who discuss things together in the spirit of inquiry: for a learner should always

state what he thinks: for no one is even trying to teach him what is false; whereas in a competition the

business of the questioner is to appear by all means to produce an effect upon the other, while that of the

answerer is to appear unaffected by him; on the other hand, in an assembly of disputants discussing in the

spirit not of a competition but of an examination and inquiry, there are as yet no articulate rules about what

the answerer should aim at, and what kind of things he should and should not grant for the correct or incorrect

defence of his position:inasmuch, then, as we have no tradition bequeathed to us by others, let us try to say

The thesis laid down by the answerer before facing the questioner's argument is bound of necessity to be one

that is either generally accepted or generally rejected or else is neither: and moreover is so accepted or

rejected either absolutely or else with a restriction, e.g. by some given person, by the speaker or by some one

else. The manner, however, of its acceptance or rejection, whatever it be, makes no difference: for the right

way to answer, i.e. to admit or to refuse to admit what has been asked, will be the same in either case. If,

then, the statement laid down by the answerer be generally rejected, the conclusion aimed at by the questioner

is bound to be one generally accepted, whereas if the former be generally accepted, the latter is generally

rejected: for the conclusion which the questioner tries to draw is always the opposite of the statement laid

down. If, on the other hand, what is laid down is generally neither rejected nor accepted, the conclusion will

be of the same type as well. Now since a man who reasons correctly demonstrates his proposed conclusion

from premisses that are more generally accepted, and more familiar, it is clear that (1) where the view laid

down by him is one that generally is absolutely rejected, the answerer ought not to grant either what is thus

absolutely not accepted at all, or what is accepted indeed, but accepted less generally than the questioner's

conclusion. For if the statement laid down by the answerer be generally rejected, the conclusion aimed at by

the questioner will be one that is generally accepted, so that the premisses secured by the questioner should

all be views generally accepted, and more generally accepted than his proposed conclusion, if the less

familiar is to be inferred through the more familiar. Consequently, if any of the questions put to him be not of

this character, the answerer should not grant them. (2) If, on the other hand, the statement laid down by the

answerer be generally accepted without qualification, clearly the conclusion sought by the questioner will be

one generally rejected without qualification. Accordingly, the answerer should admit all views that are

generally accepted and, of those that are not generally accepted, all that are less generally rejected than the

conclusion sought by the questioner. For then he will probably be thought to have argued sufficiently well.

(3) Likewise, too, if the statement laid down by the answerer be neither rejected generally nor generally

accepted; for then, too, anything that appears to be true should be granted, and, of the views not generally

accepted, any that are more generally accepted than the questioner's conclusion; for in that case the result will

be that the arguments will be more generally accepted. If, then, the view laid down by the answerer be one

that is generally accepted or rejected without qualification, then the views that are accepted absolutely must

be taken as the standard of comparison: whereas if the view laid down be one that is not generally accepted or

rejected, but only by the answerer, then the standard whereby the latter must judge what is generally accepted

or not, and must grant or refuse to grant the point asked, is himself. If, again, the answerer be defending some

one else's opinion, then clearly it will be the latter's judgement to which he must have regard in granting or

denying the various points. This is why those, too, who introduce other's opinions, e.g. that 'good and evil are

the same thing, as Heraclitus says,' refuse to admit the impossibility of contraries belonging at the same time

to the same thing; not because they do not themselves believe this, but because on Heraclitus' principles one

has to say so. The same thing is done also by those who take on the defence of one another's positions; their

It is clear, then, what the aims of the answerer should be, whether the position he lays down be a view

generally accepted without qualification or accepted by some definite person. Now every question asked is

bound to involve some view that is either generally held or generally rejected or neither, and is also bound to

be either relevant to the argument or irrelevant: if then it be a view generally accepted and irrelevant, the

answerer should grant it and remark that it is the accepted view: if it be a view not generally accepted and

irrelevant, he should grant it but add a comment that it is not generally accepted, in order to avoid the

appearance of being a simpleton. If it be relevant and also be generally accepted, he should admit that it is the

view generally accepted but say that it lies too close to the original proposition, and that if it be granted the

problem proposed collapses. If what is claimed by the questioner be relevant but too generally rejected, the

answerer, while admitting that if it be granted the conclusion sought follows, should yet protest that the

proposition is too absurd to be admitted. Suppose, again, it be a view that is neither rejected generally nor

generally accepted, then, if it be irrelevant to the argument, it may be granted without restriction; if, however,

it be relevant, the answerer should add the comment that, if it be granted, the original problem collapses. For

then the answerer will not be held to be personally accountable for what happens to him, if he grants the

several points with his eyes open, and also the questioner will be able to draw his inference, seeing that all the

premisses that are more generally accepted than the conclusion are granted him. Those who try to draw an

inference from premisses more generally rejected than the conclusion clearly do not reason correctly: hence,

The questioner should be met in a like manner also in the case of terms used obscurely, i.e. in several senses.

For the answerer, if he does not understand, is always permitted to say 'I do not understand': he is not

compelled to reply 'Yes' or 'No' to a question which may mean different things. Clearly, then, in the first

place, if what is said be not clear, he ought not to hesitate to say that he does not understand it; for often

people encounter some difficulty from assenting to questions that are not clearly put. If he understands the

question and yet it covers many senses, then supposing what it says to be universally true or false, he should

give it an unqualified assent or denial: if, on the other hand, it be partly true and partly false, he should add a

comment that it bears different senses, and also that in one it is true, in the other false: for if he leave this

distinction till later, it becomes uncertain whether originally as well he perceived the ambiguity or not. If he

does not foresee the ambiguity, but assents to the question having in view the one sense of the words, then, if

the questioner takes it in the other sense, he should say, 'That was not what I had in view when I admitted it; I

meant the other sense': for if a term or expression covers more than one thing, it is easy to disagree. If,

however, the question is both clear and simple, he should answer either 'Yes' or 'No'.

A premiss in reasoning always either is one of the constituent elements in the reasoning, or else goes to

establish one of these: (and you can always tell when it is secured in order to establish something else by the

fact of a number of similar questions being put: for as a rule people secure their universal by means either of

induction or of likeness):accordingly the particular propositions should all be admitted, if they are true and

generally held. On the other hand, against the universal one should try to bring some negative instance; for to

bring the argument to a standstill without a negative instance, either real or apparent, shows illtemper. If,

then, a man refuses to grant the universal when supported by many instances, although he has no negative

instance to show, he obviously shows illtemper. If, moreover, he cannot even attempt a counterproof that it

is not true, far more likely is he to be thought illtemperedalthough even counterproof is not enough: for

we often hear arguments that are contrary to common opinions, whose solution is yet difficult, e.g. the

argument of Zeno that it is impossible to move or to traverse the stadium;but still, this is no reason for

omitting to assert the opposites of these views. If, then, a man refuses to admit the proposition without having

either a negative instance or some counterargument to bring against it, clearly he is illtempered: for

illtemper in argument consists in answering in ways other than the above, so as to wreck the reasoning.

Before maintaining either a thesis or a definition the answerer should try his hand at attacking it by himself;

for clearly his business is to oppose those positions from which questioners demolish what he has laid down.

He should beware of maintaining a hypothesis that is generally rejected: and this it may be in two ways: for it

may be one which results in absurd statements, e.g. suppose any one were to say that everything is in motion

or that nothing is; and also there are all those which only a bad character would choose, and which are

implicitly opposed to men's wishes, e.g. that pleasure is the good, and that to do injustice is better than to

suffer it. For people then hate him, supposing him to maintain them not for the sake of argument but because

Of all arguments that reason to a false conclusion the right solution is to demolish the point on which the

fallacy that occurs depends: for the demolition of any random point is no solution, even though the point

demolished be false. For the argument may contain many falsehoods, e.g. suppose some one to secure the

premisses, 'He who sits, writes' and 'Socrates is sitting': for from these it follows that 'Socrates is writing'.

Now we may demolish the proposition 'Socrates is sitting', and still be no nearer a solution of the argument; it

may be true that the point claimed is false; but it is not on that that fallacy of the argument depends: for

supposing that any one should happen to be sitting and not writing, it would be impossible in such a case to

apply the same solution. Accordingly, it is not this that needs to be demolished, but rather that 'He who sits,

writes': for he who sits does not always write. He, then, who has demolished the point on which the fallacy

depends, has given the solution of the argument completely. Any one who knows that it is on such and such a

point that the argument depends, knows the solution of it, just as in the case of a figure falsely drawn. For it is

not enough to object, even if the point demolished be a falsehood, but the reason of the fallacy should also be

proved: for then it would be clear whether the man makes his objection with his eyes open or not.

There are four possible ways of preventing a man from working his argument to a conclusion. It can be done

either by demolishing the point on which the falsehood that comes about depends, or by stating an objection

directed against the questioner: for often when a solution has not as a matter of fact been brought, yet the

questioner is rendered thereby unable to pursue the argument any farther. Thirdly, one may object to the

questions asked: for it may happen that what the questioner wants does not follow from the questions he has

asked because he has asked them badly, whereas if something additional be granted the conclusion comes

about. If, then, the questioner be unable to pursue his argument farther, the objection would properly be

directed against the questioner; if he can do so, then it would be against his questions. The fourth and worst

kind of objection is that which is directed to the time allowed for discussion: for some people bring

objections of a kind which would take longer to answer than the length of the discussion in hand.

There are then, as we said, four ways of making objections: but of them the first alone is a solution: the others

Adverse criticism of an argument on its own merits, and of it when presented in the form of questions, are

two different things. For often the failure to carry through the argument correctly in discussion is due to the

person questioned, because he will not grant the steps of which a correct argument might have been made

against his position: for it is not in the power of the one side only to effect properly a result that depends on

both alike. Accordingly it sometimes becomes necessary to attack the speaker and not his position, when the

answerer lies in wait for the points that are contrary to the questioner and becomes abusive as well: when

people lose their tempers in this way, their argument becomes a contest, not a discussion. Moreover, since

arguments of this kind are held not for the sake of instruction but for purposes of practice and examination,

clearly one has to reason not only to true conclusions, but also to false ones, and not always through true

premisses, but sometimes through false as well. For often, when a true proposition is put forward, the

dialectician is compelled to demolish it: and then false propositions have to be formulated. Sometimes also

when a false proposition is put forward, it has to be demolished by means of false propositions: for it is

possible for a given man to believe what is not the fact more firmly than the truth. Accordingly, if the

argument be made to depend on something that he holds, it will be easier to persuade or help him. He,

however, who would rightly convert any one to a different opinion should do so in a dialectical and not in a

contentious manner, just as a geometrician should reason geometrically, whether his conclusion be false or

true: what kind of syllogisms are dialectical has already been said. The principle that a man who hinders the

common business is a bad partner, clearly applies to an argument as well; for in arguments as well there is a

common aim in view, except with mere contestants, for these cannot both reach the same goal; for more than

one cannot possibly win. It makes no difference whether he effects this as answerer or as questioner: for both

he who asks contentious questions is a bad dialectician, and also he who in answering fails to grant the

obvious answer or to understand the point of the questioner's inquiry. What has been said, then, makes it clear

that adverse criticism is not to be passed in a like strain upon the argument on its own merits, and upon the

questioner: for it may very well be that the argument is bad, but that the questioner has argued with the

answerer in the best possible way: for when men lose their tempers, it may perhaps be impossible to make

Inasmuch as it is indeterminate when people are claiming the admission of contrary things, and when they are

claiming what originally they set out to provefor often when they are talking by themselves they say

contrary things, and admit afterwards what they have previously denied; for which reason they often assent,

when questioned, to contrary things and to what originally had to be provedthe argument is sure to become

vitiated. The responsibility, however, for this rests with the answerer, because while refusing to grant other

points, he does grant points of that kind. It is, then, clear that adverse criticism is not to be passed in a like

(1) The first is when neither the proposed conclusion nor indeed any conclusion at all is drawn from the

questions asked, and when most, if not all, of the premisses on which the conclusion rests are false or

generally rejected, when, moreover, neither any withdrawals nor additions nor both together can bring the

(2) The second is, supposing the reasoning, though constructed from the premisses, and in the manner,

(3) The third is, supposing certain additions would bring an inference about but yet these additions were to be

weaker than those that were put as questions and less generally held than the conclusion.

(4) Again, supposing certain withdrawals could effect the same: for sometimes people secure more premisses

than are necessary, so that it is not through them that the inference comes about.

(5) Moreover, suppose the premisses be less generally held and less credible than the conclusion, or if,

One must not claim that the reasoning to a proposed view shall in every case equally be a view generally

accepted and convincing: for it is a direct result of the nature of things that some subjects of inquiry shall be

easier and some harder, so that if a man brings people to accept his point from opinions that are as generally

received as the case admits, he has argued his case correctly. Clearly, then, not even the argument itself is

open to the same adverse criticism when taken in relation to the proposed conclusion and when taken by

itself. For there is nothing to prevent the argument being open to reproach in itself, and yet commendable in

relation to the proposed conclusion, or again, vice versa, being commendable in itself, and yet open to

reproach in relation to the proposed conclusion, whenever there are many propositions both generally held

and also true whereby it could easily be proved. It is possible also that an argument, even though brought to a

conclusion, may sometimes be worse than one which is not so concluded, whenever the premisses of the

former are silly, while its conclusion is not so; whereas the latter, though requiring certain additions, requires

only such as are generally held and true, and moreover does not rest as an argument on these additions. With

those which bring about a true conclusion by means of false premisses, it is not fair to find fault: for a false

conclusion must of necessity always be reached from a false premiss, but a true conclusion may sometimes

Whenever by the argument stated something is demonstrated, but that something is other than what is wanted

and has no bearing whatever on the conclusion, then no inference as to the latter can be drawn from it: and if

there appears to be, it will be a sophism, not a proof. A philosopheme is a demonstrative inference: an

epichireme is a dialectical inference: a sophism is a contentious inference: an aporeme is an inference that

If something were to be shown from premisses, both of which are views generally accepted, but not accepted

with like conviction, it may very well be that the conclusion shown is something held more strongly than

either. If, on the other hand, general opinion be for the one and neither for nor against the other, or if it be for

the one and against the other, then, if the pro and con be alike in the case of the premisses, they will be alike

for the conclusion also: if, on the other hand, the one preponderates, the conclusion too will follow suit.

It is also a fault in reasoning when a man shows something through a long chain of steps, when he might

employ fewer steps and those already included in his argument: suppose him to be showing (e.g.) that one

opinion is more properly so called than another, and suppose him to make his postulates as follows:

'xinitself is more fully x than anything else': 'there genuinely exists an object of opinion in itself': therefore

'the objectofopinioninitself is more fully an object of opinion than the particular objects of opinion'.

Now 'a relative term is more fully itself when its correlate is more fully itself': and 'there exists a genuine

opinioninitself, which will be "opinion" in a more accurate sense than the particular opinions': and it has

been postulated both that 'a genuine opinioninitself exists', and that 'xinitself is more fully x than

anything else': therefore 'this will be opinion in a more accurate sense'. Wherein lies the viciousness of the

An argument is clear in one, and that the most ordinary, sense, if it be so brought to a conclusion as to make

no further questions necessary: in another sense, and this is the type most usually advanced, when the

propositions secured are such as compel the conclusion, and the argument is concluded through premisses

that are themselves conclusions: moreover, it is so also if some step is omitted that generally is firmly

An argument is called fallacious in four senses: (1) when it appears to be brought to a conclusion, and is not

really sowhat is called 'contentious' reasoning: (2) when it comes to a conclusion but not to the conclusion

proposedwhich happens principally in the case of reductiones ad impossibile: (3) when it comes to the

proposed conclusion but not according to the mode of inquiry appropriate to the case, as happens when a

nonmedical argument is taken to be a medical one, or one which is not geometrical for a geometrical

argument, or one which is not dialectical for dialectical, whether the result reached be true or false: (4) if the

conclusion be reached through false premisses: of this type the conclusion is sometimes false, sometimes

true: for while a false conclusion is always the result of false premisses, a true conclusion may be drawn even

Fallacy in argument is due to a mistake of the arguer rather than of the argument: yet it is not always the fault

of the arguer either, but only when he is not aware of it: for we often accept on its merits in preference to

many true ones an argument which demolishes some true proposition if it does so from premisses as far as

possible generally accepted. For an argument of that kind does demonstrate other things that are true: for one

of the premisses laid down ought never to be there at all, and this will then be demonstrated. If, however, a

true conclusion were to be reached through premisses that are false and utterly childish, the argument is

worse than many arguments that lead to a false conclusion, though an argument which leads to a false

conclusion may also be of this type. Clearly then the first thing to ask in regard to the argument in itself is,

'Has it a conclusion?'; the second, 'Is the conclusion true or false?'; the third, 'Of what kind of premisses does

it consist?': for if the latter, though false, be generally accepted, the argument is dialectical, whereas if,

though true, they be generally rejected, it is bad: if they be both false and also entirely contrary to general

opinion, clearly it is bad, either altogether or else in relation to the particular matter in hand.

Of the ways in which a questioner may beg the original question and also beg contraries the true account has

been given in the Analytics:' but an account on the level of general opinion must be given now.

People appear to beg their original question in five ways: the first and most obvious being if any one begs the

actual point requiring to be shown: this is easily detected when put in so many words; but it is more apt to

escape detection in the case of different terms, or a term and an expression, that mean the same thing. A

second way occurs whenever any one begs universally something which he has to demonstrate in a particular

case: suppose (e.g.) he were trying to prove that the knowledge of contraries is one and were to claim that the

knowledge of opposites in general is one: for then he is generally thought to be begging, along with a number

of other things, that which he ought to have shown by itself. A third way is if any one were to beg in

particular cases what he undertakes to show universally: e.g. if he undertook to show that the knowledge of

contraries is always one, and begged it of certain pairs of contraries: for he also is generally considered to be

begging independently and by itself what, together with a number of other things, he ought to have shown.

Again, a man begs the question if he begs his conclusion piecemeal: supposing e.g. that he had to show that

medicine is a science of what leads to health and to disease, and were to claim first the one, then the other; or,

fifthly, if he were to beg the one or the other of a pair of statements that necessarily involve one other; e.g. if

he had to show that the diagonal is incommensurable with the side, and were to beg that the side is

The ways in which people assume contraries are equal in number to those in which they beg their original

question. For it would happen, firstly, if any one were to beg an opposite affirmation and negation; secondly,

if he were to beg the contrary terms of an antithesis, e.g. that the same thing is good and evil; thirdly, suppose

any one were to claim something universally and then proceed to beg its contradictory in some particular

case, e.g. if having secured that the knowledge of contraries is one, he were to claim that the knowledge of

what makes for health or for disease is different; or, fourthly, suppose him, after postulating the latter view, to

try to secure universally the contradictory statement. Again, fifthly, suppose a man begs the contrary of the

conclusion which necessarily comes about through the premisses laid down; and this would happen suppose,

even without begging the opposites in so many words, he were to beg two premisses such that this

contradictory statement that is opposite to the first conclusion will follow from them. The securing of

contraries differs from begging the original question in this way: in the latter case the mistake lies in regard to

the conclusion; for it is by a glance at the conclusion that we tell that the original question has been begged:

whereas contrary views lie in the premisses, viz. in a certain relation which they bear to one another.

The best way to secure training and practice in arguments of this kind is in the first place to get into the habit

of converting the arguments. For in this way we shall be better equipped for dealing with the proposition

stated, and after a few attempts we shall know several arguments by heart. For by 'conversion' of an argument

is meant the taking the reverse of the conclusion together with the remaining propositions asked and so

demolishing one of those that were conceded: for it follows necessarily that if the conclusion be untrue, some

one of the premisses is demolished, seeing that, given all the premisses, the conclusion was bound to follow.

Always, in dealing with any proposition, be on the lookout for a line of argument both pro and con: and on

discovering it at once set about looking for the solution of it: for in this way you will soon find that you have

trained yourself at the same time in both asking questions and answering them. If we cannot find any one else

to argue with, we should argue with ourselves. Select, moreover, arguments relating to the same thesis and

range them side by side: for this produces a plentiful supply of arguments for carrying a point by sheer force,

and in refutation also it is of great service, whenever one is well stocked with arguments pro and con: for then

you find yourself on your guard against contrary statements to the one you wish to secure. Moreover, as

contributing to knowledge and to philosophic wisdom the power of discerning and holding in one view the

results of either of two hypotheses is no mean instrument; for it then only remains to make a right choice of

one of them. For a task of this kind a certain natural ability is required: in fact real natural ability just is the

power right to choose the true and shun the false. Men of natural ability can do this; for by a right liking or

It is best to know by heart arguments upon those questions which are of most frequent occurrence, and

particularly in regard to those propositions which are ultimate: for in discussing these answerers frequently

give up in despair. Moreover, get a good stock of definitions: and have those of familiar and primary ideas at

your fingers' ends: for it is through these that reasonings are effected. You should try, moreover, to master the

heads under which other arguments mostly tend to fall. For just as in geometry it is useful to be practised in

the elements, and in arithmetic to have the multiplication table up to ten at one's fingers' endsand indeed it

makes a great difference in one's knowledge of the multiples of other numbers toolikewise also in

arguments it is a great advantage to be well up in regard to first principles, and to have a thorough knowledge

of premisses at the tip of one's tongue. For just as in a person with a trained memory, a memory of things

themselves is immediately caused by the mere mention of their loci, so these habits too will make a man

readier in reasoning, because he has his premisses classified before his mind's eye, each under its number. It

is better to commit to memory a premiss of general application than an argument: for it is difficult to be even

Moreover, you should get into the habit of turning one argument into several, and conceal your procedure as

darkly as you can: this kind of effect is best produced by keeping as far as possible away from topics akin to

the subject of the argument. This can be done with arguments that are entirely universal, e.g. the statement

that 'there cannot be one knowledge of more than one thing': for that is the case with both relative terms and

Records of discussions should be made in a universal form, even though one has argued only some particular

case: for this will enable one to turn a single rule into several. A like rule applies in Rhetoric as well to

enthymemes. For yourself, however, you should as far as possible avoid universalizing your reasonings. You

should, moreover, always examine arguments to see whether they rest on principles of general application:

for all particular arguments really reason universally, as well, i.e. a particular demonstration always contains

a universal demonstration, because it is impossible to reason at all without using universals.

You should display your training in inductive reasoning against a young man, in deductive against an expert.

You should try, moreover, to secure from those skilled in deduction their premisses, from inductive reasoners

their parallel cases; for this is the thing in which they are respectively trained. In general, too, from your

exercises in argumentation you should try to carry away either a syllogism on some subject or a refutation or

a proposition or an objection, or whether some one put his question properly or improperly (whether it was

yourself or some one else) and the point which made it the one or the other. For this is what gives one ability,

and the whole object of training is to acquire ability, especially in regard to propositions and objections. For it

is the skilled propounder and objector who is, speaking generally, a dialectician. To formulate a proposition is

to form a number of things into onefor the conclusion to which the argument leads must be taken generally,

as a single thingwhereas to formulate an objection is to make one thing into many; for the objector either

distinguishes or demolishes, partly granting, partly denying the statements proposed.

Do not argue with every one, nor practise upon the man in the street: for there are some people with whom

any argument is bound to degenerate. For against any one who is ready to try all means in order to seem not

to be beaten, it is indeed fair to try all means of bringing about one's conclusion: but it is not good form.

Wherefore the best rule is, not lightly to engage with casual acquaintances, or bad argument is sure to result.

For you see how in practising together people cannot refrain from contentious argument.

It is best also to have readymade arguments relating to those questions in which a very small stock will

furnish us with arguments serviceable on a very large number of occasions. These are those that are universal,

and those in regard to which it is rather difficult to produce points for ourselves from matters of everyday