DISCOURSE ON THE METHOD
OF RIGHTLY CONDUCTING THE REASON,best musical shakers under 25 dollars
AND SEEKING TRUTH IN THE SCIENCES

by René Descartes

Contents

PREFATORY NOTE BY THE AUTHOR

If this Discourse appear too long to be read at once, it may be divided intosix Parts: and, in the first, will be found various considerations touching theSciences; in the second, the principal rules of the Method which the Author hasdiscovered, in the third, certain of the rules of Morals which he has deducedfrom this Method; in the fourth, the reasonings by which he establishes theexistence of God and of the Human Soul, which are the foundations of hisMetaphysic; in the fifth, the order of the Physical questions which he hasinvestigated, and, in particular, the explication of the motion of the heartand of some other difficulties pertaining to Medicine, as also the differencebetween the soul of man and that of the brutes; and, in the last, what theAuthor believes to be required in order to greater advancement in theinvestigation of Nature than has yet been made, with the reasons that haveinduced him to write.

PART I

Good sense is, of all things among men, the most equally distributed; for everyone thinks himself so abundantly provided with it, that those even who are themost difficult to satisfy in everything else, do not usually desire a largermeasure of this quality than they already possess. And in this it is not likelythat all are mistaken the conviction is rather to be held as testifying thatthe power of judging aright and of distinguishing truth from error, which isproperly 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 somebeing 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 attentionon the same objects. For to be possessed of a vigorous mind is not enough; theprime requisite is rightly to apply it. The greatest minds, as they are capableof the highest excellences, are open likewise to the greatest aberrations; andthose who travel very slowly may yet make far greater progress, provided theykeep 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 thanthose of the generality; on the contrary, I have often wished that I were equalto some others in promptitude of thought, or in clearness and distinctness ofimagination, or in fullness and readiness of memory. And besides these, I knowof no other qualities that contribute to the perfection of the mind; for as tothe reason or sense, inasmuch as it is that alone which constitutes us men, anddistinguishes us from the brutes, I am disposed to believe that it is to befound complete in each individual; and on this point to adopt the commonopinion of philosophers, who say that the difference of greater and less holdsonly among the accidents, and not among the forms or natures of individuals ofthe same species.

I will not hesitate, however, to avow my belief that it has been my singulargood fortune to have very early in life fallen in with certain tracks whichhave conducted me to considerations and maxims, of which I have formed a methodthat gives me the means, as I think, of gradually augmenting my knowledge, andof raising it by little and little to the highest point which the mediocrity ofmy talents and the brief duration of my life will permit me to reach. For Ihave already reaped from it such fruits that, although I have been accustomedto think lowly enough of myself, and although when I look with the eye of aphilosopher at the varied courses and pursuits of mankind at large, I findscarcely one which does not appear in vain and useless, I nevertheless derivethe highest satisfaction from the progress I conceive myself to have alreadymade in the search after truth, and cannot help entertaining such expectationsof the future as to believe that if, among the occupations of men as men, thereis 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 andglass, perhaps, that I take for gold and diamonds. I know how very liable weare to delusion in what relates to ourselves, and also how much the judgmentsof our friends are to be suspected when given in our favor. But I shallendeavor in this discourse to describe the paths I have followed, and todelineate my life as in a picture, in order that each one may also be able tojudge 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 towardsinstruction 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 followfor the right conduct of his reason, but solely to describe the way in which Ihave endeavored to conduct my own. They who set themselves to give preceptsmust of course regard themselves as possessed of greater skill than those towhom they prescribe; and if they err in the slightest particular, they subjectthemselves 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, therewill be found, perhaps, as many more which it were advisable not to follow, Ihope it will prove useful to some without being hurtful to any, and that myopenness will find some favor with all.

From my childhood, I have been familiar with letters; and as I was given tobelieve that by their help a clear and certain knowledge of all that is usefulin life might be acquired, I was ardently desirous of instruction. But as soonas I had finished the entire course of study, at the close of which it iscustomary to be admitted into the order of the learned, I completely changed myopinion. For I found myself involved in so many doubts and errors, that I wasconvinced I had advanced no farther in all my attempts at learning, than thediscovery at every turn of my own ignorance. And yet I was studying in one ofthe most celebrated schools in Europe, in which I thought there must be learnedmen, if such were anywhere to be found. I had been taught all that otherslearned 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 suchbranches as are esteemed the most curious and rare. I knew the judgment whichothers had formed of me; and I did not find that I was considered inferior tomy fellows, although there were among them some who were already marked out tofill the places of our instructors. And, in fine, our age appeared to me asflourishing, and as fertile in powerful minds as any preceding one. I was thusled to take the liberty of judging of all other men by myself, and ofconcluding that there was no science in existence that was of such a nature asI had previously been given to believe.

I still continued, however, to hold in esteem the studies of the schools. I wasaware that the languages taught in them are necessary to the understanding ofthe writings of the ancients; that the grace of fable stirs the mind; that thememorable deeds of history elevate it; and, if read with discretion, aid informing 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 evena studied interview, in which are discovered to us only their choicestthoughts; that eloquence has incomparable force and beauty; that poesy has itsravishing graces and delights; that in the mathematics there are many refineddiscoveries eminently suited to gratify the inquisitive, as well as further allthe arts an lessen the labour of man; that numerous highly useful precepts andexhortations to virtue are contained in treatises on morals; that theologypoints out the path to heaven; that philosophy affords the means of discoursingwith an appearance of truth on all matters, and commands the admiration of themore simple; that jurisprudence, medicine, and the other sciences, secure fortheir cultivators honors and riches; and, in fine, that it is useful to bestowsome attention upon all, even upon those abounding the most in superstition anderror, that we may be in a position to determine their real value, and guardagainst being deceived.

But I believed that I had already given sufficient time to languages, andlikewise to the reading of the writings of the ancients, to their histories andfables. For to hold converse with those of other ages and to travel, are almostthe same thing. It is useful to know something of the manners of differentnations, that we may be enabled to form a more correct judgment regarding ourown, and be prevented from thinking that everything contrary to our customs isridiculous and irrational, a conclusion usually come to by those whoseexperience has been limited to their own country. On the other hand, when toomuch 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 thoseof the present. Besides, fictitious narratives lead us to imagine thepossibility of many events that are impossible; and even the most faithfulhistories, if they do not wholly misrepresent matters, or exaggerate theirimportance to render the account of them more worthy of perusal, omit, atleast, almost always the meanest and least striking of the attendantcircumstances; hence it happens that the remainder does not represent thetruth, and that such as regulate their conduct by examples drawn from thissource, are apt to fall into the extravagances of the knight-errants ofromance, and to entertain projects that exceed their powers.

I esteemed eloquence highly, and was in raptures with poesy; but I thought thatboth were gifts of nature rather than fruits of study. Those in whom thefaculty of reason is predominant, and who most skillfully dispose theirthoughts with a view to render them clear and intelligible, are always the bestable to persuade others of the truth of what they lay down, though they shouldspeak only in the language of Lower Brittany, and be wholly ignorant of therules of rhetoric; and those whose minds are stored with the most agreeablefancies, and who can give expression to them with the greatest embellishmentand harmony, are still the best poets, though unacquainted with the art ofpoetry.

I was especially delighted with the mathematics, on account of the certitudeand evidence of their reasonings; but I had not as yet a precise knowledge oftheir true use; and thinking that they but contributed to the advancement ofthe mechanical arts, I was astonished that foundations, so strong and solid,should have had no loftier superstructure reared on them. On the other hand, Icompared the disquisitions of the ancient moralists to very towering andmagnificent palaces with no better foundation than sand and mud: they laud thevirtues very highly, and exhibit them as estimable far above anything on earth;but they give us no adequate criterion of virtue, and frequently that whichthey designate with so fine a name is but apathy, or pride, or despair, orparricide.

I revered our theology, and aspired as much as any one to reach heaven: butbeing given assuredly to understand that the way is not less open to the mostignorant than to the most learned, and that the revealed truths which lead toheaven are above our comprehension, I did not presume to subject them to theimpotency of my reason; and I thought that in order competently to undertaketheir examination, there was need of some special help from heaven, and ofbeing more than man.

Of philosophy I will say nothing, except that when I saw that it had beencultivated for many ages by the most distinguished men, and that yet there isnot a single matter within its sphere which is not still in dispute, andnothing, therefore, which is above doubt, I did not presume to anticipate thatmy success would be greater in it than that of others; and further, when Iconsidered the number of conflicting opinions touching a single matter that maybe upheld by learned men, while there can be but one true, I reckoned aswell-nigh false all that was only probable.

As to the other sciences, inasmuch as these borrow their principles fromphilosophy, I judged that no solid superstructures could be reared onfoundations so infirm; and neither the honor nor the gain held out by them wassufficient to determine me to their cultivation: for I was not, thank Heaven,in a condition which compelled me to make merchandise of science for thebettering of my fortune; and though I might not profess to scorn glory as acynic, I yet made very slight account of that honor which I hoped to acquireonly through fictitious titles. And, in fine, of false sciences I thought Iknew the worth sufficiently to escape being deceived by the professions of analchemist, the predictions of an astrologer, the impostures of a magician, orby the artifices and boasting of any of those who profess to know things ofwhich they are ignorant.

For these reasons, as soon as my age permitted me to pass from under thecontrol of my instructors, I entirely abandoned the study of letters, andresolved no longer to seek any other science than the knowledge of myself, orof 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 differentdispositions and ranks, in collecting varied experience, in proving myself inthe different situations into which fortune threw me, and, above all, in makingsuch reflection on the matter of my experience as to secure my improvement. Forit occurred to me that I should find much more truth in the reasonings of eachindividual 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, thanin those conducted by a man of letters in his study, regarding speculativematters that are of no practical moment, and followed by no consequences tohimself, farther, perhaps, than that they foster his vanity the better the moreremote they are from common sense; requiring, as they must in this case, theexercise of greater ingenuity and art to render them probable. In addition, Ihad always a most earnest desire to know how to distinguish the true from thefalse, in order that I might be able clearly to discriminate the right path inlife, and proceed in it with confidence.

It is true that, while busied only in considering the manners of other men, Ifound here, too, scarce any ground for settled conviction, and remarked hardlyless contradiction among them than in the opinions of the philosophers. So thatthe greatest advantage I derived from the study consisted in this, that,observing many things which, however extravagant and ridiculous to ourapprehension, are yet by common consent received and approved by other greatnations, I learned to entertain too decided a belief in regard to nothing ofthe truth of which I had been persuaded merely by example and custom; and thusI gradually extricated myself from many errors powerful enough to darken ournatural intelligence, and incapacitate us in great measure from listening toreason. But after I had been occupied several years in thus studying the bookof the world, and in essaying to gather some experience, I at length resolvedto make myself an object of study, and to employ all the powers of my mind inchoosing the paths I ought to follow, an undertaking which was accompanied withgreater success than it would have been had I never quitted my country or mybooks.

PART II

I was then in Germany, attracted thither by the wars in that country, whichhave not yet been brought to a termination; and as I was returning to the armyfrom the coronation of the emperor, the setting in of winter arrested me in alocality where, as I found no society to interest me, and was besidesfortunately undisturbed by any cares or passions, I remained the whole day inseclusion, 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 somuch perfection in works composed of many separate parts, upon which differenthands had been employed, as in those completed by a single master. Thus it isobservable that the buildings which a single architect has planned andexecuted, are generally more elegant and commodious than those which severalhave attempted to improve, by making old walls serve for purposes for whichthey were not originally built. Thus also, those ancient cities which, frombeing at first only villages, have become, in course of time, large towns, areusually but ill laid out compared with the regularity constructed towns which aprofessional architect has freely planned on an open plain; so that althoughthe several buildings of the former may often equal or surpass in beauty thoseof the latter, yet when one observes their indiscriminate juxtaposition, therea large one and here a small, and the consequent crookedness and irregularityof the streets, one is disposed to allege that chance rather than any humanwill guided by reason must have led to such an arrangement. And if we considerthat nevertheless there have been at all times certain officers whose duty itwas to see that private buildings contributed to public ornament, thedifficulty of reaching high perfection with but the materials of others tooperate on, will be readily acknowledged. In the same way I fancied that thosenations which, starting from a semi-barbarous state and advancing tocivilization by slow degrees, have had their laws successively determined, and,as it were, forced upon them simply by experience of the hurtfulness ofparticular crimes and disputes, would by this process come to be possessed ofless perfect institutions than those which, from the commencement of theirassociation as communities, have followed the appointments of some wiselegislator. It is thus quite certain that the constitution of the truereligion, the ordinances of which are derived from God, must be incomparablysuperior to that of every other. And, to speak of human affairs, I believe thatthe pre-eminence of Sparta was due not to the goodness of each of its laws inparticular, for many of these were very strange, and even opposed to goodmorals, but to the circumstance that, originated by a single individual, theyall tended to a single end. In the same way I thought that the sciencescontained in books (such of them at least as are made up of probablereasonings, without demonstrations), composed as they are of the opinions ofmany different individuals massed together, are farther removed from truth thanthe simple inferences which a man of good sense using his natural andunprejudiced judgment draws respecting the matters of his experience. Andbecause we have all to pass through a state of infancy to manhood, and havebeen of necessity, for a length of time, governed by our desires and preceptors(whose dictates were frequently conflicting, while neither perhaps alwayscounseled us for the best), I farther concluded that it is almost impossiblethat our judgments can be so correct or solid as they would have been, had ourreason been mature from the moment of our birth, and had we always been guidedby it alone.

It is true, however, that it is not customary to pull down all the houses of atown with the single design of rebuilding them differently, and therebyrendering the streets more handsome; but it often happens that a privateindividual takes down his own with the view of erecting it anew, and thatpeople are even sometimes constrained to this when their houses are in dangerof falling from age, or when the foundations are insecure. With this before meby way of example, I was persuaded that it would indeed be preposterous for aprivate individual to think of reforming a state by fundamentally changing itthroughout, and overturning it in order to set it up amended; and the same Ithought 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 theopinions which up to that time I had embraced, I thought that I could not dobetter than resolve at once to sweep them wholly away, that I might afterwardsbe in a position to admit either others more correct, or even perhaps the samewhen they had undergone the scrutiny of reason. I firmly believed that in thisway I should much better succeed in the conduct of my life, than if I builtonly upon old foundations, and leaned upon principles which, in my youth, I hadtaken upon trust. For although I recognized various difficulties in thisundertaking, these were not, however, without remedy, nor once to be comparedwith such as attend the slightest reformation in public affairs. Large bodies,if once overthrown, are with great difficulty set up again, or even kept erectwhen once seriously shaken, and the fall of such is always disastrous. Then ifthere are any imperfections in the constitutions of states (and that many suchexist the diversity of constitutions is alone sufficient to assure us), customhas without doubt materially smoothed their inconveniences, and has evenmanaged to steer altogether clear of, or insensibly corrected a number whichsagacity could not have provided against with equal effect; and, in fine, thedefects are almost always more tolerable than the change necessary for theirremoval; in the same manner that highways which wind among mountains, by beingmuch frequented, become gradually so smooth and commodious, that it is muchbetter to follow them than to seek a straighter path by climbing over the topsof rocks and descending to the bottoms of precipices.

Hence it is that I cannot in any degree approve of those restless and busymeddlers who, called neither by birth nor fortune to take part in themanagement of public affairs, are yet always projecting reforms; and if Ithought that this tract contained aught which might justify the suspicion thatI was a victim of such folly, I would by no means permit its publication. Ihave never contemplated anything higher than the reformation of my ownopinions, and basing them on a foundation wholly my own. And although my ownsatisfaction with my work has led me to present here a draft of it, I do not byany 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 lesteven 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 thatought not to be taken by every one. The majority of men is composed of twoclasses, for neither of which would this be at all a befitting resolution: inthe first place, of those who with more than a due confidence in their ownpowers, are precipitate in their judgments and want the patience requisite fororderly and circumspect thinking; whence it happens, that if men of this classonce take the liberty to doubt of their accustomed opinions, and quit thebeaten highway, they will never be able to thread the byway that would leadthem by a shorter course, and will lose themselves and continue to wander forlife; in the second place, of those who, possessed of sufficient sense ormodesty to determine that there are others who excel them in the power ofdiscriminating between truth and error, and by whom they may be instructed,ought rather to content themselves with the opinions of such than trust formore correct to their own reason.

For my own part, I should doubtless have belonged to the latter class, had Ireceived instruction from but one master, or had I never known the diversitiesof opinion that from time immemorial have prevailed among men of the greatestlearning. But I had become aware, even so early as during my college life, thatno opinion, however absurd and incredible, can be imagined, which has not beenmaintained by some on of the philosophers; and afterwards in the course of mytravels I remarked that all those whose opinions are decidedly repugnant toours are not in that account barbarians and savages, but on the contrary thatmany of these nations make an equally good, if not better, use of their reasonthan we do. I took into account also the very different character which aperson brought up from infancy in France or Germany exhibits, from that which,with the same mind originally, this individual would have possessed had helived always among the Chinese or with savages, and the circumstance that indress 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 atthis moment extravagant and ridiculous. I was thus led to infer that the groundof 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 aplurality of suffrages is no guarantee of truth where it is at all of difficultdiscovery, as in such cases it is much more likely that it will be found by onethan by many. I could, however, select from the crowd no one whose opinionsseemed 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 andwith such circumspection, that if I did not advance far, I would at least guardagainst falling. I did not even choose to dismiss summarily any of the opinionsthat had crept into my belief without having been introduced by reason, butfirst of all took sufficient time carefully to satisfy myself of the generalnature of the task I was setting myself, and ascertain the true method by whichto 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 someattention to logic, and among those of the mathematics to geometrical analysisand algebra,--three arts or sciences which ought, as I conceived, to contributesomething to my design. But, on examination, I found that, as for logic, itssyllogisms and the majority of its other precepts are of avail--rather in thecommunication of what we already know, or even as the art of Lully, in speakingwithout judgment of things of which we are ignorant, than in the investigationof the unknown; and although this science contains indeed a number of correctand very excellent precepts, there are, nevertheless, so many others, and theseeither injurious or superfluous, mingled with the former, that it is almostquite as difficult to effect a severance of the true from the false as it is toextract a Diana or a Minerva from a rough block of marble. Then as to theanalysis of the ancients and the algebra of the moderns, besides that theyembrace only matters highly abstract, and, to appearance, of no use, the formeris so exclusively restricted to the consideration of figures, that it canexercise the understanding only on condition of greatly fatiguing theimagination; and, in the latter, there is so complete a subjection to certainrules and formulas, that there results an art full of confusion and obscuritycalculated to embarrass, instead of a science fitted to cultivate the mind. Bythese considerations I was induced to seek some other method which wouldcomprise the advantages of the three and be exempt from their defects. And as amultitude of laws often only hampers justice, so that a state is best governedwhen, with few laws, these are rigidly administered; in like manner, instead ofthe great number of precepts of which logic is composed, I believed that thefour following would prove perfectly sufficient for me, provided I took thefirm and unwavering resolution never in a single instance to fail in observingthem.

The first was never to accept anything for true which I did not clearly know tobe such; that is to say, carefully to avoid precipitancy and prejudice, and tocomprise nothing more in my judgement than what was presented to my mind soclearly and distinctly as to exclude all ground of doubt.

The second, to divide each of the difficulties under examination into as manyparts as possible, and as might be necessary for its adequate solution.

The third, to conduct my thoughts in such order that, by commencing withobjects 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; assigningin thought a certain order even to those objects which in their own nature donot stand in a relation of antecedence and sequence.

And the last, in every case to make enumerations so complete, andreviews so general, that I might be assured that nothing was omitted.

The long chains of simple and easy reasonings by means of which geometers areaccustomed to reach the conclusions of their most difficult demonstrations, hadled 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 farremoved from us as to be beyond our reach, or so hidden that we cannot discoverit, provided only we abstain from accepting the false for the true, and alwayspreserve in our thoughts the order necessary for the deduction of one truthfrom another. And I had little difficulty in determining the objects with whichit was necessary to commence, for I was already persuaded that it must be withthe simplest and easiest to know, and, considering that of all those who havehitherto sought truth in the sciences, the mathematicians alone have been ableto find any demonstrations, that is, any certain and evident reasons, I did notdoubt but that such must have been the rule of their investigations. I resolvedto commence, therefore, with the examination of the simplest objects, notanticipating, however, from this any other advantage than that to be found inaccustoming my mind to the love and nourishment of truth, and to a distaste forall such reasonings as were unsound. But I had no intention on that account ofattempting to master all the particular sciences commonly denominatedmathematics: but observing that, however different their objects, they allagree in considering only the various relations or proportions subsisting amongthose objects, I thought it best for my purpose to consider these proportionsin the most general form possible, without referring them to any objects inparticular, except such as would most facilitate the knowledge of them, andwithout by any means restricting them to these, that afterwards I might thus bethe better able to apply them to every other class of objects to which they arelegitimately applicable. Perceiving further, that in order to understand theserelations I should sometimes have to consider them one by one and sometimesonly to bear them in mind, or embrace them in the aggregate, I thought that, inorder the better to consider them individually, I should view them assubsisting between straight lines, than which I could find no objects moresimple, or capable of being more distinctly represented to my imagination andsenses; and on the other hand, that in order to retain them in the memory orembrace an aggregate of many, I should express them by certain characters thebriefest possible. In this way I believed that I could borrow all that was bestboth in geometrical analysis and in algebra, and correct all the defects of theone by help of the other.

And, in point of fact, the accurate observance of these few precepts gave me, Itake the liberty of saying, such ease in unraveling all the questions embracedin these two sciences, that in the two or three months I devoted to theirexamination, not only did I reach solutions of questions I had formerly deemedexceedingly difficult but even as regards questions of the solution of which Icontinued ignorant, I was enabled, as it appeared to me, to determine the meanswhereby, and the extent to which a solution was possible; results attributableto 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 ofsubsequent ones Nor in this perhaps shall I appear too vain, if it beconsidered that, as the truth on any particular point is one whoever apprehendsthe 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 aparticular addition, according to rule, may be assured that he has found, withrespect to the sum of the numbers before him, and that in this instance iswithin the reach of human genius. Now, in conclusion, the method which teachesadherence to the true order, and an exact enumeration of all the conditions ofthe 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 Ihad of thereby exercising my reason in all matters, if not with absoluteperfection, at least with the greatest attainable by me: besides, I wasconscious that by its use my mind was becoming gradually habituated to clearerand more distinct conceptions of its objects; and I hoped also, from not havingrestricted this method to any particular matter, to apply it to thedifficulties of the other sciences, with not less success than to those ofalgebra. I should not, however, on this account have ventured at once on theexamination of all the difficulties of the sciences which presented themselvesto 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 borrowedfrom philosophy, in which I found nothing certain, I thought it necessary firstof 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 bedreaded, I thought that I ought not to approach it till I had reached a moremature age (being at that time but twenty-three), and had first of all employedmuch of my time in preparation for the work, as well by eradicating from mymind all the erroneous opinions I had up to that moment accepted, as byamassing variety of experience to afford materials for my reasonings, and bycontinually exercising myself in my chosen method with a view to increasedskill in its application.

PART III

And finally, as it is not enough, before commencing to rebuild the house inwhich we live, that it be pulled down, and materials and builders provided, orthat we engage in the work ourselves, according to a plan which we havebeforehand carefully drawn out, but as it is likewise necessary that we befurnished with some other house in which we may live commodiously during theoperations, so that I might not remain irresolute in my actions, while myreason compelled me to suspend my judgement, and that I might not be preventedfrom living thenceforward in the greatest possible felicity, I formed aprovisory code of morals, composed of three or four maxims, with which I amdesirous to make you acquainted.

The firstwas to obey the laws and customs of my country, adheringfirmly to the faith in which, by the grace of God, I had been educated from mychildhood and regulating my conduct in every other matter according to the mostmoderate opinions, and the farthest removed from extremes, which should happento be adopted in practice with general consent of the most judicious of thoseamong whom I might be living. For as I had from that time begun to hold my ownopinions for nought because I wished to subject them all to examination, I wasconvinced that I could not do better than follow in the meantime the opinionsof the most judicious; and although there are some perhaps among the Persiansand Chinese as judicious as among ourselves, expediency seemed to dictate thatI should regulate my practice conformably to the opinions of those with whom Ishould have to live; and it appeared to me that, in order to ascertain the realopinions of such, I ought rather to take cognizance of what they practised thanof what they said, not only because, in the corruption of our manners, thereare few disposed to speak exactly as they believe, but also because very manyare not aware of what it is that they really believe; for, as the act of mindby which a thing is believed is different from that by which we know that webelieve it, the one act is often found without the other. Also, amid manyopinions held in equal repute, I chose always the most moderate, as much forthe reason that these are always the most convenient for practice, and probablythe best (for all excess is generally vicious), as that, in the event of myfalling into error, I might be at less distance from the truth than if, havingchosen one of the extremes, it should turn out to be the other which I ought tohave adopted. And I placed in the class of extremes especially all promises bywhich somewhat of our freedom is abridged; not that I disapproved of the lawswhich, to provide against the instability of men of feeble resolution, whenwhat is sought to be accomplished is some good, permit engagements by vows andcontracts binding the parties to persevere in it, or even, for the security ofcommerce, sanction similar engagements where the purpose sought to be realizedis indifferent: but because I did not find anything on earth which was whollysuperior to change, and because, for myself in particular, I hoped gradually toperfect my judgments, and not to suffer them to deteriorate, I would havedeemed it a grave sin against good sense, if, for the reason that I approved ofsomething at a particular time, I therefore bound myself to hold it for good ata subsequent time, when perhaps it had ceased to be so, or I had ceased toesteem it such.

My secondmaxim was to be as firm and resolute in my actions as I wasable, and not to adhere less steadfastly to the most doubtful opinions, whenonce adopted, than if they had been highly certain; imitating in this theexample of travelers who, when they have lost their way in a forest, ought notto wander from side to side, far less remain in one place, but proceedconstantly towards the same side in as straight a line as possible, withoutchanging their direction for slight reasons, although perhaps it might bechance alone which at first determined the selection; for in this way, if theydo not exactly reach the point they desire, they will come at least in the endto some place that will probably be preferable to the middle of a forest. Inthe same way, since in action it frequently happens that no delay ispermissible, it is very certain that, when it is not in our power to determinewhat is true, we ought to act according to what is most probable; and evenalthough we should not remark a greater probability in one opinion than inanother, we ought notwithstanding to choose one or the other, and afterwardsconsider it, in so far as it relates to practice, as no longer dubious, butmanifestly true and certain, since the reason by which our choice has beendetermined is itself possessed of these qualities. This principle wassufficient thenceforward to rid me of all those repentings and pangs of remorsethat usually disturb the consciences of such feeble and uncertain minds as,destitute of any clear and determinate principle of choice, allow themselvesone day to adopt a course of action as the best, which they abandon the next,as the opposite.

My thirdmaxim was to endeavor always to conquer myself rather thanfortune, and change my desires rather than the order of the world, and ingeneral, accustom myself to the persuasion that, except our own thoughts, thereis nothing absolutely in our power; so that when we have done our best inthings external to us, all wherein we fail of success is to be held, as regardsus, absolutely impossible: and this single principle seemed to me sufficient toprevent me from desiring for the future anything which I could not obtain, andthus render me contented; for since our will naturally seeks those objectsalone which the understanding represents as in some way possible of attainment,it is plain, that if we consider all external goods as equally beyond ourpower, we shall no more regret the absence of such goods as seem due to ourbirth, when deprived of them without any fault of ours, than our not possessingthe kingdoms of China or Mexico, and thus making, so to speak, a virtue ofnecessity, we shall no more desire health in disease, or freedom inimprisonment, than we now do bodies incorruptible as diamonds, or the wings ofbirds to fly with. But I confess there is need of prolonged discipline andfrequently repeated meditation to accustom the mind to view all objects in thislight; and I believe that in this chiefly consisted the secret of the power ofsuch philosophers as in former times were enabled to rise superior to theinfluence of fortune, and, amid suffering and poverty, enjoy a happiness whichtheir gods might have envied. For, occupied incessantly with the considerationof the limits prescribed to their power by nature, they became so entirelyconvinced that nothing was at their disposal except their own thoughts, thatthis conviction was of itself sufficient to prevent their entertaining anydesire of other objects; and over their thoughts they acquired a sway soabsolute, that they had some ground on this account for esteeming themselvesmore rich and more powerful, more free and more happy, than other men who,whatever be the favors heaped on them by nature and fortune, if destitute ofthis philosophy, can never command the realization of all their desires.

In fine, to conclude this code of morals, I thought of reviewing the differentoccupations of men in this life, with the view of making choice of the best.And, without wishing to offer any remarks on the employments of others, I maystate that it was my conviction that I could not do better than continue inthat in which I was engaged, viz., in devoting my whole life to the culture ofmy reason, and in making the greatest progress I was able in the knowledge oftruth, on the principles of the method which I had prescribed to myself. Thismethod, from the time I had begun to apply it, had been to me the source ofsatisfaction so intense as to lead me to, believe that more perfect or moreinnocent could not be enjoyed in this life; and as by its means I dailydiscovered truths that appeared to me of some importance, and of which othermen were generally ignorant, the gratification thence arising so occupied mymind that I was wholly indifferent to every other object. Besides, the threepreceding maxims were founded singly on the design of continuing the work ofself-instruction. For since God has endowed each of us with some light ofreason by which to distinguish truth from error, I could not have believed thatI ought for a single moment to rest satisfied with the opinions of another,unless I had resolved to exercise my own judgment in examining these whenever Ishould be duly qualified for the task. Nor could I have proceeded on suchopinions without scruple, had I supposed that I should thereby forfeit anyadvantage for attaining still more accurate, should such exist. And, in fine, Icould not have restrained my desires, nor remained satisfied had I not followeda path in which I thought myself certain of attaining all the knowledge to theacquisition of which I was competent, as well as the largest amount of what istruly good which I could ever hope to secure Inasmuch as we neither seek norshun any object except in so far as our understanding represents it as good orbad, all that is necessary to right action is right judgment, and to the bestaction the most correct judgment, that is, to the acquisition of all thevirtues with all else that is truly valuable and within our reach; and theassurance of such an acquisition cannot fail to render us contented.

Having thus provided myself with these maxims, and having placed them inreserve along with the truths of faith, which have ever occupied the firstplace in my belief, I came to the conclusion that I might with freedom setabout ridding myself of what remained of my opinions. And, inasmuch as I hopedto be better able successfully to accomplish this work by holding intercoursewith mankind, than by remaining longer shut up in the retirement where thesethoughts had occurred to me, I betook me again to traveling before the winterwas well ended. And, during the nine subsequent years, I did nothing but roamfrom one place to another, desirous of being a spectator rather than an actorin the plays exhibited on the theater of the world; and, as I made it mybusiness in each matter to reflect particularly upon what might fairly bedoubted and prove a source of error, I gradually rooted out from my mind allthe errors which had hitherto crept into it. Not that in this I imitated thesceptics who doubt only that they may doubt, and seek nothing beyonduncertainty itself; for, on the contrary, my design was singly to find groundof assurance, and cast aside the loose earth and sand, that I might reach therock or the clay. In this, as appears to me, I was successful enough; for,since I endeavored to discover the falsehood or incertitude of the propositionsI examined, not by feeble conjectures, but by clear and certain reasonings, Imet with nothing so doubtful as not to yield some conclusion of adequatecertainty, although this were merely the inference, that the matter in questioncontained nothing certain. And, just as in pulling down an old house, weusually reserve the ruins to contribute towards the erection, so, in destroyingsuch of my opinions as I judged to be Ill-founded, I made a variety ofobservations and acquired an amount of experience of which I availed myself inthe establishment of more certain. And further, I continued to exercise myselfin the method I had prescribed; for, besides taking care in general to conductall my thoughts according to its rules, I reserved some hours from time to timewhich I expressly devoted to the employment of the method in the solution ofmathematical difficulties, or even in the solution likewise of some questionsbelonging to other sciences, but which, by my having detached them from suchprinciples of these sciences as were of inadequate certainty, were renderedalmost mathematical: the truth of this will be manifest from the numerousexamples contained in this volume. And thus, without in appearance livingotherwise than those who, with no other occupation than that of spending theirlives agreeably and innocently, study to sever pleasure from vice, and who,that they may enjoy their leisure without ennui, have recourse to such pursuitsas are honorable, I was nevertheless prosecuting my design, and making greaterprogress in the knowledge of truth, than I might, perhaps, have made had I beenengaged in the perusal of books merely, or in holding converse with men ofletters.

These nine years passed away, however, before I had come to any determinatejudgment respecting the difficulties which form matter of dispute among thelearned, or had commenced to seek the principles of any philosophy more certainthan the vulgar. And the examples of many men of the highest genius, who had,in former times, engaged in this inquiry, but, as appeared to me, withoutsuccess, led me to imagine it to be a work of so much difficulty, that I wouldnot perhaps have ventured on it so soon had I not heard it currently rumoredthat I had already completed the inquiry. I know not what were the grounds ofthis opinion; and, if my conversation contributed in any measure to its rise,this must have happened rather from my having confessed my Ignorance withgreater freedom than those are accustomed to do who have studied a little, andexpounded perhaps, the reasons that led me to doubt of many of those thingsthat by others are esteemed certain, than from my having boasted of any systemof philosophy. But, as I am of a disposition that makes me unwilling to beesteemed different from what I really am, I thought it necessary to endeavor byall means to render myself worthy of the reputation accorded to me; and it isnow exactly eight years since this desire constrained me to remove from allthose places where interruption from any of my acquaintances was possible, andbetake myself to this country, in which the long duration of the war has led tothe establishment of such discipline, that the armies maintained seem to be ofuse only in enabling the inhabitants to enjoy more securely the blessings ofpeace and where, in the midst of a great crowd actively engaged in business,and more careful of their own affairs than curious about those of others, Ihave been enabled to live without being deprived of any of the conveniences tobe had in the most populous cities, and yet as solitary and as retired as inthe midst of the most remote deserts.

PART IV

I am in doubt as to the propriety of making my first meditations in the placeabove mentioned matter of discourse; for these are so metaphysical, and souncommon, as not, perhaps, to be acceptable to every one. And yet, that it maybe determined whether the foundations that I have laid are sufficiently secure,I find myself in a measure constrained to advert to them. I had long beforeremarked that, in relation to practice, it is sometimes necessary to adopt, asif above doubt, opinions which we discern to be highly uncertain, as has beenalready said; but as I then desired to give my attention solely to the searchafter truth, I thought that a procedure exactly the opposite was called for,and that I ought to reject as absolutely false all opinions in regard to whichI could suppose the least ground for doubt, in order to ascertain whether afterthat there remained aught in my belief that was wholly indubitable.Accordingly, seeing that our senses sometimes deceive us, I was willing tosuppose that there existed nothing really such as they presented to us; andbecause some men err in reasoning, and fall into paralogisms, even on thesimplest matters of geometry, I, convinced that I was as open to error as anyother, rejected as false all the reasonings I had hitherto taken fordemonstrations; and finally, when I considered that the very same thoughts(presentations) which we experience when awake may also be experienced when weare asleep, while there is at that time not one of them true, I supposed thatall the objects (presentations) that had ever entered into my mind when awake,had in them no more truth than the illusions of my dreams. But immediately uponthis I observed that, whilst I thus wished to think that all was false, it wasabsolutely necessary that I, who thus thought, should be somewhat; and as Iobserved that this truth, I think, therefore I am (COGITO ERGO SUM), was socertain and of such evidence that no ground of doubt, however extravagant,could be alleged by the sceptics capable of shaking it, I concluded that Imight, without scruple, accept it as the first principle of the philosophy ofwhich I was in search.

In the next place, I attentively examined what I was and as I observed that Icould suppose that I had no body, and that there was no world nor any place inwhich I might be; but that I could not therefore suppose that I was not; andthat, on the contrary, from the very circumstance that I thought to doubt ofthe truth of other things, it most clearly and certainly followed that I was;while, on the other hand, if I had only ceased to think, although all the otherobjects which I had ever imagined had been in reality existent, I would havehad no reason to believe that I existed; I thence concluded that I was asubstance whose whole essence or nature consists only in thinking, and which,that it may exist, has need of no place, nor is dependent on any materialthing; so that “I,” that is to say, the mind by which I am what Iam, is wholly distinct from the body, and is even more easily known than thelatter, and is such, that although the latter were not, it would still continueto be all that it is.

After this I inquired in general into what is essential to the truth andcertainty of a proposition; for since I had discovered one which I knew to betrue, I thought that I must likewise be able to discover the ground of thiscertitude. And as I observed that in the words I think, therefore I am, thereis nothing at all which gives me assurance of their truth beyond this, that Isee very clearly that in order to think it is necessary to exist, I concludedthat I might take, as a general rule, the principle, that all the things whichwe very clearly and distinctly conceive are true, only observing, however, thatthere is some difficulty in rightly determining the objects which we distinctlyconceive.

In the next place, from reflecting on the circumstance that I doubted, and thatconsequently my being was not wholly perfect (for I clearly saw that it was agreater perfection to know than to doubt), I was led to inquire whence I hadlearned to think of something more perfect than myself; and I clearlyrecognized that I must hold this notion from some nature which in reality wasmore perfect. As for the thoughts of many other objects external to me, as ofthe sky, the earth, light, heat, and a thousand more, I was less at a loss toknow whence these came; for since I remarked in them nothing which seemed torender them superior to myself, I could believe that, if these were true, theywere dependencies on my own nature, in so far as it possessed a certainperfection, and, if they were false, that I held them from nothing, that is tosay, that they were in me because of a certain imperfection of my nature. Butthis could not be the case with-the idea of a nature more perfect than myself;for to receive it from nothing was a thing manifestly impossible; and, becauseit is not less repugnant that the more perfect should be an effect of, anddependence on the less perfect, than that something should proceed fromnothing, it was equally impossible that I could hold it from myself:accordingly, it but remained that it had been placed in me by a nature whichwas in reality more perfect than mine, and which even possessed within itselfall the perfections of which I could form any idea; that is to say, in a singleword, which was God. And to this I added that, since I knew some perfectionswhich I did not possess, I was not the only being in existence (I will here,with your permission, freely use the terms of the schools); but, on thecontrary, that there was of necessity some other more perfect Being upon whom Iwas dependent, and from whom I had received all that I possessed; for if I hadexisted alone, and independently of every other being, so as to have had frommyself all the perfection, however little, which I actually possessed, I shouldhave been able, for the same reason, to have had from myself the wholeremainder of perfection, of the want of which I was conscious, and thus couldof myself have become infinite, eternal, immutable, omniscient, all-powerful,and, in fine, have possessed all the perfections which I could recognize inGod. For in order to know the nature of God (whose existence has beenestablished by the preceding reasonings), as far as my own nature permitted, Ihad only to consider in reference to all the properties of which I found in mymind some idea, whether their possession was a mark of perfection; and I wasassured that no one which indicated any imperfection was in him, and that noneof the rest was awanting. Thus I perceived that doubt, inconstancy, sadness,and such like, could not be found in God, since I myself would have been happyto be free from them. Besides, I had ideas of many sensible and corporealthings; for although I might suppose that I was dreaming, and that all which Isaw or imagined was false, I could not, nevertheless, deny that the ideas werein reality in my thoughts. But, because I had already very clearly recognizedin myself that the intelligent nature is distinct from the corporeal, and as Iobserved that all composition is an evidence of dependency, and that a state ofdependency is manifestly a state of imperfection, I therefore determined thatit could not be a perfection in God to be compounded of these two natures andthat consequently he was not so compounded; but that if there were any bodiesin the world, or even any intelligences, or other natures that were not whollyperfect, their existence depended on his power in such a way that they couldnot subsist without him for a single moment.

I was disposed straightway to search for other truths and when I hadrepresented to myself the object of the geometers, which I conceived to be acontinuous body or a space indefinitely extended in length, breadth, and heightor depth, divisible into divers parts which admit of different figures andsizes, and of being moved or transposed in all manner of ways (for all this thegeometers suppose to be in the object they contemplate), I went over some oftheir simplest demonstrations. And, in the first place, I observed, that thegreat certitude which by common consent is accorded to these demonstrations, isfounded solely upon this, that they are clearly conceived in accordance withthe rules I have already laid down In the next place, I perceived that therewas nothing at all in these demonstrations which could assure me of theexistence of their object: thus, for example, supposing a triangle to be given,I distinctly perceived that its three angles were necessarily equal to tworight angles, but I did not on that account perceive anything which couldassure me that any triangle existed: while, on the contrary, recurring to theexamination of the idea of a Perfect Being, I found that the existence of theBeing was comprised in the idea in the same way that the equality of its threeangles to two right angles is comprised in the idea of a triangle, or as in theidea of a sphere, the equidistance of all points on its surface from thecenter, or even still more clearly; and that consequently it is at least ascertain that God, who is this Perfect Being, is, or exists, as anydemonstration of geometry can be.

But the reason which leads many to persuade them selves that there is adifficulty in knowing this truth, and even also in knowing what their mindreally is, is that they never raise their thoughts above sensible objects, andare so accustomed to consider nothing except by way of imagination, which is amode of thinking limited to material objects, that all that is not imaginableseems to them not intelligible. The truth of this is sufficiently manifest fromthe single circumstance, that the philosophers of the schools accept as a maximthat there is nothing in the understanding which was not previously in thesenses, in which however it is certain that the ideas of God and of the soulhave never been; and it appears to me that they who make use of theirimagination to comprehend these ideas do exactly the some thing as if, in orderto hear sounds or smell odors, they strove to avail themselves of their eyes;unless indeed that there is this difference, that the sense of sight does notafford us an inferior assurance to those of smell or hearing; in place ofwhich, neither our imagination nor our senses can give us assurance of anythingunless our understanding intervene.

Finally, if there be still persons who are not sufficiently persuaded of theexistence of God and of the soul, by the reasons I have adduced, I am desirousthat they should know that all the other propositions, of the truth of whichthey deem themselves perhaps more assured, as that we have a body, and thatthere exist stars and an earth, and such like, are less certain; for, althoughwe have a moral assurance of these things, which is so strong that there is anappearance of extravagance in doubting of their existence, yet at the same timeno one, unless his intellect is impaired, can deny, when the question relatesto a metaphysical certitude, that there is sufficient reason to exclude entireassurance, in the observation that when asleep we can in the same way imagineourselves possessed of another body and that we see other stars and anotherearth, when there is nothing of the kind. For how do we know that the thoughtswhich occur in dreaming are false rather than those other which we experiencewhen awake, since the former are often not less vivid and distinct than thelatter? And though men of the highest genius study this question as long asthey please, I do not believe that they will be able to give any reason whichcan be sufficient to remove this doubt, unless they presuppose the existence ofGod. For, in the first place even the principle which I have already taken as arule, viz., that all the things which we clearly and distinctly conceive aretrue, is certain only because God is or exists and because he is a PerfectBeing, and because all that we possess is derived from him: whence it followsthat our ideas or notions, which to the extent of their clearness anddistinctness are real, and proceed from God, must to that extent be true.Accordingly, whereas we not infrequently have ideas or notions in which somefalsity is contained, this can only be the case with such as are to some extentconfused and obscure, and in this proceed from nothing (participate ofnegation), that is, exist in us thus confused because we are not whollyperfect. And it is evident that it is not less repugnant that falsity orimperfection, in so far as it is imperfection, should proceed from God, thanthat truth or perfection should proceed from nothing. But if we did not knowthat all which we possess of real and true proceeds from a Perfect and InfiniteBeing, however clear and distinct our ideas might be, we should have no groundon that account for the assurance that they possessed the perfection of beingtrue.

But after the knowledge of God and of the soul has rendered us certain of thisrule, we can easily understand that the truth of the thoughts we experiencewhen awake, ought not in the slightest degree to be called in question onaccount of the illusions of our dreams. For if it happened that an individual,even when asleep, had some very distinct idea, as, for example, if a geometershould discover some new demonstration, the circumstance of his being asleepwould not militate against its truth; and as for the most ordinary error of ourdreams, which consists in their representing to us various objects in the sameway as our external senses, this is not prejudicial, since it leads us veryproperly to suspect the truth of the ideas of sense; for we are notinfrequently deceived in the same manner when awake; as when persons in thejaundice see all objects yellow, or when the stars or bodies at a greatdistance appear to us much smaller than they are. For, in fine, whether awakeor asleep, we ought never to allow ourselves to be persuaded of the truth ofanything unless on the evidence of our reason. And it must be noted that I sayof our reason, and not of our imagination or of our senses: thus, for example,although we very clearly see the sun, we ought not therefore to determine thatit is only of the size which our sense of sight presents; and we may verydistinctly imagine the head of a lion joined to the body of a goat, withoutbeing therefore shut up to the conclusion that a chimaera exists; for it is nota dictate of reason that what we thus see or imagine is in reality existent;but it plainly tells us that all our ideas or notions contain in them sometruth; for otherwise it could not be that God, who is wholly perfect andveracious, should have placed them in us. And because our reasonings are neverso clear or so complete during sleep as when we are awake, although sometimesthe acts of our imagination are then as lively and distinct, if not more sothan in our waking moments, reason further dictates that, since all ourthoughts cannot be true because of our partial imperfection, those possessingtruth must infallibly be found in the experience of our waking moments ratherthan in that of our dreams.

PART V

I would here willingly have proceeded to exhibit the whole chain of truthswhich I deduced from these primary but as with a view to this it would havebeen necessary now to treat of many questions in dispute among the earned, withwhom I do not wish to be embroiled, I believe that it will be better for me torefrain from this exposition, and only mention in general what these truthsare, that the more judicious may be able to determine whether a more specialaccount of them would conduce to the public advantage. I have ever remainedfirm in my original resolution to suppose no other principle than that of whichI have recently availed myself in demonstrating the existence of God and of thesoul, and to accept as true nothing that did not appear to me more clear andcertain than the demonstrations of the geometers had formerly appeared; and yetI venture to state that not only have I found means to satisfy myself in ashort time on all the principal difficulties which are usually treated of inphilosophy, but I have also observed certain laws established in nature by Godin such a manner, and of which he has impressed on our minds such notions, thatafter we have reflected sufficiently upon these, we cannot doubt that they areaccurately observed in all that exists or takes place in the world and farther,by considering the concatenation of these laws, it appears to me that I havediscovered many truths more useful and more important than all I had beforelearned, or even had expected to learn.

But because I have essayed to expound the chief of these discoveries in atreatise which certain considerations prevent me from publishing, I cannot makethe results known more conveniently than by here giving a summary of thecontents of this treatise. It was my design to comprise in it all that, beforeI set myself to write it, I thought I knew of the nature of material objects.But like the painters who, finding themselves unable to represent equally wellon a plain surface all the different faces of a solid body, select one of thechief, on which alone they make the light fall, and throwing the rest into theshade, allow them to appear only in so far as they can be seen while looking atthe principal one; so, fearing lest I should not be able to compense in mydiscourse all that was in my mind, I resolved to expound singly, though atconsiderable length, my opinions regarding light; then to take the opportunityof adding something on the sun and the fixed stars, since light almost whollyproceeds from them; on the heavens since they transmit it; on the planets,comets, and earth, since they reflect it; and particularly on all the bodiesthat are upon the earth, since they are either colored, or transparent, orluminous; and finally on man, since he is the spectator of these objects.Further, to enable me to cast this variety of subjects somewhat into the shade,and to express my judgment regarding them with greater freedom, without beingnecessitated to adopt or refute the opinions of the learned, I resolved toleave all the people here to their disputes, and to speak only of what wouldhappen in a new world, if God were now to create somewhere in the imaginaryspaces matter sufficient to compose one, and were to agitate variously andconfusedly the different parts of this matter, so that there resulted a chaosas disordered as the poets ever feigned, and after that did nothing more thanlend his ordinary concurrence to nature, and allow her to act in accordancewith the laws which he had established. On this supposition, I, in the firstplace, described this matter, and essayed to represent it in such a manner thatto my mind there can be nothing clearer and more intelligible, except what hasbeen recently said regarding God and the soul; for I even expressly supposedthat it possessed none of those forms or qualities which are so debated in theschools, nor in general anything the knowledge of which is not so natural toour minds that no one can so much as imagine himself ignorant of it. Besides, Ihave pointed out what are the laws of nature; and, with no other principle uponwhich to found my reasonings except the infinite perfection of God, Iendeavored to demonstrate all those about which there could be any room fordoubt, and to prove that they are such, that even if God had created moreworlds, there could have been none in which these laws were not observed.Thereafter, I showed how the greatest part of the matter of this chaos must, inaccordance with these laws, dispose and arrange itself in such a way as topresent the appearance of heavens; how in the meantime some of its parts mustcompose an earth and some planets and comets, and others a sun and fixed stars.And, making a digression at this stage on the subject of light, I expounded atconsiderable length what the nature of that light must be which is found in thesun and the stars, and how thence in an instant of time it traverses theimmense spaces of the heavens, and how from the planets and comets it isreflected towards the earth. To this I likewise added much respecting thesubstance, the situation, the motions, and all the different qualities of theseheavens and stars; so that I thought I had said enough respecting them to showthat there is nothing observable in the heavens or stars of our system thatmust not, or at least may not appear precisely alike in those of the systemwhich I described. I came next to speak of the earth in particular, and to showhow, even though I had expressly supposed that God had given no weight to thematter of which it is composed, this should not prevent all its parts fromtending exactly to its center; how with water and air on its surface, thedisposition of the heavens and heavenly bodies, more especially of the moon,must cause a flow and ebb, like in all its circumstances to that observed inour seas, as also a certain current both of water and air from east to west,such as is likewise observed between the tropics; how the mountains, seas,fountains, and rivers might naturally be formed in it, and the metals producedin the mines, and the plants grow in the fields and in general, how all thebodies which are commonly denominated mixed or composite might be generatedand, among other things in the discoveries alluded to inasmuch as besides thestars, I knew nothing except fire which produces light, I spared no pains toset forth all that pertains to its nature,--the manner of its production andsupport, and to explain how heat is sometimes found without light, and lightwithout heat; to show how it can induce various colors upon different bodiesand other diverse qualities; how it reduces some to a liquid state and hardensothers; how it can consume almost all bodies, or convert them into ashes andsmoke; and finally, how from these ashes, by the mere intensity of its action,it forms glass: for as this transmutation of ashes into glass appeared to me aswonderful as any other in nature, I took a special pleasure in describing it. Iwas not, however, disposed, from these circumstances, to conclude that thisworld had been created in the manner I described; for it is much more likelythat God made it at the first such as it was to be. But this is certain, and anopinion commonly received among theologians, that the action by which he nowsustains it is the same with that by which he originally created it; so thateven although he had from the beginning given it no other form than that ofchaos, provided only he had established certain laws of nature, and had lent ithis concurrence to enable it to act as it is wont to do, it may be believed,without discredit to the miracle of creation, that, in this way alone, thingspurely material might, in course of time, have become such as we observe themat present; and their nature is much more easily conceived when they are beheldcoming in this manner gradually into existence, than when they are onlyconsidered as produced at once in a finished and perfect state.

From the description of inanimate bodies and plants, I passed to animals, andparticularly to man. But since I had not as yet sufficient knowledge to enableme to treat of these in the same manner as of the rest, that is to say, bydeducing effects from their causes, and by showing from what elements and inwhat manner nature must produce them, I remained satisfied with the suppositionthat God formed the body of man wholly like to one of ours, as well in theexternal shape of the members as in the internal conformation of the organs, ofthe same matter with that I had described, and at first placed in it norational soul, nor any other principle, in room of the vegetative or sensitivesoul, beyond kindling in the heart one of those fires without light, such as Ihad already described, and which I thought was not different from the heat inhay that has been heaped together before it is dry, or that which causesfermentation in new wines before they are run clear of the fruit. For, when Iexamined the kind of functions which might, as consequences of thissupposition, exist in this body, I found precisely all those which may exist inus independently of all power of thinking, and consequently without being inany measure owing to the soul; in other words, to that part of us which isdistinct from the body, and of which it has been said above that the naturedistinctively consists in thinking, functions in which the animals void ofreason may be said wholly to resemble us; but among which I could not discoverany of those that, as dependent on thought alone, belong to us as men, while,on the other hand, I did afterwards discover these as soon as I supposed God tohave created a rational soul, and to have annexed it to this body in aparticular manner which I described.

But, in order to show how I there handled this matter, I mean here to give theexplication of the motion of the heart and arteries, which, as the first andmost general motion observed in animals, will afford the means of readilydetermining what should be thought of all the rest. And that there may be lessdifficulty in understanding what I am about to say on this subject, I advisethose who are not versed in anatomy, before they commence the perusal of theseobservations, to take the trouble of getting dissected in their presence theheart of some large animal possessed of lungs (for this is throughoutsufficiently like the human), and to have shown to them its two ventricles orcavities: in the first place, that in the right side, with which correspond twovery ample tubes, viz., the hollow vein (vena cava), which is theprincipal receptacle of the blood, and the trunk of the tree, as it were, ofwhich all the other veins in the body are branches; and the arterial vein(vena arteriosa), inappropriately so denominated, since it is in truthonly an artery, which, taking its rise in the heart, is divided, after passingout from it, into many branches which presently disperse themselves all overthe lungs; in the second place, the cavity in the left side, with whichcorrespond in the same manner two canals in size equal to or larger than thepreceding, viz., the venous artery (arteria venosa), likewiseinappropriately thus designated, because it is simply a vein which comes fromthe lungs, where it is divided into many branches, interlaced with those of thearterial vein, and those of the tube called the windpipe, through which the airwe breathe enters; and the great artery which, issuing from the heart, sendsits branches all over the body. I should wish also that such persons werecarefully shown the eleven pellicles which, like so many small valves, open andshut the four orifices that are in these two cavities, viz., three at theentrance of the hollow veins where they are disposed in such a manner as by nomeans to prevent the blood which it contains from flowing into the rightventricle of the heart, and yet exactly to prevent its flowing out; three atthe entrance to the arterial vein, which, arranged in a manner exactly theopposite of the former, readily permit the blood contained in this cavity topass into the lungs, but hinder that contained in the lungs from returning tothis cavity; and, in like manner, two others at the mouth of the venous artery,which allow the blood from the lungs to flow into the left cavity of the heart,but preclude its return; and three at the mouth of the great artery, whichsuffer the blood to flow from the heart, but prevent its reflux. Nor do we needto seek any other reason for the number of these pellicles beyond this that theorifice of the venous artery being of an oval shape from the nature of itssituation, can be adequately closed with two, whereas the others being roundare more conveniently closed with three. Besides, I wish such persons toobserve that the grand artery and the arterial vein are of much harder andfirmer texture than the venous artery and the hollow vein; and that the twolast expand before entering the heart, and there form, as it were, two pouchesdenominated the auricles of the heart, which are composed of a substancesimilar to that of the heart itself; and that there is always more warmth inthe heart than in any other part of the body--and finally, that this heat iscapable of causing any drop of blood that passes into the cavities rapidly toexpand and dilate, just as all liquors do when allowed to fall drop by dropinto a highly heated vessel.

For, after these things, it is not necessary for me to say anything more with aview to explain the motion of the heart, except that when its cavities are notfull of blood, into these the blood of necessity flows,--from the hollow veininto the right, and from the venous artery into the left; because these twovessels are always full of blood, and their orifices, which are turned towardsthe heart, cannot then be closed. But as soon as two drops of blood have thuspassed, one into each of the cavities, these drops which cannot but be verylarge, because the orifices through which they pass are wide, and the vesselsfrom which they come full of blood, are immediately rarefied, and dilated bythe heat they meet with. In this way they cause the whole heart to expand, andat the same time press home and shut the five small valves that are at theentrances of the two vessels from which they flow, and thus prevent any moreblood from coming down into the heart, and becoming more and more rarefied,they push open the six small valves that are in the orifices of the other twovessels, through which they pass out, causing in this way all the branches ofthe arterial vein and of the grand artery to expand almost simultaneously withthe heart which immediately thereafter begins to contract, as do also thearteries, because the blood that has entered them has cooled, and the six smallvalves close, and the five of the hollow vein and of the venous artery openanew and allow a passage to other two drops of blood, which cause the heart andthe arteries again to expand as before. And, because the blood which thusenters into the heart passes through these two pouches called auricles, itthence happens that their motion is the contrary of that of the heart, and thatwhen it expands they contract. But lest those who are ignorant of the force ofmathematical demonstrations and who are not accustomed to distinguish truereasons from mere verisimilitudes, should venture, without examination, to denywhat has been said, I wish it to be considered that the motion which I have nowexplained follows as necessarily from the very arrangement of the parts, whichmay be observed in the heart by the eye alone, and from the heat which may befelt with the fingers, and from the nature of the blood as learned fromexperience, as does the motion of a clock from the power, the situation, andshape of its counterweights and wheels.

But if it be asked how it happens that the blood in the veins, flowing in thisway continually into the heart, is not exhausted, and why the arteries do notbecome too full, since all the blood which passes through the heart flows intothem, I need only mention in reply what has been written by a physician ofEngland, who has the honor of having broken the ice on this subject, and ofhaving been the first to teach that there are many small passages at theextremities of the arteries, through which the blood received by them from theheart passes into the small branches of the veins, whence it again returns tothe heart; so that its course amounts precisely to a perpetual circulation. Ofthis we have abundant proof in the ordinary experience of surgeons, who, bybinding the arm with a tie of moderate straitness above the part where theyopen the vein, cause the blood to flow more copiously than it would have donewithout any ligature; whereas quite the contrary would happen were they to bindit below; that is, between the hand and the opening, or were to make theligature above the opening very tight. For it is manifest that the tie,moderately straightened, while adequate to hinder the blood already in the armfrom returning towards the heart by the veins, cannot on that account preventnew blood from coming forward through the arteries, because these are situatedbelow the veins, and their coverings, from their greater consistency, are moredifficult to compress; and also that the blood which comes from the heart tendsto pass through them to the hand with greater force than it does to return fromthe hand to the heart through the veins. And since the latter current escapesfrom the arm by the opening made in one of the veins, there must of necessitybe certain passages below the ligature, that is, towards the extremities of thearm through which it can come thither from the arteries. This physicianlikewise abundantly establishes what he has advanced respecting the motion ofthe blood, from the existence of certain pellicles, so disposed in variousplaces along the course of the veins, in the manner of small valves, as not topermit the blood to pass from the middle of the body towards the extremities,but only to return from the extremities to the heart; and farther, fromexperience which shows that all the blood which is in the body may flow out ofit in a very short time through a single artery that has been cut, evenalthough this had been closely tied in the immediate neighborhood of the heartand cut between the heart and the ligature, so as to prevent the suppositionthat the blood flowing out of it could come from any other quarter than theheart.

But there are many other circumstances which evince that what I have alleged isthe true cause of the motion of the blood: thus, in the first place, thedifference that is observed between the blood which flows from the veins, andthat from the arteries, can only arise from this, that being rarefied, and, asit were, distilled by passing through the heart, it is thinner, and more vivid,and warmer immediately after leaving the heart, in other words, when in thearteries, than it was a short time before passing into either, in other words,when it was in the veins; and if attention be given, it will be found that thisdifference is very marked only in the neighborhood of the heart; and is not soevident in parts more remote from it. In the next place, the consistency of thecoats of which the arterial vein and the great artery are composed,sufficiently shows that the blood is impelled against them with more force thanagainst the veins. And why should the left cavity of the heart and the greatartery be wider and larger than the right cavity and the arterial vein, were itnot that the blood of the venous artery, having only been in the lungs after ithas passed through the heart, is thinner, and rarefies more readily, and in ahigher degree, than the blood which proceeds immediately from the hollow vein?And what can physicians conjecture from feeling the pulse unless they know thataccording as the blood changes its nature it can be rarefied by the warmth ofthe heart, in a higher or lower degree, and more or less quickly than before?And if it be inquired how this heat is communicated to the other members, mustit not be admitted that this is effected by means of the blood, which, passingthrough the heart, is there heated anew, and thence diffused over all the body?Whence it happens, that if the blood be withdrawn from any part, the heat islikewise withdrawn by the same means; and although the heart were as-hot asglowing iron, it would not be capable of warming the feet and hands as atpresent, unless it continually sent thither new blood. We likewise perceivefrom this, that the true use of respiration is to bring sufficient fresh airinto the lungs, to cause the blood which flows into them from the rightventricle of the heart, where it has been rarefied and, as it were, changedinto vapors, to become thick, and to convert it anew into blood, before itflows into the left cavity, without which process it would be unfit for thenourishment of the fire that is there. This receives confirmation from thecircumstance, that it is observed of animals destitute of lungs that they havealso but one cavity in the heart, and that in children who cannot use themwhile in the womb, there is a hole through which the blood flows from thehollow vein into the left cavity of the heart, and a tube through which itpasses from the arterial vein into the grand artery without passing through thelung. In the next place, how could digestion be carried on in the stomachunless the heart communicated heat to it through the arteries, and along withthis certain of the more fluid parts of the blood, which assist in thedissolution of the food that has been taken in? Is not also the operation whichconverts the juice of food into blood easily comprehended, when it isconsidered that it is distilled by passing and repassing through the heartperhaps more than one or two hundred times in a day? And what more need beadduced to explain nutrition, and the production of the different humors of thebody, beyond saying, that the force with which the blood, in being rarefied,passes from the heart towards the extremities of the arteries, causes certainof its parts to remain in the members at which they arrive, and there occupythe place of some others expelled by them; and that according to the situation,shape, or smallness of the pores with which they meet, some rather than othersflow into certain parts, in the same way that some sieves are observed to act,which, by being variously perforated, serve to separate different species ofgrain? And, in the last place, what above all is here worthy of observation, isthe generation of the animal spirits, which are like a very subtle wind, orrather a very pure and vivid flame which, continually ascending in greatabundance from the heart to the brain, thence penetrates through the nervesinto the muscles, and gives motion to all the members; so that to account forother parts of the blood which, as most agitated and penetrating, are thefittest to compose these spirits, proceeding towards the brain, it is notnecessary to suppose any other cause, than simply, that the arteries whichcarry them thither proceed from the heart in the most direct lines, and that,according to the rules of mechanics which are the same with those of nature,when many objects tend at once to the same point where there is not sufficientroom for all (as is the case with the parts of the blood which flow forth fromthe left cavity of the heart and tend towards the brain), the weaker and lessagitated parts must necessarily be driven aside from that point by the strongerwhich alone in this way reach it I had expounded all these matters withsufficient minuteness in the treatise which I formerly thought of publishing.And after these, I had shown what must be the fabric of the nerves and musclesof the human body to give the animal spirits contained in it the power to movethe members, as when we see heads shortly after they have been struck off stillmove and bite the earth, although no longer animated; what changes must takeplace in the brain to produce waking, sleep, and dreams; how light, sounds,odors, tastes, heat, and all the other qualities of external objects impress itwith different ideas by means of the senses; how hunger, thirst, and the otherinternal affections can likewise impress upon it divers ideas; what must beunderstood by the common sense (sensus communis) in which these ideasare received, by the memory which retains them, by the fantasy which can changethem in various ways, and out of them compose new ideas, and which, by the samemeans, distributing the animal spirits through the muscles, can cause themembers of such a body to move in as many different ways, and in a manner assuited, whether to the objects that are presented to its senses or to itsinternal affections, as can take place in our own case apart from the guidanceof the will. Nor will this appear at all strange to those who are acquaintedwith the variety of movements performed by the different automata, or movingmachines fabricated by human industry, and that with help of but few piecescompared with the great multitude of bones, muscles, nerves, arteries, veins,and other parts that are found in the body of each animal. Such persons willlook upon this body as a machine made by the hands of God, which isincomparably better arranged, and adequate to movements more admirable than isany machine of human invention. And here I specially stayed to show that, werethere such machines exactly resembling organs and outward form an ape or anyother irrational animal, we could have no means of knowing that they were inany respect of a different nature from these animals; but if there weremachines bearing the image of our bodies, and capable of imitating our actionsas far as it is morally possible, there would still remain two most certaintests whereby to know that they were not therefore really men. Of these thefirst is that they could never use words or other signs arranged in such amanner as is competent to us in order to declare our thoughts to others: for wemay easily conceive a machine to be so constructed that it emits vocables, andeven that it emits some correspondent to the action upon it of external objectswhich cause a change in its organs; for example, if touched in a particularplace it may demand what we wish to say to it; if in another it may cry outthat it is hurt, and such like; but not that it should arrange them variouslyso as appositely to reply to what is said in its presence, as men of the lowestgrade of intellect can do. The second test is, that although such machinesmight execute many things with equal or perhaps greater perfection than any ofus, they would, without doubt, fail in certain others from which it could bediscovered that they did not act from knowledge, but solely from thedisposition of their organs: for while reason is an universal instrument thatis alike available on every occasion, these organs, on the contrary, need aparticular arrangement for each particular action; whence it must be morallyimpossible that there should exist in any machine a diversity of organssufficient to enable it to act in all the occurrences of life, in the way inwhich our reason enables us to act. Again, by means of these two tests we maylikewise know the difference between men and brutes. For it is highly deservingof remark, that there are no men so dull and stupid, not even idiots, as to beincapable of joining together different words, and thereby constructing adeclaration by which to make their thoughts understood; and that on the otherhand, there is no other animal, however perfect or happily circumstanced, whichcan do the like. Nor does this inability arise from want of organs: for weobserve that magpies and parrots can utter words like ourselves, and are yetunable to speak as we do, that is, so as to show that they understand what theysay; in place of which men born deaf and dumb, and thus not less, but rathermore than the brutes, destitute of the organs which others use in speaking, arein the habit of spontaneously inventing certain signs by which they discovertheir thoughts to those who, being usually in their company, have leisure tolearn their language. And this proves not only that the brutes have less reasonthan man, but that they have none at all: for we see that very little isrequired to enable a person to speak; and since a certain inequality ofcapacity is observable among animals of the same species, as well as among men,and since some are more capable of being instructed than others, it isincredible that the most perfect ape or parrot of its species, should not inthis be equal to the most stupid infant of its kind or at least to one that wascrack-brained, unless the soul of brutes were of a nature wholly different fromours. And we ought not to confound speech with the natural movements whichindicate the passions, and can be imitated by machines as well as manifested byanimals; nor must it be thought with certain of the ancients, that the brutesspeak, although we do not understand their language. For if such were the case,since they are endowed with many organs analogous to ours, they could as easilycommunicate their thoughts to us as to their fellows. It is also very worthy ofremark, that, though there are many animals which manifest more industry thanwe in certain of their actions, the same animals are yet observed to show noneat all in many others: so that the circumstance that they do better than wedoes not prove that they are endowed with mind, for it would thence follow thatthey possessed greater reason than any of us, and could surpass us in allthings; on the contrary, it rather proves that they are destitute of reason,and that it is nature which acts in them according to the disposition of theirorgans: thus it is seen, that a clock composed only of wheels and weights cannumber the hours and measure time more exactly than we with all our skin.

I had after this described the reasonable soul, and shown that it could by nomeans be educed from the power of matter, as the other things of which I hadspoken, but that it must be expressly created; and that it is not sufficientthat it be lodged in the human body exactly like a pilot in a ship, unlessperhaps to move its members, but that it is necessary for it to be joined andunited more closely to the body, in order to have sensations and appetitessimilar to ours, and thus constitute a real man. I here entered, in conclusion,upon the subject of the soul at considerable length, because it is of thegreatest moment: for after the error of those who deny the existence of God, anerror which I think I have already sufficiently refuted, there is none that ismore powerful in leading feeble minds astray from the straight path of virtuethan the supposition that the soul of the brutes is of the same nature with ourown; and consequently that after this life we have nothing to hope for or fear,more than flies and ants; in place of which, when we know how far they differwe much better comprehend the reasons which establish that the soul is of anature wholly independent of the body, and that consequently it is not liableto die with the latter and, finally, because no other causes are observedcapable of destroying it, we are naturally led thence to judge that it isimmortal.

PART VI

Three years have now elapsed since I finished the treatise containing all thesematters; and I was beginning to revise it, with the view to put it into thehands of a printer, when I learned that persons to whom I greatly defer, andwhose authority over my actions is hardly less influential than is my ownreason over my thoughts, had condemned a certain doctrine in physics, publisheda short time previously by another individual to which I will not say that Iadhered, but only that, previously to their censure I had observed in itnothing which I could imagine to be prejudicial either to religion or to thestate, and nothing therefore which would have prevented me from givingexpression to it in writing, if reason had persuaded me of its truth; and thisled me to fear lest among my own doctrines likewise some one might be found inwhich I had departed from the truth, notwithstanding the great care I havealways taken not to accord belief to new opinions of which I had not the mostcertain demonstrations, and not to give expression to aught that might tend tothe hurt of any one. This has been sufficient to make me alter my purpose ofpublishing them; for although the reasons by which I had been induced to takethis resolution were very strong, yet my inclination, which has always beenhostile to writing books, enabled me immediately to discover otherconsiderations sufficient to excuse me for not undertaking the task. And thesereasons, on one side and the other, are such, that not only is it in somemeasure my interest here to state them, but that of the public, perhaps, toknow them.

I have never made much account of what has proceeded from my own mind; and solong as I gathered no other advantage from the method I employ beyondsatisfying myself on some difficulties belonging to the speculative sciences,or endeavoring to regulate my actions according to the principles it taught me,I never thought myself bound to publish anything respecting it. For in whatregards manners, every one is so full of his own wisdom, that there might befound as many reformers as heads, if any were allowed to take upon themselvesthe task of mending them, except those whom God has constituted the supremerulers of his people or to whom he has given sufficient grace and zeal to beprophets; and although my speculations greatly pleased myself, I believed thatothers had theirs, which perhaps pleased them still more. But as soon as I hadacquired some general notions respecting physics, and beginning to make trialof them in various particular difficulties, had observed how far they can carryus, and how much they differ from the principles that have been employed up tothe present time, I believed that I could not keep them concealed withoutsinning grievously against the law by which we are bound to promote, as far asin us lies, the general good of mankind. For by them I perceived it to bepossible to arrive at knowledge highly useful in life; and in room of thespeculative philosophy usually taught in the schools, to discover a practical,by means of which, knowing the force and action of fire, water, air the stars,the heavens, and all the other bodies that surround us, as distinctly as weknow the various crafts of our artisans, we might also apply them in the sameway to all the uses to which they are adapted, and thus render ourselves thelords and possessors of nature. And this is a result to be desired, not only inorder to the invention of an infinity of arts, by which we might be enabled toenjoy without any trouble the fruits of the earth, and all its comforts, butalso and especially for the preservation of health, which is without doubt, ofall the blessings of this life, the first and fundamental one; for the mind isso intimately dependent upon the condition and relation of the organs of thebody, that if any means can ever be found to render men wiser and moreingenious than hitherto, I believe that it is in medicine they must be soughtfor. It is true that the science of medicine, as it now exists, contains fewthings whose utility is very remarkable: but without any wish to depreciate it,I am confident that there is no one, even among those whose profession it is,who does not admit that all at present known in it is almost nothing incomparison of what remains to be discovered; and that we could free ourselvesfrom an infinity of maladies of body as well as of mind, and perhaps also evenfrom the debility of age, if we had sufficiently ample knowledge of theircauses, and of all the remedies provided for us by nature. But since I designedto employ my whole life in the search after so necessary a science, and since Ihad fallen in with a path which seems to me such, that if any one follow it hemust inevitably reach the end desired, unless he be hindered either by theshortness of life or the want of experiments, I judged that there could be nomore effectual provision against these two impediments than if I werefaithfully to communicate to the public all the little I might myself havefound, and incite men of superior genius to strive to proceed farther, bycontributing, each according to his inclination and ability, to the experimentswhich it would be necessary to make, and also by informing the public of allthey might discover, so that, by the last beginning where those before them hadleft off, and thus connecting the lives and labours of many, we mightcollectively proceed much farther than each by himself could do.

I remarked, moreover, with respect to experiments, that they become always morenecessary the more one is advanced in knowledge; for, at the commencement, itis better to make use only of what is spontaneously presented to our senses,and of which we cannot remain ignorant, provided we bestow on it anyreflection, however slight, than to concern ourselves about more uncommon andrecondite phenomena: the reason of which is, that the more uncommon often onlymislead us so long as the causes of the more ordinary are still unknown; andthe circumstances upon which they depend are almost always so special andminute as to be highly difficult to detect. But in this I have adopted thefollowing order: first, I have essayed to find in general the principles, orfirst causes of all that is or can be in the world, without taking intoconsideration for this end anything but God himself who has created it, andwithout educing them from any other source than from certain germs of truthsnaturally existing in our minds In the second place, I examined what were thefirst and most ordinary effects that could be deduced from these causes; and itappears to me that, in this way, I have found heavens, stars, an earth, andeven on the earth water, air, fire, minerals, and some other things of thiskind, which of all others are the most common and simple, and hence the easiestto know. Afterwards when I wished to descend to the more particular, so manydiverse objects presented themselves to me, that I believed it to be impossiblefor the human mind to distinguish the forms or species of bodies that are uponthe earth, from an infinity of others which might have been, if it had pleasedGod to place them there, or consequently to apply them to our use, unless werise to causes through their effects, and avail ourselves of many particularexperiments. Thereupon, turning over in my mind I the objects that had everbeen presented to my senses I freely venture to state that I have neverobserved any which I could not satisfactorily explain by the principles haddiscovered. But it is necessary also to confess that the power of nature is soample and vast, and these principles so simple and general, that I have hardlyobserved a single particular effect which I cannot at once recognize as capableof being deduced in man different modes from the principles, and that mygreatest difficulty usually is to discover in which of these modes the effectis dependent upon them; for out of this difficulty cannot otherwise extricatemyself than by again seeking certain experiments, which may be such that theirresult is not the same, if it is in the one of these modes at we must explainit, as it would be if it were to be explained in the other. As to what remains,I am now in a position to discern, as I think, with sufficient clearness whatcourse must be taken to make the majority those experiments which may conduceto this end: but I perceive likewise that they are such and so numerous, thatneither my hands nor my income, though it were a thousand times larger than itis, would be sufficient for them all; so that according as henceforward I shallhave the means of making more or fewer experiments, I shall in the sameproportion make greater or less progress in the knowledge of nature. This waswhat I had hoped to make known by the treatise I had written, and so clearly toexhibit the advantage that would thence accrue to the public, as to induce allwho have the common good of man at heart, that is, all who are virtuous intruth, and not merely in appearance, or according to opinion, as well tocommunicate to me the experiments they had already made, as to assist me inthose that remain to be made.

But since that time other reasons have occurred to me, by which I have been ledto change my opinion, and to think that I ought indeed to go on committing towriting all the results which I deemed of any moment, as soon as I should havetested their truth, and to bestow the same care upon them as I would have donehad it been my design to publish them. This course commended itself to me, aswell because I thus afforded myself more ample inducement to examine themthoroughly, for doubtless that is always more narrowly scrutinized which webelieve will be read by many, than that which is written merely for our privateuse (and frequently what has seemed to me true when I first conceived it, hasappeared false when I have set about committing it to writing), as because Ithus lost no opportunity of advancing the interests of the public, as far as inme lay, and since thus likewise, if my writings possess any value, those intowhose hands they may fall after my death may be able to put them to what usethey deem proper. But I resolved by no means to consent to their publicationduring my lifetime, lest either the oppositions or the controversies to whichthey might give rise, or even the reputation, such as it might be, which theywould acquire for me, should be any occasion of my losing the time that I hadset apart for my own improvement. For though it be true that every one is boundto promote to the extent of his ability the good of others, and that to beuseful to no one is really to be worthless, yet it is likewise true that ourcares ought to extend beyond the present, and it is good to omit doing whatmight perhaps bring some profit to the living, when we have in view theaccomplishment of other ends that will be of much greater advantage toposterity. And in truth, I am quite willing it should be known that the littleI have hitherto learned is almost nothing in comparison with that of which I amignorant, and to the knowledge of which I do not despair of being able toattain; for it is much the same with those who gradually discover truth in thesciences, as with those who when growing rich find less difficulty in makinggreat acquisitions, than they formerly experienced when poor in makingacquisitions of much smaller amount. Or they may be compared to the commandersof armies, whose forces usually increase in proportion to their victories, andwho need greater prudence to keep together the residue of their troops after adefeat than after a victory to take towns and provinces. For he truly engagesin battle who endeavors to surmount all the difficulties and errors whichprevent him from reaching the knowledge of truth, and he is overcome in fightwho admits a false opinion touching a matter of any generality and importance,and he requires thereafter much more skill to recover his former position thanto make great advances when once in possession of thoroughly ascertainedprinciples. As for myself, if I have succeeded in discovering any truths in thesciences (and I trust that what is contained in this volume I will show that Ihave found some), I can declare that they are but the consequences and resultsof five or six principal difficulties which I have surmounted, and myencounters with which I reckoned as battles in which victory declared for me. Iwill not hesitate even to avow my belief that nothing further is wanting toenable me fully to realize my designs than to gain two or three similarvictories; and that I am not so far advanced in years but that, according tothe ordinary course of nature, I may still have sufficient leisure for thisend. But I conceive myself the more bound to husband the time that remains thegreater my expectation of being able to employ it aright, and I shoulddoubtless have much to rob me of it, were I to publish the principles of myphysics: for although they are almost all so evident that to assent to them nomore is needed than simply to understand them, and although there is not one ofthem of which I do not expect to be able to give demonstration, yet, as it isimpossible that they can be in accordance with all the diverse opinions ofothers, I foresee that I should frequently be turned aside from my granddesign, on occasion of the opposition which they would be sure to awaken.

It may be said, that these oppositions would be useful both in making me awareof my errors, and, if my speculations contain anything of value, in bringingothers to a fuller understanding of it; and still farther, as many can seebetter than one, in leading others who are now beginning to avail themselves ofmy principles, to assist me in turn with their discoveries. But though Irecognize my extreme liability to error, and scarce ever trust to the firstthoughts which occur to me, yet-the experience I have had of possibleobjections to my views prevents me from anticipating any profit from them. ForI have already had frequent proof of the judgments, as well of those I esteemedfriends, as of some others to whom I thought I was an object of indifference,and even of some whose malignancy and envy would, I knew, determine them toendeavor to discover what partiality concealed from the eyes of my friends. Butit has rarely happened that anything has been objected to me which I had myselfaltogether overlooked, unless it were something far removed from the subject:so that I have never met with a single critic of my opinions who did not appearto me either less rigorous or less equitable than myself. And further, I havenever observed that any truth before unknown has been brought to light by thedisputations that are practised in the schools; for while each strives for thevictory, each is much more occupied in making the best of mere verisimilitude,than in weighing the reasons on both sides of the question; and those who havebeen long good advocates are not afterwards on that account the better judges.

As for the advantage that others would derive from the communication of mythoughts, it could not be very great; because I have not yet so far prosecutedthem as that much does not remain to be added before they can be applied topractice. And I think I may say without vanity, that if there is any one whocan carry them out that length, it must be myself rather than another: not thatthere may not be in the world many minds incomparably superior to mine, butbecause one cannot so well seize a thing and make it one’s own, when ithas been learned from another, as when one has himself discovered it. And sotrue is this of the present subject that, though I have often explained some ofmy opinions to persons of much acuteness, who, whilst I was speaking, appearedto understand them very distinctly, yet, when they repeated them, I haveobserved that they almost always changed them to such an extent that I could nolonger acknowledge them as mine. I am glad, by the way, to take thisopportunity of requesting posterity never to believe on hearsay that anythinghas proceeded from me which has not been published by myself; and I am not atall astonished at the extravagances attributed to those ancient philosopherswhose own writings we do not possess; whose thoughts, however, I do not on thataccount suppose to have been really absurd, seeing they were among the ablestmen of their times, but only that these have been falsely represented to us. Itis observable, accordingly, that scarcely in a single instance has any one oftheir disciples surpassed them; and I am quite sure that the most devoted ofthe present followers of Aristotle would think themselves happy if they had asmuch knowledge of nature as he possessed, were it even under the condition thatthey should never afterwards attain to higher. In this respect they are likethe ivy which never strives to rise above the tree that sustains it, and whichfrequently even returns downwards when it has reached the top; for it seems tome that they also sink, in other words, render themselves less wise than theywould be if they gave up study, who, not contented with knowing all that isintelligibly explained in their author, desire in addition to find in him thesolution of many difficulties of which he says not a word, and never perhaps somuch as thought. Their fashion of philosophizing, however, is well suited topersons whose abilities fall below mediocrity; for the obscurity of thedistinctions and principles of which they make use enables them to speak of allthings with as much confidence as if they really knew them, and to defend allthat they say on any subject against the most subtle and skillful, without itsbeing possible for any one to convict them of error. In this they seem to me tobe like a blind man, who, in order to fight on equal terms with a person thatsees, should have made him descend to the bottom of an intensely dark cave: andI may say that such persons have an interest in my refraining from publishingthe principles of the philosophy of which I make use; for, since these are of akind the simplest and most evident, I should, by publishing them, do much thesame as if I were to throw open the windows, and allow the light of day toenter the cave into which the combatants had descended. But even superior menhave no reason for any great anxiety to know these principles, for if what theydesire is to be able to speak of all things, and to acquire a reputation forlearning, they will gain their end more easily by remaining satisfied with theappearance of truth, which can be found without much difficulty in all sorts ofmatters, than by seeking the truth itself which unfolds itself but slowly andthat only in some departments, while it obliges us, when we have to speak ofothers, freely to confess our ignorance. If, however, they prefer the knowledgeof some few truths to the vanity of appearing ignorant of none, as suchknowledge is undoubtedly much to be preferred, and, if they choose to follow acourse similar to mine, they do not require for this that I should say anythingmore than I have already said in this discourse. For if they are capable ofmaking greater advancement than I have made, they will much more be able ofthemselves to discover all that I believe myself to have found; since as I havenever examined aught except in order, it is certain that what yet remains to bediscovered is in itself more difficult and recondite, than that which I havealready been enabled to find, and the gratification would be much less inlearning it from me than in discovering it for themselves. Besides this, thehabit which they will acquire, by seeking first what is easy, and then passingonward slowly and step by step to the more difficult, will benefit them morethan all my instructions. Thus, in my own case, I am persuaded that if I hadbeen taught from my youth all the truths of which I have since sought outdemonstrations, and had thus learned them without labour, I should never,perhaps, have known any beyond these; at least, I should never have acquiredthe habit and the facility which I think I possess in always discovering newtruths in proportion as I give myself to the search. And, in a single word, ifthere is any work in the world which cannot be so well finished by another asby him who has commenced it, it is that at which I labour.

It is true, indeed, as regards the experiments which may conduce to this end,that one man is not equal to the task of making them all; but yet he canadvantageously avail himself, in this work, of no hands besides his own, unlessthose of artisans, or parties of the same kind, whom he could pay, and whom thehope of gain (a means of great efficacy) might stimulate to accuracy in theperformance of what was prescribed to them. For as to those who, throughcuriosity or a desire of learning, of their own accord, perhaps, offer himtheir services, besides that in general their promises exceed theirperformance, and that they sketch out fine designs of which not one is everrealized, they will, without doubt, expect to be compensated for their troubleby the explication of some difficulties, or, at least, by compliments anduseless speeches, in which he cannot spend any portion of his time without lossto himself. And as for the experiments that others have already made, evenalthough these parties should be willing of themselves to communicate them tohim (which is what those who esteem them secrets will never do), theexperiments are, for the most part, accompanied with so many circumstances andsuperfluous elements, as to make it exceedingly difficult to disentangle thetruth from its adjuncts--besides, he will find almost all of them so illdescribed, or even so false (because those who made them have wished to see inthem only such facts as they deemed conformable to their principles), that, ifin the entire number there should be some of a nature suited to his purpose,still their value could not compensate for the time what would be necessary tomake the selection. So that if there existed any one whom we assuredly knew tobe capable of making discoveries of the highest kind, and of the greatestpossible utility to the public; and if all other men were therefore eager byall means to assist him in successfully prosecuting his designs, I do not seethat they could do aught else for him beyond contributing to defray theexpenses of the experiments that might be necessary; and for the rest, preventhis being deprived of his leisure by the unseasonable interruptions of any one.But besides that I neither have so high an opinion of myself as to be willingto make promise of anything extraordinary, nor feed on imaginations so vain asto fancy that the public must be much interested in my designs; I do not, onthe other hand, own a soul so mean as to be capable of accepting from any one afavor of which it could be supposed that I was unworthy.

These considerations taken together were the reason why, for the last threeyears, I have been unwilling to publish the treatise I had on hand, and why Ieven resolved to give publicity during my life to no other that was so general,or by which the principles of my physics might be understood. But since then,two other reasons have come into operation that have determined me here tosubjoin some particular specimens, and give the public some account of mydoings and designs. Of these considerations, the first is, that if I failed todo so, many who were cognizant of my previous intention to publish somewritings, might have imagined that the reasons which induced me to refrain fromso doing, were less to my credit than they really are; for although I am notimmoderately desirous of glory, or even, if I may venture so to say, although Iam averse from it in so far as I deem it hostile to repose which I hold ingreater account than aught else, yet, at the same time, I have never sought toconceal my actions as if they were crimes, nor made use of many precautionsthat I might remain unknown; and this partly because I should have thought sucha course of conduct a wrong against myself, and partly because it would haveoccasioned me some sort of uneasiness which would again have been contrary tothe perfect mental tranquillity which I court. And forasmuch as, while thusindifferent to the thought alike of fame or of forgetfulness, I have yet beenunable to prevent myself from acquiring some sort of reputation, I have thoughtit incumbent on me to do my best to save myself at least from being ill-spokenof. The other reason that has determined me to commit to writing thesespecimens of philosophy is, that I am becoming daily more and more alive to thedelay which my design of self-instruction suffers, for want of the infinity ofexperiments I require, and which it is impossible for me to make without theassistance of others: and, without flattering myself so much as to expect thepublic to take a large share in my interests, I am yet unwilling to be found sofar wanting in the duty I owe to myself, as to give occasion to those who shallsurvive me to make it matter of reproach against me some day, that I might haveleft them many things in a much more perfect state than I have done, had I nottoo much neglected to make them aware of the ways in which they could havepromoted the accomplishment of my designs.

And I thought that it was easy for me to select some matters which shouldneither be obnoxious to much controversy, nor should compel me to expound moreof my principles than I desired, and which should yet be sufficient clearly toexhibit what I can or cannot accomplish in the sciences. Whether or not I havesucceeded in this it is not for me to say; and I do not wish to forestall thejudgments of others by speaking myself of my writings; but it will gratify meif they be examined, and, to afford the greater inducement to this I requestall who may have any objections to make to them, to take the trouble offorwarding these to my publisher, who will give me notice of them, that I mayendeavor to subjoin at the same time my reply; and in this way readers seeingboth at once will more easily determine where the truth lies; for I do notengage in any case to make prolix replies, but only with perfect frankness toavow my errors if I am convinced of them, or if I cannot perceive them, simplyto state what I think is required for defense of the matters I have written,adding thereto no explication of any new matte that it may not be necessary topass without end from one thing to another.

If some of the matters of which I have spoken in the beginning of the“Dioptrics” and “Meteorics” should offend at firstsight, because I call them hypotheses and seem indifferent about giving proofof them, I request a patient and attentive reading of the whole, from which Ihope those hesitating will derive satisfaction; for it appears to me that thereasonings are so mutually connected in these treatises, that, as the last aredemonstrated by the first which are their causes, the first are in their turndemonstrated by the last which are their effects. Nor must it be imagined thatI here commit the fallacy which the logicians call a circle; for sinceexperience renders the majority of these effects most certain, the causes fromwhich I deduce them do not serve so much to establish their reality as toexplain their existence; but on the contrary, the reality of the causes isestablished by the reality of the effects. Nor have I called them hypotheseswith any other end in view except that it may be known that I think I am ableto deduce them from those first truths which I have already expounded; and yetthat I have expressly determined not to do so, to prevent a certain class ofminds from thence taking occasion to build some extravagant philosophy uponwhat they may take to be my principles, and my being blamed for it. I refer tothose who imagine that they can master in a day all that another has takentwenty years to think out, as soon as he has spoken two or three words to themon the subject; or who are the more liable to error and the less capable ofperceiving truth in very proportion as they are more subtle and lively. As tothe opinions which are truly and wholly mine, I offer no apology for them asnew,--persuaded as I am that if their reasons be well considered they will befound to be so simple and so conformed, to common sense as to appear lessextraordinary and less paradoxical than any others which can be held on thesame subjects; nor do I even boast of being the earliest discoverer of any ofthem, but only of having adopted them, neither because they had nor becausethey had not been held by others, but solely because reason has convinced me oftheir truth.

Though artisans may not be able at once to execute the invention which isexplained in the “Dioptrics,” I do not think that any one on thataccount is entitled to condemn it; for since address and practice are requiredin order so to make and adjust the machines described by me as not to overlookthe smallest particular, I should not be less astonished if they succeeded onthe first attempt than if a person were in one day to become an accomplishedperformer on the guitar, by merely having excellent sheets of music set upbefore him. And if I write in French, which is the language of my country, inpreference to Latin, which is that of my preceptors, it is because I expectthat those who make use of their unprejudiced natural reason will be betterjudges of my opinions than those who give heed to the writings of the ancientsonly; and as for those who unite good sense with habits of study, whom alone Idesire for judges, they will not, I feel assured, be so partial to Latin as torefuse to listen to my reasonings merely because I expound them in the vulgartongue.

In conclusion, I am unwilling here to say anything very specific of theprogress which I expect to make for the future in the sciences, or to bindmyself to the public by any promise which I am not certain of being able tofulfill; but this only will I say, that I have resolved to devote what time Imay still have to live to no other occupation than that of endeavoring toacquire some knowledge of Nature, which shall be of such a kind as to enable ustherefrom to deduce rules in medicine of greater certainty than those atpresent in use; and that my inclination is so much opposed to all otherpursuits, especially to such as cannot be useful to some without being hurtfulto others, that if, by any circumstances, I had been constrained to engage insuch, I do not believe that I should have been able to succeed. Of this I heremake a public declaration, though well aware that it cannot serve to procurefor me any consideration in the world, which, however, I do not in the leastaffect; and I shall always hold myself more obliged to those through whosefavor I am permitted to enjoy my retirement without interruption than to anywho might offer me the highest earthly preferments.