Rene Descartes

This work is one of the most influential in history. The famous

phrase, "COGITO ERGO SUM" (I think, therefore I am) is a central

theme. Descartes' beliefs on that dual nature of mind and body,

and his emphasis on the role of doubt in all inquiry, formed the

basis for centuries of science and social thought.

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DISCOURSE ON THE METHOD OF RIGHTLY CONDUCTING THE REASON,

AND SEEKING TRUTH IN THE SCIENCES

by Rene Descartes

PREFATORY NOTE BY THE AUTHOR

If this Discourse appear too long to be read at once, it may be divided

into six Parts: and, in the first, will be found various considerations

touching the Sciences; in the second, the principal rules of the Method

which the Author has discovered, in the third, certain of the rules of

Morals which he has deduced from this Method; in the fourth, the

reasonings by which he establishes the existence of God and of the Human

Soul, which are the foundations of his Metaphysic; in the fifth, the order

of the Physical questions which he has investigated, and, in particular,

the explication of the motion of the heart and of some other difficulties

pertaining to Medicine, as also the difference between the soul of man and

that of the brutes; and, in the last, what the Author believes to be

required in order to greater advancement in the investigation of Nature

than has yet been made, with the reasons that have induced him to write.

PART 1

Good sense is, of all things among men, the most equally distributed; for

every one thinks himself so abundantly provided with it, that those even

who are the most difficult to satisfy in everything else, do not usually

desire a larger measure of this quality than they already possess. And in

this it is not likely that all are mistaken the conviction is rather to be

held as testifying that the power of judging aright and of distinguishing

truth from error, which is properly what is called good sense or reason,

is by nature equal in all men; and that the diversity of our opinions,

consequently, does not arise from some being endowed with a larger share

of reason than others, but solely from this, that we conduct our thoughts

along different ways, and do not fix our attention on the same objects.

For to be possessed of a vigorous mind is not enough; the prime requisite

is rightly to apply it. The greatest minds, as they are capable of the

highest excellences, are open likewise to the greatest aberrations; and

those who travel very slowly may yet make far greater progress, provided

they keep always to the straight road, than those who, while they run,

forsake it.

For myself, I have never fancied my mind to be in any respect more perfect

than those of the generality; on the contrary, I have often wished that I

were equal to some others in promptitude of thought, or in clearness and

distinctness of imagination, or in fullness and readiness of memory. And

besides these, I know of no other qualities that contribute to the

perfection of the mind; for as to the reason or sense, inasmuch as it is

that alone which constitutes us men, and distinguishes us from the brutes,

I am disposed to believe that it is to be found complete in each

individual; and on this point to adopt the common opinion of philosophers,

who say that the difference of greater and less holds only among the

accidents, and not among the forms or natures of individuals of the same

species.

I will not hesitate, however, to avow my belief that it has been my

singular good fortune to have very early in life fallen in with certain

tracks which have conducted me to considerations and maxims, of which I

have formed a method that gives me the means, as I think, of gradually

augmenting my knowledge, and of raising it by little and little to the

highest point which the mediocrity of my talents and the brief duration of

my life will permit me to reach. For I have already reaped from it such

fruits that, although I have been accustomed to think lowly enough of

myself, and although when I look with the eye of a philosopher at the

varied courses and pursuits of mankind at large, I find scarcely one which

does not appear in vain and useless, I nevertheless derive the highest

satisfaction from the progress I conceive myself to have already made in

the search after truth, and cannot help entertaining such expectations of

the future as to believe that if, among the occupations of men as men, there

is any one really excellent and important, it is that which I have chosen.

After all, it is possible I may be mistaken; and it is but a little

copper and glass, perhaps, that I take for gold and diamonds. I know how

very liable we are to delusion in what relates to ourselves, and also how

much the judgments of our friends are to be suspected when given in our

favor. But I shall endeavor in this discourse to describe the paths I

have followed, and to delineate my life as in a picture, in order that

each one may also be able to judge of them for himself, and that in the

general opinion entertained of them, as gathered from current report, I

myself may have a new help towards instruction to be added to those I have

been in the habit of employing.

My present design, then, is not to teach the method which each ought to

follow for the right conduct of his reason, but solely to describe the way

in which I have endeavored to conduct my own. They who set themselves to

give precepts must of course regard themselves as possessed of greater skill

than those to whom they prescribe; and if they err in the slightest particular,

they subject themselves to censure. But as this tract is put forth merely

as a history, or, if you will, as a tale, in which, amid some examples worthy

of imitation, there will be found, perhaps, as many more which it were

advisable not to follow, I hope it will prove useful to some without being

hurtful to any, and that my openness will find some favor with all.

From my childhood, I have been familiar with letters; and as I was given

to believe that by their help a clear and certain knowledge of all that is

useful in life might be acquired, I was ardently desirous of instruction.

But as soon as I had finished the entire course of study, at the close of

which it is customary to be admitted into the order of the learned, I

completely changed my opinion. For I found myself involved in so many

doubts and errors, that I was convinced I had advanced no farther in all

my attempts at learning, than the discovery at every turn of my own

ignorance. And yet I was studying in one of the most celebrated schools in

Europe, in which I thought there must be learned men, if such were

anywhere to be found. I had been taught all that others learned there;

and not contented with the sciences actually taught us, I had, in

addition, read all the books that had fallen into my hands, treating of

such branches as are esteemed the most curious and rare. I knew the

judgment which others had formed of me; and I did not find that I was

considered inferior to my fellows, although there were among them some who

were already marked out to fill the places of our instructors. And, in

fine, our age appeared to me as flourishing, and as fertile in powerful

minds as any preceding one. I was thus led to take the liberty of judging

of all other men by myself, and of concluding that there was no science in

existence that was of such a nature as I had previously been given to believe.

I still continued, however, to hold in esteem the studies of the schools.

I was aware that the languages taught in them are necessary to the

understanding of the writings of the ancients; that the grace of fable

stirs the mind; that the memorable deeds of history elevate it; and, if

read with discretion, aid in forming the judgment; that the perusal of all

excellent books is, as it were, to interview with the noblest men of past

ages, who have written them, and even a studied interview, in which are

discovered to us only their choicest thoughts; that eloquence has

incomparable force and beauty; that poesy has its ravishing graces and

delights; that in the mathematics there are many refined discoveries

eminently suited to gratify the inquisitive, as well as further all the

arts an lessen the labour of man; that numerous highly useful precepts and

exhortations to virtue are contained in treatises on morals; that theology

points out the path to heaven; that philosophy affords the means of

discoursing with an appearance of truth on all matters, and commands the

admiration of the more simple; that jurisprudence, medicine, and the other

sciences, secure for their cultivators honors and riches; and, in fine,

that it is useful to bestow some attention upon all, even upon those

abounding the most in superstition and error, that we may be in a position

to determine their real value, and guard against being deceived.

But I believed that I had already given sufficient time to languages, and

likewise to the reading of the writings of the ancients, to their

histories and fables. For to hold converse with those of other ages and

to travel, are almost the same thing. It is useful to know something of

the manners of different nations, that we may be enabled to form a more

correct judgment regarding our own, and be prevented from thinking that

everything contrary to our customs is ridiculous and irrational, a

conclusion usually come to by those whose experience has been limited to

their own country. On the other hand, when too much time is occupied in

traveling, we become strangers to our native country; and the over

curious in the customs of the past are generally ignorant of those of the

present. Besides, fictitious narratives lead us to imagine the possibility

of many events that are impossible; and even the most faithful histories,

if they do not wholly misrepresent matters, or exaggerate their importance

to render the account of them more worthy of perusal, omit, at least, almost

always the meanest and least striking of the attendant circumstances; hence

it happens that the remainder does not represent the truth, and that such as

regulate their conduct by examples drawn from this source, are apt to fall

into the extravagances of the knight-errants of romance, and to entertain

projects that exceed their powers.

I esteemed eloquence highly, and was in raptures with poesy; but I thought

that both were gifts of nature rather than fruits of study. Those in whom

the faculty of reason is predominant, and who most skillfully dispose their

thoughts with a view to render them clear and intelligible, are always the

best able to persuade others of the truth of what they lay down, though

they should speak only in the language of Lower Brittany, and be wholly

ignorant of the rules of rhetoric; and those whose minds are stored with

the most agreeable fancies, and who can give expression to them with the

greatest embellishment and harmony, are still the best poets, though

unacquainted with the art of poetry.

I was especially delighted with the mathematics, on account of the

certitude and evidence of their reasonings; but I had not as yet a

precise knowledge of their true use; and thinking that they but

contributed to the advancement of the mechanical arts, I was astonished

that foundations, so strong and solid, should have had no loftier

superstructure reared on them. On the other hand, I compared the

disquisitions of the ancient moralists to very towering and magnificent

palaces with no better foundation than sand and mud: they laud the virtues

very highly, and exhibit them as estimable far above anything on earth;

but they give us no adequate criterion of virtue, and frequently that

which they designate with so fine a name is but apathy, or pride,

or despair, or parricide.

I revered our theology, and aspired as much as any one to reach heaven:

but being given assuredly to understand that the way is not less open to

the most ignorant than to the most learned, and that the revealed truths

which lead to heaven are above our comprehension, I did not presume to

subject them to the impotency of my reason; and I thought that in order

competently to undertake their examination, there was need of some special

help from heaven, and of being more than man.

Of philosophy I will say nothing, except that when I saw that it had been

cultivated for many ages by the most distinguished men, and that yet there

is not a single matter within its sphere which is not still in dispute,

and nothing, therefore, which is above doubt, I did not presume to

anticipate that my success would be greater in it than that of others; and

further, when I considered the number of conflicting opinions touching a

single matter that may be upheld by learned men, while there can be but

one true, I reckoned as well-nigh false all that was only probable.

As to the other sciences, inasmuch as these borrow their principles from

philosophy, I judged that no solid superstructures could be reared on

foundations so infirm; and neither the honor nor the gain held out by them

was sufficient to determine me to their cultivation: for I was not, thank

Heaven, in a condition which compelled me to make merchandise of science

for the bettering of my fortune; and though I might not profess to scorn

glory as a cynic, I yet made very slight account of that honor which I

hoped to acquire only through fictitious titles. And, in fine, of false

sciences I thought I knew the worth sufficiently to escape being deceived

by the professions of an alchemist, the predictions of an astrologer, the

impostures of a magician, or by the artifices and boasting of any of those

who profess to know things of which they are ignorant.

For these reasons, as soon as my age permitted me to pass from under the

control of my instructors, I entire y abandoned the study of letters, and

resolved no longer to seek any other science than the knowledge of myself,

or of the great book of the world. I spent the remainder of my youth in

traveling, in visiting courts and armies, in holding intercourse with men

of different dispositions and ranks, in collecting varied experience, in

proving myself in the different situations into which fortune threw me,

and, above all, in making such reflection on the matter of my experience

as to secure my improvement. For it occurred to me that I should find

much more truth in the reasonings of each individual with reference to the

affairs in which he is personally interested, and the issue of which must

presently punish him if he has judged amiss, than in those conducted by a

man of letters in his study, regarding speculative matters that are of no

practical moment, and followed by no consequences to himself, farther,

perhaps, than that they foster his vanity the better the more remote they

are from common sense; requiring, as they must in this case, the exercise

of greater ingenuity and art to render them probable. In addition, I had

always a most earnest desire to know how to distinguish the true from the

false, in order that I might be able clearly to discriminate the right

path in life, and proceed in it with confidence.

It is true that, while busied only in considering the manners of other

men, I found here, too, scarce any ground for settled conviction, and

remarked hardly less contradiction among them than in the opinions of the

philosophers. So that the greatest advantage I derived from the study

consisted in this, that, observing many things which, however extravagant

and ridiculous to our apprehension, are yet by common consent received and

approved by other great nations, I learned to entertain too decided a

belief in regard to nothing of the truth of which I had been persuaded

merely by example and custom; and thus I gradually extricated myself from

many errors powerful enough to darken our natural intelligence, and

incapacitate us in great measure from listening to reason. But after I had

been occupied several years in thus studying the book of the world, and in

essaying to gather some experience, I at length resolved to make myself an

object of study, and to employ all the powers of my mind in choosing the

paths I ought to follow, an undertaking which was accompanied with greater

success than it would have been had I never quitted my country or my books.

PART II

I was then in Germany, attracted thither by the wars in that country,

which have not yet been brought to a termination; and as I was returning

to the army from the coronation of the emperor, the setting in of winter

arrested me in a locality where, as I found no society to interest me, and

was besides fortunately undisturbed by any cares or passions, I remained

the whole day in seclusion, with full opportunity to occupy my attention

with my own thoughts. Of these one of the very first that occurred to me

was, that there is seldom so much perfection in works composed of many

separate parts, upon which different hands had been employed, as in those

completed by a single master. Thus it is observable that the buildings

which a single architect has planned and executed, are generally more

elegant and commodious than those which several have attempted to improve,

by making old walls serve for purposes for which they were not originally

built. Thus also, those ancient cities which, from being at first only

villages, have become, in course of time, large towns, are usually but ill

laid out compared with the regularity constructed towns which a

professional architect has freely planned on an open plain; so that

although the several buildings of the former may often equal or surpass in

beauty those of the latter, yet when one observes their indiscriminate

juxtaposition, there a large one and here a small, and the consequent

crookedness and irregularity of the streets, one is disposed to allege

that chance rather than any human will guided by reason must have led to

such an arrangement. And if we consider that nevertheless there have been

at all times certain officers whose duty it was to see that private

buildings contributed to public ornament, the difficulty of reaching high

perfection with but the materials of others to operate on, will be readily

acknowledged. In the same way I fancied that those nations which, starting

from a semi-barbarous state and advancing to civilization by slow degrees,

have had their laws successively determined, and, as it were, forced upon

them simply by experience of the hurtfulness of particular crimes and

disputes, would by this process come to be possessed of less perfect

institutions than those which, from the commencement of their association

as communities, have followed the appointments of some wise legislator. It

is thus quite certain that the constitution of the true religion, the

ordinances of which are derived from God, must be incomparably superior to

that of every other. And, to speak of human affairs, I believe that the

pre-eminence of Sparta was due not to the goodness of each of its laws in

particular, for many of these were very strange, and even opposed to good

morals, but to the circumstance that, originated by a single individual,

they all tended to a single end. In the same way I thought that the

sciences contained in books (such of them at least as are made up of

probable reasonings, without demonstrations), composed as they are of the

opinions of many different individuals massed together, are farther

removed from truth than the simple inferences which a man of good sense

using his natural and unprejudiced judgment draws respecting the matters

of his experience. And because we have all to pass through a state of

infancy to manhood, and have been of necessity, for a length of time,

governed by our desires and preceptors (whose dictates were frequently

conflicting, while neither perhaps always counseled us for the best), I

farther concluded that it is almost impossible that our judgments can be

so correct or solid as they would have been, had our reason been mature

from the moment of our birth, and had we always been guided by it alone.

It is true, however, that it is not customary to pull down all the houses

of a town with the single design of rebuilding them differently, and

thereby rendering the streets more handsome; but it often happens that a

private individual takes down his own with the view of erecting it anew,

and that people are even sometimes constrained to this when their houses

are in danger of falling from age, or when the foundations are insecure.

With this before me by way of example, I was persuaded that it would

indeed be preposterous for a private individual to think of reforming a

state by fundamentally changing it throughout, and overturning it in order

to set it up amended; and the same I thought was true of any similar

project for reforming the body of the sciences, or the order of teaching

them established in the schools: but as for the opinions which up to that

time I had embraced, I thought that I could not do better than resolve at

once to sweep them wholly away, that I might afterwards be in a position

to admit either others more correct, or even perhaps the same when they

had undergone the scrutiny of reason. I firmly believed that in this way I

should much better succeed in the conduct of my life, than if I built only

upon old foundations, and leaned upon principles which, in my youth, I had

taken upon trust. For although I recognized various difficulties in this

undertaking, these were not, however, without remedy, nor once to be

compared with such as attend the slightest reformation in public affairs.

Large bodies, if once overthrown, are with great difficulty set up again,

or even kept erect when once seriously shaken, and the fall of such is

always disastrous. Then if there are any imperfections in the

constitutions of states (and that many such exist the diversity of

constitutions is alone sufficient to assure us), custom has without doubt

materially smoothed their inconveniences, and has even managed to steer

altogether clear of, or insensibly corrected a number which sagacity could

not have provided against with equal effect; and, in fine, the defects are

almost always more tolerable than the change necessary for their removal;

in the same manner that highways which wind among mountains, by being much

frequented, become gradually so smooth and commodious, that it is much

better to follow them than to seek a straighter path by climbing over the

tops of rocks and descending to the bottoms of precipices.

Hence it is that I cannot in any degree approve of those restless and busy

meddlers who, called neither by birth nor fortune to take part in the

management of public affairs, are yet always projecting reforms; and if I

thought that this tract contained aught which might justify the suspicion

that I was a victim of such folly, I would by no means permit its

publication. I have never contemplated anything higher than the

reformation of my own opinions, and basing them on a foundation wholly my

own. And although my own satisfaction with my work has led me to present

here a draft of it, I do not by any means therefore recommend to every one

else to make a similar attempt. Those whom God has endowed with a larger

measure of genius will entertain, perhaps, designs still more exalted; but

for the many I am much afraid lest even the present undertaking be more

than they can safely venture to imitate. The single design to strip one's

self of all past beliefs is one that ought not to be taken by every one.

The majority of men is composed of two classes, for neither of which would

this be at all a befitting resolution: in the first place, of those who

with more than a due confidence in their own powers, are precipitate in

their judgments and want the patience requisite for orderly and

circumspect thinking; whence it happens, that if men of this class once

take the liberty to doubt of their accustomed opinions, and quit the

beaten highway, they will never be able to thread the byway that would

lead them by a shorter course, and will lose themselves and continue to

wander for life; in the second place, of those who, possessed of

sufficient sense or modesty to determine that there are others who excel

them in the power of discriminating between truth and error, and by whom

they may be instructed, ought rather to content themselves with the

opinions of such than trust for more correct to their own reason.

For my own part, I should doubtless have belonged to the latter class, had

I received instruction from but one master, or had I never known the

diversities of opinion that from time immemorial have prevailed among men

of the greatest learning. But I had become aware, even so early as during

my college life, that no opinion, however absurd and incredible, can be

imagined, which has not been maintained by some on of the philosophers;

and afterwards in the course of my travels I remarked that all those whose

opinions are decidedly repugnant to ours are not in that account

barbarians and savages, but on the contrary that many of these nations

make an equally good, if not better, use of their reason than we do. I

took into account also the very different character which a person brought

up from infancy in France or Germany exhibits, from that which, with the

same mind originally, this individual would have possessed had he lived

always among the Chinese or with savages, and the circumstance that in

dress itself the fashion which pleased us ten years ago, and which may

again, perhaps, be received into favor before ten years have gone,

appears to us at this moment extravagant and ridiculous. I was thus led

to infer that the ground of our opinions is far more custom and example

than any certain knowledge. And, finally, although such be the ground of

our opinions, I remarked that a plurality of suffrages is no guarantee of

truth where it is at all of difficult discovery, as in such cases it is

much more likely that it will be found by one than by many. I could,

however, select from the crowd no one whose opinions seemed worthy of

preference, and thus I found myself constrained, as it were, to use my own

reason in the conduct of my life.

But like one walking alone and in the dark, I resolved to proceed so

slowly and with such circumspection, that if I did not advance far, I

would at least guard against falling. I did not even choose to dismiss

summarily any of the opinions that had crept into my belief without having

been introduced by reason, but first of all took sufficient time carefully

to satisfy myself of the general nature of the task I was setting myself,

and ascertain the true method by which to arrive at the knowledge of

whatever lay within the compass of my powers.

Among the branches of philosophy, I had, at an earlier period, given some

attention to logic, and among those of the mathematics to geometrical

analysis and algebra, -- three arts or sciences which ought, as I

conceived, to contribute something to my design. But, on examination, I

found that, as for logic, its syllogisms and the majority of its other

precepts are of avail- rather in the communication of what we already

know, or even as the art of Lully, in speaking without judgment of things

of which we are ignorant, than in the investigation of the unknown; and

although this science contains indeed a number of correct and very

excellent precepts, there are, nevertheless, so many others, and these

either injurious or superfluous, mingled with the former, that it is

almost quite as difficult to effect a severance of the true from the false

as it is to extract a Diana or a Minerva from a rough block of marble.

Then as to the analysis of the ancients and the algebra of the moderns,

besides that they embrace only matters highly abstract, and, to

appearance, of no use, the former is so exclusively restricted to the

consideration of figures, that it can exercise the understanding only on

condition of greatly fatiguing the imagination; and, in the latter, there

is so complete a subjection to certain rules and formulas, that there

results an art full of confusion and obscurity calculated to embarrass,

instead of a science fitted to cultivate the mind. By these considerations

I was induced to seek some other method which would comprise the

advantages of the three and be exempt from their defects. And as a

multitude of laws often only hampers justice, so that a state is best

governed when, with few laws, these are rigidly administered; in like

manner, instead of the great number of precepts of which logic is

composed, I believed that the four following would prove perfectly

sufficient for me, provided I took the firm and unwavering resolution

never in a single instance to fail in observing them.

The first was never to accept anything for true which I did not clearly know

to be such; that is to say, carefully to avoid precipitancy and prejudice,

and to comprise nothing more in my judgement than what was presented to

my mind so clearly and distinctly as to exclude all ground of doubt.

The second, to divide each of the difficulties under examination into as many

parts as possible, and as might be necessary for its adequate solution.

The third, to conduct my thoughts in such order that, by commencing with

objects the simplest and easiest to know, I might ascend by little and

little, and, as it were, step by step, to the knowledge of the more complex;

assigning in thought a certain order even to those objects which in their

own nature do not stand in a relation of antecedence and sequence.

And the last, in every case to make enumerations so complete, and reviews

so general, that I might be assured that nothing was omitted.

The long chains of simple and easy reasonings by means of which

geometers are accustomed to reach the conclusions of their most

difficult demonstrations, had led me to imagine that all things,

to the knowledge of which man is competent, are mutually connected

in the same way, and that there is nothing so far removed from us

as to be beyond our reach, or so hidden that we cannot discover it,

provided only we abstain from accepting the false for the true, and

always preserve in our thoughts the order necessary for the deduction

of one truth from another. And I had little difficulty in determining

the objects with which it was necessary to commence, for I was already

persuaded that it must be with the simplest and easiest to know, and,

considering that of all those who have hitherto sought truth in the sciences,

the mathematicians alone have been able to find any demonstrations, that is,

any certain and evident reasons, I did not doubt but that such must have been

the rule of their investigations. I resolved to commence, therefore, with the

examination of the simplest objects, not anticipating, however, from this any

other advantage than that to be found in accustoming my mind to the love and

nourishment of truth, and to a distaste for all such reasonings as were

unsound. But I had no intention on that account of attempting to master all

the particular sciences commonly denominated mathematics: but observing that,

however different their objects, they all agree in considering only the

various relations or proportions subsisting among those objects, I thought

it best for my purpose to consider these proportions in the most general

form possible, without referring them to any objects in particular, except

such as would most facilitate the knowledge of them, and without by any

means restricting them to these, that afterwards I might thus be the

better able to apply them to every other class of objects to which they

are legitimately applicable. Perceiving further, that in order to

understand these relations I should sometimes have to consider them one by

one and sometimes only to bear them in mind, or embrace them in the

aggregate, I thought that, in order the better to consider them

individually, I should view them as subsisting between straight lines,

than which I could find no objects more simple, or capable of being more

distinctly represented to my imagination and senses; and on the other

hand, that in order to retain them in the memory or embrace an aggregate

of many, I should express them by certain characters the briefest

possible. In this way I believed that I could borrow all that was best

both in geometrical analysis and in algebra, and correct all the defects

of the one by help of the other.

And, in point of fact, the accurate observance of these few precepts gave me,

I take the liberty of saying, such ease in unraveling all the questions

embraced in these two sciences, that in the two or three months

I devoted to their examination, not only did I reach solutions of

questions I had formerly deemed exceedingly difficult but even as regards

questions of the solution of which I continued ignorant, I was enabled, as

it appeared to me, to determine the means whereby, and the extent to which

a solution was possible; results attributable to the circumstance that I

commenced with the simplest and most general truths, and that thus each

truth discovered was a rule available in the discovery of subsequent ones

Nor in this perhaps shall I appear too vain, if it be considered that, as

the truth on any particular point is one whoever apprehends the truth,

knows all that on that point can be known. The child, for example, who

has been instructed in the elements of arithmetic, and has made a

particular addition, according to rule, may be assured that he has found,

with respect to the sum of the numbers before him, and that in this

instance is within the reach of human genius. Now, in conclusion, the

method which teaches adherence to the true order, and an exact enumeration

of all the conditions of the thing .sought includes all that gives

certitude to the rules of arithmetic.

But the chief ground of my satisfaction with thus method, was the

assurance I had of thereby exercising my reason in all matters, if not

with absolute perfection, at least with the greatest attainable by me:

besides, I was conscious that by its use my mind was becoming gradually

habituated to clearer and more distinct conceptions of its objects; and I

hoped also, from not having restricted this method to any particular

matter, to apply it to the difficulties of the other sciences, with not

less success than to those of algebra. I should not, however, on this

account have ventured at once on the examination of all the difficulties

of the sciences which presented themselves to me, for this would have been

contrary to the order prescribed in the method, but observing that the

knowledge of such is dependent on principles borrowed from philosophy, in

which I found nothing certain, I thought it necessary first of all to

endeavor to establish its principles. .And because I observed, besides,

that an inquiry of this kind was of all others of the greatest moment, and

one in which precipitancy and anticipation in judgment were most to be

dreaded, I thought that I ought not to approach it till I had reached a

more mature age (being at that time but twenty-three), and had first of

all employed much of my time in preparation for the work, as well by

eradicating from my mind all the erroneous opinions I had up to that

moment accepted, as by amassing variety of experience to afford materials

for my reasonings, and by continually exercising myself in my chosen

method with a view to increased skill in its application.