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+DISCOURSE ON THE METHOD 
+OF RIGHTLY CONDUCTING THE REASON,
+AND SEEKING TRUTH IN THE SCIENCES
+
+by René Descartes
+
+Contents
+
+ PREFATORY NOTE
+ PART I
+ PART II
+ PART III
+ PART IV
+ PART V
+ PART VI
+
+PREFATORY NOTE BY THE AUTHOR
+
+If this Discourse appear too long to be read at once, it may be divided
+into six Parts: and, in the first, will be found various considerations
+touching the Sciences; in the second, the principal rules of the Method
+which the Author has discovered, in the third, certain of the rules of
+Morals which he has deduced from this Method; in the fourth, the
+reasonings by which he establishes the existence of God and of the
+Human Soul, which are the foundations of his Metaphysic; in the fifth,
+the order of the Physical questions which he has investigated, and, in
+particular, the explication of the motion of the heart and of some
+other difficulties pertaining to Medicine, as also the difference
+between the soul of man and that of the brutes; and, in the last, what
+the Author believes to be required in order to greater advancement in
+the investigation of Nature than has yet been made, with the reasons
+that have induced him to write.
+
+PART I
+
+Good sense is, of all things among men, the most equally distributed;
+for every one thinks himself so abundantly provided with it, that those
+even who are the most difficult to satisfy in everything else, do not
+usually desire a larger measure of this quality than they already
+possess. And in this it is not likely that all are mistaken the
+conviction is rather to be held as testifying that the power of judging
+aright and of distinguishing truth from error, which is properly what
+is called good sense or reason, is by nature equal in all men; and that
+the diversity of our opinions, consequently, does not arise from some
+being endowed with a larger share of reason than others, but solely
+from this, that we conduct our thoughts along different ways, and do
+not fix our attention on the same objects. For to be possessed of a
+vigorous mind is not enough; the prime requisite is rightly to apply
+it. The greatest minds, as they are capable of the highest excellences,
+are open likewise to the greatest aberrations; and those who travel
+very slowly may yet make far greater progress, provided they keep
+always to the straight road, than those who, while they run, forsake
+it.
+
+For myself, I have never fancied my mind to be in any respect more
+perfect than those of the generality; on the contrary, I have often
+wished that I were equal to some others in promptitude of thought, or
+in clearness and distinctness of imagination, or in fullness and
+readiness of memory. And besides these, I know of no other qualities
+that contribute to the perfection of the mind; for as to the reason or
+sense, inasmuch as it is that alone which constitutes us men, and
+distinguishes us from the brutes, I am disposed to believe that it is
+to be found complete in each individual; and on this point to adopt the
+common opinion of philosophers, who say that the difference of greater
+and less holds only among the accidents, and not among the forms or
+natures of individuals of the same species.
+
+I will not hesitate, however, to avow my belief that it has been my
+singular good fortune to have very early in life fallen in with certain
+tracks which have conducted me to considerations and maxims, of which I
+have formed a method that gives me the means, as I think, of gradually
+augmenting my knowledge, and of raising it by little and little to the
+highest point which the mediocrity of my talents and the brief duration
+of my life will permit me to reach. For I have already reaped from it
+such fruits that, although I have been accustomed to think lowly enough
+of myself, and although when I look with the eye of a philosopher at
+the varied courses and pursuits of mankind at large, I find scarcely
+one which does not appear in vain and useless, I nevertheless derive
+the highest satisfaction from the progress I conceive myself to have
+already made in the search after truth, and cannot help entertaining
+such expectations of the future as to believe that if, among the
+occupations of men as men, there is any one really excellent and
+important, it is that which I have chosen.
+
+After all, it is possible I may be mistaken; and it is but a little
+copper and glass, perhaps, that I take for gold and diamonds. I know
+how very liable we are to delusion in what relates to ourselves, and
+also how much the judgments of our friends are to be suspected when
+given in our favor. But I shall endeavor in this discourse to describe
+the paths I have followed, and to delineate my life as in a picture, in
+order that each one may also be able to judge of them for himself, and
+that in the general opinion entertained of them, as gathered from
+current report, I myself may have a new help towards instruction to be
+added to those I have been in the habit of employing.
+
+My present design, then, is not to teach the method which each ought to
+follow for the right conduct of his reason, but solely to describe the
+way in which I have endeavored to conduct my own. They who set
+themselves to give precepts must of course regard themselves as
+possessed of greater skill than those to whom they prescribe; and if
+they err in the slightest particular, they subject themselves to
+censure. But as this tract is put forth merely as a history, or, if you
+will, as a tale, in which, amid some examples worthy of imitation,
+there will be found, perhaps, as many more which it were advisable not
+to follow, I hope it will prove useful to some without being hurtful to
+any, and that my openness will find some favor with all.
+
+From my childhood, I have been familiar with letters; and as I was
+given to believe that by their help a clear and certain knowledge of
+all that is useful in life might be acquired, I was ardently desirous
+of instruction. But as soon as I had finished the entire course of
+study, at the close of which it is customary to be admitted into the
+order of the learned, I completely changed my opinion. For I found
+myself involved in so many doubts and errors, that I was convinced I
+had advanced no farther in all my attempts at learning, than the
+discovery at every turn of my own ignorance. And yet I was studying in
+one of the most celebrated schools in Europe, in which I thought there
+must be learned men, if such were anywhere to be found. I had been
+taught all that others learned there; and not contented with the
+sciences actually taught us, I had, in addition, read all the books
+that had fallen into my hands, treating of such branches as are
+esteemed the most curious and rare. I knew the judgment which others
+had formed of me; and I did not find that I was considered inferior to
+my fellows, although there were among them some who were already marked
+out to fill the places of our instructors. And, in fine, our age
+appeared to me as flourishing, and as fertile in powerful minds as any
+preceding one. I was thus led to take the liberty of judging of all
+other men by myself, and of concluding that there was no science in
+existence that was of such a nature as I had previously been given to
+believe.
+
+I still continued, however, to hold in esteem the studies of the
+schools. I was aware that the languages taught in them are necessary to
+the understanding of the writings of the ancients; that the grace of
+fable stirs the mind; that the memorable deeds of history elevate it;
+and, if read with discretion, aid in forming the judgment; that the
+perusal of all excellent books is, as it were, to interview with the
+noblest men of past ages, who have written them, and even a studied
+interview, in which are discovered to us only their choicest thoughts;
+that eloquence has incomparable force and beauty; that poesy has its
+ravishing graces and delights; that in the mathematics there are many
+refined discoveries eminently suited to gratify the inquisitive, as
+well as further all the arts an lessen the labour of man; that numerous
+highly useful precepts and exhortations to virtue are contained in
+treatises on morals; that theology points out the path to heaven; that
+philosophy affords the means of discoursing with an appearance of truth
+on all matters, and commands the admiration of the more simple; that
+jurisprudence, medicine, and the other sciences, secure for their
+cultivators honors and riches; and, in fine, that it is useful to
+bestow some attention upon all, even upon those abounding the most in
+superstition and error, that we may be in a position to determine their
+real value, and guard against being deceived.
+
+But I believed that I had already given sufficient time to languages,
+and likewise to the reading of the writings of the ancients, to their
+histories and fables. For to hold converse with those of other ages and
+to travel, are almost the same thing. It is useful to know something of
+the manners of different nations, that we may be enabled to form a more
+correct judgment regarding our own, and be prevented from thinking that
+everything contrary to our customs is ridiculous and irrational, a
+conclusion usually come to by those whose experience has been limited
+to their own country. On the other hand, when too much time is occupied
+in traveling, we become strangers to our native country; and the over
+curious in the customs of the past are generally ignorant of those of
+the present. Besides, fictitious narratives lead us to imagine the
+possibility of many events that are impossible; and even the most
+faithful histories, if they do not wholly misrepresent matters, or
+exaggerate their importance to render the account of them more worthy
+of perusal, omit, at least, almost always the meanest and least
+striking of the attendant circumstances; hence it happens that the
+remainder does not represent the truth, and that such as regulate their
+conduct by examples drawn from this source, are apt to fall into the
+extravagances of the knight-errants of romance, and to entertain
+projects that exceed their powers.
+
+I esteemed eloquence highly, and was in raptures with poesy; but I
+thought that both were gifts of nature rather than fruits of study.
+Those in whom the faculty of reason is predominant, and who most
+skillfully dispose their thoughts with a view to render them clear and
+intelligible, are always the best able to persuade others of the truth
+of what they lay down, though they should speak only in the language of
+Lower Brittany, and be wholly ignorant of the rules of rhetoric; and
+those whose minds are stored with the most agreeable fancies, and who
+can give expression to them with the greatest embellishment and
+harmony, are still the best poets, though unacquainted with the art of
+poetry.
+
+I was especially delighted with the mathematics, on account of the
+certitude and evidence of their reasonings; but I had not as yet a
+precise knowledge of their true use; and thinking that they but
+contributed to the advancement of the mechanical arts, I was astonished
+that foundations, so strong and solid, should have had no loftier
+superstructure reared on them. On the other hand, I compared the
+disquisitions of the ancient moralists to very towering and magnificent
+palaces with no better foundation than sand and mud: they laud the
+virtues very highly, and exhibit them as estimable far above anything
+on earth; but they give us no adequate criterion of virtue, and
+frequently that which they designate with so fine a name is but apathy,
+or pride, or despair, or parricide.
+
+I revered our theology, and aspired as much as any one to reach heaven:
+but being given assuredly to understand that the way is not less open
+to the most ignorant than to the most learned, and that the revealed
+truths which lead to heaven are above our comprehension, I did not
+presume to subject them to the impotency of my reason; and I thought
+that in order competently to undertake their examination, there was
+need of some special help from heaven, and of being more than man.
+
+Of philosophy I will say nothing, except that when I saw that it had
+been cultivated for many ages by the most distinguished men, and that
+yet there is not a single matter within its sphere which is not still
+in dispute, and nothing, therefore, which is above doubt, I did not
+presume to anticipate that my success would be greater in it than that
+of others; and further, when I considered the number of conflicting
+opinions touching a single matter that may be upheld by learned men,
+while there can be but one true, I reckoned as well-nigh false all that
+was only probable.
+
+As to the other sciences, inasmuch as these borrow their principles
+from philosophy, I judged that no solid superstructures could be reared
+on foundations so infirm; and neither the honor nor the gain held out
+by them was sufficient to determine me to their cultivation: for I was
+not, thank Heaven, in a condition which compelled me to make
+merchandise of science for the bettering of my fortune; and though I
+might not profess to scorn glory as a cynic, I yet made very slight
+account of that honor which I hoped to acquire only through fictitious
+titles. And, in fine, of false sciences I thought I knew the worth
+sufficiently to escape being deceived by the professions of an
+alchemist, the predictions of an astrologer, the impostures of a
+magician, or by the artifices and boasting of any of those who profess
+to know things of which they are ignorant.
+
+For these reasons, as soon as my age permitted me to pass from under
+the control of my instructors, I entirely abandoned the study of
+letters, and resolved no longer to seek any other science than the
+knowledge of myself, or of the great book of the world. I spent the
+remainder of my youth in traveling, in visiting courts and armies, in
+holding intercourse with men of different dispositions and ranks, in
+collecting varied experience, in proving myself in the different
+situations into which fortune threw me, and, above all, in making such
+reflection on the matter of my experience as to secure my improvement.
+For it occurred to me that I should find much more truth in the
+reasonings of each individual with reference to the affairs in which he
+is personally interested, and the issue of which must presently punish
+him if he has judged amiss, than in those conducted by a man of letters
+in his study, regarding speculative matters that are of no practical
+moment, and followed by no consequences to himself, farther, perhaps,
+than that they foster his vanity the better the more remote they are
+from common sense; requiring, as they must in this case, the exercise
+of greater ingenuity and art to render them probable. In addition, I
+had always a most earnest desire to know how to distinguish the true
+from the false, in order that I might be able clearly to discriminate
+the right path in life, and proceed in it with confidence.
+
+It is true that, while busied only in considering the manners of other
+men, I found here, too, scarce any ground for settled conviction, and
+remarked hardly less contradiction among them than in the opinions of
+the philosophers. So that the greatest advantage I derived from the
+study consisted in this, that, observing many things which, however
+extravagant and ridiculous to our apprehension, are yet by common
+consent received and approved by other great nations, I learned to
+entertain too decided a belief in regard to nothing of the truth of
+which I had been persuaded merely by example and custom; and thus I
+gradually extricated myself from many errors powerful enough to darken
+our natural intelligence, and incapacitate us in great measure from
+listening to reason. But after I had been occupied several years in
+thus studying the book of the world, and in essaying to gather some
+experience, I at length resolved to make myself an object of study, and
+to employ all the powers of my mind in choosing the paths I ought to
+follow, an undertaking which was accompanied with greater success than
+it would have been had I never quitted my country or my books.
+
+PART II
+
+I was then in Germany, attracted thither by the wars in that country,
+which have not yet been brought to a termination; and as I was
+returning to the army from the coronation of the emperor, the setting
+in of winter arrested me in a locality where, as I found no society to
+interest me, and was besides fortunately undisturbed by any cares or
+passions, I remained the whole day in seclusion, with full opportunity
+to occupy my attention with my own thoughts. Of these one of the very
+first that occurred to me was, that there is seldom so much perfection
+in works composed of many separate parts, upon which different hands
+had been employed, as in those completed by a single master. Thus it is
+observable that the buildings which a single architect has planned and
+executed, are generally more elegant and commodious than those which
+several have attempted to improve, by making old walls serve for
+purposes for which they were not originally built. Thus also, those
+ancient cities which, from being at first only villages, have become,
+in course of time, large towns, are usually but ill laid out compared
+with the regularity constructed towns which a professional architect
+has freely planned on an open plain; so that although the several
+buildings of the former may often equal or surpass in beauty those of
+the latter, yet when one observes their indiscriminate juxtaposition,
+there a large one and here a small, and the consequent crookedness and
+irregularity of the streets, one is disposed to allege that chance
+rather than any human will guided by reason must have led to such an
+arrangement. And if we consider that nevertheless there have been at
+all times certain officers whose duty it was to see that private
+buildings contributed to public ornament, the difficulty of reaching
+high perfection with but the materials of others to operate on, will be
+readily acknowledged. In the same way I fancied that those nations
+which, starting from a semi-barbarous state and advancing to
+civilization by slow degrees, have had their laws successively
+determined, and, as it were, forced upon them simply by experience of
+the hurtfulness of particular crimes and disputes, would by this
+process come to be possessed of less perfect institutions than those
+which, from the commencement of their association as communities, have
+followed the appointments of some wise legislator. It is thus quite
+certain that the constitution of the true religion, the ordinances of
+which are derived from God, must be incomparably superior to that of
+every other. And, to speak of human affairs, I believe that the
+pre-eminence of Sparta was due not to the goodness of each of its laws
+in particular, for many of these were very strange, and even opposed to
+good morals, but to the circumstance that, originated by a single
+individual, they all tended to a single end. In the same way I thought
+that the sciences contained in books (such of them at least as are made
+up of probable reasonings, without demonstrations), composed as they
+are of the opinions of many different individuals massed together, are
+farther removed from truth than the simple inferences which a man of
+good sense using his natural and unprejudiced judgment draws respecting
+the matters of his experience. And because we have all to pass through
+a state of infancy to manhood, and have been of necessity, for a length
+of time, governed by our desires and preceptors (whose dictates were
+frequently conflicting, while neither perhaps always counseled us for
+the best), I farther concluded that it is almost impossible that our
+judgments can be so correct or solid as they would have been, had our
+reason been mature from the moment of our birth, and had we always been
+guided by it alone.
+
+It is true, however, that it is not customary to pull down all the
+houses of a town with the single design of rebuilding them differently,
+and thereby rendering the streets more handsome; but it often happens
+that a private individual takes down his own with the view of erecting
+it anew, and that people are even sometimes constrained to this when
+their houses are in danger of falling from age, or when the foundations
+are insecure. With this before me by way of example, I was persuaded
+that it would indeed be preposterous for a private individual to think
+of reforming a state by fundamentally changing it throughout, and
+overturning it in order to set it up amended; and the same I thought
+was true of any similar project for reforming the body of the sciences,
+or the order of teaching them established in the schools: but as for
+the opinions which up to that time I had embraced, I thought that I
+could not do better than resolve at once to sweep them wholly away,
+that I might afterwards be in a position to admit either others more
+correct, or even perhaps the same when they had undergone the scrutiny
+of reason. I firmly believed that in this way I should much better
+succeed in the conduct of my life, than if I built only upon old
+foundations, and leaned upon principles which, in my youth, I had taken
+upon trust. For although I recognized various difficulties in this
+undertaking, these were not, however, without remedy, nor once to be
+compared with such as attend the slightest reformation in public
+affairs. Large bodies, if once overthrown, are with great difficulty
+set up again, or even kept erect when once seriously shaken, and the
+fall of such is always disastrous. Then if there are any imperfections
+in the constitutions of states (and that many such exist the diversity
+of constitutions is alone sufficient to assure us), custom has without
+doubt materially smoothed their inconveniences, and has even managed to
+steer altogether clear of, or insensibly corrected a number which
+sagacity could not have provided against with equal effect; and, in
+fine, the defects are almost always more tolerable than the change
+necessary for their removal; in the same manner that highways which
+wind among mountains, by being much frequented, become gradually so
+smooth and commodious, that it is much better to follow them than to
+seek a straighter path by climbing over the tops of rocks and
+descending to the bottoms of precipices.
+
+Hence it is that I cannot in any degree approve of those restless and
+busy meddlers who, called neither by birth nor fortune to take part in
+the management of public affairs, are yet always projecting reforms;
+and if I thought that this tract contained aught which might justify
+the suspicion that I was a victim of such folly, I would by no means
+permit its publication. I have never contemplated anything higher than
+the reformation of my own opinions, and basing them on a foundation
+wholly my own. And although my own satisfaction with my work has led me
+to present here a draft of it, I do not by any means therefore
+recommend to every one else to make a similar attempt. Those whom God
+has endowed with a larger measure of genius will entertain, perhaps,
+designs still more exalted; but for the many I am much afraid lest even
+the present undertaking be more than they can safely venture to
+imitate. The single design to strip one's self of all past beliefs is
+one that ought not to be taken by every one. The majority of men is
+composed of two classes, for neither of which would this be at all a
+befitting resolution: in the first place, of those who with more than a
+due confidence in their own powers, are precipitate in their judgments
+and want the patience requisite for orderly and circumspect thinking;
+whence it happens, that if men of this class once take the liberty to
+doubt of their accustomed opinions, and quit the beaten highway, they
+will never be able to thread the byway that would lead them by a
+shorter course, and will lose themselves and continue to wander for
+life; in the second place, of those who, possessed of sufficient sense
+or modesty to determine that there are others who excel them in the
+power of discriminating between truth and error, and by whom they may
+be instructed, ought rather to content themselves with the opinions of
+such than trust for more correct to their own reason.
+
+For my own part, I should doubtless have belonged to the latter class,
+had I received instruction from but one master, or had I never known
+the diversities of opinion that from time immemorial have prevailed
+among men of the greatest learning. But I had become aware, even so
+early as during my college life, that no opinion, however absurd and
+incredible, can be imagined, which has not been maintained by some on
+of the philosophers; and afterwards in the course of my travels I
+remarked that all those whose opinions are decidedly repugnant to ours
+are not in that account barbarians and savages, but on the contrary
+that many of these nations make an equally good, if not better, use of
+their reason than we do. I took into account also the very different
+character which a person brought up from infancy in France or Germany
+exhibits, from that which, with the same mind originally, this
+individual would have possessed had he lived always among the Chinese
+or with savages, and the circumstance that in dress itself the fashion
+which pleased us ten years ago, and which may again, perhaps, be
+received into favor before ten years have gone, appears to us at this
+moment extravagant and ridiculous. I was thus led to infer that the
+ground of our opinions is far more custom and example than any certain
+knowledge. And, finally, although such be the ground of our opinions, I
+remarked that a plurality of suffrages is no guarantee of truth where
+it is at all of difficult discovery, as in such cases it is much more
+likely that it will be found by one than by many. I could, however,
+select from the crowd no one whose opinions seemed worthy of
+preference, and thus I found myself constrained, as it were, to use my
+own reason in the conduct of my life.
+
+But like one walking alone and in the dark, I resolved to proceed so
+slowly and with such circumspection, that if I did not advance far, I
+would at least guard against falling. I did not even choose to dismiss
+summarily any of the opinions that had crept into my belief without
+having been introduced by reason, but first of all took sufficient time
+carefully to satisfy myself of the general nature of the task I was
+setting myself, and ascertain the true method by which to arrive at the
+knowledge of whatever lay within the compass of my powers.
+
+Among the branches of philosophy, I had, at an earlier period, given
+some attention to logic, and among those of the mathematics to
+geometrical analysis and algebra,--three arts or sciences which ought,
+as I conceived, to contribute something to my design. But, on
+examination, I found that, as for logic, its syllogisms and the
+majority of its other precepts are of avail--rather in the
+communication of what we already know, or even as the art of Lully, in
+speaking without judgment of things of which we are ignorant, than in
+the investigation of the unknown; and although this science contains
+indeed a number of correct and very excellent precepts, there are,
+nevertheless, so many others, and these either injurious or
+superfluous, mingled with the former, that it is almost quite as
+difficult to effect a severance of the true from the false as it is to
+extract a Diana or a Minerva from a rough block of marble. Then as to
+the analysis of the ancients and the algebra of the moderns, besides
+that they embrace only matters highly abstract, and, to appearance, of
+no use, the former is so exclusively restricted to the consideration of
+figures, that it can exercise the understanding only on condition of
+greatly fatiguing the imagination; and, in the latter, there is so
+complete a subjection to certain rules and formulas, that there results
+an art full of confusion and obscurity calculated to embarrass, instead
+of a science fitted to cultivate the mind. By these considerations I
+was induced to seek some other method which would comprise the
+advantages of the three and be exempt from their defects. And as a
+multitude of laws often only hampers justice, so that a state is best
+governed when, with few laws, these are rigidly administered; in like
+manner, instead of the great number of precepts of which logic is
+composed, I believed that the four following would prove perfectly
+sufficient for me, provided I took the firm and unwavering resolution
+never in a single instance to fail in observing them.
+
+The first was never to accept anything for true which I did not clearly
+know to be such; that is to say, carefully to avoid precipitancy and
+prejudice, and to comprise nothing more in my judgement than what was
+presented to my mind so clearly and distinctly as to exclude all ground
+of doubt.
+
+The second, to divide each of the difficulties under examination into
+as many parts as possible, and as might be necessary for its adequate
+solution.
+
+The third, to conduct my thoughts in such order that, by commencing
+with objects the simplest and easiest to know, I might ascend by little
+and little, and, as it were, step by step, to the knowledge of the more
+complex; assigning in thought a certain order even to those objects
+which in their own nature do not stand in a relation of antecedence and
+sequence.
+
+And the _last_, in every case to make enumerations so complete, and
+reviews so general, that I might be assured that nothing was omitted.
+
+The long chains of simple and easy reasonings by means of which
+geometers are accustomed to reach the conclusions of their most
+difficult demonstrations, had led me to imagine that all things, to the
+knowledge of which man is competent, are mutually connected in the same
+way, and that there is nothing so far removed from us as to be beyond
+our reach, or so hidden that we cannot discover it, provided only we
+abstain from accepting the false for the true, and always preserve in
+our thoughts the order necessary for the deduction of one truth from
+another. And I had little difficulty in determining the objects with
+which it was necessary to commence, for I was already persuaded that it
+must be with the simplest and easiest to know, and, considering that of
+all those who have hitherto sought truth in the sciences, the
+mathematicians alone have been able to find any demonstrations, that
+is, any certain and evident reasons, I did not doubt but that such must
+have been the rule of their investigations. I resolved to commence,
+therefore, with the examination of the simplest objects, not
+anticipating, however, from this any other advantage than that to be
+found in accustoming my mind to the love and nourishment of truth, and
+to a distaste for all such reasonings as were unsound. But I had no
+intention on that account of attempting to master all the particular
+sciences commonly denominated mathematics: but observing that, however
+different their objects, they all agree in considering only the various
+relations or proportions subsisting among those objects, I thought it
+best for my purpose to consider these proportions in the most general
+form possible, without referring them to any objects in particular,
+except such as would most facilitate the knowledge of them, and without
+by any means restricting them to these, that afterwards I might thus be
+the better able to apply them to every other class of objects to which
+they are legitimately applicable. Perceiving further, that in order to
+understand these relations I should sometimes have to consider them one
+by one and sometimes only to bear them in mind, or embrace them in the
+aggregate, I thought that, in order the better to consider them
+individually, I should view them as subsisting between straight lines,
+than which I could find no objects more simple, or capable of being
+more distinctly represented to my imagination and senses; and on the
+other hand, that in order to retain them in the memory or embrace an
+aggregate of many, I should express them by certain characters the
+briefest possible. In this way I believed that I could borrow all that
+was best both in geometrical analysis and in algebra, and correct all
+the defects of the one by help of the other.
+
+And, in point of fact, the accurate observance of these few precepts
+gave me, I take the liberty of saying, such ease in unraveling all the
+questions embraced in these two sciences, that in the two or three
+months I devoted to their examination, not only did I reach solutions
+of questions I had formerly deemed exceedingly difficult but even as
+regards questions of the solution of which I continued ignorant, I was
+enabled, as it appeared to me, to determine the means whereby, and the
+extent to which a solution was possible; results attributable to the
+circumstance that I commenced with the simplest and most general
+truths, and that thus each truth discovered was a rule available in the
+discovery of subsequent ones Nor in this perhaps shall I appear too
+vain, if it be considered that, as the truth on any particular point is
+one whoever apprehends the truth, knows all that on that point can be
+known. The child, for example, who has been instructed in the elements
+of arithmetic, and has made a particular addition, according to rule,
+may be assured that he has found, with respect to the sum of the
+numbers before him, and that in this instance is within the reach of
+human genius. Now, in conclusion, the method which teaches adherence to
+the true order, and an exact enumeration of all the conditions of the
+thing sought includes all that gives certitude to the rules of
+arithmetic.
+
+But the chief ground of my satisfaction with thus method, was the
+assurance I had of thereby exercising my reason in all matters, if not
+with absolute perfection, at least with the greatest attainable by me:
+besides, I was conscious that by its use my mind was becoming gradually
+habituated to clearer and more distinct conceptions of its objects; and
+I hoped also, from not having restricted this method to any particular
+matter, to apply it to the difficulties of the other sciences, with not
+less success than to those of algebra. I should not, however, on this
+account have ventured at once on the examination of all the
+difficulties of the sciences which presented themselves to me, for this
+would have been contrary to the order prescribed in the method, but
+observing that the knowledge of such is dependent on principles
+borrowed from philosophy, in which I found nothing certain, I thought
+it necessary first of all to endeavor to establish its principles. And
+because I observed, besides, that an inquiry of this kind was of all
+others of the greatest moment, and one in which precipitancy and
+anticipation in judgment were most to be dreaded, I thought that I
+ought not to approach it till I had reached a more mature age (being at
+that time but twenty-three), and had first of all employed much of my
+time in preparation for the work, as well by eradicating from my mind
+all the erroneous opinions I had up to that moment accepted, as by
+amassing variety of experience to afford materials for my reasonings,
+and by continually exercising myself in my chosen method with a view to
+increased skill in its application.
+
+PART III
+
+And finally, as it is not enough, before commencing to rebuild the
+house in which we live, that it be pulled down, and materials and
+builders provided, or that we engage in the work ourselves, according
+to a plan which we have beforehand carefully drawn out, but as it is
+likewise necessary that we be furnished with some other house in which
+we may live commodiously during the operations, so that I might not
+remain irresolute in my actions, while my reason compelled me to
+suspend my judgement, and that I might not be prevented from living
+thenceforward in the greatest possible felicity, I formed a provisory
+code of morals, composed of three or four maxims, with which I am
+desirous to make you acquainted.
+
+The _first_ was to obey the laws and customs of my country, adhering
+firmly to the faith in which, by the grace of God, I had been educated
+from my childhood and regulating my conduct in every other matter
+according to the most moderate opinions, and the farthest removed from
+extremes, which should happen to be adopted in practice with general
+consent of the most judicious of those among whom I might be living.
+For as I had from that time begun to hold my own opinions for nought
+because I wished to subject them all to examination, I was convinced
+that I could not do better than follow in the meantime the opinions of
+the most judicious; and although there are some perhaps among the
+Persians and Chinese as judicious as among ourselves, expediency seemed
+to dictate that I should regulate my practice conformably to the
+opinions of those with whom I should have to live; and it appeared to
+me that, in order to ascertain the real opinions of such, I ought
+rather to take cognizance of what they practised than of what they
+said, not only because, in the corruption of our manners, there are few
+disposed to speak exactly as they believe, but also because very many
+are not aware of what it is that they really believe; for, as the act
+of mind by which a thing is believed is different from that by which we
+know that we believe it, the one act is often found without the other.
+Also, amid many opinions held in equal repute, I chose always the most
+moderate, as much for the reason that these are always the most
+convenient for practice, and probably the best (for all excess is
+generally vicious), as that, in the event of my falling into error, I
+might be at less distance from the truth than if, having chosen one of
+the extremes, it should turn out to be the other which I ought to have
+adopted. And I placed in the class of extremes especially all promises
+by which somewhat of our freedom is abridged; not that I disapproved of
+the laws which, to provide against the instability of men of feeble
+resolution, when what is sought to be accomplished is some good, permit
+engagements by vows and contracts binding the parties to persevere in
+it, or even, for the security of commerce, sanction similar engagements
+where the purpose sought to be realized is indifferent: but because I
+did not find anything on earth which was wholly superior to change, and
+because, for myself in particular, I hoped gradually to perfect my
+judgments, and not to suffer them to deteriorate, I would have deemed
+it a grave sin against good sense, if, for the reason that I approved
+of something at a particular time, I therefore bound myself to hold it
+for good at a subsequent time, when perhaps it had ceased to be so, or
+I had ceased to esteem it such.
+
+My _second_ maxim was to be as firm and resolute in my actions as I was
+able, and not to adhere less steadfastly to the most doubtful opinions,
+when once adopted, than if they had been highly certain; imitating in
+this the example of travelers who, when they have lost their way in a
+forest, ought not to wander from side to side, far less remain in one
+place, but proceed constantly towards the same side in as straight a
+line as possible, without changing their direction for slight reasons,
+although perhaps it might be chance alone which at first determined the
+selection; for in this way, if they do not exactly reach the point they
+desire, they will come at least in the end to some place that will
+probably be preferable to the middle of a forest. In the same way,
+since in action it frequently happens that no delay is permissible, it
+is very certain that, when it is not in our power to determine what is
+true, we ought to act according to what is most probable; and even
+although we should not remark a greater probability in one opinion than
+in another, we ought notwithstanding to choose one or the other, and
+afterwards consider it, in so far as it relates to practice, as no
+longer dubious, but manifestly true and certain, since the reason by
+which our choice has been determined is itself possessed of these
+qualities. This principle was sufficient thenceforward to rid me of all
+those repentings and pangs of remorse that usually disturb the
+consciences of such feeble and uncertain minds as, destitute of any
+clear and determinate principle of choice, allow themselves one day to
+adopt a course of action as the best, which they abandon the next, as
+the opposite.
+
+My _third_ maxim was to endeavor always to conquer myself rather than
+fortune, and change my desires rather than the order of the world, and
+in general, accustom myself to the persuasion that, except our own
+thoughts, there is nothing absolutely in our power; so that when we
+have done our best in things external to us, all wherein we fail of
+success is to be held, as regards us, absolutely impossible: and this
+single principle seemed to me sufficient to prevent me from desiring
+for the future anything which I could not obtain, and thus render me
+contented; for since our will naturally seeks those objects alone which
+the understanding represents as in some way possible of attainment, it
+is plain, that if we consider all external goods as equally beyond our
+power, we shall no more regret the absence of such goods as seem due to
+our birth, when deprived of them without any fault of ours, than our
+not possessing the kingdoms of China or Mexico, and thus making, so to
+speak, a virtue of necessity, we shall no more desire health in
+disease, or freedom in imprisonment, than we now do bodies
+incorruptible as diamonds, or the wings of birds to fly with. But I
+confess there is need of prolonged discipline and frequently repeated
+meditation to accustom the mind to view all objects in this light; and
+I believe that in this chiefly consisted the secret of the power of
+such philosophers as in former times were enabled to rise superior to
+the influence of fortune, and, amid suffering and poverty, enjoy a
+happiness which their gods might have envied. For, occupied incessantly
+with the consideration of the limits prescribed to their power by
+nature, they became so entirely convinced that nothing was at their
+disposal except their own thoughts, that this conviction was of itself
+sufficient to prevent their entertaining any desire of other objects;
+and over their thoughts they acquired a sway so absolute, that they had
+some ground on this account for esteeming themselves more 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 of this
+philosophy, can never command the realization of all their desires.
+
+In fine, to conclude this code of morals, I thought of reviewing the
+different occupations 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 may state that it was my conviction that I
+could not do better than continue in that in which I was engaged, viz.,
+in devoting my whole life to the culture of my reason, and in making
+the greatest progress I was able in the knowledge of truth, on the
+principles of the method which I had prescribed to myself. This method,
+from the time I had begun to apply it, had been to me the source of
+satisfaction so intense as to lead me to, believe that more perfect or
+more innocent could not be enjoyed in this life; and as by its means I
+daily discovered truths that appeared to me of some importance, and of
+which other men were generally ignorant, the gratification thence
+arising so occupied my mind that I was wholly indifferent to every
+other object. Besides, the three preceding maxims were founded singly
+on the design of continuing the work of self-instruction. For since God
+has endowed each of us with some light of reason by which to
+distinguish truth from error, I could not have believed that I 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 I should be duly qualified for the task. Nor could I have
+proceeded on such opinions without scruple, had I supposed that I
+should thereby forfeit any advantage for attaining still more accurate,
+should such exist. And, in fine, I could not have restrained my
+desires, nor remained satisfied had I not followed a path in which I
+thought myself certain of attaining all the knowledge to the
+acquisition of which I was competent, as well as the largest amount of
+what is truly good which I could ever hope to secure Inasmuch as we
+neither seek nor shun any object except in so far as our understanding
+represents it as good or bad, all that is necessary to right action is
+right judgment, and to the best action the most correct judgment, that
+is, to the acquisition of all the virtues with all else that is truly
+valuable and within our reach; and the assurance of such an acquisition
+cannot fail to render us contented.
+
+Having thus provided myself with these maxims, and having placed them
+in reserve along with the truths of faith, which have ever occupied the
+first place in my belief, I came to the conclusion that I might with
+freedom set about ridding myself of what remained of my opinions. And,
+inasmuch as I hoped to be better able successfully to accomplish this
+work by holding intercourse with mankind, than by remaining longer shut
+up in the retirement where these thoughts had occurred to me, I betook
+me again to traveling before the winter was well ended. And, during the
+nine subsequent years, I did nothing but roam from one place to
+another, desirous of being a spectator rather than an actor in the
+plays exhibited on the theater of the world; and, as I made it my
+business in each matter to reflect particularly upon what might fairly
+be doubted and prove a source of error, I gradually rooted out from my
+mind all the errors which had hitherto crept into it. Not that in this
+I imitated the sceptics who doubt only that they may doubt, and seek
+nothing beyond uncertainty itself; for, on the contrary, my design was
+singly to find ground of assurance, and cast aside the loose earth and
+sand, that I might reach the rock 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 propositions I examined, not by feeble
+conjectures, but by clear and certain reasonings, I met with nothing so
+doubtful as not to yield some conclusion of adequate certainty,
+although this were merely the inference, that the matter in question
+contained nothing certain. And, just as in pulling down an old house,
+we usually reserve the ruins to contribute towards the erection, so, in
+destroying such of my opinions as I judged to be Ill-founded, I made a
+variety of observations and acquired an amount of experience of which I
+availed myself in the establishment of more certain. And further, I
+continued to exercise myself in the method I had prescribed; for,
+besides taking care in general to conduct all my thoughts according to
+its rules, I reserved some hours from time to time which I expressly
+devoted to the employment of the method in the solution of mathematical
+difficulties, or even in the solution likewise of some questions
+belonging to other sciences, but which, by my having detached them from
+such principles of these sciences as were of inadequate certainty, were
+rendered almost mathematical: the truth of this will be manifest from
+the numerous examples contained in this volume. And thus, without in
+appearance living otherwise than those who, with no other occupation
+than that of spending their lives agreeably and innocently, study to
+sever pleasure from vice, and who, that they may enjoy their leisure
+without ennui, have recourse to such pursuits as are honorable, I was
+nevertheless prosecuting my design, and making greater progress in the
+knowledge of truth, than I might, perhaps, have made had I been engaged
+in the perusal of books merely, or in holding converse with men of
+letters.
+
+These nine years passed away, however, before I had come to any
+determinate judgment respecting the difficulties which form matter of
+dispute among the learned, or had commenced to seek the principles of
+any philosophy more certain than 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, without success, led me to imagine it
+to be a work of so much difficulty, that I would not perhaps have
+ventured on it so soon had I not heard it currently rumored that I had
+already completed the inquiry. I know not what were the grounds of this
+opinion; and, if my conversation contributed in any measure to its
+rise, this must have happened rather from my having confessed my
+Ignorance with greater freedom than those are accustomed to do who have
+studied a little, and expounded perhaps, the reasons that led me to
+doubt of many of those things that by others are esteemed certain, than
+from my having boasted of any system of philosophy. But, as I am of a
+disposition that makes me unwilling to be esteemed different from what
+I really am, I thought it necessary to endeavor by all means to render
+myself worthy of the reputation accorded to me; and it is now exactly
+eight years since this desire constrained me to remove from all those
+places where interruption from any of my acquaintances was possible,
+and betake myself to this country, in which the long duration of the
+war has led to the establishment of such discipline, that the armies
+maintained seem to be of use only in enabling the inhabitants to enjoy
+more securely the blessings of peace 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, I have been enabled to live
+without being deprived of any of the conveniences to be had in the most
+populous cities, and yet as solitary and as retired as in the midst of
+the most remote deserts.
+
+PART IV
+
+I am in doubt as to the propriety of making my first meditations in the
+place above mentioned matter of discourse; for these are so
+metaphysical, and so uncommon, as not, perhaps, to be acceptable to
+every one. And yet, that it may be 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 before remarked that, in
+relation to practice, it is sometimes necessary to adopt, as if above
+doubt, opinions which we discern to be highly uncertain, as has been
+already said; but as I then desired to give my attention solely to the
+search after 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 which I could suppose the least ground for doubt, in order
+to ascertain whether after that there remained aught in my belief that
+was wholly indubitable. Accordingly, seeing that our senses sometimes
+deceive us, I was willing to suppose that there existed nothing really
+such as they presented to us; and because some men err in reasoning,
+and fall into paralogisms, even on the simplest matters of geometry, I,
+convinced that I was as open to error as any other, rejected as false
+all the reasonings I had hitherto taken for demonstrations; and
+finally, when I considered that the very same thoughts (presentations)
+which we experience when awake may also be experienced when we are
+asleep, while there is at that time not one of them true, I supposed
+that all 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 upon this I observed that, whilst I thus wished to
+think that all was false, it was absolutely necessary that I, who thus
+thought, should be somewhat; and as I observed that this truth, I
+think, therefore I am (COGITO ERGO SUM), was so certain and of such
+evidence that no ground of doubt, however extravagant, could be alleged
+by the sceptics capable of shaking it, I concluded that I might,
+without scruple, accept it as the first principle of the philosophy of
+which I was in search.
+
+In the next place, I attentively examined what I was and as I observed
+that I could suppose that I had no body, and that there was no world
+nor any place in which I might be; but that I could not therefore
+suppose that I was not; and that, on the contrary, from the very
+circumstance that I thought to doubt of the 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 other objects
+which I had ever imagined had been in reality existent, I would have
+had no reason to believe that I existed; I thence concluded that I was
+a substance 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 material thing; so that "I," that is to say, the mind by which I am
+what I am, is wholly distinct from the body, and is even more easily
+known than the latter, and is such, that although the latter were not,
+it would still continue to be all that it is.
+
+After this I inquired in general into what is essential to the truth
+and certainty of a proposition; for since I had discovered one which I
+knew to be true, I thought that I must likewise be able to discover the
+ground of this certitude. And as I observed that in the words I think,
+therefore I am, there is nothing at all which gives me assurance of
+their truth beyond this, that I see very clearly that in order to think
+it is necessary to exist, I concluded that I might take, as a general
+rule, the principle, that all the things which we very clearly and
+distinctly conceive are true, only observing, however, that there is
+some difficulty in rightly determining the objects which we distinctly
+conceive.
+
+In the next place, from reflecting on the circumstance that I doubted,
+and that consequently my being was not wholly perfect (for I clearly
+saw that it was a greater perfection to know than to doubt), I was led
+to inquire whence I had learned to think of something more perfect than
+myself; and I clearly recognized that I must hold this notion from some
+nature which in reality was more perfect. As for the thoughts of many
+other objects external to me, as of the sky, the earth, light, heat,
+and a thousand more, I was less at a loss to know whence these came;
+for since I remarked in them nothing which seemed to render them
+superior to myself, I could believe that, if these were true, they were
+dependencies on my own nature, in so far as it possessed a certain
+perfection, and, if they were false, that I held them from nothing,
+that is to say, that they were in me because of a certain imperfection
+of my nature. But this 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, because it is not less repugnant that the
+more perfect should be an effect of, and dependence on the less
+perfect, than that something should proceed from nothing, 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 which was in
+reality more perfect than mine, and which even possessed within itself
+all the perfections of which I could form any idea; that is to say, in
+a single word, which was God. And to this I added that, since I knew
+some perfections which 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 the contrary, that there was of necessity some
+other more perfect Being upon whom I was dependent, and from whom I had
+received all that I possessed; for if I had existed alone, and
+independently of every other being, so as to have had from myself all
+the perfection, however little, which I actually possessed, I should
+have been able, for the same reason, to have had from myself the whole
+remainder of perfection, of the want of which I was conscious, and thus
+could of myself have become infinite, eternal, immutable, omniscient,
+all-powerful, and, in fine, have possessed all the perfections which I
+could recognize in God. For in order to know the nature of God (whose
+existence has been established by the preceding reasonings), as far as
+my own nature permitted, I had only to consider in reference to all the
+properties of which I found in my mind some idea, whether their
+possession was a mark of perfection; and I was assured that no one
+which indicated any imperfection was in him, and that none of 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
+happy to be free from them. Besides, I had ideas of many sensible and
+corporeal things; for although I might suppose that I was dreaming, and
+that all which I saw or imagined was false, I could not, nevertheless,
+deny that the ideas were in reality in my thoughts. But, because I had
+already very clearly recognized in myself that the intelligent nature
+is distinct from the corporeal, and as I observed that all composition
+is an evidence of dependency, and that a state of dependency is
+manifestly a state of imperfection, I therefore determined that it
+could not be a perfection in God to be compounded of these two natures
+and that consequently he was not so compounded; but that if there were
+any bodies in the world, or even any intelligences, or other natures
+that were not wholly perfect, their existence depended on his power in
+such a way that they could not subsist without him for a single moment.
+
+I was disposed straightway to search for other truths and when I had
+represented to myself the object of the geometers, which I conceived to
+be a continuous body or a space indefinitely extended in length,
+breadth, and height or depth, divisible into divers parts which admit
+of different figures and sizes, and of being moved or transposed in all
+manner of ways (for all this the geometers suppose to be in the object
+they contemplate), I went over some of their simplest demonstrations.
+And, in the first place, I observed, that the great certitude which by
+common consent is accorded to these demonstrations, is founded solely
+upon this, that they are clearly conceived in accordance with the rules
+I have already laid down In the next place, I perceived that there was
+nothing at all in these demonstrations which could assure me of the
+existence of their object: thus, for example, supposing a triangle to
+be given, I distinctly perceived that its three angles were necessarily
+equal to two right angles, but I did not on that account perceive
+anything which could assure me that any triangle existed: while, on the
+contrary, recurring to the examination of the idea of a Perfect Being,
+I found that the existence of the Being was comprised in the idea in
+the same way that the equality of its three angles to two right angles
+is comprised in the idea of a triangle, or as in the idea of a sphere,
+the equidistance of all points on its surface from the center, or even
+still more clearly; and that consequently it is at least as certain
+that God, who is this Perfect Being, is, or exists, as any
+demonstration of geometry can be.
+
+But the reason which leads many to persuade them selves that there is a
+difficulty in knowing this truth, and even also in knowing what their
+mind really is, is that they never raise their thoughts above sensible
+objects, and are so accustomed to consider nothing except by way of
+imagination, which is a mode of thinking limited to material objects,
+that all that is not imaginable seems to them not intelligible. The
+truth of this is sufficiently manifest from the single circumstance,
+that the philosophers of the schools accept as a maxim that there is
+nothing in the understanding which was not previously in the senses, in
+which however it is certain that the ideas of God and of the soul have
+never been; and it appears to me that they who make use of their
+imagination to comprehend these ideas do exactly the some thing as if,
+in order to 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 not afford us an inferior assurance to those of
+smell or hearing; in place of which, neither our imagination nor our
+senses can give us assurance of anything unless our understanding
+intervene.
+
+Finally, if there be still persons who are not sufficiently persuaded
+of the existence of God and of the soul, by the reasons I have adduced,
+I am desirous that they should know that all the other propositions, of
+the truth of which they deem themselves perhaps more assured, as that
+we have a body, and that there exist stars and an earth, and such like,
+are less certain; for, although we have a moral assurance of these
+things, which is so strong that there is an appearance of extravagance
+in doubting of their existence, yet at the same time no one, unless his
+intellect is impaired, can deny, when the question relates to a
+metaphysical certitude, that there is sufficient reason to exclude
+entire assurance, in the observation that when asleep we can in the
+same way imagine ourselves possessed of another body and that we see
+other stars and another earth, when there is nothing of the kind. For
+how do we know that the thoughts which occur in dreaming are false
+rather than those other which we experience when awake, since the
+former are often not less vivid and distinct than the latter? And
+though men of the highest genius study this question as long as they
+please, I do not believe that they will be able to give any reason
+which can be sufficient to remove this doubt, unless they presuppose
+the existence of God. For, in the first place even the principle which
+I have already taken as a rule, viz., that all the things which we
+clearly and distinctly conceive are true, is certain only because God
+is or exists and because he is a Perfect Being, and because all that we
+possess is derived from him: whence it follows that our ideas or
+notions, which to the extent of their clearness and distinctness are
+real, and proceed from God, must to that extent be true. Accordingly,
+whereas we not infrequently have ideas or notions in which some falsity
+is contained, this can only be the case with such as are to some extent
+confused and obscure, and in this proceed from nothing (participate of
+negation), that is, exist in us thus confused because we are not wholly
+perfect. And it is evident that it is not less repugnant that falsity
+or imperfection, in so far as it is imperfection, should proceed from
+God, than that truth or perfection should proceed from nothing. But if
+we did not know that all which we possess of real and true proceeds
+from a Perfect and Infinite Being, however clear and distinct our ideas
+might be, we should have no ground on that account for the assurance
+that they possessed the perfection of being true.
+
+But after the knowledge of God and of the soul has rendered us certain
+of this rule, we can easily understand that the truth of the thoughts
+we experience when awake, ought not in the slightest degree to be
+called in question on account 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 geometer should discover some new
+demonstration, the circumstance of his being asleep would not militate
+against its truth; and as for the most ordinary error of our dreams,
+which consists in their representing to us various objects in the same
+way as our external senses, this is not prejudicial, since it leads us
+very properly to suspect the truth of the ideas of sense; for we are
+not infrequently deceived in the same manner when awake; as when
+persons in the jaundice see all objects yellow, or when the stars or
+bodies at a great distance appear to us much smaller than they are.
+For, in fine, whether awake or asleep, we ought never to allow
+ourselves to be persuaded of the truth of anything unless on the
+evidence of our reason. And it must be noted that I say of 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 that it is only of the size which our sense of sight
+presents; and we may very distinctly imagine the head of a lion joined
+to the body of a goat, without being therefore shut up to the
+conclusion that a chimaera exists; for it is not a 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 some truth; for
+otherwise it could not be that God, who is wholly perfect and
+veracious, should have placed them in us. And because our reasonings
+are never so clear or so complete during sleep as when we are awake,
+although sometimes the acts of our imagination are then as lively and
+distinct, if not more so than in our waking moments, reason further
+dictates that, since all our thoughts cannot be true because of our
+partial imperfection, those possessing truth must infallibly be found
+in the experience of our waking moments rather than in that of our
+dreams.
+
+PART V
+
+I would here willingly have proceeded to exhibit the whole chain of
+truths which I deduced from these primary but as with a view to this it
+would have been necessary now to treat of many questions in dispute
+among the earned, with whom I do not wish to be embroiled, I believe
+that it will be better for me to refrain from this exposition, and only
+mention in general what these truths are, that the more judicious may
+be able to determine whether a more special account of them would
+conduce to the public advantage. I have ever remained firm in my
+original resolution to suppose no other principle than that of which I
+have recently availed myself in demonstrating the existence of God and
+of the soul, and to accept as true nothing that did not appear to me
+more clear and certain than the demonstrations of the geometers had
+formerly appeared; and yet I venture to state that not only have I
+found means to satisfy myself in a short time on all the principal
+difficulties which are usually treated of in philosophy, but I have
+also observed certain laws established in nature by God in such a
+manner, and of which he has impressed on our minds such notions, that
+after we have reflected sufficiently upon these, we cannot doubt that
+they are accurately 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 have discovered many truths more useful and more
+important than all I had before learned, or even had expected to learn.
+
+But because I have essayed to expound the chief of these discoveries in
+a treatise which certain considerations prevent me from publishing, I
+cannot make the results known more conveniently than by here giving a
+summary of the contents of this treatise. It was my design to comprise
+in it all that, before I 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 well on a plain surface all the
+different faces of a solid body, select one of the chief, on which
+alone they make the light fall, and throwing the rest into the shade,
+allow them to appear only in so far as they can be seen while looking
+at the principal one; so, fearing lest I should not be able to compense
+in my discourse all that was in my mind, I resolved to expound singly,
+though at considerable length, my opinions regarding light; then to
+take the opportunity of adding something on the sun and the fixed
+stars, since light almost wholly proceeds from them; on the heavens
+since they transmit it; on the planets, comets, and earth, since they
+reflect it; and particularly on all the bodies that are upon the earth,
+since they are either colored, or transparent, or luminous; 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 being
+necessitated to adopt or refute the opinions of the learned, I resolved
+to leave all the people here to their disputes, and to speak only of
+what would happen in a new world, if God were now to create somewhere
+in the imaginary spaces matter sufficient to compose one, and were to
+agitate variously and confusedly the different parts of this matter, so
+that there resulted a chaos as disordered as the poets ever feigned,
+and after that did nothing more than lend his ordinary concurrence to
+nature, and allow her to act in accordance with the laws which he had
+established. On this supposition, I, in the first place, described this
+matter, and essayed to represent it in such a manner that to my mind
+there can be nothing clearer and more intelligible, except what has
+been recently said regarding God and the soul; for I even expressly
+supposed that it possessed none of those forms or qualities which are
+so debated in the schools, nor in general anything the knowledge of
+which is not so natural to our minds that no one can so much as imagine
+himself ignorant of it. Besides, I have pointed out what are the laws
+of nature; and, with no other principle upon which to found my
+reasonings except the infinite perfection of God, I endeavored to
+demonstrate all those about which there could be any room for doubt,
+and to prove that they are such, that even if God had created more
+worlds, 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, in accordance with these laws, dispose and arrange
+itself in such a way as to present the appearance of heavens; how in
+the meantime some of its parts must compose 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 at considerable
+length what the nature of that light must be which is found in the sun
+and the stars, and how thence in an instant of time it traverses the
+immense spaces of the heavens, and how from the planets and comets it
+is reflected towards the earth. To this I likewise added much
+respecting the substance, the situation, the motions, and all the
+different qualities of these heavens and stars; so that I thought I had
+said enough respecting them to show that there is nothing observable in
+the heavens or stars of our system that must not, or at least may not
+appear precisely alike in those of the system which I described. I came
+next to speak of the earth in particular, and to show how, even though
+I had expressly supposed that God had given no weight to the matter of
+which it is composed, this should not prevent all its parts from
+tending exactly to its center; how with water and air on its surface,
+the disposition 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 in our 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 produced in the mines, and the plants
+grow in the fields and in general, how all the bodies which are
+commonly denominated mixed or composite might be generated and, among
+other things in the discoveries alluded to inasmuch as besides the
+stars, I knew nothing except fire which produces light, I spared no
+pains to set forth all that pertains to its nature,--the manner of its
+production and support, and to explain how heat is sometimes found
+without light, and light without heat; to show how it can induce
+various colors upon different bodies and other diverse qualities; how
+it reduces some to a liquid state and hardens others; how it can
+consume almost all bodies, or convert them into ashes and smoke; 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 as wonderful as any other in nature, I took a special pleasure in
+describing it. I was not, however, disposed, from these circumstances,
+to conclude that this world had been created in the manner I described;
+for it is much more likely that God made it at the first such as it was
+to be. But this is certain, and an opinion commonly received among
+theologians, that the action by which he now sustains it is the same
+with that by which he originally created it; so that even although he
+had from the beginning given it no other form than that of chaos,
+provided only he had established certain laws of nature, and had lent
+it his 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, things purely material might, in course of time, have become
+such as we observe them at present; and their nature is much more
+easily conceived when they are beheld coming in this manner gradually
+into existence, than when they are only considered as produced at once
+in a finished and perfect state.
+
+From the description of inanimate bodies and plants, I passed to
+animals, and particularly to man. But since I had not as yet sufficient
+knowledge to enable me to treat of these in the same manner as of the
+rest, that is to say, by deducing effects from their causes, and by
+showing from what elements and in what manner nature must produce them,
+I remained satisfied with the supposition that God formed the body of
+man wholly like to one of ours, as well in the external shape of the
+members as in the internal conformation of the organs, of the same
+matter with that I had described, and at first placed in it no rational
+soul, nor any other principle, in room of the vegetative or sensitive
+soul, beyond kindling in the heart one of those fires without light,
+such as I had already described, and which I thought was not different
+from the heat in hay that has been heaped together before it is dry, or
+that which causes fermentation in new wines before they are run clear
+of the fruit. For, when I examined the kind of functions which might,
+as consequences of this supposition, exist in this body, I found
+precisely all those which may exist in us independently of all power of
+thinking, and consequently without being in any measure owing to the
+soul; in other words, to that part of us which is distinct from the
+body, and of which it has been said above that the nature distinctively
+consists in thinking, functions in which the animals void of reason may
+be said wholly to resemble us; but among which I could not discover any
+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 to have created a rational soul, and to have annexed it to
+this body in a particular manner which I described.
+
+But, in order to show how I there handled this matter, I mean here to
+give the explication of the motion of the heart and arteries, which, as
+the first and most general motion observed in animals, will afford the
+means of readily determining what should be thought of all the rest.
+And that there may be less difficulty in understanding what I am about
+to say on this subject, I advise those who are not versed in anatomy,
+before they commence the perusal of these observations, to take the
+trouble of getting dissected in their presence the heart of some large
+animal possessed of lungs (for this is throughout sufficiently like the
+human), and to have shown to them its two ventricles or cavities: in
+the first place, that in the right side, with which correspond two very
+ample tubes, viz., the hollow vein (_vena cava_), which is the
+principal receptacle of the blood, and the trunk of the tree, as it
+were, of which all the other veins in the body are branches; and the
+arterial vein (_vena arteriosa_), inappropriately so denominated, since
+it is in truth only an artery, which, taking its rise in the heart, is
+divided, after passing out from it, into many branches which presently
+disperse themselves all over the lungs; in the second place, the cavity
+in the left side, with which correspond in the same manner two canals
+in size equal to or larger than the preceding, viz., the venous artery
+(_arteria venosa_), likewise inappropriately thus designated, because
+it is simply a vein which comes from the lungs, where it is divided
+into many branches, interlaced with those of the arterial vein, and
+those of the tube called the windpipe, through which the air we breathe
+enters; and the great artery which, issuing from the heart, sends its
+branches all over the body. I should wish also that such persons were
+carefully shown the eleven pellicles which, like so many small valves,
+open and shut the four orifices that are in these two cavities, viz.,
+three at the entrance of the hollow veins where they are disposed in
+such a manner as by no means to prevent the blood which it contains
+from flowing into the right ventricle of the heart, and yet exactly to
+prevent its flowing out; three at the entrance to the arterial vein,
+which, arranged in a manner exactly the opposite of the former, readily
+permit the blood contained in this cavity to pass into the lungs, but
+hinder that contained in the lungs from returning to this 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, which suffer the blood to flow from the heart, but prevent its
+reflux. Nor do we need to seek any other reason for the number of these
+pellicles beyond this that the orifice of the venous artery being of an
+oval shape from the nature of its situation, can be adequately closed
+with two, whereas the others being round are more conveniently closed
+with three. Besides, I wish such persons to observe that the grand
+artery and the arterial vein are of much harder and firmer texture than
+the venous artery and the hollow vein; and that the two last expand
+before entering the heart, and there form, as it were, two pouches
+denominated the auricles of the heart, which are composed of a
+substance similar to that of the heart itself; and that there is always
+more warmth in the heart than in any other part of the body--and
+finally, that this heat is capable of causing any drop of blood that
+passes into the cavities rapidly to expand and dilate, just as all
+liquors do when allowed to fall drop by drop into a highly heated
+vessel.
+
+For, after these things, it is not necessary for me to say anything
+more with a view to explain the motion of the heart, except that when
+its cavities are not full of blood, into these the blood of necessity
+flows,--from the hollow vein into the right, and from the venous artery
+into the left; because these two vessels are always full of blood, and
+their orifices, which are turned towards the heart, cannot then be
+closed. But as soon as two drops of blood have thus passed, one into
+each of the cavities, these drops which cannot but be very large,
+because the orifices through which they pass are wide, and the vessels
+from which they come full of blood, are immediately rarefied, and
+dilated by the heat they meet with. In this way they cause the whole
+heart to expand, and at the same time press home and shut the five
+small valves that are at the entrances of the two vessels from which
+they flow, and thus prevent any more blood 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 two vessels, through
+which they pass out, causing in this way all the branches of the
+arterial vein and of the grand artery to expand almost simultaneously
+with the heart which immediately thereafter begins to contract, as do
+also the arteries, because the blood that has entered them has cooled,
+and the six small valves close, and the five of the hollow vein and of
+the venous artery open anew and allow a passage to other two drops of
+blood, which cause the heart and the arteries again to expand as
+before. And, because the blood which thus enters into the heart passes
+through these two pouches called auricles, it thence happens that their
+motion is the contrary of that of the heart, and that when it expands
+they contract. But lest those who are ignorant of the force of
+mathematical demonstrations and who are not accustomed to distinguish
+true reasons from mere verisimilitudes, should venture, without
+examination, to deny what has been said, I wish it to be considered
+that the motion which I have now explained follows as necessarily from
+the very arrangement of the parts, which may be observed in the heart
+by the eye alone, and from the heat which may be felt with the fingers,
+and from the nature of the blood as learned from experience, as does
+the motion of a clock from the power, the situation, and shape of its
+counterweights and wheels.
+
+But if it be asked how it happens that the blood in the veins, flowing
+in this way continually into the heart, is not exhausted, and why the
+arteries do not become too full, since all the blood which passes
+through the heart flows into them, I need only mention in reply what
+has been written by a physician of England, who has the honor of having
+broken the ice on this subject, and of having been the first to teach
+that there are many small passages at the extremities of the arteries,
+through which the blood received by them from the heart passes into the
+small branches of the veins, whence it again returns to the heart; so
+that its course amounts precisely to a perpetual circulation. Of this
+we have abundant proof in the ordinary experience of surgeons, who, by
+binding the arm with a tie of moderate straitness above the part where
+they open the vein, cause the blood to flow more copiously than it
+would have done without any ligature; whereas quite the contrary would
+happen were they to bind it below; that is, between the hand and the
+opening, or were to make the ligature above the opening very tight. For
+it is manifest that the tie, moderately straightened, while adequate to
+hinder the blood already in the arm from returning towards the heart by
+the veins, cannot on that account prevent new blood from coming forward
+through the arteries, because these are situated below the veins, and
+their coverings, from their greater consistency, are more difficult to
+compress; and also that the blood which comes from the heart tends to
+pass through them to the hand with greater force than it does to return
+from the hand to the heart through the veins. And since the latter
+current escapes from the arm by the opening made in one of the veins,
+there must of necessity be certain passages below the ligature, that
+is, towards the extremities of the arm through which it can come
+thither from the arteries. This physician likewise abundantly
+establishes what he has advanced respecting the motion of the blood,
+from the existence of certain pellicles, so disposed in various places
+along the course of the veins, in the manner of small valves, as not to
+permit 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, from experience which shows that all the blood which is in the
+body may flow out of it in a very short time through a single artery
+that has been cut, even although this had been closely tied in the
+immediate neighborhood of the heart and cut between the heart and the
+ligature, so as to prevent the supposition that the blood flowing out
+of it could come from any other quarter than the heart.
+
+But there are many other circumstances which evince that what I have
+alleged is the true cause of the motion of the blood: thus, in the
+first place, the difference that is observed between the blood which
+flows from the veins, and that from the arteries, can only arise from
+this, that being rarefied, and, as it 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 the
+arteries, 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 this difference is very marked only in the neighborhood of
+the heart; and is not so evident in parts more remote from it. In the
+next place, the consistency of the coats of which the arterial vein and
+the great artery are composed, sufficiently shows that the blood is
+impelled against them with more force than against the veins. And why
+should the left cavity of the heart and the great artery be wider and
+larger than the right cavity and the arterial vein, were it not that
+the blood of the venous artery, having only been in the lungs after it
+has passed through the heart, is thinner, and rarefies more readily,
+and in a higher degree, than the blood which proceeds immediately from
+the hollow vein? And what can physicians conjecture from feeling the
+pulse unless they know that according as the blood changes its nature
+it can be rarefied by the warmth of the 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, must it not be admitted
+that this is effected by means of the blood, which, passing through 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 is likewise withdrawn by the same means; and although the heart
+were as-hot as glowing iron, it would not be capable of warming the
+feet and hands as at present, unless it continually sent thither new
+blood. We likewise perceive from this, that the true use of respiration
+is to bring sufficient fresh air into the lungs, to cause the blood
+which flows into them from the right ventricle of the heart, where it
+has been rarefied and, as it were, changed into vapors, to become
+thick, and to convert it anew into blood, before it flows into the left
+cavity, without which process it would be unfit for the nourishment of
+the fire that is there. This receives confirmation from the
+circumstance, that it is observed of animals destitute of lungs that
+they have also but one cavity in the heart, and that in children who
+cannot use them while in the womb, there is a hole through which the
+blood flows from the hollow vein into the left cavity of the heart, and
+a tube through which it passes from the arterial vein into the grand
+artery without passing through the lung. In the next place, how could
+digestion be carried on in the stomach unless the heart communicated
+heat to it through the arteries, and along with this certain of the
+more fluid parts of the blood, which assist in the dissolution of the
+food that has been taken in? Is not also the operation which converts
+the juice of food into blood easily comprehended, when it is considered
+that it is distilled by passing and repassing through the heart perhaps
+more than one or two hundred times in a day? And what more need be
+adduced to explain nutrition, and the production of the different
+humors of the body, beyond saying, that the force with which the blood,
+in being rarefied, passes from the heart towards the extremities of the
+arteries, causes certain of its parts to remain in the members at which
+they arrive, and there occupy the 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 others flow into certain
+parts, in the same way that some sieves are observed to act, which, by
+being variously perforated, serve to separate different species of
+grain? And, in the last place, what above all is here worthy of
+observation, is the generation of the animal spirits, which are like a
+very subtle wind, or rather a very pure and vivid flame which,
+continually ascending in great abundance from the heart to the brain,
+thence penetrates through the nerves into the muscles, and gives motion
+to all the members; so that to account for other parts of the blood
+which, as most agitated and penetrating, are the fittest to compose
+these spirits, proceeding towards the brain, it is not necessary to
+suppose any other cause, than simply, that the arteries which carry
+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 sufficient room for all (as is the case with the parts of the blood
+which flow forth from the left cavity of the heart and tend towards the
+brain), the weaker and less agitated parts must necessarily be driven
+aside from that point by the stronger which alone in this way reach it
+I had expounded all these matters with sufficient 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 muscles of the human
+body to give the animal spirits contained in it the power to move the
+members, as when we see heads shortly after they have been struck off
+still move and bite the earth, although no longer animated; what
+changes must take place in the brain to produce waking, sleep, and
+dreams; how light, sounds, odors, tastes, heat, and all the other
+qualities of external objects impress it with different ideas by means
+of the senses; how hunger, thirst, and the other internal affections
+can likewise impress upon it divers ideas; what must be understood by
+the common sense (_sensus communis_) in which these ideas are received,
+by the memory which retains them, by the fantasy which can change them
+in various ways, and out of them compose new ideas, and which, by the
+same means, distributing the animal spirits through the muscles, can
+cause the members of such a body to move in as many different ways, and
+in a manner as suited, whether to the objects that are presented to its
+senses or to its internal affections, as can take place in our own case
+apart from the guidance of the will. Nor will this appear at all
+strange to those who are acquainted with the variety of movements
+performed by the different automata, or moving machines fabricated by
+human industry, and that with help of but few pieces compared with the
+great multitude of bones, muscles, nerves, arteries, veins, and other
+parts that are found in the body of each animal. Such persons will look
+upon this body as a machine made by the hands of God, which is
+incomparably better arranged, and adequate to movements more admirable
+than is any machine of human invention. And here I specially stayed to
+show that, were there such machines exactly resembling organs and
+outward form an ape or any other irrational animal, we could have no
+means of knowing that they were in any respect of a different nature
+from these animals; but if there were machines bearing the image of our
+bodies, and capable of imitating our actions as far as it is morally
+possible, there would still remain two most certain tests whereby to
+know that they were not therefore really men. Of these the first is
+that they could never use words or other signs arranged in such a
+manner as is competent to us in order to declare our thoughts to
+others: for we may easily conceive a machine to be so constructed that
+it emits vocables, and even that it emits some correspondent to the
+action upon it of external objects which cause a change in its organs;
+for example, if touched in a particular place it may demand what we
+wish to say to it; if in another it may cry out that it is hurt, and
+such like; but not that it should arrange them variously so as
+appositely to reply to what is said in its presence, as men of the
+lowest grade of intellect can do. The second test is, that although
+such machines might execute many things with equal or perhaps greater
+perfection than any of us, they would, without doubt, fail in certain
+others from which it could be discovered that they did not act from
+knowledge, but solely from the disposition of their organs: for while
+reason is an universal instrument that is alike available on every
+occasion, these organs, on the contrary, need a particular arrangement
+for each particular action; whence it must be morally impossible that
+there should exist in any machine a diversity of organs sufficient to
+enable it to act in all the occurrences of life, in the way in which
+our reason enables us to act. Again, by means of these two tests we may
+likewise know the difference between men and brutes. For it is highly
+deserving of remark, that there are no men so dull and stupid, not even
+idiots, as to be incapable of joining together different words, and
+thereby constructing a declaration by which to make their thoughts
+understood; and that on the other hand, there is no other animal,
+however perfect or happily circumstanced, which can do the like. Nor
+does this inability arise from want of organs: for we observe that
+magpies and parrots can utter words like ourselves, and are yet unable
+to speak as we do, that is, so as to show that they understand what
+they say; in place of which men born deaf and dumb, and thus not less,
+but rather more than the brutes, destitute of the organs which others
+use in speaking, are in the habit of spontaneously inventing certain
+signs by which they discover their thoughts to those who, being usually
+in their company, have leisure to learn their language. And this proves
+not only that the brutes have less reason than man, but that they have
+none at all: for we see that very little is required to enable a person
+to speak; and since a certain inequality of capacity 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 is incredible that
+the most perfect ape or parrot of its species, should not in this be
+equal to the most stupid infant of its kind or at least to one that was
+crack-brained, unless the soul of brutes were of a nature wholly
+different from ours. And we ought not to confound speech with the
+natural movements which indicate the passions, and can be imitated by
+machines as well as manifested by animals; nor must it be thought with
+certain of the ancients, that the brutes speak, 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 easily
+communicate their thoughts to us as to their fellows. It is also very
+worthy of remark, that, though there are many animals which manifest
+more industry than we in certain of their actions, the same animals are
+yet observed to show none at all in many others: so that the
+circumstance that they do better than we does not prove that they are
+endowed with mind, for it would thence follow that they possessed
+greater reason than any of us, and could surpass us in all things; 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
+their organs: thus it is seen, that a clock composed only of wheels and
+weights can number 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 no means be educed from the power of matter, as the other things of
+which I had spoken, but that it must be expressly created; and that it
+is not sufficient that it be lodged in the human body exactly like a
+pilot in a ship, unless perhaps to move its members, but that it is
+necessary for it to be joined and united more closely to the body, in
+order to have sensations and appetites similar 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 the greatest
+moment: for after the error of those who deny the existence of God, an
+error which I think I have already sufficiently refuted, there is none
+that is more powerful in leading feeble minds astray from the straight
+path of virtue than the supposition that the soul of the brutes is of
+the same nature with our own; 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 differ we much better comprehend the
+reasons which establish that the soul is of a nature wholly independent
+of the body, and that consequently it is not liable to die with the
+latter and, finally, because no other causes are observed capable of
+destroying it, we are naturally led thence to judge that it is
+immortal.
+
+PART VI
+
+Three years have now elapsed since I finished the treatise containing
+all these matters; and I was beginning to revise it, with the view to
+put it into the hands of a printer, when I learned that persons to whom
+I greatly defer, and whose authority over my actions is hardly less
+influential than is my own reason over my thoughts, had condemned a
+certain doctrine in physics, published a short time previously by
+another individual to which I will not say that I adhered, but only
+that, previously to their censure I had observed in it nothing which I
+could imagine to be prejudicial either to religion or to the state, and
+nothing therefore which would have prevented me from giving expression
+to it in writing, if reason had persuaded me of its truth; and this led
+me to fear lest among my own doctrines likewise some one might be found
+in which I had departed from the truth, notwithstanding the great care
+I have always taken not to accord belief to new opinions of which I had
+not the most certain demonstrations, and not to give expression to
+aught that might tend to the hurt of any one. This has been sufficient
+to make me alter my purpose of publishing them; for although the
+reasons by which I had been induced to take this resolution were very
+strong, yet my inclination, which has always been hostile to writing
+books, enabled me immediately to discover other considerations
+sufficient to excuse me for not undertaking the task. And these
+reasons, on one side and the other, are such, that not only is it in
+some measure my interest here to state them, but that of the public,
+perhaps, to know them.
+
+I have never made much account of what has proceeded from my own mind;
+and so long as I gathered no other advantage from the method I employ
+beyond satisfying 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 what regards manners, every one is so
+full of his own wisdom, that there might be found as many reformers as
+heads, if any were allowed to take upon themselves the task of mending
+them, except those whom God has constituted the supreme rulers of his
+people or to whom he has given sufficient grace and zeal to be
+prophets; and although my speculations greatly pleased myself, I
+believed that others had theirs, which perhaps pleased them still more.
+But as soon as I had acquired some general notions respecting physics,
+and beginning to make trial of them in various particular difficulties,
+had observed how far they can carry us, and how much they differ from
+the principles that have been employed up to the present time, I
+believed that I could not keep them concealed without sinning
+grievously against the law by which we are bound to promote, as far as
+in us lies, the general good of mankind. For by them I perceived it to
+be possible to arrive at knowledge highly useful in life; and in room
+of the speculative 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 we know the various crafts of our
+artisans, we might also apply them in the same way to all the uses to
+which they are adapted, and thus render ourselves the lords and
+possessors of nature. And this is a result to be desired, not only in
+order to the invention of an infinity of arts, by which we might be
+enabled to enjoy without any trouble the fruits of the earth, and all
+its comforts, but also and especially for the preservation of health,
+which is without doubt, of all the blessings of this life, the first
+and fundamental one; for the mind is so intimately dependent upon the
+condition and relation of the organs of the body, that if any means can
+ever be found to render men wiser and more ingenious than hitherto, I
+believe that it is in medicine they must be sought for. It is true that
+the science of medicine, as it now exists, contains few things 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 in comparison of what remains to be discovered; and that we
+could free ourselves from an infinity of maladies of body as well as of
+mind, and perhaps also even from the debility of age, if we had
+sufficiently ample knowledge of their causes, and of all the remedies
+provided for us by nature. But since I designed to employ my whole life
+in the search after so necessary a science, and since I had fallen in
+with a path which seems to me such, that if any one follow it he must
+inevitably reach the end desired, unless he be hindered either by the
+shortness of life or the want of experiments, I judged that there could
+be no more effectual provision against these two impediments than if I
+were faithfully to communicate to the public all the little I might
+myself have found, and incite men of superior genius to strive to
+proceed farther, by contributing, each according to his inclination and
+ability, to the experiments which it would be necessary to make, and
+also by informing the public of all they might discover, so that, by
+the last beginning where those before them had left off, and thus
+connecting the lives and labours of many, we might collectively proceed
+much farther than each by himself could do.
+
+I remarked, moreover, with respect to experiments, that they become
+always more necessary the more one is advanced in knowledge; for, at
+the commencement, it is 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 any reflection, however slight, than
+to concern ourselves about more uncommon and recondite phenomena: the
+reason of which is, that the more uncommon often only mislead us so
+long as the causes of the more ordinary are still unknown; and the
+circumstances upon which they depend are almost always so special and
+minute as to be highly difficult to detect. But in this I have adopted
+the following order: first, I have essayed to find in general the
+principles, or first causes of all that is or can be in the world,
+without taking into consideration for this end anything but God himself
+who has created it, and without educing them from any other source than
+from certain germs of truths naturally existing in our minds In the
+second place, I examined what were the first and most ordinary effects
+that could be deduced from these causes; and it appears to me that, in
+this way, I have found heavens, stars, an earth, and even on the earth
+water, air, fire, minerals, and some other things of this kind, which
+of all others are the most common and simple, and hence the easiest to
+know. Afterwards when I wished to descend to the more particular, so
+many diverse objects presented themselves to me, that I believed it to
+be impossible for the human mind to distinguish the forms or species of
+bodies that are upon the earth, from an infinity of others which might
+have been, if it had pleased God to place them there, or consequently
+to apply them to our use, unless we rise to causes through their
+effects, and avail ourselves of many particular experiments. Thereupon,
+turning over in my mind I the objects that had ever been presented to
+my senses I freely venture to state that I have never observed any
+which I could not satisfactorily explain by the principles had
+discovered. But it is necessary also to confess that the power of
+nature is so ample and vast, and these principles so simple and
+general, that I have hardly observed a single particular effect which I
+cannot at once recognize as capable of being deduced in man different
+modes from the principles, and that my greatest difficulty usually is
+to discover in which of these modes the effect is dependent upon them;
+for out of this difficulty cannot otherwise extricate myself than by
+again seeking certain experiments, which may be such that their result
+is not the same, if it is in the one of these modes at we must explain
+it, 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 what course must be taken to make the majority those
+experiments which may conduce to this end: but I perceive likewise that
+they are such and so numerous, that neither my hands nor my income,
+though it were a thousand times larger than it is, would be sufficient
+for them all; so that according as henceforward I shall have the means
+of making more or fewer experiments, I shall in the same proportion
+make greater or less progress in the knowledge of nature. This was what
+I had hoped to make known by the treatise I had written, and so clearly
+to exhibit the advantage that would thence accrue to the public, as to
+induce all who have the common good of man at heart, that is, all who
+are virtuous in truth, and not merely in appearance, or according to
+opinion, as well to communicate to me the experiments they had already
+made, as to assist me in those that remain to be made.
+
+But since that time other reasons have occurred to me, by which I have
+been led to change my opinion, and to think that I ought indeed to go
+on committing to writing all the results which I deemed of any moment,
+as soon as I should have tested their truth, and to bestow the same
+care upon them as I would have done had it been my design to publish
+them. This course commended itself to me, as well because I thus
+afforded myself more ample inducement to examine them thoroughly, for
+doubtless that is always more narrowly scrutinized which we believe
+will be read by many, than that which is written merely for our private
+use (and frequently what has seemed to me true when I first conceived
+it, has appeared false when I have set about committing it to writing),
+as because I thus lost no opportunity of advancing the interests of the
+public, as far as in me lay, and since thus likewise, if my writings
+possess any value, those into whose hands they may fall after my death
+may be able to put them to what use they deem proper. But I resolved by
+no means to consent to their publication during my lifetime, lest
+either the oppositions or the controversies to which they might give
+rise, or even the reputation, such as it might be, which they would
+acquire for me, should be any occasion of my losing the time that I had
+set apart for my own improvement. For though it be true that every one
+is bound to promote to the extent of his ability the good of others,
+and that to be useful to no one is really to be worthless, yet it is
+likewise true that our cares ought to extend beyond the present, and it
+is good to omit doing what might perhaps bring some profit to the
+living, when we have in view the accomplishment of other ends that will
+be of much greater advantage to posterity. And in truth, I am quite
+willing it should be known that the little I have hitherto learned is
+almost nothing in comparison with that of which I am ignorant, and to
+the knowledge of which I do not despair of being able to attain; for it
+is much the same with those who gradually discover truth in the
+sciences, as with those who when growing rich find less difficulty in
+making great acquisitions, than they formerly experienced when poor in
+making acquisitions of much smaller amount. Or they may be compared to
+the commanders of armies, whose forces usually increase in proportion
+to their victories, and who need greater prudence to keep together the
+residue of their troops after a defeat than after a victory to take
+towns and provinces. For he truly engages in battle who endeavors to
+surmount all the difficulties and errors which prevent him from
+reaching the knowledge of truth, and he is overcome in fight who admits
+a false opinion touching a matter of any generality and importance, and
+he requires thereafter much more skill to recover his former position
+than to make great advances when once in possession of thoroughly
+ascertained principles. As for myself, if I have succeeded in
+discovering any truths in the sciences (and I trust that what is
+contained in this volume I will show that I have found some), I can
+declare that they are but the consequences and results of five or six
+principal difficulties which I have surmounted, and my encounters with
+which I reckoned as battles in which victory declared for me. I will
+not hesitate even to avow my belief that nothing further is wanting to
+enable me fully to realize my designs than to gain two or three similar
+victories; and that I am not so far advanced in years but that,
+according to the ordinary course of nature, I may still have sufficient
+leisure for this end. But I conceive myself the more bound to husband
+the time that remains the greater my expectation of being able to
+employ it aright, and I should doubtless have much to rob me of it,
+were I to publish the principles of my physics: for although they are
+almost all so evident that to assent to them no more is needed than
+simply to understand them, and although there is not one of them of
+which I do not expect to be able to give demonstration, yet, as it is
+impossible that they can be in accordance with all the diverse opinions
+of others, I foresee that I should frequently be turned aside from my
+grand design, 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 aware of my errors, and, if my speculations contain anything of
+value, in bringing others to a fuller understanding of it; and still
+farther, as many can see better than one, in leading others who are now
+beginning to avail themselves of my principles, to assist me in turn
+with their discoveries. But though I recognize my extreme liability to
+error, and scarce ever trust to the first thoughts which occur to me,
+yet-the experience I have had of possible objections to my views
+prevents me from anticipating any profit from them. For I have already
+had frequent proof of the judgments, as well of those I esteemed
+friends, 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 to endeavor to discover what partiality concealed from
+the eyes of my friends. But it has rarely happened that anything has
+been objected to me which I had myself altogether 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 appear to me either
+less rigorous or less equitable than myself. And further, I have never
+observed that any truth before unknown has been brought to light by the
+disputations that are practised in the schools; for while each strives
+for the victory, 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 have been long good advocates are not
+afterwards on that account the better judges.
+
+As for the advantage that others would derive from the communication of
+my thoughts, it could not be very great; because I have not yet so far
+prosecuted them as that much does not remain to be added before they
+can be applied to practice. And I think I may say without vanity, that
+if there is any one who can carry them out that length, it must be
+myself rather than another: not that there may not be in the world many
+minds incomparably superior to mine, but because one cannot so well
+seize a thing and make it one's own, when it has been learned from
+another, as when one has himself discovered it. And so true is this of
+the present subject that, though I have often explained some of my
+opinions to persons of much acuteness, who, whilst I was speaking,
+appeared to understand them very distinctly, yet, when they repeated
+them, I have observed that they almost always changed them to such an
+extent that I could no longer acknowledge them as mine. I am glad, by
+the way, to take this opportunity of requesting posterity never to
+believe on hearsay that anything has proceeded from me which has not
+been published by myself; and I am not at all astonished at the
+extravagances attributed to those ancient philosophers whose own
+writings we do not possess; whose thoughts, however, I do not on that
+account suppose to have been really absurd, seeing they were among the
+ablest men of their times, but only that these have been falsely
+represented to us. It is observable, accordingly, that scarcely in a
+single instance has any one of their disciples surpassed them; and I am
+quite sure that the most devoted of the present followers of Aristotle
+would think themselves happy if they had as much knowledge of nature as
+he possessed, were it even under the condition that they should never
+afterwards attain to higher. In this respect they are like the ivy
+which never strives to rise above the tree that sustains it, and which
+frequently even returns downwards when it has reached the top; for it
+seems to me that they also sink, in other words, render themselves less
+wise than they would be if they gave up study, who, not contented with
+knowing all that is intelligibly explained in their author, desire in
+addition to find in him the solution of many difficulties of which he
+says not a word, and never perhaps so much as thought. Their fashion of
+philosophizing, however, is well suited to persons whose abilities fall
+below mediocrity; for the obscurity of the distinctions and principles
+of which they make use enables them to speak of all things with as much
+confidence as if they really knew them, and to defend all that they say
+on any subject against the most subtle and skillful, without its being
+possible for any one to convict them of error. In this they seem to me
+to be like a blind man, who, in order to fight on equal terms with a
+person that sees, should have made him descend to the bottom of an
+intensely dark cave: and I may say that such persons have an interest
+in my refraining from publishing the principles of the philosophy of
+which I make use; for, since these are of a kind the simplest and most
+evident, I should, by publishing them, do much the same as if I were to
+throw open the windows, and allow the light of day to enter the cave
+into which the combatants had descended. But even superior men have no
+reason for any great anxiety to know these principles, for if what they
+desire is to be able to speak of all things, and to acquire a
+reputation for learning, they will gain their end more easily by
+remaining satisfied with the appearance of truth, which can be found
+without much difficulty in all sorts of matters, than by seeking the
+truth itself which unfolds itself but slowly and that only in some
+departments, while it obliges us, when we have to speak of others,
+freely to confess our ignorance. If, however, they prefer the knowledge
+of some few truths to the vanity of appearing ignorant of none, as such
+knowledge is undoubtedly much to be preferred, and, if they choose to
+follow a course similar to mine, they do not require for this that I
+should say anything more than I have already said in this discourse.
+For if they are capable of making greater advancement than I have made,
+they will much more be able of themselves to discover all that I
+believe myself to have found; since as I have never examined aught
+except in order, it is certain that what yet remains to be discovered
+is in itself more difficult and recondite, than that which I have
+already been enabled to find, and the gratification would be much less
+in learning it from me than in discovering it for themselves. Besides
+this, the habit which they will acquire, by seeking first what is easy,
+and then passing onward slowly and step by step to the more difficult,
+will benefit them more than all my instructions. Thus, in my own case,
+I am persuaded that if I had been taught from my youth all the truths
+of which I have since sought out demonstrations, and had thus learned
+them without labour, I should never, perhaps, have known any beyond
+these; at least, I should never have acquired the habit and the
+facility which I think I possess in always discovering new truths in
+proportion as I give myself to the search. And, in a single word, if
+there is any work in the world which cannot be so well finished by
+another as by 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 can advantageously avail himself, in this work, of no hands
+besides his own, unless those of artisans, or parties of the same kind,
+whom he could pay, and whom the hope of gain (a means of great
+efficacy) might stimulate to accuracy in the performance of what was
+prescribed to them. For as to those who, through curiosity or a desire
+of learning, of their own accord, perhaps, offer him their services,
+besides that in general their promises exceed their performance, and
+that they sketch out fine designs of which not one is ever realized,
+they will, without doubt, expect to be compensated for their trouble by
+the explication of some difficulties, or, at least, by compliments and
+useless speeches, in which he cannot spend any portion of his time
+without loss to himself. And as for the experiments that others have
+already made, even although these parties should be willing of
+themselves to communicate them to him (which is what those who esteem
+them secrets will never do), the experiments are, for the most part,
+accompanied with so many circumstances and superfluous elements, as to
+make it exceedingly difficult to disentangle the truth from its
+adjuncts--besides, he will find almost all of them so ill described, or
+even so false (because those who made them have wished to see in them
+only such facts as they deemed conformable to their principles), that,
+if in 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 to make the selection. So that if there existed any one
+whom we assuredly knew to be capable of making discoveries of the
+highest kind, and of the greatest possible utility to the public; and
+if all other men were therefore eager by all means to assist him in
+successfully prosecuting his designs, I do not see that they could do
+aught else for him beyond contributing to defray the expenses of the
+experiments that might be necessary; and for the rest, prevent his
+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 willing to make promise of anything extraordinary, nor feed on
+imaginations so vain as to fancy that the public must be much
+interested in my designs; I do not, on the other hand, own a soul so
+mean as to be capable of accepting from any one a favor of which it
+could be supposed that I was unworthy.
+
+These considerations taken together were the reason why, for the last
+three years, I have been unwilling to publish the treatise I had on
+hand, and why I even 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 to subjoin some particular
+specimens, and give the public some account of my doings and designs.
+Of these considerations, the first is, that if I failed to do so, many
+who were cognizant of my previous intention to publish some writings,
+might have imagined that the reasons which induced me to refrain from
+so doing, were less to my credit than they really are; for although I
+am not immoderately desirous of glory, or even, if I may venture so to
+say, although I am averse from it in so far as I deem it hostile to
+repose which I hold in greater account than aught else, yet, at the
+same time, I have never sought to conceal my actions as if they were
+crimes, nor made use of many precautions that I might remain unknown;
+and this partly because I should have thought such a course of conduct
+a wrong against myself, and partly because it would have occasioned me
+some sort of uneasiness which would again have been contrary to the
+perfect mental tranquillity which I court. And forasmuch as, while thus
+indifferent to the thought alike of fame or of forgetfulness, I have
+yet been unable to prevent myself from acquiring some sort of
+reputation, I have thought it incumbent on me to do my best to save
+myself at least from being ill-spoken of. The other reason that has
+determined me to commit to writing these specimens of philosophy is,
+that I am becoming daily more and more alive to the delay which my
+design of self-instruction suffers, for want of the infinity of
+experiments I require, and which it is impossible for me to make
+without the assistance of others: and, without flattering myself so
+much as to expect the public to take a large share in my interests, I
+am yet unwilling to be found so far wanting in the duty I owe to
+myself, as to give occasion to those who shall survive me to make it
+matter of reproach against me some day, that I might have left them
+many things in a much more perfect state than I have done, had I not
+too much neglected to make them aware of the ways in which they could
+have promoted the accomplishment of my designs.
+
+And I thought that it was easy for me to select some matters which
+should neither be obnoxious to much controversy, nor should compel me
+to expound more of my principles than I desired, and which should yet
+be sufficient clearly to exhibit what I can or cannot accomplish in the
+sciences. Whether or not I have succeeded in this it is not for me to
+say; and I do not wish to forestall the judgments of others by speaking
+myself of my writings; but it will gratify me if they be examined, and,
+to afford the greater inducement to this I request all who may have any
+objections to make to them, to take the trouble of forwarding these to
+my publisher, who will give me notice of them, that I may endeavor to
+subjoin at the same time my reply; and in this way readers seeing both
+at once will more easily determine where the truth lies; for I do not
+engage in any case to make prolix replies, but only with perfect
+frankness to avow my errors if I am convinced of them, or if I cannot
+perceive them, simply to 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 to pass 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 first sight, because I
+call them hypotheses and seem indifferent about giving proof of them, I
+request a patient and attentive reading of the whole, from which I hope
+those hesitating will derive satisfaction; for it appears to me that
+the reasonings are so mutually connected in these treatises, that, as
+the last are demonstrated by the first which are their causes, the
+first are in their turn demonstrated by the last which are their
+effects. Nor must it be imagined that I here commit the fallacy which
+the logicians call a circle; for since experience renders the majority
+of these effects most certain, the causes from which I deduce them do
+not serve so much to establish their reality as to explain their
+existence; but on the contrary, the reality of the causes is
+established by the reality of the effects. Nor have I called them
+hypotheses with any other end in view except that it may be known that
+I think I am able to deduce them from those first truths which I have
+already expounded; and yet that I have expressly determined not to do
+so, to prevent a certain class of minds from thence taking occasion to
+build some extravagant philosophy upon what they may take to be my
+principles, and my being blamed for it. I refer to those who imagine
+that they can master in a day all that another has taken twenty years
+to think out, as soon as he has spoken two or three words to them on
+the subject; or who are the more liable to error and the less capable
+of perceiving truth in very proportion as they are more subtle and
+lively. As to the opinions which are truly and wholly mine, I offer no
+apology for them as new,--persuaded as I am that if their reasons be
+well considered they will be found to be so simple and so conformed, to
+common sense as to appear less extraordinary and less paradoxical than
+any others which can be held on the same subjects; nor do I even boast
+of being the earliest discoverer of any of them, but only of having
+adopted them, neither because they had nor because they had not been
+held by others, but solely because reason has convinced me of their
+truth.
+
+Though artisans may not be able at once to execute the invention which
+is explained in the "Dioptrics," I do not think that any one on that
+account is entitled to condemn it; for since address and practice are
+required in order so to make and adjust the machines described by me as
+not to overlook the smallest particular, I should not be less
+astonished if they succeeded on the first attempt than if a person were
+in one day to become an accomplished performer on the guitar, by merely
+having excellent sheets of music set up before him. And if I write in
+French, which is the language of my country, in preference to Latin,
+which is that of my preceptors, it is because I expect that those who
+make use of their unprejudiced natural reason will be better judges of
+my opinions than those who give heed to the writings of the ancients
+only; and as for those who unite good sense with habits of study, whom
+alone I desire for judges, they will not, I feel assured, be so partial
+to Latin as to refuse to listen to my reasonings merely because I
+expound them in the vulgar tongue.
+
+In conclusion, I am unwilling here to say anything very specific of the
+progress which I expect to make for the future in the sciences, or to
+bind myself to the public by any promise which I am not certain of
+being able to fulfill; but this only will I say, that I have resolved
+to devote what time I may still have to live to no other occupation
+than that of endeavoring to acquire some knowledge of Nature, which
+shall be of such a kind as to enable us therefrom to deduce rules in
+medicine of greater certainty than those at present in use; and that my
+inclination is so much opposed to all other pursuits, especially to
+such as cannot be useful to some without being hurtful to others, that
+if, by any circumstances, I had been constrained to engage in such, I
+do not believe that I should have been able to succeed. Of this I here
+make a public declaration, though well aware that it cannot serve to
+procure for me any consideration in the world, which, however, I do not
+in the least affect; and I shall always hold myself more obliged to
+those through whose favor I am permitted to enjoy my retirement without
+interruption than to any who might offer me the highest earthly
+preferments.
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