George Berkeley......................................................................................................................................1

THE ANALYST: A Discourse addressed to an Infidel Mathematician ..................................................1

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And

whether there be any need of considering quantities either infinitely great or infinitely small? ..........16

1. Though I am a stranger to your person, yet I am not, Sir, a stranger to the reputation you have acquired in

that branch of learning which hath been your peculiar study; nor to the authority that you therefore assume in

things foreign to your profession; nor to the abuse that you, and too many more of the like character, are

known to make use of such undue authority, to the misleading of unwary persons in matters of the highest

concernment, and whereof your mathematical knowledge can by no means qualify you to be a competent

judge. Equity indeed and good sense would incline one to disregard the judgment of men, in points which

they have not considered or examined. But several who make the loudest claim to those qualities do

nevertheless the very thing they would seem to despise, clothing themselves in the livery of other men's

opinions, and putting on a general deference for the judgment of you, Gentlemen, who are presumed to be of

all men the greatest masters of reason, to be most conversant about distinct ideas, and never to take things on

trust, but always clearly to see your way, as men whose constant employment is the deducing truth by the

justest inference from the most evident principles. With this bias on their minds, they submit to your

decisions where you have no right to decide. And that this is one short way of making Infidels, I am credibly

2. Whereas then it is supposed that you apprehend more distinctly, consider more closely, infer more justly,

and conclude more accurately than other men, and that you are therefore less religious because more

judicious, I shall claim the privilege of a Freethinker; and take the liberty to inquire into the object,

principles, and method of demonstration admitted by the mathematicians of the present age, with the same

freedom that you presume to treat the principles and mysteries of Religion; to the end that all men may see

what right you have to lead, or what encouragement others have to follow you. It hath been an old remark,

that Geometry is an excellent Logic. And it must be owned that when the definitions are clear; when the

postulata cannot be refused, nor the axioms denied; when from the distinct contemplation and comparison of

figures, their properties are derived, by a perpetual wellconnected chain of consequences, the objects being

still kept in view, and the attention ever fixed upon them; there is acquired a habit of reasoning, close and

exact and methodical: which habit strengthens and sharpens the mind, and being transferred to other subjects

is of general use in the inquiry after truth. But how far this is the case of our geometrical analysts, it may be

3. The method of Fluxions is the general key by help whereof the modern mathematicians unlock the secrets

of Geometry, and consequently of Nature. And, as it is that which hath enabled them so remarkably to outgo

the ancients in discovering theorems and solving problems, the exercise and application thereof is become the

main if not sole employment of all those who in this age pass for profound geometers. But whether this

method be clear or obscure, consistent or repugnant, demonstrative or precarious, as I shall inquire with the

utmost impartiality, so I submit my inquiry to your own judgment, and that of every candid reader. Lines are

supposed to be generated [`Introd. ad Quadraturam Curvarum.'] by the motion of points, planes by the motion

of lines, and solids by the motion of planes. And whereas quantities generated in equal times are greater or

lesser according to the greater or lesser velocity wherewith they increase and are generated, a method hath

been found to determine quantities from the velocities of their generating motions. And such velocities are

called fluxions: and the quantities generated are called flowing quantities. These fluxions are said to be nearly

as the increments of the flowing quantities, generated in the least equal particles of time; and to be accurately

in the first proportion of the nascent, or in the last of the evanescent increments. Sometimes, instead of

velocities, the momentaneous increments or decrements of undetermined flowing quantities are considered,

4. By moments we are not to understand finite particles. These are said not to be moments, but quantities

generated from moments, which last are only the nascent principles of finite quantities. It is said that the

minutest errors are not to be neglected in mathematics: that the fluxions are celerities, not proportional to the

finite increments, though ever so small; but only to the moments or nascent increments, whereof the

proportion alone, and not the magnitude, is considered. And of the aforesaid fluxions there be other fluxions,

which fluxions of fluxions are called second fluxions. And the fluxions of these second fluxions are called

third fluxions: and so on, fourth, fifth, sixth, ad infinitum. Now, as our Sense is strained and puzzled with the

perception of objects extremely minute, even so the Imagination, which faculty derives from sense, is very

much strained and puzzled to frame clear ideas of the least particles of time, or the least increments generated

therein: and much more so to comprehend the moments, or those increments of the flowing quantities in statu

nascenti, in their very first origin or beginning to exist, before they become finite particles. And it seems still

more difficult to conceive the abstracted velocities of such nascent imperfect entities. But the velocities of the

velocities, the second, third, fourth, and fifth velocities, exceed, if I mistake not, all human understanding.

The further the mind analyseth and pursueth these fugitive ideas the more it is lost and bewildered; the

objects, at first fleeting and minute, soon vanishing out of sight. Certainly, in any sense, a second or third

fluxion seems an obscure Mystery. The incipient celerity of an incipient celerity, the nascent augment of a

nascent augment, i.e. of a thing which hath no magnitude: take it in what light you please, the clear

conception of it will, if I mistake not, be found impossible; whether it be so or no I appeal to the trial of every

thinking reader. And if a second fluxion be inconceivable, what are we to think of third, fourth, fifth fluxions,

5. The foreign mathematicians are supposed by some, even of our own, to proceed in a manner less accurate,

perhaps, and geometrical, yet more intelligible. Instead of flowing quantities and their fluxions, they consider

the variable finite quantities as increasing or diminishing by the continual addition or subduction of infinitely

small quantities. Instead of the velocities wherewith increments are generated, they consider the increments

or decrements themselves, which they call differences, and which are supposed to be infinitely small. The

difference of a line is an infinitely little line: of a plane an infinitely little plane. They suppose finite

quantities to consist of parts infinitely little, and curves to be polygons, whereof the sides are infinitely little,

which by the angles they make one with another determine the curvity of the line. Now to conceive a quantity

infinitely small, that is, infinitely less than any sensible or imaginable quantity, or any the least finite

magnitude, is, I confess, above my capacity. But to conceive a part of such infinitely small quantity that shall

be still infinitely less than it, and consequently though multiplied infinitely shall never equal the minutest

finite quantity, is, I suspect, an infinite difficulty to any man whatsoever; and will be allowed such by those

who candidly say what they think; provided they really think and reflect, and do not take things upon trust.

6. And yet in the calculus differentialis, which method serves to all the same intents and ends with that of

fluxions, our modern analysts are not content to consider only the differences of finite quantities: they also

consider the differences of those differences, and the differences of the differences of the first differences:

and so on ad infinitum. That is, they consider quantities infinitely less than the least discernible quantity; and

others infinitely less than those infinitely small ones; and still others infinitely less than the preceding

infinitesimals, and so on without end or limit. Insomuch that we are to admit an infinite succession of

infinitesimals, each infinitely less than the foregoing, and infinitely greater than the following. As there are

first, second, third, fourth, fifth fluxions, so there are differences, first, second, third fourth, in an infinite

progression towards nothing, which you still approach and never arrive at. And (which is most strange)

although you should take a million of millions of these infinitesimals, each whereof is supposed infinitely

greater than some other real magnitude, and add them to the least given quantity, it shall never be the bigger.

For this is one of the modest postulata of our modern mathematicians, and is a cornerstone or groundwork

7. All these points, I say, are supposed and believed by certain rigorous exactors of evidence in religion, men

who pretend to believe no further than they can see. That men who have been conversant only about clear

points should with difficulty admit obscure ones might not seem altogether unaccountable. But he who can

digest a second or third fluxion, a second or third difference, need not, methinks, be squeamish about any

point in Divinity. There is a natural presumption that men's faculties are made alike. It is on this supposition

that they attempt to argue and convince one another. What therefore shall appear evidently impossible and

repugnant to one may be presumed the same to another. But with what appearance of reason shall any man

presume to say that mysteries may not be objects of faith, at the same time that he himself admits such

8. It must indeed be acknowledged the modern mathematicians do not consider these points as mysteries, but

as clearly conceived and mastered by their comprehensive minds. They scruple not to say that by the help of

these new analytics they can penetrate into infinity itself: that they can even extend their views beyond

infinity: that their art comprehends not only infinite, but infinite of infinite (as they express it), or an infinity

of infinites. But, notwithstanding all these assertions and pretensions, it may be justly questioned whether, as

other men in other inquiries are often deceived by words or terms, so they likewise are not wonderfully

deceived and deluded by their own peculiar signs, symbols or species. Nothing is easier than to devise

expressions or notations for fluxions and infinitesimals of the first, second, third, fourth, and subsequent

orders, proceeding in the same regular form without end or limit , , , or dx, ddx, dddx, ddddx These

expressions, indeed, are clear and distinct, and the mind finds no difficulty in conceiving them to be

continued beyond any assignable bounds. But if we remove the veil and look underneath, if, laying aside the

expressions, we set ourselves attentively to consider the things themselves which are supposed to be

expressed or marked thereby, we shall discover much emptiness, darkness, and confusion; nay, if I mistake

not, direct impossibilities and contradictions. Whether this be the case or no, every thinking reader is

9. Having considered the object, I proceed to consider the principles of this new analysis by momentums,

fluxions, or infinitesimals; wherein if it shall appear that your capital points, upon which the rest are

supposed to depend, include error and false reasoning; it will then follow that you, who are at a loss to

conduct yourselves, cannot with any decency set up for guides to other men. The main point in the method of

fluxions is to obtain the fluxion or momentum of the rectangle or product of two indeterminate quantities.

Inasmuch as from thence are derived rules for obtaining the fluxions of all other products and powers; be the

coefficients or the indexes what they will, integers or fractions, rational or surd. Now, this fundamental point

one would think should be very clearly made out, considering how much is built upon it, and that its

influence extends throughout the whole analysis. But let the reader judge. This is given for demonstration.

[`Naturalis Philosophiae Principia Mathematica,' lib. ii., lem. 2.] Suppose the product or rectangle AB

increased by continual motion: and that the momentaneous increments of the sides A and B are a and b.

When the sides A and B were deficient, or lesser by one half of their moments, the rectangle was

, i.e., . And as soon as the sides A and B are increased by the other two halves of their moments, the rectangle

becomes or . From the latter rectangle subduct the former, and the remaining difference will be aB + bA.

Therefore the increment of the rectangle generated by the entire increments a and b is aB + bA. Q.E.D. But it

is plain that the direct and true method to obtain the moment or increment of the rectangle AB, is to take the

sides as increased by their whole increments, and so multiply them together, A + a by B + b, the product

whereof AB + aB + bA + ab is the augmented rectangle; whence, if we subduct AB the remainder aB + bA +

ab will be the true increment of the rectangle, exceeding that which was obtained by the former illegitimate

and indirect method by the quantity ab. And this holds universally be the quantities a and b what they will,

big or little, finite or infinitesimal, increments, moments, or velocities. Nor will it avail to say that ab is a

quantity exceeding small: since we are told that in rebus mathematicis errores quam minimi non sunt

10. Such [`Introd. ad Quadraturam Curvarum.'] reasoning as this for demonstration, nothing but the obscurity

of the subject could have encouraged or induced the great author of the fluxionary method to put upon his

followers, and nothing but an implicit deference to authority could move them to admit. The case indeed is

difficult. There can be nothing done till you have got rid of the quantity ab. In order to this the notion of

fluxions is shifted: it is placed in various lights: points which should be as clear as first principles are

puzzled; and terms which should be steadily used are ambiguous. But, notwithstanding all this address and

skill, the point of getting rid of ab cannot be obtained by legitimate reasoning. If a man, by methods not

geometrical or demonstrative, shall have satisfied himself of the usefulness of certain rules; which he

afterwards shall propose to his disciples for undoubted truths; which he undertakes to demonstrate in a subtile

manner, and by the help of nice and intricate notions; it is not hard to conceive that such his disciples may, to

save themselves the trouble of thinking, be inclined to confound the usefulness of a rule with the certainty of

a truth, and accept the one for the other; especially if they are men accustomed rather to compute than to

think; earnest rather to go on fast and far, than solicitous to set out warily and see their way distinctly.

11. The points or mere limits of nascent lines are undoubtedly equal, as having no more magnitude one than

another, a limit as such being no quantity. If by a momentum you mean more than the very initial limit, it

must be either a finite quantity or an infinitesimal. But all finite quantities are expressly excluded from the

notion of a momentum. Therefore the momentum must be an infinitesimal. And, indeed, though much artifice

hath been employed to escape or avoid the admission of quantities infinitely small, yet it seems ineffectual.

For aught I see, you can admit no quantity as a medium between a finite quantity and nothing, without

admitting infinitesimals. An increment generated in a finite particle of time is itself a finite particle; and

cannot therefore be a momentum. You must therefore take an infinitesimal part of time wherein to generate

your momentum. It is said, the magnitude of moments is not considered; and yet these same moments are

supposed to be divided into parts. This is not easy to conceive, no more than it is why we should take

quantities less than A and B in order to obtain the increment of AB, of which proceeding it must be owned

the final cause or motive is obvious; but it is not so obvious or easy to explain a just and legitimate reason for

12. From the foregoing principle, so demonstrated, the general rule for finding the fluxion of any power of a

flowing quantity is derived. [`Philosophiae Naturalis Principia Mathematica,' lib. ii., lem. 2.] But, as there

seems to have been some inward scruple or consciousness of defect in the foregoing demonstration, and as

this finding the fluxion of a given power is a point of primary importance, it hath therefore been judged

proper to demonstrate the same in a different manner, independent of the foregoing demonstration. But

whether this other method be more legitimate and conclusive than the former, I proceed now to examine; and

in order thereto shall premise the following lemma: `If, with a view to demonstrate any proposition, a

certain point is supposed, by virtue of which certain other points are attained; and such supposed point be

itself afterwards destroyed or rejected by a contrary supposition; in that case, all the other points attained

thereby, and consequent thereupon, must also be destroyed and rejected, so as from thenceforward to be no

more supposed or applied in the demonstration.' This is so plain as to need no proof.

13. Now, the other method of obtaining a rule to find the fluxion of any power is as follows. Let the quantity

x flow uniformly, and be it proposed to find the fluxion of . In the same time that x by flowing becomes x +

and the increments are to one another as Let now the increments vanish, and their last proportion will be 1 to .

But it should seem that this reasoning is not fair or conclusive. For when it is said, let the increments vanish,

i.e. let the increments be nothing, or let there be no increments, the former supposition that the increments

were something, or that there were increments, is destroyed, and yet a consequence of that supposition, i.e. an

expression got by virtue thereof, is retained. Which, by the foregoing lemma, is a false way of reasoning.

Certainly when we suppose the increments to vanish, we must suppose their proportions, their expressions,

and everything else derived from the supposition of their existence to vanish with them.

14. To make this point plainer, I shall unfold the reasoning, and propose it in a fuller light to your view. It

amounts therefore to this, or may in other words be thus expressed. I suppose that the quantity x flows, and

by flowing is increased, and its increment I call o, so that by flowing it becomes x + o. And as x increaseth, it

follows that every power of x is likewise increased in a due proportion. Therefore as x becomes x + o, will

And if from the two augmented quantities we subduct the root and the power respectively, we shall have

remaining the two increments, to wit, which increments, being both divided by the common divisor o, yield

the quotients which are therefore exponents of the ratio of the increments. Hitherto I have supposed that x

flows, that x hath a real increment, that o is something. And I have proceeded all along on that supposition,

without which I should not have been able to have made so much as one single step. From that supposition it

is that I get at the increment of , that I am able to compare it with the increment of x, and that I find the

proportion between the two increments. I now beg leave to make a new supposition contrary to the first, i.e. I

will suppose that there is no increment of x, or that o is nothing; which second supposition destroys my first,

and is inconsistent with it, and therefore with everything that supposeth it. I do nevertheless beg leave to

retain , which is an expression obtained in virtue of my first supposition, which necessarily presupposed such

supposition, and which could not be obtained without it. All which seems a most inconsistent way of arguing,

15. Nothing is plainer than that no just conclusion can be directly drawn from two inconsistent suppositions.

You may indeed suppose anything possible; but afterwards you may not suppose anything that destroys what

you first supposed: or, if you do, you must begin de novo. If therefore you suppose that the augments vanish,

i.e. that there are no augments, you are to begin again and see what follows from such supposition. But

nothing will follow to your purpose. You cannot by that means ever arrive at your conclusion, or succeed in

what is called by the celebrated author, the investigation of the first or last proportions of nascent and

evanescent quantities, by instituting the analysis in finite ones. I repeat it again: you are at liberty to make any

possible supposition: and you may destroy one supposition by another: but then you may not retain the

consequences, or any part of the consequences, of your first supposition so destroyed. I admit that signs may

be made to denote either anything or nothing: and consequently that in the original notation x + o, o might

have signified either an increment or nothing. But then, which of these soever you make it signify, you must

argue consistently with such its signification, and not proceed upon a double meaning: which to do were a

manifest sophism. Whether you argue in symbols or in words the rules of right reason are still the same. Nor

can it be supposed you will plead a privilege in mathematics to be exempt from them.

16. If you assume at first a quantity increased by nothing, and in the expression x + o, o stands for nothing,

upon this supposition, as there is no increment of the root, so there will be no increment of the power; and

consequently there will be none except the first of all those members of the series constituting the power of

the binomial; you will therefore never come at your expression of a fluxion legitimately by such method.

Hence you are driven into the fallacious way of proceeding to a certain point on the supposition of an

increment, and then at once shifting your supposition to that of no increment. There may seem great skill in

doing this at a certain point or period. Since, if this second supposition had been made before the common

division by o, all had vanished at once, and you must have got nothing by your supposition. Whereas, by this

artifice of first dividing and then changing your supposition, you retain 1 and . But, notwithstanding all this

address to cover it, the fallacy is still the same. For, whether it be done sooner or later, when once the second

supposition or assumption is made, in the same instant the former assumption and all that you got by it is

destroyed, and goes out together. And this is universally true, be the subject what it will, throughout all the

branches of human knowledge; in any other of which, I believe, men would hardly admit such a reasoning as

17. It may not be amiss to observe that the method for finding the fluxion of a rectangle of two flowing

quantities, as it is set forth in the Treatise of Quadratures, differs from the abovementioned taken from the

second book of the Principles, and is in effect the same with that used in the calculus differentialis. [`Analyse

des Infiniment Petits,' Part I., prop. 2.] For the supposing a quantity infinitely diminished, and therefore

rejecting it, is in effect the rejecting an infinitesimal; and indeed it requires a marvellous sharpness of

discernment to be able to distinguish between evanescent increments and infinitesimal differences. It may

perhaps be said that the quantity being infinitely diminished becomes nothing, and so nothing is rejected. But,

according to the received principles, it is evident that no geometrical quantity can by any division or

subdivision whatsoever be exhausted, or reduced to nothing. Considering the various arts and devices used by

the great author of the fluxionary method; in how many lights he placeth his fluxions; and in what different

ways he attempts to demonstrate the same point; one would be inclined to think, he was himself suspicious of

the justness of his own demonstrations, and that he was not enough pleased with any notion steadily to adhere

to it. Thus much at least is plain, that he owned himself satisfied concerning certain points which nevertheless

he would not undertake to demonstrate to others. [See `Letter to John Collins,' Nov. 8, 1676.] Whether this

satisfaction arose from tentative methods or inductions, which have often been admitted by mathematicians

(for instance, by Dr. Wallis, in his Arithmetic of Infinites), is what I shall not pretend to determine. But,

whatever the case might have been with respect to the author, it appears that his followers have shown

themselves more eager in applying his method, than accurate in examining his principles.

18. It is curious to observe what subtlety and skill this great genius employs to struggle with an insuperable

difficulty; and through what labyrinths he endeavours to escape the doctrine of infinitesimals; which as it

intrudes upon him whether he will or no, so it is admitted and embraced by others without the least

repugnance; Leibnitz and his followers in their calculus differentialis making no manner of scruple, first to

suppose, and secondly to reject, quantities infinitely small; with what clearness in the apprehension and

justness in the reasoning, any thinking man, who is not prejudiced in favour of those things, may easily

discern. The notion or idea of an infinitesimal quantity, as it is an object simply apprehended by the mind,

hath already been considered. [Sect. 5 and 6.] I shall now only observe as to the method of getting rid of such

quantities, that it is done without the least ceremony. As in fluxions the point of first importance, and which

paves the way to the rest, is to find the fluxion of a product of two indeterminate quantities, so in the calculus

differentialis (which method is supposed to have been borrowed from the former with some small alterations)

the main point is to obtain the difference of such product. Now the rule for this is got by rejecting the product

or rectangle of the differences. And in general it is supposed that no quantity is bigger or lesser for the

addition or subduction of its infinitesimal: and that consequently no error can arise from such rejection of

19. And yet it should seem that, whatever errors are admitted in the premises, proportional errors ought to be

apprehended in the conclusion, be they finite or infinitesimal: and that therefore the of geometry requires

nothing should be neglected or rejected. In answer to this you will perhaps say, that the conclusions are

accurately true, and that therefore the principles and methods from whence they are derived must be so too.

But this inverted way of demonstrating your principles by your conclusions, as it would be peculiar to you

gentlemen, so it is contrary to the rules of logic. The truth of the conclusion will not prove either the form or

the matter of a syllogism to be true; inasmuch as the illation might have been wrong or the premises false,

and the conclusion nevertheless true, though not in virtue of such illation or of such premises. I say that in

every other science men prove their conclusions by their principles, and not their principles by the

conclusions. But if in yours you should allow yourselves this unnatural way of proceeding, the consequence

would be that you must take up with Induction, and bid adieu to Demonstration. And if you submit to this,

20. I have no controversy about your conclusions, but only about your logic and method: how you

demonstrate? what objects you are conversant with, and whether you conceive them clearly? what principles

you proceed upon; how sound they may be; and how you apply them? It must be remembered that I am not

concerned about the truth of your theorems, but only about the way of coming at them; whether it be

legitimate or illegitimate, clear or obscure, scientific or tentative. To prevent all possibility of your mistaking

me, I beg leave to repeat and insist, that I consider the geometrical analyst as a logician, i.e. so far forth as he

reasons and argues; and his mathematical conclusions, not in themselves, but in their premises; not as true or

false, useful or insignificant, but as derived from such principles, and by such inferences. And, forasmuch as

it may perhaps seem an unaccountable paradox that mathematicians should deduce true propositions from

false principles, be right in the conclusion and yet err in the premises; I shall endeavour particularly to

explain why this may come to pass, and show how error may bring forth truth, though it cannot bring forth

21. In order therefore to clear up this point, we will suppose for instance that a tangent is to be drawn to a

parabola, and examine the progress of this affair as it is performed by infinitesimal differences.

Let AB be a curve, the abscissa AP = x, the ordinate PB = y, the difference of the abscissa PM = dx, the

difference of the ordinate RN = dy. Now, by supposing the curve to be a polygon, and consequently BN, the

increment or difference of the curve to be a straight line coincident with the tangent, and the differential

triangle BRN to be similar to the triangle TPB, the subtangent PT is found a fourth proportional to RN : RB :

PB: that is, to dy : dx : y. Hence the subtangent will be But herein there is an error arising from the

aforementioned false supposition, whence the value of PT comes out greater than the truth: for in reality it is

not the triangle RNB but RLB which is similar to PBT, and therefore (instead of RN) RL should have been

the first term of the proportion, i.e. RN + NL, i.e. dy + z: whence the true expression for the subtangent

should have been There was therefore an error of defect in making dy the divisor; which error was equal to z,

i.e. NL the line comprehended between the curve and the tangent. Now by the nature of the curve yy = px,

supposing p to be the parameter, whence by the rule of differences 2y dy = p dx and But if you multiply y +

dy by itself, and retain the whole product without rejecting the square of the difference, it will then come out,

by substituting the augmented quantities in the equation of the curve, that truly. There was therefore an error

of excess in making which followed from the erroneous rule of differences. And the measure of this second

error is Therefore the two errors being equal and contrary destroy each other; the first error of defect being

22. If you had committed only one error, you would not have come at a true solution of the problem. But by

virtue of a twofold mistake you arrive, though not at science, yet at truth. For science it cannot be called,

when you proceed blindfold, and arrive at the truth not knowing how or by what means. To demonstrate that

let BR or dx be m and RN or dy be n. By the thirtythird proposition of the first book of the Conics of

Apollonius, and from similar triangles, as 2x to y so is m to Likewise from the nature of the parabola yy +

2yn + nn = xp + mp, and 2yn + nn = mp: wherefore and because yy = px, will be equal to x. Therefore

substituting these values instead of m and x we shall have i.e. which being reduced gives

23. Now, I observe, in the first place, that the conclusion comes out right, not because the rejected square of

dy was infinitely small, but because this error was compensated by another contrary and equal error. I

observe, in the second place, that whatever is rejected, be it every so small, if it be real, and consequently

makes a real error in the premises, it will produce a proportional real error in the conclusion. Your theorems

therefore cannot be accurately true, nor your problems accurately solved, in virtue of premises which

themselves are not accurate; it being a rule in logic that conclusio sequitur partem debiliorem. Therefore, I

observe, in the third place, that when the conclusion is evident and the premises obscure, or the conclusion

accurate and the premises inaccurate, we may safely pronounce that such conclusion is neither evident nor

accurate, in virtue of those obscure inaccurate premises or principles; but in virtue of some other principles,

which perhaps the demonstrator himself never knew or thought of. I observe, in the last place, that in case the

differences are supposed finite quantities ever so great, the conclusion will nevertheless come out the same:

inasmuch as the rejected quantities are legitimately thrown out, not for their smallness, but for another reason,

to wit, because of contrary errors, which, destroying each other, do, upon the whole, cause that nothing is

really, though something is, apparently, thrown out. And this reason holds equally with respect to quantities

finite as well as infinitesimal, great as well as small, a foot or a yard long as well as the minutest increment.

24. For the fuller illustration of this point, I shall consider it in another light, and proceeding in finite

Suppose the straight line MQ cuts the curve AT in the points R and S. Suppose LR a tangent at the point R,

AN the abscissa, NR and OS ordinates. Let AN be produced to O, and RP be drawn parallel to NO. Suppose

AN = x, NR = y, NO = v, PS = z, the subsecant MN = s. Let the equation y = xx express the nature of the

curve: and supposing y and x increased by their finite increments we get y + z = xx + 2xv + vv; whence the

former equation being subducted, there remains z = 2xv + vv. And by reason of similar triangles wherein if

for y and z we substitute their values, we get And supposing NO to be infinitely diminished, the subsecant

NM will in that case coincide with the subtangent NL, and v as an infinitesimal may be rejected, whence it

follows that which is the true value of the subtangent. And, since this was obtained by one only error, i.e. by

once ejecting one only infinitesimal, it should seem, contrary to what hath been said, that an infinitesimal

quantity or difference may be neglected or thrown away, and the conclusion nevertheless be accurately true,

although there was no double mistake or rectifying of one error by another, as in the first case. But, if this

point be thoroughly considered, we shall find there is even here a double mistake, and that one compensates

or rectifies the other. For, in the first place, it was supposed that when NO is infinitely diminished or becomes

an infinitesimal then the subsecant NM becomes equal to the subtangent NL. But this is a plain mistake; for it

is evident that as a secant cannot be a tangent, so a subsecant cannot be a subtangent. Be the difference ever

so small, yet still there is a difference. And, if NO be infinitely small, there will even then be an infinitely

small difference between NM and NL. Therefore NM or s was too little for your supposition (when you

supposed it equal to NL); and this error was compensated by a second error in throwing out v, which last

error made s bigger than its true value, and in lieu thereof gave the value of the subtangent. This is the true

state of the case, however it may be disguised. And to this in reality it amounts, and is at bottom the same

thing, if we should pretend to find the subtangent by having first found, from the equation of the curve and

similar triangles, a general expression for all subsecants, and then reducing the subtangent under this general

25. Upon the whole I observe, First, that v can never be nothing, so long as there is a secant. Secondly, that

the same line cannot be both tangent and secant. Thirdly, that when v and NO [See the foregoing figure]

vanisheth, PS and SR do also vanish, and with them the proportionality of the similar triangles. Consequently

the whole expression, which was obtained by means thereof and grounded thereupon, vanisheth when v

vanisheth. Fourthly, that the method for finding secants or the expression of secants, be it ever so general,

cannot in common sense extend any farther than to all secants whatsoever: and, as it necessarily supposed

similar triangles, it cannot be supposed to take place where there are not similar triangles. Fifthly, that the

subsecant will always be less than the subtangent, and can never coincide with it; which coincidence to

suppose would be absurd; for it would be supposing the same line at the same time to cut and not to cut

another given line; which is a manifest contradiction, such as subverts the hypothesis and gives a

demonstration of its falsehood. Sixthly, if this be not admitted, I demand a reason why any other apagogical

demonstration, or demonstration ad absurdum should be admitted in geometry rather than this: or that some

real difference be assigned between this and others as such. Seventhly, I observe that it is sophistical to

suppose NO or RP, PS, and SR to be finite real lines in order to form the triangle, RPS, in order to obtain

proportions by similar triangles; and afterwards to suppose there are no such lines, nor consequently similar

triangles, and nevertheless to retain the consequence of the first supposition, after such supposition hath been

destroyed by a contrary one. Eighthly, that although, in the present case, by inconsistent suppositions truth

may be obtained, yet such truth is not demonstrated: that such method is not conformable to the rules of logic

and right reason: that, however useful it may be, it must be considered only as a presumption, as a knack, an

26. The doctrine premised may be further illustrated by the following simple and easy case, wherein I shall

Suppose AB = x, BC = y, BD = o, and that xx is equal to the area ABC: it is proposed to find the ordinate y

or BC. When x by flowing becomes x + o, then xx becomes xx + 2xo + oo: and the area ABC becomes ADH,

and the increment of xx will be equal to BDHC, the increment of the area, i.e. to BCFD + CFH. And if we

suppose the curvilinear space CFH to be qoo, then 2xo + oo = yo = qoo, which divided by o give 2x + o = y +

qo. And, supposing o to vanish, 2x = y, in which case ACH will be a straight line, and the areas ABC, CFH

triangles. Now with regard to this reasoning, it hath been already remarked, [Sect. 12 and 13 supra.] that it is

not legitimate or logical to suppose o to vanish, i.e. to be nothing, i.e. that there is no increment, unless we

reject at the same time with the increment itself every consequence of such increment, i.e. whatsoever could

not be obtained by supposing such increment. It must nevertheless be acknowledged that the problem is

rightly solved, and the conclusion true, to which we are led by this method. It will therefore be asked, how

comes it to pass that the throwing out o is attended with no error in the conclusion? I answer, the true reason

hereof is plainly this: because q being unit, qo is equal to o: and therefore 2x + o qo = y = 2x, the equal

27. As, on the one hand, it were absurd to get rid of o by saying, Let me contradict myself; let me subvert my

own hypothesis; let me take it for granted that there is no increment, at the same time that I retain a quantity

which I could never have got at but by assuming an increment: so, on the other hand, it would be equally

wrong to imagine that in a geometrical demonstration we may be allowed to admit any error, though ever so

small, or that it is possible, in the nature of things, an accurate conclusion should be derived from inaccurate

principles. Therefore o cannot be thrown out as an infinitesimal, or upon the principle that infinitesimals may

be safely neglected; but only because it is destroyed by an equal quantity with a negative sign, whence o po

is equal to nothing. And as it is illegitimate to reduce an equation, by subducting from one side a quantity

when it is not to be destroyed, or when an equal quantity is not subducted from the other side of the equation:

so it must be allowed a very logical and just method of arguing to conclude that if from equals either nothing

or equal quantities are subducted they shall still remain equal. And this is a true reason why no error is at last

produced by the rejecting of o. Which therefore must not be ascribed to the doctrine of differences, or

28. Suppose the case to be general, and that is equal to the area ABC whence by the method of fluxions the

ordinate is found , which we admit for true, and shall inquire how it is arrived at. Now if we are content to

come at the conclusion in a summary way, by supposing that the ratio of the fluxions of x and is found [Sect.

13.] to be 1 and , and that the ordinate of the area is considered as its fluxion, we shall not so clearly see our

way, or perceive how the truth comes out, that method as we have shewed before being obscure and illogical.

But if we fairly delineate the area and its increment, and divide the latter into two parts BCFD and CFH, [See

the figure in sect. 26.] and proceed regularly by equations between the algebraical and geometrical quantities,

the reason of the thing will plainly appear. For as is equal to the area ABC, so is the increment of equal to the

And only the first members on each side of the equation being retained, = BDFC: and dividing both sides by

o or BD, we shall get = BC. Admitting therefore that the curvilinear space CFH is equal to the rejectaneous

quantity and that when this is rejected on one side, that is rejected on the other, the reasoning becomes just

and the conclusion true. And it is all one whatever magnitude you allow to BD, whether that of an

infinitesimal difference or a finite increment ever so great. It is therefore plain that the supposing the

rejectaneous algebraical quantity to be an infinitely small or evanescent quantity, and therefore to be

neglected, must have produced an error, had it not been for the curvilinear spaces being equal thereto, and at

the same time subducted from the other part or side of the equation, agreeably to the axiom, If from equals

you subduct equals, the remainders will be equal. For those quantities which by the analysts are said to be

neglected, or made to vanish, are in reality subducted. If therefore the conclusion be true, it is absolutely

necessary that the finite space CFH be equal to the remainder of the increment expressed by equal, I say, to

29. Therefore, be the power what you please, there will arise on one side an algebraical expression, on the

other a geometrical quantity, each of which naturally divides itself into three members. The algebraical or

fluxionary expression, into one which includes neither the expression of the increment of the abscissa nor of

any power thereof; another which includes the expression of the increment itself; and the third including the

expression of the powers of the increment. The geometrical quantity also or whole increased area consists of

three parts or members, the first of which is the given area; the second a rectangle under the ordinate and the

increment of the abscissa; the third a curvilinear space. And, comparing the homologous or correspondent

members on both sides, we find that as the first member of the expression is the expression of the given area,

so the second member of the expression will express the rectangle or second member of the geometrical

quantity, and the third, containing the powers of the increment, will express the curvilinear space, or third

member of the geometrical quantity. This hint may perhaps be further extended, and applied to good purpose,

by those who have leisure and curiosity for such matters. The use I make of it is to shew, that the analysis

cannot obtain in augments or differences, but it must also obtain in finite quantities, be they ever so great, as

30. It seems therefore, upon the whole, that we may safely pronounce the conclusion cannot be right, if in

order thereto any quantity be made to vanish, or be neglected, except that either one error is redressed by

another; or that, secondly, on the same side of an equation equal quantities are destroyed by contrary signs, so

that the quantity we mean to reject is first annihilated; or, lastly, that from opposite sides equal quantities are

subducted. And therefore to get rid of quantities by the received principles of fluxions or of differences is

neither good geometry nor good logic. When the augments vanish, the velocities also vanish. The velocities

or fluxions are said to be primo and ultimo, as the augments nascent and evanescent. Take therefore the ratio

of the evanescent quantities, it is the same with that of the fluxions. It will therefore answer all intents as well.

Why then are fluxions introduced? Is it not to shun or rather to palliate the use of quantities infinitely small?

But we have no notion whereby to conceive and measure various degrees of velocity besides space and time;

or, when the times are given, besides space alone. We have even no notion of velocity prescinded from time

and space. When therefore a point is supposed to move in given times, we have no notion of greater or lesser

velocities, or of proportions between velocities, but only of longer and shorter lines, and of proportions

31. A point may be the limit of a line: a line may be the limit of a surface: a moment may terminate time. But

how can we conceive a velocity by the help of such limits? It necessarily implies both time and space, and

cannot be conceived without them. And if the velocities of nascent and evanescent quantities, i.e. abstracted

from time and space, may not be comprehended, how can we comprehend and demonstrate their proportions;

or consider their rationes primae and ultimae? For, to consider the proportion or ratio of things implies that

such things have magnitude; that such their magnitudes may be measured, and their relations to each other

known. But, as there is no measure of velocity except time and space, the proportion of velocities being only

compounded of the direct proportion of the spaces, and the reciprocal proportion of the times; doth it not

follow that to talk of investigating, obtaining, and considering the proportions of velocities, exclusively of

32. But you will say that, in the use and application of fluxions, men do not overstrain their faculties to a

precise conception of the abovementioned velocities, increments, infinitesimals, or any other suchlike

ideas of a nature so nice, subtile, and evanescent. And therefore you will perhaps maintain that problems may

be solved without those inconceivable suppositions; and that, consequently, the doctrine of fluxions, as to the

practical part, stands clear of all such difficulties. I answer that if in the use or application of this method

those difficult and obscure points are not attended to, they are nevertheless supposed. They are the

foundations on which the moderns build, the principles on which they proceed, in solving problems and

discovering theorems. It is with the method of fluxions as with all other methods, which presuppose their

respective principles and are grounded thereon; although the rules may be practised by men who neither

attend to, nor perhaps know the principles. In like manner, therefore, as a sailor may practically apply certain

rules derived from astronomy and geometry, the principles whereof he doth not understand; and as any

ordinary man may solve divers numerical questions, by the vulgar rules and operations of arithmetic, which

he performs and applies without knowing the reasons of them: even so it cannot be denied that you may apply

the rules of the fluxionary method: you may compare and reduce particular cases to general forms: you may

operate and compute and solve problems thereby, not only without an actual attention to, or an actual

knowledge of, the grounds of that method, and the principles whereon it depends, and whence it is deduced,

33. But then it must be remembered that in such case, although you may pass for an artist, computist, or

analyst, yet you may not be justly esteemed a man of science and demonstration. Nor should any man, in

virtue of being conversant in such obscure analytics, imagine his rational faculties to be more improved than

those of other men which have been exercised in a different manner and on different subjects; much less erect

himself into a judge and an oracle concerning matters that have no sort of connexion with or dependence on

those species, symbols, or signs, in the management whereof he is so conversant and expert. As you, who are

a skilful computist or analyst, may not therefore be deemed skilful in anatomy; or vice versa, as a man who

can dissect with art may, nevertheless, be ignorant in your art of computing: even so you may both,

notwithstanding your peculiar skill in your respective arts, be alike unqualified to decide upon logic, or

metaphysics, or ethics, or religion. And this would be true, even admitting that you understood your own

34. If it is said that fluxions may be expounded or expressed by finite lines proportional to them; which finite

lines, as they may be distinctly conceived and known and reasoned upon, so they may be substituted for the

fluxions, and their mutual relations or proportions be considered as the proportions of fluxions by which

means the doctrine becomes clear and useful. I answer that if, in order to arrive at these finite lines

proportional to the fluxions, there be certain steps made use of which are obscure and inconceivable, be those

finite lines themselves ever so clearly conceived, it must nevertheless be acknowledged that your proceeding

For instance, it is supposed that AB being the abscissa, BC the ordinate, and VCH a tangent of the curve AC,

Bb or CE the increment of the abscissa, Ec the increment of the ordinate, which produced meets VH in the

point T and Cc the increment of the curve. The right line Cc being produced to K, there are formed three

small triangles, the rectilinear CEc, the mixtilinear CEc, and the rectilinear triangle CET. It is evident that

these three triangles are different from each other, the rectilinear CEc being less than the mixtilinear CEc,

whose sides are the three increments above mentioned, and this still less than the triangle CET. It is supposed

that the ordinate bc moves into the place BC, so that the point c is coincident with the point C; and the right

line CK, and consequently the curve Cc, is coincident with the tangent CH. In which case the mixtilinear

evanescent triangle CEc will, in its last form, be similar to the triangle CET: and its evanescent sides CE, Ec

and Cc, will be proportional to CE, ET and CT, the sides of the triangle CET. And therefore it is concluded

that the fluxions of the lines AB, BC, and AC, being in the last ratio of their evanescent increments, are

proportional to the sides of the triangle CET, or, which is all one, of the triangle VBC similar thereunto.

[`Introd. ad Quadraturam Curvarum.'] It is particularly remarked and insisted on by the great author, that the

points C and c must not be distant one from another, by any the least interval whatsoever: but that, in order to

find the ultimate proportions of the lines CE, Ec, and Cc (i.e. the proportions of the fluxions or velocities)

expressed by the finite sides of the triangle VBC, the points C and c must be accurately coincident, i.e. one

and the same. A point therefore is considered as a triangle, or a triangle is supposed to be formed in a point.

Which to conceive seems quite impossible. Yet some there are who, though they shrink at all other mysteries,

35. I know not whether it be worth while to observe, that possibly some men may hope to operate by symbols

and suppositions, in such sort as to avoid the use of fluxions, momentums, and infinitesimals, after the

following manner. Suppose x to be one abscissa of a curve, and z another abscissa of the same curve.

Suppose also that the respective areas are xxx and zzz: and that z x is the increment of the abscissa, and zzz

xxx the increment of the area, without considering how great or how small those increments may be.

Divide now zzz xxx by z x, and the quotient will be zz + zx + xx: and, supposing that z and x are equal,

the same quotient will be 3xx, which in that case is the ordinate, which therefore may be thus obtained

independently of fluxions and infinitesimals. But herein is a direct fallacy: for in the first place, it is supposed

that the abscissae z and x are unequal, without such supposition no one step could have been made; and in the

second place, it is supposed they are equal; which is a manifest inconsistency, and amounts to the same thing

that hath been before considered. [Sect. 15.] And there is indeed reason to apprehend that all attempts for

setting the abstruse and fine geometry on a right foundation, and avoiding the doctrine of velocities,

momentums, will be found impracticable, till such time as the object and the end of geometry are better

understood than hitherto they seem to have been. The great author of the method of fluxions felt this

difficulty, and therefore he gave in to those nice abstractions and geometrical metaphysics without which he

saw nothing could be done on the received principles: and what in the way of demonstration he hath done

with them the reader will judge. It must, indeed, be acknowledged that he used fluxions, like the scaffold of a

building, as things to be laid aside or got rid of as soon as finite lines were found proportional to them. But

then these finite exponents are found by the help of fluxions. Whatever therefore is got by such exponents

and proportions is to be ascribed to fluxions: which must therefore be previously understood. And what are

these fluxions? The velocities of evanescent increments. And what are these same evanescent increments?

They are neither finite quantities nor quantities infinitely small, nor yet nothing. May we not call them the

36. Men too often impose on themselves and others as if they conceived and understood things expressed by

signs, when in truth they have no idea, save only of the very signs themselves. And there are some grounds to

apprehend that this may be the present case. The velocities of evanescent or nascent quantities are supposed

to be expressed, both by finite lines of a determinate magnitude, and by algebraical notes or signs: but I

suspect that many who, perhaps never having examined the matter take it for granted, would, upon a narrow

scrutiny, find it impossible to frame any idea or notion whatsoever of those velocities, exclusive of such finite

Suppose the line KP described by the motion of a point continually accelerated, and that in equal particles of

time the unequal parts KL, LM, MN, NO, are generated. Suppose also that a, b, c, d, e, denote the velocities

of the generating point, at the several periods of the parts or increments so generated. It is easy to observe that

these increments are each proportional to the sum of the velocities with which it is described: that,

consequently, the several sums of the velocities, generated in equal parts of time, may be set forth by the

respective lines KL, LM, MN, generated in the same times. It is likewise an easy matter to say, that the last

velocity generated in the first particle of time may be expressed by the symbol a, the last in the second by b,

the last in the third by c, and so on: that a is the velocity of LM in statu nascenti, and b, c, d, e, are the

velocities of the increments MN, NO, OP, in their respective nascent estates. You may proceed and consider

these velocities themselves as flowing or increasing quantities, taking the velocities of the velocities, and the

velocities of the velocities of the velocities, i.e. the first, second, third velocities ad infinitum: which

succeeding series of velocities may be thus expressed, a, b a, c 2b + a , d 3c + 3b a which you may

call by the names of the first, second, third, fourth fluxions. And for an apter expression you may denote the

variable flowing line KL, KM, KN, by the letter x; and the first fluxions by , the second by , the third by , and

37. Nothing is easier than to assign names, signs, or expressions to these fluxions; and it is not difficult to

compute and operate by means of such signs. But it will be found much more difficult to omit the signs and

yet retain in our minds the things which we suppose to be signified by them. To consider the exponents,

whether geometrical, or algebraical, or fluxionary, is no difficult matter. But to form a precise idea of a third

velocity for instance, in itself and by itself, Hoc opus, hic labor. Nor indeed is it an easy point to form a clear

and distinct idea of any velocity at all, exclusive of and prescinding from all length of time and space; as also

from all notes, signs, or symbols whatsoever. This, if I may be allowed to judge of others by myself, is

impossible. To me it seems evident that measures and signs are absolutely necessary in order to conceive or

reason about velocities; and that consequently, when we think to conceive the velocities simply and in

38. It may perhaps be thought by some an easier method of conceiving fluxions to suppose them the

velocities wherewith the infinitesimal differences are generated. So that the first fluxions shall be the

velocities of the first differences, the second the velocities of the second differences, the third fluxions the

velocities of the third differences, and so on ad infinitum. But, not to mention the insurmountable difficulty of

admitting or conceiving infinitesimals, and infinitesimals of infinitesimals, it is evident that this notion of

fluxions would not consist with the great author's view; who held that the minutest quantity ought not to be

neglected, that therefore the doctrine of infinitesimal differences was not to be admitted in geometry, and

who plainly appears to have introduced the use of velocities or fluxions, on purpose to exclude or do without

39. To others it may possibly seem that we should form a juster idea of fluxions by assuming the finite,

unequal, isochronal increments KL, LM, MN, and considering them in statu nascenti, also their increments in

statu nascenti, and the nascent increments of those increments, and so on, supposing the first nascent

increments to be proportional to the first fluxions or velocities, the nascent increments of those increments to

be proportional to the second fluxions, the third nascent increments to be proportional to the third fluxions,

and so onwards. And, as the first fluxions are the velocities of the first nascent increments, so the second

fluxions may be conceived to be the velocities of the second nascent increments, rather than the velocities of

velocities. But which means the analogy of fluxions may seem better preserved, and the notion rendered more

40. And indeed it should seem that in the way of obtaining the second or third fluxion of an equation the

given fluxions were considered rather as increments than velocities. But the considering them sometimes in

one sense, sometimes in another, one while in themselves, another in their exponents, seems to have

occasioned no small share of that confusion and obscurity which are found in the doctrine of fluxions. It may

seem therefore that the notion might be still mended, and that instead of fluxions of fluxions, of fluxions of

fluxions of fluxions, and instead of second, third, or fourth, fluxions of a given quantity, it might be more

consistent and less liable to exception to say, the fluxion of the first nascent increment, i.e. the second

fluxion; the fluxion of the second nascent increment i.e. the third fluxion; the fluxion of the third nascent

increment, i.e. the fourth fluxion which fluxions are conceived respectively proportional, each to the

41. For the more distinct conception of all which it may be considered that if the finite increment LM [See the

foregoing scheme in sect. 36.] be divided into the isochronal parts Lm, mn, no, oM; and the increment MN

divided into the parts Mp, pq, qr, rN isochronal to the former; as the whole increments LM, MN are

proportional to the sums of their describing velocities, even so the homologous particles Lm, Mp are also

proportional to the respective accelerated velocities with which they are described. And, as the velocity with

which Mp is generated, exceeds that with which Lm was generated, even so the particle Mp exceeds the

particle Lm. And in general, as the isochronal velocities describing the particles of MN exceed the isochronal

velocities describing the particles of LM, even so the particles of the former exceed the correspondent

particles of the latter. And so this will hold, be the said particles ever so small. MN therefore will exceed LM

if they are both taken in their nascent states: and that excess will be proportional to the excess of the velocity

b above the velocity a. Hence we may see that this last account of fluxions comes, in the upshot, to the same

42. But, notwithstanding what hath been said, it must still be acknowledged that the finite particles Lm or

Mp, though taken ever so small, are not proportional to the velocities a and b; but each to a series of

velocities changing every moment, or which is the same thing, to an accelerated velocity, by which it is

generated during a certain minute particle of time: that the nascent beginnings or evanescent endings of finite

quantities, which are produced in moments or infinitely small parts of time, are alone proportional to given

velocities: that therefore, in order to conceive the first fluxions, we must conceive time divided into moments,

increments generated in those moments, and velocities proportional to those increments: that, in order to

conceive second and third fluxions, we must suppose that the nascent principles or momentaneous increments

have themselves also other momentaneous increments, which are proportional to their respective generating

velocities: that the velocities of these second momentaneous increments are second fluxions: those of their

43. By subducting the increment generated in the first moment from that generated in the second, we get the

increment of an increment. And by subducting the velocity generating in the first moment from that

generating in the second, we get a fluxion of a fluxion. In like manner, by subducting the difference of the

velocities generating in the two first moments from the excess of the velocity in the third above that in the

second moment, we obtain the third fluxion. And after the same analogy we may proceed to fourth, fifth,

sixth fluxions And if we call the velocities of the first, second, third, fourth moments, a, b, c, d, the series of

fluxions will be as above, a, b a, c 2b + a, d 3c + 3b a, ad infinitum, i.e. , , , , ad infinitum.

44. Thus fluxions may be conceived in sundry lights and shapes, which seem all equally difficult to conceive.

And, indeed, as it is impossible to conceive velocity without time or space, without either finite length or

finite duration, [Sect. 31] it must seem above the powers of men to comprehend even the first fluxions. And if

the first are incomprehensible, what shall we say of the second and third fluxions, He who can conceive the

beginning of a beginning, or the end of an end, somewhat before the first or after the last, may be perhaps

sharpsighted enough to conceive these things. But most men will, I believe, find it impossible to understand

45. One would think that men could not speak too exactly on so nice a subject. And yet, as was before hinted,

we may often observe that the exponents of fluxions, or notes representing fluxions are compounded with the

fluxions themselves. Is not this the case when, just after the fluxions of flowing quantities were said to be the

celerities of their increasing, and the second fluxions to be the mutations of the first fluxions or celerities, we

[`De Quadratura Curvarum.'] represents a series of quantities whereof each subsequent quantity is the fluxion

of the preceding: and each foregoing is a fluent quantity having the following one for its fluxion?

46. Divers series of quantities and expressions, geometrical and algebraical, may be easily conceived, in

lines, in surfaces, in species, to be continued without end or limit. But it will not be found so easy to conceive

a series, either of mere velocities or of mere nascent increments, distinct therefrom and corresponding

thereunto. Some perhaps may be led to think the author intended a series of ordinates, wherein each ordinate

was the fluxion of the preceding and fluent of the following, i.e. that the fluxion of one ordinate was itself the

ordinate of another curve; and the fluxion of this last ordinate was the ordinate of yet another curve; and so

on ad infinitum. But who can conceive how the fluxion (whether velocity or nascent increment) of an

ordinate should be itself an ordinate? Or more than that each preceding quantity or fluent is related to its

subsequent or fluxion, as the area of a curvilinear figure to its ordinate; agreeably to what the author remarks,

that each preceding quantity in such series is as the area of a curvilinear figure, whereof the abscissa is z, and

47. Upon the whole it appears that the celerities are dismissed, and instead thereof areas and ordinates are

introduced. But, however expedient such analogies or such expressions may be found for facilitating the

modern quadratures, yet we shall not find any light given us thereby into the original real nature of fluxions;

or that we are enabled to frame from thence just ideas of fluxions considered in themselves. In all this the

general ultimate drift of the author is very clear, but his principles are obscure. But perhaps those theories of

the great author are not minutely considered or canvassed by his disciples; who seem eager, as was before

hinted, rather to operate than to know, rather to apply his rules and his forms than to understand his principles

and enter into his notions. It is nevertheless certain that, in order to follow him in his quadratures, they must

find fluents from fluxions; and in order to this, they must know to find fluxions from fluents; and in order to

find fluxions, they must first know what fluxions are. Otherwise they proceed without clearness and without

science. Thus the direct method precedes the inverse, and the knowledge of the principles is supposed in

both. But as for operating according to rules, and by the help of general forms, whereof the original principles

and reasons are not understood, this is to be esteemed merely technical. Be the principles therefore ever so

abstruse and metaphysical, they must be studied by whoever would comprehend the doctrine of fluxions. Nor

can any geometrician have a right to apply the rules of the great author, without first considering his

metaphysical notions whence they were derived. These, however necessary soever in order to science, which

can never be obtained without a precise, clear, and accurate conception of the principles are nevertheless by

several carelessly passed over; while the expressions alone are dwelt on and considered and treated with great

skill and management, thence to obtain other expressions by methods suspicious and indirect (to say the

least) if considered in themselves, however recommended by Induction and Authority; two motives which are

acknowledged sufficient to beget a rational faith and moral persuasion, but nothing higher.

48. You may possibly hope to evade the force of all that hath been said, and to screen false principles and

inconsistent reasonings, by a general pretence that these objections and remarks are metaphysical. But this is

a vain pretence. For the plain sense and truth of what is advanced in the foregoing remarks, I appeal to the

understanding of every unprejudiced intelligent reader. To the same I appeal, whether the points remarked

upon are not most incomprehensible metaphysics. And metaphysics not of mine, but your own. I would not

be understood to infer that your notions are false or vain because they are metaphysical. Nothing is either true

of false for that reason. Whether a point be called metaphysical or no avails little. The question is, whether it

49. Although momentaneous increments, nascent and evanescent quantities, fluxions and infinitesimals of all

degrees are in truth such shadowy entities, so difficult to imagine or conceive distinctly, that (to say the least)

they cannot be admitted as principles or objects of clear and accurate science; and although this obscurity and

incomprehensibility of your metaphysics had been alone sufficient to allay your pretensions to evidence; yet

it hath, if I mistake not, been further shewn, that your inferences are no more just than your conceptions are

clear, and that your logics are as exceptionable as your metaphysics. It would seem, therefore, upon the

whole, that your conclusions are not attained by just reasoning from clear principles: consequently, that the

employment of modern analysts, however useful in mathematical calculations and constructions, doth not

habituate and qualify the mind to apprehend clearly and infer justly; and, consequently, that you have no

right, in virtue of such habits, to dictate out of your proper sphere, beyond which your judgment is to pass for

50. Of a long time I have suspected that these modern analytics were not scientifical, and gave some hints

thereof to the public about twentyfive years ago. Since which time, I have been diverted by other

occupations, and imagined I might employ myself better than in deducing and laying together my thoughts on

so nice a subject. And though of late I have been called upon to make good my suggestions; yet, as the person

who made this call doth not appear to think maturely enough to understand either those metaphysics which he

would refute, or mathematics which he would patronize, I should have spared myself the trouble of writing

for his conviction. Nor should I now have troubled you or myself with this address, after so long an

intermission of these studies, were it not to prevent, so far as I am able, your imposing on yourself and others

in matters of much higher moment and concern. And, to the end that you may more clearly comprehend the

force and design of the foregoing remarks, and pursue them still farther in your own meditations, I shall

Qu. 2. Whether the end of geometry be not to measure assignable finite extension? And whether this practical

Qu. 3. Whether the mistaking the object and end of geometry hath not created needless difficulties, and

Qu. 4. Whether men may properly be said to proceed in a scientific method, without clearly conceiving the

object they are conversant about, the end proposed, and the method by which it is pursued?

Qu. 5. Whether it doth not suffice, that every assignable number of parts may be contained in some

assignable magnitude? And whether it be not unnecessary, as well as absurd, to suppose that finite extension

Qu. 6. Whether the diagrams in a geometrical demonstration are not to be considered as signs of all possible

finite figures, of all sensible and imaginable extensions or magnitudes of the same kind?

Qu. 7. Whether it be possible to free geometry from insuperable difficulties and absurdities, so long as either

the abstract general idea of extension, or absolute external extension be supposed its true object?

Qu. 8. Whether the notions of absolute time, absolute place, and absolute motion be not most abstractedly

Qu. 9. Whether mathematicians do not engage themselves in disputes and paradoxes concerning what they

neither do nor can conceive? And whether the doctrine of forces be not a sufficient proof of this? [See a Latin

Qu. 10. Whether in geometry it may not suffice to consider assignable finite magnitude, without concerning

ourselves with infinity? And whether it would not be righter to measure large polygons having finite sides,

instead of curves, than to suppose curves are polygons of infinitesimal sides, a supposition neither true nor

Qu. 11. Whether many points which are not readily assented to are not nevertheless true? And whose in the

Qu. 12. Whether it be possible that we should have had an idea or notion of extension prior to motion? Or

whether, if a man had never perceived motion, he would ever have known or conceived one thing to be

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And whether there be any need of considering quantities either infinitely great or infinitely small? 16

Qu. 13. Whether geometrical quantity hath coexistent parts? And whether all quantity be not in a flux as

Qu. 14. Whether extension can be supposed an attribute of a Being immutable and eternal?

Qu. 15. Whether to decline examining the principles, and unravelling the methods used in mathematics would

Qu. 16. Whether certain maxims do not pass current among analysts which are shocking to good sense? And

whether the common assumption, that a finite quantity divided by nothing is infinite, be not of this number?

Qu. 17. Whether the considering geometrical diagrams absolutely or in themselves, rather than as

representatives of all assignable magnitudes or figures of the same kind, be not a principle cause of the

supposing finite extension infinitely divisible; and of all the difficulties and absurdities consequent

Qu. 18. Whether, from geometrical propositions being general, and the lines in diagrams being therefore

general substitutes or representatives, it doth not follow that we may not limit or consider the number of parts

Qu. 19. When it is said or implied, that such a certain line delineated on paper contains more than any

assignable number of parts, whether any more in truth ought to be understood, than that it is a sign

indifferently representing all finite lines, be they ever so great. In which relative capacity it contains, i.e.

stands for more than any assignable number of parts? And whether it be not altogether absurd to suppose a

finite line, considered in itself or in its own positive nature, should contain an infinite number of parts?

Qu. 20. Whether all arguments for the infinite divisibility of finite extension do not suppose and imply, either

general abstract ideas, or absolute external extension to be the object of geometry? And, therefore, whether,

Qu. 21. Whether the supposed infinite divisibility of finite extension hath not been a snare to mathematicians

and a thorn in their sides? And whether a quantity infinitely diminished and a quantity infinitely small are not

Qu. 22. Whether it be necessary to consider velocities of nascent or evanescent quantities, or moments, or

infinitesimals? And whether the introducing of things so inconceivable be not a reproach to mathematics?

Qu. 23. Whether inconsistencies can be truths? Whether points repugnant and absurd are to be admitted upon

any subjects, or in any science? And whether the use of infinites ought to be allowed as a sufficient pretext

Qu. 24. Whether a quantity be not properly said to be known, when we know its proportion to given

quantities? And whether this proportion can be known but by expressions or exponents, either geometrical,

algebraical, or arithmetical? And whether expressions in lines or species can be useful but so far forth as they

Qu. 25. Whether the finding out proper expressions or notations of quantity be not the most general character

and tendency of the mathematics? And arithmetical operation that which limits and defines their use?

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And whether there be any need of considering quantities either infinitely great or infinitely small? 17

Qu. 26. Whether mathematicians have sufficiently considered the analogy and use of signs? And how far the

Qu. 27. Whether because, in stating a general case of pure algebra, we are at full liberty to make a character

denote either a positive or a negative quantity, or nothing at all, we may therefore, in a geometrical case,

limited by hypotheses and reasonings from particular properties and relations of figures, claim the same

Qu. 28. Whether the shifting of the hypothesis, or (as we may call it) the fallacia suppositionis be not a

sophism that far and wide infects the modern reasonings, both in the mechanical philosophy and in the

Qu. 29. Whether we can form an idea or notion of velocity distinct from and exclusive of its measures, as we

can of heat distinct from and exclusive of the degrees on the thermometer by which it is measured? And

Qu. 30. Whether motion can be conceived in a point of space? And if motion cannot, whether velocity can?

And if not, whether a first or last velocity can be conceived in a mere limit, either initial or final, of the

Qu. 31. Where there are no increments, whether there can be any ratio of increments? Whether nothings can

be considered as proportional to real quantities? Or whether to talk of their proportions be not to talk

nonsense? Also in what sense we are to understand the proportion of a surface to a line, of an area to an

ordinate? And whether species or numbers, though properly expressing quantities which are not

Qu. 32. Whether if all assignable circles may be squared, the circle is not, to all intents and purposes, squared

as well as the parabola? Of whether a parabolic area can in fact be measured more accurately than a circular?

Qu. 33. Whether it would not be righter to approximate fairly than to endeavour at accuracy by sophisms?

Qu. 34. Whether it would not be more decent to proceed by trials and inductions, than to pretend to

Qu. 35. Whether there be not a way of arriving at truth, although the principles are not scientific, nor the

Qu. 36. Whether there can be science of the conclusion where there is not evidence of the principles? And

whether a man can have evidence of the principles without understanding them? And therefore, whether the

mathematicians of the present age act like men of science, in taking so much more pains to apply their

Qu. 37. Whether the greatest genius wrestling with false principles may not be foiled? And whether accurate

quadratures can be obtained without new postulata or assumptions? And if not, whether those which are

intelligible and consistent ought not to be preferred to the contrary? See sect. 28 and 29.

Qu. 38. Whether tedious calculations in algebra and fluxions be the likeliest method to improve the mind?

And whether men's being accustomed to reason altogether about mathematical signs and figures doth not

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And whether there be any need of considering quantities either infinitely great or infinitely small? 18

Qu. 39. Whether, whatever readiness analysts acquire in stating a problem, or finding apt expressions for

mathematical quantities, the same doth necessarily infer a proportionable ability in conceiving and expressing

Qu. 40. Whether it be not a general case or rule, that one and the same coefficient dividing equal products

gives equal quotients? And yet whether such coefficient can be interpreted by o or nothing? Or whether any

one will say that if the equation 2 o = 5 o be divided by o, the quotients on both sides are equal? Whether

therefore a case may not be general with respect to all quantities and yet not extend to nothings, or include the

case of nothing? And whether the bringing nothing under the notion of quantity may not have betrayed men

Qu. 41. Whether in the most general reasonings about equalities and proportions men may not demonstrate as

well as in geometry? Whether in such demonstrations they are not obliged to the same strict reasoning as in

geometry? And whether such their reasonings are not deduced from the same axioms with those in geometry?

Qu. 42. Whether men may not reason in species as well as in words? Whether the same rules of logic do not

obtain in both cases? And whether we have not a right to expect and demand the same evidence in both?

Qu. 43. Whether an algebraist, fluxionist, geometrician, or demonstrator of any kind can expect indulgence

for obscure principles or incorrect reasonings? And whether an algebraical note or species can at the end of a

process be interpreted in a sense which could not have been substituted for it at the beginning? Or whether

any particular supposition can come under a general case which doth not consist with the reasoning thereof?

Qu. 44. Whether the difference between a mere computer and a man of science be not, that the one computes

on principles clearly conceived, and by rules evidently demonstrated, whereas the other doth not?

Qu. 45. Whether, although geometry be a science, and algebra allowed to be a science, and the analytical a

most excellent method, in the application, nevertheless, of the analysis to geometry, men may not have

Qu. 46. Whether, although algebraical reasonings are admitted to be ever so just, when confined to signs or

species as general representatives of quantity, you may not nevertheless fall into error, if, when you limit

them to stand for particular things, you do not limit yourself to reason consistently with the nature of such

Qu. 47. Whether the view of modern mathematicians doth not rather seem to be the coming at an expression

Qu. 48. Whether there may not be sound metaphysics as well as unsound? Sound as well as unsound logic?

And whether the modern analytics may not be brought under one of these denominations, and which?

Qu. 49. Whether there be not really a philosophia prima, a certain transcendental science superior to and

more extensive than mathematics, which it might behove our modern analysts rather to learn than despise?

Qu. 50. Whether, ever since the recovery of mathematical learning, there have not been perpetual disputes

and controversies among the mathematicians? And whether this doth not disparage the evidence of their

Qu. 51. Whether anything but metaphysics and logic can open the eyes of mathematicians and extricate them

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And whether there be any need of considering quantities either infinitely great or infinitely small? 19

Qu. 52. Whether, upon the received principles, a quantity can by any division or subdivision, though carried

Qu. 53. Whether, if the end of geometry be practice, and this practice be measuring, and we measure only

assignable extensions, it will not follow that unlimited approximations completely answer the intention of

Qu. 54. Whether the same things which are now done by infinites may not be done by finite quantities? And

whether this would not be a great relief to the imaginations and understandings of mathematical men?

Qu. 55. Whether those philomathematical physicians, anatomists, and dealers in the animal economy, who

admit the doctrine of fluxions with an implicit faith, can with a good grace insult other men for believing

Qu. 56. Whether the corpuscularian, experimental, and mathematical philosophy, so much cultivated in the

last age, hath not too much engrossed men's attention; some part whereof it might have usefully employed?

Qu. 57. Whether, from this and other concurring causes, the minds of speculative men have not been borne

downward, to the debasing and stupifying of the higher faculties? And whether we may not hence account for

that prevailing narrowness and bigotry among many who pass for men of science, their incapacity for things

moral, intellectual, or theological, their proneness to measure all truths by sense and experience of animal

Qu. 58. Whether it be really an effect of thinking, that the same men admire the great author for his fluxions,

Qu. 59. If certain philosophical virtuosi of the present age have no religion, whether it can be said to be want

Qu. 60. Whether it be not a juster way of reasoning, to recommend points of faith from their effects, than to

Qu. 61. Whether it be not less exceptionable to admit points above reason than contrary to reason?

Qu. 62. Whether mysteries may not with better right be allowed of in Divine Faith than in human science?

Qu. 63. Whether such mathematicians as cry out against mysteries have ever examined their own principles?

Qu. 64. Whether mathematicians, who are so delicate in religious points, are strictly scrupulous in their own

science? Whether they do not submit to authority, take things upon trust, and believe points inconceivable?

Whether they have not their mysteries, and what is more, their repugnances and contradictions?

Qu. 65. Whether it might not become men who are puzzled and perplexed about their own principles, to

Qu. 66. Whether the modern analytics do not furnish a strong argumentum ad hominem against the

Qu. 67. Whether it follows from the abovementioned remarks, that accurate and just reasoning is the

peculiar character of the present age? And whether the modern growth of infidelity can be ascribed to a

Query 1. Whether the object of geometry be not the proportions of assignable extensions? And whether there be any need of considering quantities either infinitely great or infinitely small? 20

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