Discourse on the Method
谈谈方法
原题：Discours de la méthode（法语）
勒内·笛卡尔 René Descartes（1596–1650）
译者：John Veitch（1829–1894），1850 年
1637 年；1850 年英译

冷冻图书馆 · 开架书库 · S-005017 · https://coldlibrary.com/s/005017
权利：法文原作 1637 年出版；笛卡尔卒于 1650 年。译者约翰·维奇卒于 1894 年；译本 1850 年初版。已按澳大利亚、欧盟、英国、中国大陆和美国的规则核对（截至 2026 年 10 月 11 日）。仅供参考，不是法律意见。
来源：Wikisource，https://en.wikisource.org/wiki/Discourse_on_the_Method（取于 2026-10-11）
中文译文：Claude（AI），2026 · CC0 1.0
生成于 2026-10-14，来自 https://coldlibrary.com/open-stacks/discourse-on-method

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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 excellencies, 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 fulness 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 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 favour. But I shall endeavour 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 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 endeavoured 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 favour 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 and 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 honours 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 travelling, 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 skilfully 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 honour 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 honour 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 travelling, 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 have 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 regularly 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 civilisation 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 past 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 counselled 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 leant upon principles which, in my youth, I had taken upon trust. For although I recognised 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 inconveniencies, 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 byeway 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 one 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 on that account barbarians and savages, but on the contrary that many of these nations make an equally good, if not a 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 favour 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 judgment 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 unravelling 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, all 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 this 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 endeavour 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 judgment, 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 travellers 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 endeavour 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 respect of 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 favours 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 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 travelling 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 theatre 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 endeavoured 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 honourable, 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 rumoured 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 endeavour 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, hence I am*, 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, hence 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 recognised 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 recognise 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 recognised 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 centre, 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 themselves 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 same thing as if, in order to hear sounds or smell odours, 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 unfrequently 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 unfrequently 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 chimæra 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 learned, 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 comprise 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 coloured, 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 endeavoured 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 centre; 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 colours 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 shewn to them its two ventricles or cavities: in 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 shewn 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 vein, 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 honour 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 straitened, 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 neighbourhood 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 neighbourhood 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 vapours, 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 humours 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 shewn 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, odours, 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 in 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 skill.

I had after this described the Reasonable Soul, and shewn 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 endeavouring 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 artizans, 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 phænomena: 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 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 all 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 I 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 recognise as capable of being deduced in many 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 I 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 that 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 of 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 endeavours 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 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 recognise 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 malignity and envy would, I knew, determine them to endeavour 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 skilful, 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 that 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 favour 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 endeavour 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 defence of the matters I have written, adding thereto no explication of any new matter 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 fulfil; 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 endeavouring 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 favour I am permitted to enjoy my retirement without interruption than to any who might offer me the highest earthly preferments.

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中文译文 · Claude（AI）译

作者前言

如果这篇谈话显得太长，不便一口气读完，可以把它分成六个部分：第一部分是关于各门学问的种种考察；第二部分是作者所发现的方法的主要规则；第三部分是他从这个方法中推出的若干道德规则；第四部分是他用来证明上帝和人的灵魂存在的推理，这些是他的形而上学的基础；第五部分是他所研究过的物理问题的次序，特别是对心脏运动和医学上其他一些难题的解释，以及人的灵魂和禽兽的灵魂之间的区别；最后一部分是作者认为要在自然的研究中取得比迄今更大的进展需要些什么，以及促使他写作的理由。


第一部分

良知，在人间的一切东西里，是分配得最均匀的；因为每个人都认为自己在这方面禀赋十足，就连那些在其他一切事情上最难满足的人，通常也不想要比他们已有的更多的良知。在这一点上，不大可能人人都错了；这种确信，倒应当看作是证明：正确地判断、辨别真假的能力，也就是所谓的良知或理性，天生在一切人身上都是相等的；因此，我们意见的分歧，并不是因为有些人比别人禀有更多的理性，而只是因为我们引导思想的途径不同，注意的不是同样的对象。因为单有强健的心智是不够的；首要的是正确地运用它。最伟大的心灵，既能达到最高的卓越，也同样会犯最大的偏差；走得很慢的人，只要始终沿着直路走，可以比那些奔跑着却离开了直路的人前进得远得多。

至于我自己，我从来没有设想过我的心智在任何方面比一般人更完善；相反，我常常希望自己在思想的敏捷上，或者在想象的清楚分明上，或者在记忆的丰富和迅捷上，能比得上某些别人。除了这些，我不知道还有什么别的品质有助于心智的完善；因为至于理性或良知，既然只有它使我们成为人，使我们区别于禽兽，我就愿意相信它在每个人身上都是完整的；在这一点上，我愿采纳哲学家们的共同意见，他们说，多少之分只存在于偶性之间，而不存在于同一*种*的各个*个体*的*形式*或*本性*之间。

不过，我愿毫不犹豫地承认，我相信我有一种特别的幸运，很早就在生活中碰上了某些路径，它们把我引向一些考虑和准则，我由此形成了一种方法；我想，这个方法给了我一种手段，使我能逐步增加我的知识，一点一点地把它提高到我平庸的才能和短暂的生命所允许我达到的最高点。因为我已经从中收获了这样的果实：尽管我一向习惯于把自己看得相当低，尽管当我用哲学家的眼光去看人类的种种行径和追求时，几乎找不到一样不显得虚妄无用的，我却从自认为在寻求真理上已经取得的进展中得到了最大的满足，并且禁不住对未来怀着这样的期望：如果在人作为人所从事的种种职业之中，真有哪一种是真正卓越而重要的，那就是我所选择的这一种。

毕竟，我也可能是错的；我当作黄金和钻石的，也许只是一点铜和玻璃。我知道，在与我们自己有关的事情上，我们多么容易受骗；也知道朋友们作出对我们有利的判断时，是多么值得怀疑。但我要在这篇谈话里努力描述我所走过的道路，像画一幅画那样描绘我的生活，好让每个人都能自己去判断；也好让我从流传的议论中得知人们对它们的一般看法，从而在我惯用的那些求教的办法之外，再添一种新的帮助。

所以，我现在的打算，不是教人每个人为了正确引导自己的理性所应当遵循的方法，而只是描述我曾怎样努力引导我自己的理性。给别人立规矩的人，当然必须认为自己比他所指教的人更有本领；只要在最小的细节上出了错，就要受到指责。但这篇文章只是作为一段历史，或者如果你愿意，作为一个故事拿出来的，其中有一些值得效法的例子，也许还有同样多最好不要照着做的例子；所以我希望它对一些人有用，而对任何人都无害，也希望我的坦率能得到所有人的一点好感。

我从童年起就熟悉文字；人们让我相信，借助它们，可以获得对生活中一切有用之事的清楚而确实的知识，所以我热切地渴望受教。但我一读完全部课程——按照惯例，读完以后就被接纳进学者的行列——我的看法就完全改变了。因为我发现自己陷入了那么多的怀疑和错误之中，以至于我确信，我一切求学的努力，除了处处发现自己的无知以外，没有得到任何进展。然而我是在欧洲最著名的学校之一读书，我想，如果世上哪里有博学的人，那里一定会有。别人在那里学的，我都学了；而且我不满足于实际教给我们的那些学问，还读遍了落到我手里的一切书，那些书讨论的是被认为最奇特、最罕见的学科。我知道别人对我的评价；我并不觉得自己被认为不如同学，尽管他们中间已经有些人被选定要接替我们老师的位置。总之，在我看来，我们这个时代和以往任何一个时代一样繁荣，一样富于强健的心灵。于是我就冒昧地以我自己来判断其他一切人，并且断定，世上并没有一种学问是像我先前被引导去相信的那样的。

不过，我仍然继续尊重学校里的学业。我知道，学校里教的语言，对于理解古人的著作是必要的；寓言的优美能唤起心灵；历史上值得纪念的事迹能提升心灵，如果读得审慎，还能帮助形成判断力；阅读一切好书，就仿佛是与写这些书的过去时代最高贵的人物会谈，而且是一种经过准备的会谈，在其中他们只向我们披露他们最精选的思想；雄辩有无与伦比的力量和美；诗有令人心醉的优雅和乐趣；数学里有许多精妙的发现，最适合满足好奇的人，也能促进一切技艺，减轻人的劳动；论道德的著作里包含着许多极有用的箴言和对美德的劝勉；神学指出通往天国的路；哲学提供了一种手段，使人能对一切事情说得似乎有理，博得较单纯的人的赞叹；法学、医学和其他学问，给研究它们的人带来荣誉和财富；总之，对一切学问，甚至对那些充满迷信和谬误的学问，都花些注意是有益的，这样我们就能确定它们真正的价值，防止受骗。

但我认为，我已经在语言上，同样也在阅读古人的著作、他们的历史和寓言上，花了足够的时间。因为与别的时代的人交谈，和旅行差不多是一回事。了解一点不同民族的风俗是有益的，这样我们就能对自己的风俗作出更正确的判断，不至于认为一切与我们的习俗相反的东西都是可笑的、不合理的——那些阅历只限于本国的人，通常就会得出这样的结论。另一方面，旅行占去的时间太多，我们就成了本国的陌生人；对过去的风俗过分好奇的人，通常对现在的风俗一无所知。此外，虚构的故事使我们想象许多不可能的事情是可能的；即使最忠实的历史，如果不是完全歪曲事情，或者为了使叙述更值得一读而夸大它们的重要性，至少也几乎总是略去了伴随着的那些最卑微、最不显眼的情节；因此，剩下的部分就不能表现真相，而那些按照从这个来源中取来的例子来规范自己行为的人，就容易陷入传奇里游侠骑士的那种荒唐，怀抱超出自己能力的计划。

我非常推崇雄辩，也醉心于诗；但我认为两者都是天赋，而不是学习的成果。那些理性能力占优势、最善于安排自己的思想使之清楚易懂的人，总是最能使别人相信他们所提出的东西是真的，哪怕他们只会说下布列塔尼的方言，对修辞学的规则一无所知；而那些头脑里装满了最可爱的幻想、能用最多的修饰与和谐把它们表达出来的人，仍然是最好的诗人，哪怕他们不懂作诗法。

我特别喜爱数学，因为它的推理确实而明显；但我当时还不确切地知道它真正的用处；我以为它只有助于机械技艺的进步，便惊奇于这样坚固结实的基础上，竟没有建起更高大的建筑。另一方面，我把古代道德学家的论述，比作一座座高耸而壮丽的宫殿，它们的基础却不过是沙子和泥土：他们把美德捧得很高，把它们说得比世上任何东西都可贵得多；但他们没有给我们任何充分的美德的标准，而他们冠以这样美好名称的东西，常常只是冷漠，或骄傲，或绝望，或弑亲。

我崇敬我们的神学，也和任何人一样渴望升入天国；但我确实得知，通往天国的路，对最无知的人和对最博学的人同样敞开，而引人升入天国的启示真理是超出我们理解的；所以我不敢把它们交给我无能的理性去审察；我认为，要胜任地着手审察它们，就需要有来自上天的某种特别的帮助，就需要超出于人。

关于哲学，我什么也不说，只说这一点：我看到它经过许多世纪最杰出的人物的钻研，却没有一个问题不在争论之中，因而没有一样是无可怀疑的，所以我不敢指望自己在其中会比别人更成功；而且，当我考虑到，在同一个问题上，博学的人们可以坚持那么多相互冲突的意见，而真的只能有一个时，我就把一切仅仅是可能的东西都差不多看作是假的。

至于其他学问，既然它们的原理是从哲学借来的，我就断定，在这样不牢靠的基础上，建不起什么坚固的建筑；它们所许诺的荣誉和利益，也都不足以使我决心去钻研它们，因为谢天谢地，我的处境并不迫使我把学问当作商品来改善我的境况；尽管我不敢像犬儒派那样自称蔑视荣誉，我却很不看重那种只希望通过虚假的头衔得到的荣誉。最后，至于那些伪学问，我想我已经充分知道它们的价值，不至于被炼金术士的许诺、占星家的预言、魔术师的骗术，或者任何自称知道其实并不知道的事情的人的诡计和吹嘘所欺骗。

由于这些理由，我的年龄一到可以脱离老师管束的时候，我就完全放弃了书本的学问，决心不再寻求别的学问，只寻求关于我自己、或者关于世界这本大书的知识。我用青年时代余下的时光去旅行，去访问宫廷和军队，与不同性情、不同地位的人交往，收集各种经验，在命运把我抛入的种种处境中考验自己，尤其是对我经验中的事物作这样的反思，以求有所长进。因为我想到，每个人在与他切身利益有关的事情上所作的推理，如果判断错了，结果很快就会惩罚他，这种推理里所能找到的真理，比一个文人在书房里就一些没有实际意义的思辨问题所作的推理里的真理要多得多；后者对他自己不产生任何后果，也许只除了一点：它们离常识越远，就越能助长他的虚荣，因为在这种情况下，他必须运用更多的机巧和技艺，才能使它们显得可信。此外，我一向极其渴望学会分辨真假，好在生活中清楚地辨明正确的道路，满怀信心地走下去。

诚然，当我只忙于考察别人的风俗时，我在这里也几乎找不到什么可以使我坚定信念的根据，我注意到其中的矛盾并不比哲学家们的意见中少。所以，我从这番研究中得到的最大好处在于：我观察到许多事情，在我们看来尽管荒唐可笑，却被其他伟大的民族普遍接受和认可，于是我学会了不要过于坚定地相信任何仅仅凭着先例和习俗而使我信服的东西；这样，我就逐渐摆脱了许多错误，这些错误足以遮蔽我们天赋的智慧，使我们在很大程度上不能倾听理性。但是，在这样研究世界这本大书、努力收集一些经验，花了好几年之后，我终于决心把我自己也当作研究的对象，用我心智的全部力量来选择我应当走的道路；这件事做得比我从未离开我的国家和我的书本要成功得多。


第二部分

那时我在德国，是被那里至今尚未结束的战争吸引去的；当我参加了皇帝的加冕典礼回军队去时，冬季的来临把我阻留在一个地方；在那里，我找不到有趣的交际，又幸而没有任何忧虑或激情来打扰，便整天独自关在屋里，有充分的机会专心于自己的思想。在这些思想中，我最早想到的一个是：由许多部分拼成、经过许多不同的人之手的作品，往往不如由一位大师独力完成的作品那样完善。因此可以看到，由一位建筑师设计并建造的房屋，通常比那些由好几个人试图改建、利用原本不是为此目的而建的旧墙的房屋更雅致、更适用。同样，那些古老的城市，起初只是村落，经过时间的推移成了大城镇，与一位专业建筑师在一片空旷平原上自由规划、整齐建造的城镇相比，通常布局很差；所以，尽管前者的各座建筑往往在美观上等于或超过后者的建筑，但当人们看到它们杂乱地挨在一起，这里一座大的，那里一座小的，街道因此弯弯曲曲、参差不齐，就会说，造成这种布局的，与其说是某种受理性指导的人的意志，不如说是偶然。如果我们再考虑到，尽管如此，历来总有一些官员，负责使私人建筑有助于公共的美观，那么，只用别人的材料来加工，要达到很高的完善是多么困难，就很容易承认了。同样，我设想，那些从半野蛮的状态出发、逐步走向文明的民族，他们的法律是相继确定的，可以说只是因为经验到某些罪行和争端的害处，才不得不定下来的，这些民族由此所得的制度，比不上那些从结成社会之初就遵循某位贤明立法者的规定的民族的制度那样完善。因此，十分确定的是，真正的宗教的体制，它的律例是出自上帝的，必定无比地优于其他一切宗教的体制。至于人间的事，我相信斯巴达过去之所以卓越，不是因为它的每一条法律本身都好，因为其中许多条十分奇怪，甚至违背善良的风俗，而是因为这些法律出自一个人之手，都趋向于同一个目的。同样，我想，书本里所包含的学问（至少是那些由或然的推理构成、没有证明的学问），既然是由许多不同的人的意见堆积而成的，就比一个有良知的人用他天然的、没有成见的判断力对他经验中的事情所作的简单推论，离真理更远。又因为我们都必须经过婴儿期才长成大人，在很长一段时间里必然受我们的欲望和老师的支配（他们的指示常常互相冲突，而且也许没有一方总是给我们最好的劝告），我进一步断定，我们的判断几乎不可能像我们的理性从出生那一刻起就已成熟、我们一直只受理性指导时那样正确、那样坚实。

不过，诚然，人们并没有为了把一座城里的房屋全部改建成别的样子、使街道更美观，而把它们全部拆掉的习惯；但常常有私人把自己的房子拆掉，打算重新建造；当房子因年久而有倒塌的危险，或者地基不牢靠时，人们有时甚至不得不这样做。以此为例，我相信，一个私人想通过从根本上彻底改变一个国家、把它推翻再重新建立起来，来改革这个国家，确实是荒谬的；我想，任何类似的改革学问体系、或者改革学校里所确立的教学次序的计划，也是如此；但至于我直到那时所接受的意见，我想我最好是下定决心，一下子把它们统统扫除干净，以便以后可以接受另一些更正确的意见，或者，也许在它们经过理性的审察之后，仍然接受原来那些意见。我坚信，这样做，我在引导自己的生活上，会比只在旧的基础上建造、只依靠我年轻时不加考察就接受的原则要成功得多。因为尽管我认识到这项事业有种种困难，这些困难却并非无法补救，也根本不能与公共事务中哪怕最轻微的改革所带来的困难相比。庞大的机体一旦被推翻，就很难再竖起来，甚至一旦受到严重的动摇，就很难保持直立，而它们的倒塌总是灾难性的。其次，如果国家的体制中有什么缺陷（体制的多样就足以使我们确信这样的缺陷很多），习俗无疑已经大大缓和了它们的不便，甚至完全避开了、或者不知不觉地纠正了许多缺陷，这是聪明才智所不能同样有效地预防的；最后，这些缺陷几乎总是比为消除它们所必需的变革更可以忍受；就像在山间蜿蜒的大路，因为经常有人走，渐渐变得平坦好走，沿着它走，比爬过岩石的顶峰、下到悬崖的底部去寻找一条更直的路要好得多。

因此，我决不能赞成那些好动多事的人：他们无论出身还是境遇都没有被召去参与管理公共事务，却总在筹划改革；如果我认为这篇文章里有什么东西可以使人怀疑我也染上了这种愚蠢，我是决不会允许把它发表的。我所想过的，从来不过是改造我自己的意见，把它们建立在一个完全属于我自己的基础上。尽管我对自己的工作感到满意，因而在这里拿出它的一个草样，我却决不因此劝每一个人都作类似的尝试。上帝赋予了更多才智的人，也许会怀有更高远的计划；但对许多人来说，我很担心，即使是眼前这项事业，也超出了他们能安全地仿效的程度。决心抛弃自己以往的一切信念，并不是每个人都应当采取的。大多数人由两类人组成，对于他们，这都不是一个合适的决心：第一类人，对自己的能力过于自信，判断急躁，缺乏有条理地、审慎地思考所需要的耐心；因此，这类人一旦冒昧地怀疑他们习以为常的意见，离开了走惯的大路，就永远找不到那条能引他们抄近路的小径，会迷失方向，一辈子徘徊下去；第二类人，有足够的见识或谦逊，断定有别人比他们更善于辨别真假，可以向别人求教，他们就应当满足于这些人的意见，而不是指望靠自己的理性找到更正确的意见。

就我自己而言，假如我只跟从过一位老师，或者从不知道自古以来最有学问的人之间就存在着种种意见分歧，我无疑也会属于后一类人。可是早在求学的时候我就已经明白，无论多么荒谬、多么难以置信的意见，没有一种是哲学家当中没有人主张过的；后来在旅行中我又注意到，那些意见与我们截然相反的人，并不因此就是野蛮人和未开化的人，恰恰相反，这些民族中有许多运用理性的本领与我们一样好，甚至比我们更好。我也考虑到，一个从小在法国或德国长大的人，与这同一个人、带着同样的天资、若一直生活在中国人当中或野蛮人当中时会有的品性，是多么不同；还考虑到，就连衣着上，十年前讨我们喜欢、也许不到十年又会重新时兴的式样，此刻在我们看来却古怪可笑。由此我推断，我们意见的根据，远远更多是习惯和先例，而不是任何确定的知识。最后，虽然我们的意见有这样的根据，我也注意到，凡是较难发现的真理，多数人的赞同并不能保证它是真的，因为在这种情形下，它被一个人发现的可能，远比被许多人发现的可能大。然而，我又不能从众人之中挑出一个人，他的意见似乎值得优先采纳，于是我发现自己可以说是不得不在生活的指导上运用我自己的理性。

但我像一个独自在黑暗中行走的人那样，决心走得很慢、很谨慎，即使走不远，至少也要防止跌倒。那些没有经过理性引入、却悄悄爬进我信念里的意见，我甚至也不愿草率地一概抛弃，而是首先花足够的时间，仔细弄清我给自己定下的这项工作的大致性质，并确定那条真正的方法，借以达到我能力范围之内一切事物的知识。

在哲学的各个分支里，我早些时候曾留意过逻辑学；在数学的各个分支里，留意过几何分析和代数；我以为这三门技艺或学问应当能为我的计划有所贡献。但仔细考察之后，我发现，就逻辑学而言，它的三段论和它大部分其他规则，与其说有助于探究未知，不如说有助于把我们已经知道的东西传达给别人，甚至像卢尔的技艺那样，有助于不加判断地谈论我们并不知道的事情；而且这门学问虽然确实包含许多正确而极好的规则，但混杂在其中的有害的或多余的规则也那么多，要把真的与假的分开，几乎同从一块粗糙的大理石中凿出一尊狄安娜或密涅瓦一样困难。至于古人的分析和今人的代数，它们除了只涉及高度抽象、看来毫无用处的事情之外，前者完全局限于对图形的考察，只有在使想象力极度疲劳的条件下才能锻炼理解力；后者则那样完全受制于某些规则和公式，结果成了一门充满混乱和晦涩、只会使人困惑的技艺，而不是一门适于培养心灵的学问。出于这些考虑，我便去寻找另一种方法，它要包含这三者的长处，而没有它们的缺点。正如法律繁多常常只会妨碍正义，一个国家法律少而执行严，才治理得最好；同样，我相信，只要我下定坚定不移的决心，一次也不违背，那么，不用构成逻辑学的那一大堆规则，以下四条就完全够用了。

*第一条*是：凡是我没有明确地认识到是真的东西，决不把它当作真的接受；也就是说，小心避免轻率和偏见，在我的判断里，除了清楚分明地呈现在我心中、使我毫无理由怀疑的东西之外，不放进任何别的东西。

*第二条*是：把我所审察的每一个难题，按照可能和必要的程度，分成尽可能多的部分，以便更好地解决它。

*第三条*是：按次序引导我的思想，从最简单、最容易认识的对象开始，一点一点地，可以说是一级一级地，上升到对更复杂的对象的认识；即使是那些本性上并无先后次序的对象，也要在思想中给它们设定一个次序。

*最后一条*是：在一切情形下，都要作尽量完全的列举、尽量普遍的复查，使我确信没有遗漏任何东西。

几何学家惯于用一长串简单而容易的推理，达到他们最困难的证明的结论，这使我设想：人所能认识的一切事物，都是以同样的方式彼此联系着的；只要我们不把假的当作真的接受，并且始终在思想中保持从一个真理推出另一个真理所必需的次序，就没有什么东西远到我们够不着，也没有什么东西隐蔽到我们发现不了。我也没有费多大力气就确定了必须从哪些对象开始，因为我已经相信，必须从最简单、最容易认识的对象开始；而且考虑到，在迄今为止所有在各门学问中寻求真理的人当中，只有数学家能够找到一些证明，也就是一些确实而明显的理由，我毫不怀疑，他们的研究所遵循的必定就是这样的规则。因此，我决心从考察最简单的对象开始，不过并不指望由此得到别的好处，只希望使我的心灵习惯于爱真理、以真理为养料，厌恶一切不健全的推理。但我并不因此就打算去掌握通常称为数学的所有特殊学科；我注意到，它们的对象尽管不同，却都一致地只考察这些对象之间存在的各种关系或比例，所以我认为，为了我的目的，最好是以尽可能普遍的形式来考察这些比例，不把它们归于任何特定的对象，除非是那些最便于认识它们的对象，而且决不把它们局限于这些对象，好让我以后能更好地把它们应用于它们可以正当地应用的其他一切种类的对象。我又看出，为了理解这些关系，我有时需要逐个地考察它们，有时只需要记住它们，或者把它们总括起来，于是我想，为了更好地逐个考察它们，我应当把它们看作存在于直线之间的关系，因为我找不到比直线更简单、更能清楚分明地呈现在我的想象和感官面前的对象了；另一方面，为了把它们记在心里，或者把许多关系总括起来，我应当用一些尽可能简短的符号来表示它们。我相信，这样我就可以借取几何分析和代数中最好的一切，并且用一方来纠正另一方的一切缺点。事实上，我敢说，确切地遵守这几条规则，使我在解开这两门学问所包含的一切问题时如此得心应手，以至于在我专心考察它们的两三个月里，我不仅解决了一些我以前认为极其困难的问题，而且即使对那些我仍然不知道怎样解决的问题，在我看来，我也能够确定用什么手段、在什么程度上可以解决它们；这些成果应当归功于这样一个情况：我是从最简单、最普遍的真理开始的，因而所发现的每一条真理，都成了可以用来发现以后的真理的一条规则。如果考虑到在任何一个特定的问题上真理只有一个，谁领会了这个真理，谁就知道了在这个问题上所能知道的一切，那么，我这样说也许就不会显得太自负了。比如，一个学过算术初步的孩子，按照规则做了一道加法，就可以确信，关于摆在他面前的这些数的和，他已经找到了在这个例子中人的才智所能达到的一切。总之，那教人遵循真正的次序、准确列举所求之物的一切条件的方法，包含了使算术规则具有确实性的一切。

但我对这个方法感到满意，主要的根据在于：我确信，通过它，我能在一切事情上运用我的理性，即使不是绝对完善，至少也是我所能达到的最完善的程度；此外，我意识到，通过运用它，我的心灵正逐渐习惯于对它的对象形成更清楚、更分明的概念；而且，既然我没有把这个方法局限于任何特定的题材，我也希望能把它应用于其他学问的难题，其成功不亚于应用于代数的难题。不过，我并没有因此就立刻冒险去审察摆在我面前的各门学问的一切难题，因为那样做就违背了这个方法所规定的次序；我注意到，这些学问的知识依赖于从哲学借来的原理，而我在哲学里找不到任何确实的东西，于是我想，首先必须努力确立哲学的原理。又因为我还注意到，这一类研究是一切研究中最重要的，在其中最要提防判断上的轻率和先入之见，我想，在我达到更成熟的年龄（我那时才二十三岁）之前，在我先花许多时间为这项工作作准备之前，我不应着手去做；这种准备，既在于把我直到那时所接受的一切错误意见从心中根除，也在于积累各种经验，为我的推理提供材料，还在于不断地用我选定的方法来练习，以求运用起来更加熟练。


第三部分

最后，在动手重建我们所住的房子之前，光是把它拆掉、准备好材料和工匠，或者按照事先仔细画好的图样亲自动手，是不够的，还必须给自己准备另一所房子，以便在施工期间能舒适地住在里面；同样，为了在理性迫使我暂停判断的时候，我在行动上不至于犹豫不决，为了从此以后仍能尽可能幸福地生活，我给自己定下了一套临时的道德规范，由三四条准则组成，我愿意把它们告诉你们。

*第一条*是：服从我国的法律和习俗，坚定地持守我靠上帝的恩典从童年起就受其教育的信仰，在其他一切事情上，按照最温和、离极端最远的意见来规范我的行为，这些意见是我生活在其中的人们里最明智的那些人在实践中普遍一致采纳的。因为，我从那时起已经开始把自己的意见看作毫无价值，因为我想把它们全部交付审察，所以我确信，在这期间我最好是遵从最明智的人的意见；尽管在波斯人和中国人中间，也许有些人和我们中间的人一样明智，但从便利出发，似乎我应当按照那些我将与之一起生活的人的意见来规范我的实践；而且在我看来，为了弄清这些人真正的意见，我应当注意他们做的是什么，而不是他们说的是什么；这不仅是因为在我们风气败坏的时候，很少有人愿意完全照自己所相信的那样说话，还因为有很多人并不知道自己真正相信的是什么；因为，相信一件事情的心灵活动，与我们知道自己相信它的心灵活动是不同的，常常有前一种而没有后一种。还有，在许多同样受到尊重的意见之中，我总是选择最温和的，这既是因为这些意见总是最便于实行的，也许也是最好的（因为一切过度通常都是坏的），也是为了万一我犯了错，离真理不至于太远，不像选了一个极端、结果却发现我本应采取的是另一个极端时那样。我把一切多少剥夺我们自由的承诺，特别归入极端之列；这并不是说，我不赞成那些法律：它们为了防范意志薄弱的人反复无常，在所要实现的是某种善的时候，允许人们用誓言和契约来约束双方坚持下去；甚至为了商业的安全，在所要实现的目的无所谓善恶的时候，也认可类似的约定；而是因为我在世上找不到任何东西是完全不变的，又因为我自己特别希望逐步完善我的判断，而不让它们变坏，所以我认为，如果因为我在某个时候赞成某件事，就约束自己在以后的时候也认为它是好的，而那时它也许已经不再是好的，或者我已经不再认为它是好的，那就是严重地违背了良知。

我的*第二条*准则是：在行动上尽可能坚定果断，一旦采取了最可疑的意见，也要像它们是十分确定的那样坚定地遵循；在这一点上，我效法那些在森林里迷了路的旅人，他们不应该东一头西一头地乱走，更不应该停在一个地方不动，而应该朝着同一个方向尽可能笔直地一直往前走，不因为一些微不足道的理由而改变方向，尽管当初决定选择这个方向的也许只是偶然；因为这样，即使他们不能恰好到达想去的地方，最后至少也会到达某个地方，那里大概总比在森林中间要好。同样，既然在行动中常常不容拖延，十分确定的是，当我们无力断定什么是真的时，就应当按照最可能的去做；即使我们看不出一种意见比另一种更可能，我们也仍然应当选定其中一种，然后就其与实践有关的方面而言，不再把它看作可疑的，而看作显然真实、确定的，因为决定我们这样选择的理由本身是具有这些性质的。这条原则从此足以使我摆脱一切悔恨和良心的谴责，这些悔恨和谴责通常扰乱着那些软弱而游移不定的心灵，他们没有任何清楚确定的选择原则，今天采取一种做法，认为它最好，明天又把它抛弃，当作是相反的东西。

我的*第三条*准则是：永远努力克服自己，而不是克服命运；改变自己的欲望，而不是改变世界的秩序；总之，使自己习惯于相信，除了我们自己的思想以外，没有什么是完全在我们能力之内的；所以，在对我们身外的事情尽了最大的努力之后，凡是我们没有成功的，对我们来说都应当看作是绝对不可能的；在我看来，单是这一条原则就足以使我今后不再想望任何我得不到的东西，从而使我知足；因为既然我们的意志天然只追求那些理智表明在某种程度上可能得到的对象，那么很明显，如果我们把一切身外之物都看作同样在我们能力之外，那么，当我们并非因为自己的过错而失去了那些似乎是我们的出身应得的好东西时，我们就不会为缺少它们而遗憾，正如不会为没有拥有中国或墨西哥的王国而遗憾一样；这样，可以说是把必然变成美德，我们在生病时就不会想望健康，在囚禁中就不会想望自由，正如我们现在不想望有像钻石一样不朽坏的身体，或者有鸟的翅膀可以飞翔一样。但我承认，要使心灵习惯于从这个角度看待一切对象，需要长期的锻炼和反复的沉思；我相信，从前那些能够超脱命运的影响、在痛苦和贫困之中享受连他们的神都会嫉妒的幸福的哲学家，他们力量的秘密主要就在于此。因为他们不断地考虑自然给他们的能力所规定的界限，以至于完全确信，除了他们自己的思想，没有什么东西是由他们支配的，单是这种确信就足以使他们不再对别的对象怀有任何欲望；他们对自己的思想获得了那样绝对的支配，因此有一定的理由认为自己比别人更富有、更有力量、更自由、更幸福；而那些别人，不管自然和命运给了他们多少恩惠，如果没有这种哲学，就永远不能使自己的一切欲望都得到实现。

最后，为了给这套道德规范作个结束，我想到要检视一下人们在这一生中从事的各种职业，以便从中选出最好的一种。我不想对别人的职业发表什么议论，只想说：我确信，我最好是继续从事我正在从事的那件事，也就是用我的整个一生来培养我的理性，按照我给自己规定的方法的原则，在认识真理上尽我所能取得最大的进步。这个方法，自从我开始运用它以来，给了我如此强烈的满足，使我相信在这一生中不能享受到更完美、更纯洁的满足了；而且，既然借助它，我每天都发现一些在我看来有点重要、而别人一般都不知道的真理，由此产生的快乐占满了我的心，使我对其他一切对象都完全淡漠了。此外，前面那三条准则，都只是建立在继续自我教育这个打算之上的。因为既然上帝给了我们每个人某种理性之光，用来辨别真假，我就不能相信我应当有片刻满足于别人的意见，除非我已经决心在我有足够资格的时候，运用自己的判断去审察这些意见。如果我认为这样做会使我丧失获得更准确的意见（如果有的话）的任何便利，我也不能毫无顾虑地按照这些意见行事。最后，如果我不是走在一条我认为肯定能获得我力所能及的一切知识、同时也能获得我所能希望得到的最多的真正的好东西的路上，我就不能节制我的欲望，也不能感到满足。既然我们追求或避开任何对象，都只是因为我们的理智把它表现为好的或坏的，那么，要行动正确，只需判断正确；要行动得最好，只需判断得最正确——也就是说，获得一切美德以及我们力所能及的其他一切真正有价值的东西；而确信能获得这些，就不会不使我们感到满足。

我就这样给自己准备好这些准则，把它们和那些在我的信念中一向占首位的信仰真理一起存放起来，然后我断定，我可以自由地着手清除我其余的意见了。又因为我希望通过与人交往，能比继续关在我产生这些思想的那个隐居之处更好地完成这项工作，所以冬天还没有完全过去，我就又出去旅行了。在以后的九年里，我什么也不做，只是到处漫游，想在世界这个舞台上演出的戏剧里做一个观众，而不做一个演员；我在每一件事情上都特别注意反省其中有哪些可以合理地怀疑、可能成为错误的来源，这样，我就逐渐把先前悄悄进入我心中的一切错误都根除了。这并不是说我在这方面效法了怀疑派，他们只为怀疑而怀疑，除了不确定本身以外什么也不追求；恰恰相反，我的打算只是要找到可靠的根据，把松散的泥土和沙子挖掉，以便找到岩石或黏土。在这一点上，我觉得我是相当成功的；因为我努力发现我所审察的命题的虚假或不确定，不是靠薄弱的猜测，而是靠清楚而确实的推理，所以我没有遇到什么东西可疑到不能得出某种足够确实的结论，哪怕这个结论只是：所讨论的事情里没有任何确实的东西。正如在拆除一座旧房子时，我们通常保留下拆下的材料，用来建造新房子；同样，在推翻我认为根据不足的那些意见时，我作了种种观察，获得了许多经验，后来我就利用它们来建立更确实的意见。此外，我继续用我给自己规定的方法来练习；因为除了一般地注意按照它的规则来引导我的一切思想以外，我还不时留出几个小时，专门用这个方法来解决数学上的难题，甚至也用它来解决属于其他学问的一些问题，但这些问题，由于我把它们从这些学问中不够确实的原理上分离了出来，就变得差不多是数学问题了：这本书里所包含的许多例子，会显示这一点是真的。这样，我表面上和那些人的生活并无二致：他们没有别的事，只是愉快而清白地度过一生，努力把快乐与恶习分开，为了享受闲暇而不感到无聊，就去从事种种正当的消遣；但我却在推进我的计划，在认识真理上取得的进步，也许比我只读书或只与文人交谈所能取得的还要大。

然而，这九年过去了，我对学者们所争论的那些难题，还没有作出任何确定的判断，也还没有开始寻求任何比通俗哲学更确实的哲学的原理。许多最有天才的人，从前曾从事这种研究，但在我看来并没有成功，他们的例子使我设想，这是一件极其困难的工作，要不是我听到外面普遍传说我已经完成了这项研究，我也许不会这么早就冒险去做。我不知道这种看法有什么根据；如果我的谈话对它的产生多少起了点作用，那也一定是因为我比那些稍微读过一点书的人惯常所做的更坦率地承认了我的无知，或许还说明了使我怀疑许多别人认为确实的事情的理由，而不是因为我夸耀过什么哲学体系。但是，因为我的性情使我不愿被人看作与我实际所是的不同，我想必须尽一切办法努力使自己配得上人们给我的名声；正好八年前，这种愿望迫使我离开了一切可能被熟人打扰的地方，来到这个国家；在这里，长期的战争使纪律如此严明，以至于所维持的军队似乎只是为了使居民能更安全地享受和平的福祉；在这里，在一大群忙于事务、关心自己的事情多于好奇别人的事情的人中间，我能够生活得既不缺少人烟最稠密的城市里所能有的任何便利，又像在最偏远的荒漠之中一样孤独、一样隐退。


第四部分

我不知道是否应该把我在上面说的那个地方所作的最初的沉思拿来讨论；因为它们太形而上学、太不寻常了，也许不是每个人都能接受。然而，为了能判断我所奠定的基础是否足够牢靠，我发现自己在某种程度上不得不谈到它们。我早就注意到，在实践方面，有时必须把我们看出是很不确定的意见当作无可怀疑的来采纳，这在前面已经说过；但由于那时我只想专心寻求真理，我想必须采取恰恰相反的做法，凡是我能设想有一点点可疑之处的意见，都应当作绝对虚假的加以抛弃，以便看看这样做了之后，我的信念中是否还剩下什么完全无可怀疑的东西。因此，既然我们的感官有时欺骗我们，我就愿意假定，没有任何东西真像感官向我们呈现的那样存在；又因为有些人在推理中犯错，甚至在几何学最简单的问题上也会陷入谬误推理，而我确信自己和任何别人一样容易犯错，我就把我先前当作证明的一切推理都当作假的抛弃了；最后，当我考虑到，我们醒着时所经验到的同样的思想（表象），在我们睡着时也能经验到，而那时其中没有一个是真的，我就假定，一切曾在我醒着时进入我心中的对象（表象），并不比我梦中的幻觉有更多的真实性。但是紧接着我就注意到，当我这样想要认为一切都是假的时候，这样想的我，就必然应当是某种东西；我注意到，*我思，故我在*这条真理是如此确实、如此明显，怀疑派提出的任何理由，哪怕再荒诞，都不能动摇它，于是我断定，我可以毫无顾虑地把它当作我所寻求的哲学的第一原理。

其次，我仔细地审察我是什么；我注意到，我可以设想我没有身体，可以设想没有世界，也没有我所在的任何地方，却不能因此就设想我不存在；相反，正是从我想到要怀疑其他事物的真实性这一点，就非常清楚、非常确定地推出我是存在的；而另一方面，只要我停止了思想，即使我所想象过的其他一切对象都真的存在，我也没有任何理由相信我存在；由此我断定，我是一个实体，它的全部本质或本性只在于思想，它为了存在，不需要任何地点，也不依赖任何物质的东西；所以，这个“我”，也就是使我成为我的那个心灵，是与身体完全不同的，甚至比身体更容易认识，即使身体不存在，它也仍然会是它现在的一切。

此后，我一般地探究一个命题之为真、之为确实需要些什么；因为既然我已经发现了一个我知道是真的命题，我想我也必定能发现这种确实性的根据。我注意到，在*我思，故我在*这句话里，除了我非常清楚地看到要思想就必须存在以外，根本没有任何东西使我确信它是真的；于是我断定，我可以把这一条当作一般的规则：凡是我们非常清楚、非常分明地设想到的东西，都是真的；只是要注意，要正确地确定哪些是我们分明地设想到的对象，有些困难。

其次，我反省到我在怀疑，因而我的存在并不是完全完满的（因为我清楚地看到，认识比怀疑是更大的完满），于是我就去探究，我是从哪里学会想到某种比我更完满的东西的；我清楚地认识到，我必定是从某个确实更完满的本性那里得到这个观念的。至于我对我以外的许多其他对象的思想，如天空、大地、光、热以及其他成千种东西，我倒不大难知道它们是从哪里来的；因为我在它们里面看不出有什么东西似乎使它们比我优越，所以我可以相信，如果它们是真的，它们就是依赖于我的本性的，只要我的本性具有某种完满性；如果它们是假的，那我就是从无中得到它们的，也就是说，它们之所以在我心中，是因为我的本性有某种缺陷。但对于一个比我更完满的本性的观念，情况就不可能是这样；因为从无中得到它，显然是不可能的；又因为说较完满的东西是较不完满的东西的结果、依赖于较不完满的东西，与说某种东西出自无，同样是矛盾的，所以我也同样不可能从我自己得到它；因此，只剩下一种可能：它是由一个确实比我更完满的本性放进我心中的，这个本性甚至在自身之中具有我所能形成任何观念的一切完满性；一句话，这就是上帝。我还补充说，既然我知道一些我所不具有的完满性，我就不是唯一存在的东西（请允许我在这里随意使用经院的术语）；相反，必然有另一个更完满的存在者，我依赖于他，我所具有的一切都是从他那里得来的；因为如果我是单独存在、不依赖其他任何存在者的，以致我实际具有的那一点点完满性都是从我自己得来的，那么，出于同样的理由，我也就能从我自己得到我意识到自己所缺少的其余一切完满性，从而能够由我自己变成无限的、永恒的、不变的、全知的、全能的，总之，具有我在上帝身上所能认识到的一切完满性。因为，为了在我的本性所允许的范围内认识上帝的本性（他的存在已由前面的推理确立），我只需考虑，对于我在心中有某种观念的一切属性，具有它们是不是一种完满性的标志；我确信，凡是表示某种不完满的，都不在他身上，而其余的一切，他都不缺少。这样，我看出怀疑、无常、悲伤之类的东西不可能在上帝身上，因为我自己也会乐于摆脱它们。此外，我有许多可感的、有形的东西的观念；因为尽管我可以假定我在做梦，假定我所看见或想象的一切都是假的，我却不能否认这些观念确实在我的思想之中。但是，因为我已经非常清楚地在我自己身上认识到，有理智的本性与有形体的本性是不同的，又因为我注意到，一切组合都是依赖的证据，而依赖的状态显然是一种不完满的状态，所以我断定，由这两种本性组合而成，不可能是上帝的一种完满性，因而他并不是这样组合成的；但如果世界上有什么物体，或者甚至有什么理智，或者其他并非完全完满的本性，它们的存在就依赖于他的能力，以致它们没有他就一刻也不能存在。

我随即想去寻求其他的真理；我向自己展示几何学家的对象，我把它设想为一个连续的物体，或者一个在长、宽、高或深上无限延伸的空间，可以分成各个部分，这些部分可以有不同的形状和大小，可以以各种方式移动或调换位置（因为几何学家假定他们所思考的对象里有这一切），然后我把他们一些最简单的证明温习了一遍。首先，我注意到，人们一致承认这些证明具有的高度确实性，只是建立在这一点上：它们是按照我已经定下的那些规则被清楚地设想的。其次，我看出，这些证明里根本没有任何东西能使我确信它们的对象存在：比如，假定给出一个三角形，我分明地看出它的三个角必然等于两直角，但我并不因此就看出有什么东西能使我确信有任何三角形存在；相反，当我回过头来审察一个完满的存在者的观念时，我发现这个存在者的存在就包含在这个观念之中，正如三角形三个角等于两直角包含在三角形的观念之中，或者球面上所有的点与球心距离相等包含在球的观念之中一样，甚至还更清楚；因此，上帝这个完满的存在者是有的、存在着的，这至少和任何几何学证明一样确实。

但有许多人之所以相信认识这条真理有困难，甚至认识他们的心灵究竟是什么也有困难，是因为他们从不把思想提升到可感对象之上，太习惯于只用想象来考察一切，而想象是一种局限于物质对象的思想方式，以致凡是不能想象的东西，在他们看来都不可理解。只要看经院哲学家们把这当作一条准则：凡是在理智之中的，无不先在感官之中，这一点就足够明显了；然而，上帝和灵魂的观念确实从来没有在感官之中；在我看来，那些用想象来理解这些观念的人，正好像是为了听声音或闻气味而努力用眼睛一样；只不过有这样一个区别：视觉给我们的确信，并不比嗅觉或听觉给的差；而我们的想象和感官，如果没有理智介入，就不能使我们确信任何东西。

最后，如果还有人对我所举出的理由不够信服，不相信上帝和灵魂的存在，我希望他们知道：其他一切他们也许认为更有把握的命题，例如我们有一个身体，有星辰和大地存在，诸如此类，都是更不确实的；因为，尽管我们对这些事情有一种实践上的确信，强烈到怀疑它们的存在似乎就是荒唐，然而，当问题涉及形而上学的确实性时，只要理智没有受损，谁也不能否认，有足够的理由排除完全的确信：只要注意到，我们在睡着时，同样可以想象自己有另一个身体，看见另一些星辰和另一个大地，而其实并没有这样的东西。因为我们怎么知道梦中出现的思想是假的，而不是我们醒着时经验到的那些思想是假的呢？前者往往并不比后者更不生动、更不分明。即使最有天才的人愿意研究这个问题多久就研究多久，我也不相信他们能提出什么足以消除这个怀疑的理由，除非他们预先假定上帝存在。因为，首先，即使是我已经当作规则的那条原则，即凡是我们清楚分明地设想到的东西都是真的，之所以确实，也只是因为上帝是有的、存在着的，因为他是一个完满的存在者，因为我们所具有的一切都是从他那里来的；由此可见，我们的观念或概念，就其清楚分明而言，是实在的，是出自上帝的，所以在这个程度上必定是真的。因此，我们常常有一些含有某种虚假的观念或概念，这只能发生在那些在某种程度上混乱模糊的观念上，在这一点上，它们是出自无的（分有了否定），也就是说，它们之所以这样混乱地存在于我们心中，是因为我们并不完全完满。显然，说虚假或不完满，就其为不完满而言，出自上帝，与说真理或完满出自无，同样是矛盾的。但如果我们不知道我们所具有的一切实在的、真的东西都出自一个完满而无限的存在者，那么，不管我们的观念多么清楚分明，我们也没有根据因此确信它们具有真实这一完满性。

但在对上帝和灵魂的认识使我们确信了这条规则之后，我们就很容易理解：我们醒着时所经验到的思想的真实性，丝毫不应因为我们梦中的幻觉而受到怀疑。因为如果碰巧有一个人，即使在睡着的时候，也有某个非常分明的观念，比如一位几何学家发现了某个新的证明，他睡着这一情况并不妨碍这个证明是真的；至于我们梦中最常见的错误，就是它们像我们的外感官一样向我们呈现各种对象，这也无害，因为它恰好使我们有理由怀疑感官观念的真实性；因为我们醒着时也常常以同样的方式受骗；比如害黄疸病的人看一切东西都是黄的，又如星辰或很远的物体在我们看来比实际小得多。因为，总之，不论醒着还是睡着，我们都决不应让自己相信任何东西是真的，除非有我们理性的明证。必须注意，我说的是我们的*理性*，而不是我们的想象或感官：比如，尽管我们非常清楚地看见太阳，我们却不应因此就断定它只有我们的视觉所呈现的那么大；我们可以非常分明地想象一个狮子头接在一个山羊身上，却不必因此就得出结论说有一个喀迈拉存在；因为理性并没有告诉我们，我们这样看见或想象的东西是实际存在的；但它明白地告诉我们，我们的一切观念或概念里都含有某种真理；否则，完全完满、真实无欺的上帝，就不可能把它们放进我们心中。又因为我们在睡梦中的推理，从来不像醒着时那样清楚、那样完整，尽管有时那时的想象活动和醒着时一样生动分明，甚至更生动分明，所以理性还告诉我们：既然由于我们部分的不完满，我们的思想不可能全都是真的，那么，具有真理的那些思想，必定是在我们醒着时的经验中，而不是在梦中，才能确实无误地找到。


第五部分

我在这里本愿意把我从这些最初的真理推出的整个真理链条都展示出来；但为此我现在就得讨论许多在学者之间有争议的问题，而我并不想与他们纠缠，所以我相信，最好还是不作这番阐述，只一般地提一提这些真理是什么，好让较明智的人能判断，对它们作更专门的叙述是否会有益于公众。我始终坚持我当初的决心：除了我刚才用来证明上帝和灵魂存在的那条原则以外，不假定任何别的原则；凡是在我看来不比从前几何学家的证明更清楚、更确实的东西，都不当作真的接受；然而我敢说，我不仅找到了办法，在短时间里就使自己在哲学通常讨论的一切主要难题上得到满意的解答，而且还观察到了某些法则，它们是上帝以这样的方式在自然中确立的，并且他把关于它们的概念印在了我们心中，使我们在充分思考之后，不能怀疑它们在世界上存在或发生的一切中都被准确地遵守着；此外，通过考察这些法则的相互联系，我觉得我发现了许多真理，比我以前所学到的、甚至所期望学到的一切都更有用、更重要。

但因为我曾试图在一篇论著里阐述这些发现中的主要部分，而某些考虑使我不能发表它，所以我要使人知道这些成果，最方便的办法就是在这里概述一下那篇论著的内容。我原打算在其中包括我在动笔之前自认为知道的关于物质对象的本性的一切。但是，就像画家们发现自己不能在一个平面上同样好地画出一个立体的所有不同的面，便选择其中主要的一面，只让光落在这一面上，把其余的面放进阴影里，只让它们在看着主要的那一面时能看到的程度上显现出来；同样，我怕不能把我心中的一切都包括进我的论述，便决心只详细地阐述我对光的看法；然后乘机补充一些关于太阳和恒星的话，因为光几乎全是从它们发出的；关于天空的话，因为天空传送光；关于行星、彗星和地球的话，因为它们反射光；特别是关于地球上一切物体的话，因为它们或者是有颜色的，或者是透明的，或者是发光的；最后是关于人的话，因为人是这些对象的观看者。此外，为了能把这许多题材多少放进阴影里，更自由地表达我对它们的判断，而不必采纳或驳斥学者们的意见，我决心让这里所有的人去争论他们的，只谈谈在一个新的世界里会发生什么：假如上帝现在在想象的空间里的某处，创造出足以构成一个世界的物质，并把这物质的各个部分以各种方式杂乱地搅动起来，使之成为一团混沌，像诗人们所虚构过的任何混沌一样混乱，然后他不再做别的，只是给自然以他通常的协助，让她按照他所确立的法则行事。根据这个假定，我首先描述了这种物质，并试图把它表现得在我看来除了刚才关于上帝和灵魂所说的以外，没有什么比它更清楚、更可理解的了；因为我甚至明确地假定，它没有经院中争论不休的那些形式或性质，总之，没有任何一样东西，其知识不是对我们的心灵如此自然，以至于谁也不能想象自己对它无知。此外，我指出了自然的法则是什么；除了上帝无限的完满性以外，我不以任何别的原则作为推理的根据，努力证明了其中一切可能有怀疑余地的法则，并证明它们是这样的：即使上帝创造了更多的世界，也不可能有哪一个世界不遵守这些法则。此后，我说明了这团混沌的物质的绝大部分，怎样必定按照这些法则自行布置、安排，以致呈现出天空的样子；与此同时，它的一些部分怎样必定构成一个地球、一些行星和彗星，另一些部分则构成一个太阳和恒星。在这里，我离开正题谈到光，相当详细地阐述了太阳和星辰中的光必定具有什么样的本性，它怎样从那里在一瞬间穿过天空的广大空间，又怎样从行星和彗星反射到地球上。对此我还补充了许多关于这些天空和星辰的实体、位置、运动以及一切不同性质的话；所以我想，关于它们我已经说得够多了，足以表明：在我们这个体系的天空和星辰里能观察到的一切，没有一样不必定、或者至少不可能在我所描述的那个体系的天空和星辰里同样显现出来。接着我特别谈到地球，说明尽管我明确地假定上帝没有给构成它的物质以任何重量，这也不妨碍它的所有部分都恰好趋向它的中心；说明地球表面既有水和空气，天空和天体的布置，特别是月亮的布置，怎样必定引起一种潮涨潮落，在一切情形上都与我们在海里观察到的相似，还引起一种水和空气从东向西的流动，就像在回归线之间也能观察到的那样；说明山、海、泉、河怎样可以在地球上自然形成，金属怎样在矿中产生，植物怎样在田野里生长；总之，说明一切通常称为混合物或复合物的物体怎样可以产生出来：在我提到的这些发现中，除了星辰之外，我知道能发光的只有火，所以我不遗余力地阐明属于火的本性的一切——它怎样产生、怎样维持，并解释为什么有时有热而无光，有时有光而无热；说明它怎样能使不同的物体呈现各种颜色和其他各种性质；怎样使一些物体熔化，使另一些物体变硬；怎样能烧掉几乎一切物体，或者把它们化为灰和烟；最后，怎样仅仅凭着它作用的强烈，就从这些灰中造出玻璃：因为在我看来，灰变成玻璃，和自然中任何其他转化一样奇妙，所以我特别乐于描述它。

然而，我并不打算从这些情况断定，这个世界是按照我所描述的方式被创造的；因为更可能的是，上帝一开始就把它造成了它应当有的样子。但这一点是确实的，也是神学家们普遍接受的意见：上帝现在用来维持世界的那个作用，和他当初用来创造世界的作用是同一个；所以，即使他一开始只给了世界混沌的形式，只要他确立了某些自然法则，并给它以协助，使它能照它惯常的那样行事，那么，我们可以相信，这无损于创造的奇迹：单单这样，纯粹物质的东西经过时间的推移，就能变成我们现在看到的样子；而且，当我们看到它们以这种方式逐渐生成时，比只把它们看作一下子就以完成的、完满的状态被造出来时，更容易理解它们的本性。

从对无生命的物体和植物的描述，我转到动物，特别是人。但由于我当时还没有足够的知识，能像论述其余的东西那样来论述它们，也就是说，从原因推出结果，说明自然必定从什么元素、以什么方式产生它们，我就满足于这样一个假定：上帝造了一个人的身体，无论是肢体的外形，还是器官的内部构造，都和我们的身体完全一样，所用的物质就是我所描述过的那种物质；起初并没有在其中放进理性灵魂，也没有放进别的任何东西来代替植物灵魂或感觉灵魂，只是在心脏里点燃了一种我已经描述过的那种无光之火，我认为这种火和没干就堆起来的干草里的热，或者新酒在与果渣分离之前使它发酵的那种热，并没有什么不同。因为当我审察根据这个假定这个身体里可能有哪些功能时，我发现的恰恰是我们身上可能有的、不依赖任何思想能力、因而丝毫不是由灵魂引起的那些功能；灵魂，也就是我们身上与身体不同的那一部分，上面已经说过，它的本性独特地在于思想；在这些功能上，可以说无理性的动物与我们完全相似；但在这些功能之中，我找不到任何一种只依赖于思想、因而属于我们作为人的功能；另一方面，当我假定上帝创造了一个理性灵魂，并按我所描述的某种特殊方式把它与这个身体结合起来以后，我立刻就发现了这些功能。

但为了表明我在那里是怎样处理这个题材的，我想在这里解释一下心脏和动脉的运动；这是在动物身上观察到的最初的、最普遍的运动，可以使人容易确定对其余一切运动应当作何看法。为了使人们较容易理解我就这个题目要说的话，我劝那些不熟悉解剖学的人，在开始读这些观察之前，费点事请人当着他们的面解剖某种有肺的大动物的心脏（因为它在各方面都和人的心脏够相似），并请人给他们看它的两个心室或腔：首先是右边那个，与它相连的有两根很粗的管子，即腔静脉（*vena cava*），它是血液的主要容器，可以说是一棵树的树干，身体里所有其他的静脉都是它的分枝；还有动脉性静脉（*vena arteriosa*），这个名称取得不恰当，因为它其实只是一根动脉，从心脏发出，出来以后分成许多分枝，随即遍布整个肺部；其次是左边那个腔，与它同样相连的有两根管子，大小等于或大于前面那两根，即静脉性动脉（*arteria venosa*），这个名称同样取得不恰当，因为它只是一根来自肺部的静脉，在肺里分成许多分枝，与动脉性静脉的分枝、与那根叫作气管的管子的分枝交织在一起，我们吸进的空气就是从气管进去的；还有大动脉，它从心脏发出，把它的分枝送到全身。我还希望给这些人仔细看看那十一片薄膜，它们像许多小阀门一样，开闭着这两个腔里的四个口：三片在腔静脉的入口，它们的布置方式丝毫不妨碍腔静脉里的血流进心脏的右心室，却恰好阻止它流出来；三片在动脉性静脉的入口，布置得与前者恰好相反，很容易让这个腔里的血流进肺部，却阻止肺里的血回到这个腔里；同样，另外两片在静脉性动脉的口上，让来自肺部的血流进心脏的左腔，却阻止它倒流；还有三片在大动脉的口上，让血从心脏流出，却阻止它回流。这些薄膜的数目，也不必去找别的理由，只因为静脉性动脉的口由于它所处的位置是椭圆形的，用两片就能充分关闭，而其他的口是圆形的，用三片关闭更为方便。此外，我希望这些人注意到，大动脉和动脉性静脉的组织比静脉性动脉和腔静脉坚硬结实得多；后两者在进入心脏之前扩大，在那里形成两个可以说是囊袋的东西，叫作心耳，它们由一种与心脏本身相似的物质构成；心脏里总是比身体任何其他部分都更热；最后，这种热能使任何一滴进入心腔的血迅速膨胀、扩张，就像一切液体一滴一滴地滴进一个烧得很热的容器时那样。

因为在说了这些以后，要解释心脏的运动，我就不必再多说什么了，只需说：当心腔里没有充满血时，血就必然流进去——从腔静脉流进右腔，从静脉性动脉流进左腔；因为这两根血管总是充满了血，它们朝向心脏的口那时又不能关闭。但一旦有两滴血这样进去了，每个腔里一滴，这两滴血，由于它们所经过的口很宽，它们所来自的血管又充满了血，就不能不是很大的，一遇到那里的热，就立刻稀化、膨胀。这样，它们使整个心脏扩张，同时把它们所来自的那两根血管入口处的五片小阀门推紧、关上，从而阻止更多的血流进心脏；它们越来越稀化，就推开另外两根血管口上的六片小阀门，从那里流出去，这样使动脉性静脉和大动脉的所有分枝几乎与心脏同时扩张——心脏随即开始收缩，动脉也随之收缩，因为进入它们的血已经冷却了，于是那六片小阀门关上，腔静脉和静脉性动脉的五片阀门重新打开，让另外两滴血通过，这两滴血又使心脏和动脉像先前那样扩张。又因为这样进入心脏的血要经过那两个叫作心耳的囊袋，所以它们的运动与心脏的运动相反，心脏扩张时，它们收缩。但是，为了不让那些不知道数学证明的力量、不习惯于分辨真正的理由和仅仅是似乎有理的东西的人，不加审察就冒然否认上面所说的话，我希望人们考虑：我刚才解释的这种运动，必然地出自单凭眼睛就能在心脏中观察到的各部分的布置，出自用手指就能感到的热，出自由经验得知的血的本性，正如一座钟的运动必然地出自它的重锤和齿轮的力量、位置和形状一样。

但如果有人问：静脉里的血这样不断地流进心脏，怎么不会流尽？动脉既然接受了经过心脏的全部的血，为什么不会胀得太满？我只需提一提一位英国医生所写的东西来回答；他有幸在这个问题上破了冰，第一个教人知道：在动脉的末端有许多细小的通道，动脉从心脏接受的血，经过这些通道进入静脉的细小分枝，再从那里回到心脏；所以血的流程恰恰就是一种永不停息的循环。外科医生的日常经验为此提供了充分的证明：他们在切开静脉的部位上方，用松紧适中的带子把胳膊扎住，使血流得比不扎的时候更多；而如果他们扎在下方，也就是在手和切口之间，或者在切口上方扎得很紧，情况就会恰恰相反。因为很明显，松紧适中的带子虽然足以阻止已经在胳膊里的血经由静脉回到心脏，却不能因此阻止新的血经由动脉流过来，因为动脉位于静脉下面，它们的管壁比较坚韧，更难压紧；而且从心脏来的血经由动脉流向手的力量，也比它经由静脉从手回到心脏的力量更大。既然后一股血流从切开的一根静脉的口子流出胳膊，那么在扎带的下方，也就是靠近胳膊末端的地方，就必然有某些通道，血可以通过它们从动脉流到那里。这位医生还从以下几点充分地证实了他关于血的运动的说法：一是沿着静脉的路径，在各处有一些薄膜，像小阀门一样布置着，不让血从身体中部流向四肢末端，只让它从四肢末端回到心脏；二是经验表明，身体里所有的血可以在很短的时间里从一根被切断的动脉流出去，即使这根动脉紧靠着心脏被紧紧扎住，并在心脏和扎带之间被切断，使人无法设想从它流出的血会来自心脏以外的任何地方。

但还有许多其他情况证明，我所说的正是血液运动的真正原因：首先，从静脉流出的血与从动脉流出的血之间所看到的差别，只能是由于这一点：血经过心脏时被稀化，可以说被蒸馏了，所以在刚离开心脏的时候，也就是在动脉里的时候，比它在进入心脏之前不久，也就是在静脉里的时候，更稀薄、更鲜活、更温暖；如果留意观察，就会发现，这种差别只在心脏附近非常显著，在离心脏较远的部位就不那么明显。其次，构成动脉性静脉和大动脉的那些管壁的坚韧，足以表明血冲击它们的力量比冲击静脉的更大。如果不是因为静脉性动脉的血在经过心脏以后只在肺里待过，比直接从腔静脉来的血更稀薄，更容易、更大程度地稀化，那么，心脏的左腔和大动脉为什么要比右腔和动脉性静脉更宽、更大呢？医生们按脉的时候，如果不知道血随着本性的变化，能被心脏的热稀化得比先前程度更高或更低、更快或更慢，他们又能推测出什么呢？如果有人问这种热是怎样传到其他肢体的，难道不必承认这是靠血来完成的吗？血经过心脏，在那里重新被加热，再从那里散布到全身。因此，如果从任何部位把血抽走，热也就同样随之被抽走；即使心脏像烧红的铁那样热，如果它不是不断地把新的血送到手和脚那里，也不能像现在这样使它们温暖。我们也由此看出，呼吸的真正用处，在于把足够的新鲜空气带进肺里，使那些从心脏右心室流进肺里、在右心室里已被稀化、可以说已变成蒸汽的血，变得浓稠，在流进左腔之前重新变成血；没有这个过程，它就不适于养那里的火。这一点可以从以下情况得到证实：人们观察到，没有肺的动物，心脏里也只有一个腔；还有在母腹中不能用肺的胎儿，有一个孔，血可以经过它从腔静脉流进心脏的左腔，还有一根管子，血可以经过它从动脉性静脉流进大动脉，而不经过肺。其次，如果心脏不经由动脉把热传给胃，并且随热一起送去血中某些较流动的部分，帮助溶解吃进的食物，胃里的消化又怎么能进行呢？考虑到食物的汁液每天也许要在心脏里来回经过一两百次以上而被蒸馏，那么，把它变成血的那种作用不也就很容易理解了吗？要解释营养以及身体里各种体液的产生，还需要举出什么别的东西呢？只需说：血在被稀化时从心脏流向动脉末端的那股力量，使它的某些部分留在它们所到达的肢体里，占据被它们赶走的另一些部分的位置；并且按照它们所遇到的孔隙的位置、形状或细小程度，有些部分比另一些部分更多地流进某些地方，就像人们看到的某些筛子那样，它们打着各种不同的孔，用来把不同种类的谷物分开。最后，在这里尤其值得注意的，是动物精气的产生；它们像一种非常精微的风，或者更像一种非常纯粹、非常鲜活的火焰，不断地从心脏大量上升到大脑，再从大脑通过神经进入肌肉，使一切肢体运动；所以，要说明血中另一些部分，因为最激荡、最有穿透力，最适于构成这些精气，为什么会流向大脑，不必假定别的原因，只需说：把它们输送到那里的动脉是从心脏沿着最直的线路发出的；而按照与自然法则相同的力学规则，当许多东西同时趋向同一个点，那里又没有足够的地方容纳它们全部时（从心脏左腔流出、趋向大脑的血的各个部分就是这种情形），较弱、较不激荡的部分就必然被较强的部分从那个点挤开，只有较强的部分才能这样到达那里。

所有这些事情，我在以前想发表的那篇论著里都已相当详细地阐述过了。在这些之后，我还说明了：人体的神经和肌肉必须有什么样的构造，才能使其中的动物精气有能力推动肢体，就像我们看到的，头刚被砍下不久，虽然已经没有了生命，却仍然会动，会啃地；大脑里必须发生什么样的变化，才能产生醒、睡和梦；光、声音、气味、味道、热以及外物的其他一切性质，怎样通过感官在大脑上印下不同的观念；饥、渴以及其他内部的感受，怎样也能在大脑上印下种种观念；应当怎样理解接受这些观念的共通感（*sensus communis*），保存这些观念的记忆，以及能以各种方式改变这些观念、用它们组成新观念的幻想；幻想又怎样以同样的方式把动物精气分布到肌肉里，能使这样一个身体的肢体以那么多不同的方式运动，而且无论是对呈现给它感官的对象，还是对它内部的感受，都运动得那样适当，就像我们自己在不受意志指导时所能做到的那样。对于那些熟悉人的技艺所造出的各种自动机、或者说会动的机器能做出多少种运动的人来说，这一点也就毫不奇怪了；这些机器所用的零件，与每一个动物身体里那大量的骨骼、肌肉、神经、动脉、静脉和其他部分相比，少之又少。这样的人会把这个身体看作一台由上帝之手造出的机器，它的构造比人所发明的任何机器都要精良得无可比拟，能做出的运动也更令人赞叹。我在这里特意停下来说明：如果有这样的机器，在器官和外形上与一只猿或别的什么无理性的动物一模一样，我们就没有办法知道它们在任何方面与这些动物有不同的本性；但如果有一些机器，带着我们身体的形象，并且在实际可能的范围内模仿我们的行为，那么我们仍然有两个最可靠的检验，可以知道它们并不因此就真的是人。第一个检验是：它们永远不能像我们那样，使用经过安排的言辞或其他符号，向别人表达我们的思想；因为我们完全可以设想，一台机器被造得能发出词语，甚至能发出一些与作用于它、引起它器官变化的外物相对应的词语；比如，在某个地方碰它一下，它会问我们想对它说什么；在另一个地方碰它，它会叫喊说它疼，诸如此类；但我们不能设想它能把这些词语作各种安排，以便恰当地回答在它面前所说的话，而这是智力最低下的人也能做到的。第二个检验是：这样的机器虽然可以把许多事情做得和我们任何人一样完美，甚至更完美，但它们无疑会在另一些事情上失败，由此就可以发现，它们不是凭认识行事，而只是凭它们器官的配置行事：因为理性是一种普遍的工具，在一切场合都同样可用，而这些器官则相反，每一个特定的动作都需要一种特定的配置；所以，任何机器里要有足够多样的器官，使它能在生活的一切情况下像我们的理性使我们那样行事，实际上必定是不可能的。再者，借助这两个检验，我们也可以知道人与禽兽的区别。因为非常值得注意的是，没有哪个人愚钝到、哪怕是白痴也不例外，不能把不同的词语连在一起，组成一句话来让人明白他的思想；而另一方面，没有别的任何动物，无论多么完善、境况多么优越，能做到这一点。这种无能并不是由于缺少器官：因为我们看到，喜鹊和鹦鹉能像我们一样说出词语，却不能像我们那样说话，也就是说，不能表明它们懂得自己所说的话；而天生聋哑的人，缺少别人用来说话的器官，比禽兽缺得不是更少而是更多，却惯于自发地发明某些符号，用来向那些常和他们在一起、有空学习他们语言的人表达自己的思想。这不仅证明禽兽的理性比人少，而且证明它们根本没有理性：因为我们看到，一个人要能说话，只需要很少的东西；而且同一物种的动物之间，和人与人之间一样，可以看到能力上的某种不平等，有些比另一些更容易教会，所以，除非禽兽的灵魂与我们的灵魂本性全然不同，否则难以置信，同类中最完善的猿或鹦鹉，在这一点上竟比不上同类中最愚笨的婴儿，或者至少比不上一个头脑有毛病的婴儿。我们不应当把言语与那些表示情感的自然动作混为一谈，这些动作机器可以模仿，动物也可以表现；也不应当像某些古人那样认为，禽兽也说话，只是我们听不懂它们的语言。因为如果真是这样，既然它们有许多与我们相似的器官，它们就能像向同类表达思想一样容易地向我们表达思想。还有一点也非常值得注意：虽然有许多动物在某些行动中表现出比我们更多的灵巧，可是同样这些动物在另外许多行动中却毫无灵巧可言；所以，它们做得比我们好这一事实，并不证明它们有心灵，因为若是那样，就会推出它们的理性比我们任何人都多，在一切事情上都能胜过我们；恰恰相反，这倒证明它们没有理性，是自然按照它们器官的配置在它们身上起作用：正如我们看到的，一座只由齿轮和重锤组成的钟，能比我们凭全部技巧更准确地计算钟点、测量时间。

此后，我描述了理性灵魂，并说明它决不能像我所谈到的其他东西那样从物质的力量中引出来，而必须是被特别创造出来的；说明它像舵手在船上那样住在人体里是不够的，除非也许只是为了推动肢体；它必须与身体更紧密地结合、联合在一起，才能有和我们一样的感觉和欲望，从而构成一个真正的人。最后，我在这里相当详细地谈了灵魂这个题目，因为它是最重要的：因为除了否认上帝存在的那种错误（我想我已经充分驳斥了它）以外，再没有什么错误比这样一种假定更能把软弱的心灵引离美德的正路：以为禽兽的灵魂与我们的灵魂本性相同，因而我们在这一生之后，和苍蝇、蚂蚁一样，没有什么可希望的，也没有什么可害怕的；而当我们知道了它们相差多远，就能更好地理解那些证明灵魂具有完全独立于身体的本性、因而不会随身体一起死亡的理由；最后，既然看不到有别的原因能毁灭它，我们就自然地由此断定它是不朽的。


第六部分

自从我完成那篇包含所有这些内容的论著以来，已经过去三年了；我正开始修订它，打算交给印刷商，这时我得知，有一些人——我非常敬重他们，他们对我行为的权威，几乎不亚于我自己的理性对我思想的权威——谴责了不久前另一个人发表的某种物理学学说；我不愿说我曾赞同这种学说，只想说，在他们谴责它之前，我在其中没有看出任何我能想象到有害于宗教或国家的东西，因而也没有任何东西会阻止我把它写出来，如果理性使我相信它是真的；这使我担心，在我自己的学说中，是否也会有某一条背离了真理，尽管我一向十分小心，不相信任何我没有最确实的证明的新意见，也不写出任何可能伤害别人的东西。这已足以使我改变发表它们的打算；因为尽管使我下定那个决心的理由非常有力，但我一向不喜欢写书的性情，使我立刻就发现了别的一些理由，足以为我不承担这项工作开脱。这些正反两方面的理由是这样的：不仅在这里把它们说出来在某种程度上符合我的利益，而且让公众知道它们，也许也符合公众的利益。

我从来不大看重出自我自己心灵的东西；只要我从所用的方法中得到的好处，不过是在思辨学问的某些难题上使自己满意，或者努力按照它教给我的原则来规范我的行动，我就从来不认为自己有义务发表关于它的任何东西。因为在风俗方面，每个人都那样充满了自己的智慧，如果允许除了上帝立为他子民的最高统治者的人、或者上帝赐予了足够的恩典和热忱使之成为先知的人以外，任何人都来承担改良风俗的任务，那么，有多少颗脑袋，就会有多少个改革家；尽管我的思辨使我自己非常喜欢，我相信别人也有他们的思辨，也许使他们更喜欢。但一旦我获得了一些关于物理学的一般概念，开始在各种特殊的难题上试用它们，看出它们能把我们带多远，看出它们与迄今所用的原则有多大的不同，我就相信，如果把它们隐藏起来，就严重地违背了那条要求我们尽己所能增进人类普遍福祉的法则。因为我看出，借助它们，可以获得对生活非常有用的知识；可以发现一种实践的哲学，来代替学校里通常讲授的思辨哲学；借助这种实践哲学，我们认识了火、水、空气、星辰、天空以及环绕我们的其他一切物体的力量和作用，就像我们认识工匠们的各种手艺一样分明，我们也就能以同样的方式把它们应用于一切适合的用途，从而使我们成为自然的主人和占有者。这是一个值得向往的成果，不仅是为了发明无数的技艺，使我们能毫不费力地享受大地的果实和它所有的便利，而且也是、尤其是为了保持健康，健康无疑是这一生中一切福祉里首要的、根本的福祉；因为心灵如此密切地依赖于身体器官的状况和关系，所以如果有朝一日能找到什么办法使人比迄今更聪明、更灵巧，我相信必须到医学里去寻找。诚然，现有的医学里，用处很显著的东西很少；但我无意贬低它，我确信，即使在以医学为业的人当中，也没有一个人不承认，目前在医学中所知道的一切，与尚待发现的相比几乎等于零；如果我们对身体和心灵的无数疾病的原因，对自然为我们准备的一切药物，有了足够充分的知识，我们就能摆脱这些疾病，也许甚至能摆脱衰老的虚弱。但是，既然我打算用我的整个一生来寻求这样一门必要的学问，既然我碰上了一条道路，在我看来，谁走上它，只要不被生命的短促或实验的缺乏所阻碍，就必定能到达所希望的终点，我便断定，要防止这两种障碍，最有效的办法莫过于：我把自己所能发现的一点点东西都忠实地传达给公众，并激励那些才智更高的人努力继续前进，各自按照自己的志趣和能力，为必须做的实验出一份力，也把他们所发现的一切告诉公众；这样，后来的人从前人止步的地方开始，把许多人的生命和劳动连接起来，我们大家一起就能比每个人单独走得远得多。

此外，关于实验，我注意到，一个人的知识越进步，实验就越必要；因为在开始的时候，最好只利用那些自动呈现给我们感官的东西，只要我们对它们稍加思考，就不会对它们无知，而不要去关心那些较罕见、较深奥的现象：理由是，只要较平常的现象的原因还不知道，较罕见的现象往往只会把我们引入歧途；而且它们所依赖的情况几乎总是那样特殊、那样细微，极难察觉。但在这方面，我采取了以下的次序：首先，我努力一般地找出世界上存在的或可能存在的一切东西的原理或第一原因，为此我只考虑创造世界的上帝本身，并且只从我们心中天然存在的某些真理的种子中把它们引出来。其次，我审察了从这些原因可以推出的最初的、最平常的结果是什么；在我看来，我用这种方法找到了天空、星辰、一个地球，甚至在地球上找到了水、空气、火、矿物以及其他一些这类东西，它们是一切东西中最平常、最简单的，因而也最容易认识。此后，当我想下降到更特殊的东西时，呈现在我面前的对象是那样多种多样，以至于我相信，人的心灵不可能把地球上现有的物体的形式或种类，与上帝如果愿意本可以放在那里的无数其他物体区分开来，因而也不可能把它们应用于我们的用途，除非我们通过结果上升到原因，并利用许多特殊的实验。于是，我在心中把曾经呈现于我感官的一切对象都翻检了一遍，我敢坦率地说，我从来没有观察到任何一个我不能用我所发现的原理圆满解释的对象。但也必须承认，自然的力量是那样丰富广大，而这些原理又那样简单、那样普遍，所以我几乎没有观察到哪一个特殊的结果，我不能立刻认出它可以用许多不同的方式从这些原理推出来；我最大的困难通常在于发现这个结果是以其中哪一种方式依赖于这些原理的；因为要摆脱这个困难，我没有别的办法，只能再去寻找某些实验，它们的结果，如果我们必须用其中一种方式来解释，就会与必须用另一种方式来解释时不同。至于其余的，我想我现在已经能相当清楚地看出，为了做大多数可能有助于这个目的的实验，应当采取什么途径；但我也看出，这些实验是这样一些实验，而且数目这样多，以至于我的双手和我的收入，即使比现在多一千倍，也不够做完它们全部；所以，从今以后，我有条件做多少实验，我在认识自然上就会相应地取得多少进步。这就是我曾希望通过我写的那篇论著让人知道的，我希望那样清楚地展示由此会给公众带来的好处，以致能促使一切真心关怀人类共同福祉的人，也就是一切真正有德、而不只是外表上或在舆论看来有德的人，既把他们已经做过的实验告诉我，也帮助我做那些尚待去做的实验。

但从那时以来，我又想到了另一些理由，使我改变了看法，认为我确实应该继续把我认为有点重要的一切成果，一经检验其真实，就写下来，并且像打算发表它们那样用心对待它们。我之所以认为这样做好，一方面是因为这样我就给了自己更充分的动力去彻底审察它们，因为我们相信会有许多人读的东西，无疑总比只写给自己私用的东西审察得更仔细（常常有这样的事：我最初想到某个东西时觉得它是真的，着手把它写下来时，却觉得它是假的）；另一方面是因为这样我就不会失去任何尽我所能增进公众利益的机会，而且这样一来，如果我的著作有什么价值，在我死后得到它们的人，也就能把它们派上他们认为适当的用场。但我决心决不同意在我生前发表它们，免得它们可能引起的反对或争论，甚至它们可能给我带来的无论什么样的名声，会使我失去我为自我改进而留出的时间。因为尽管每个人确实都有义务尽自己的能力增进别人的福利，对谁都没有用处确实就是毫无价值，但同样真实的是，我们的关怀应当超出现在；当我们着眼于完成其他对后代有大得多的好处的目的时，不去做那些也许能给活着的人带来一点利益的事，是好的。说实话，我很愿意让人知道，我迄今学到的那一点点东西，与我所不知道的、而我并不绝望能够认识的东西相比，几乎等于零；因为在各门学问中逐步发现真理的人，就像那些发了财的人一样：他们发财以后获取大笔财富，比从前贫穷时获取小得多的数目还容易。或者可以把他们比作军队的统帅，他们的兵力通常随着胜利而增长，打了败仗之后要保全残余的部队，比打了胜仗之后攻城略地，需要更多的谨慎。因为真正在作战的，是那个努力克服一切阻碍他认识真理的困难和错误的人；在战斗中被打败的，是那个在任何有一定普遍性和重要性的问题上接受了错误意见的人，他此后要恢复原来的阵地，比一旦掌握了彻底确定的原理之后大举推进，需要多得多的本领。至于我自己，如果我在各门学问中成功地发现了一些真理（我相信这本书里所包含的东西会表明我已经发现了一些），我可以宣布，它们只不过是我所克服的五六个主要难题的结果和产物，我把同这些难题的交锋算作一场场战役，胜利都归于我。我甚至毫不犹豫地承认，我相信要充分实现我的计划，只需再打两三场同样的胜仗；而且我的年纪还不算太大，按照自然的通常进程，我还会有足够的闲暇来达到这个目的。但我越是期望能够正确地利用剩下的时间，就越认为自己有责任珍惜它；而如果我发表我的物理学原理，无疑会有许多事情来夺走我的时间：因为尽管这些原理几乎都那样明显，只要理解了它们就会赞同，尽管其中没有一条是我不期望能够给出证明的，但是，既然它们不可能与别人的种种不同意见都相符，我预见到，由于它们必定会引起的反对，我会常常被引离我的伟大计划。

也许有人会说，这些反对是有用的，既能使我意识到自己的错误，又能在我的思辨中有什么有价值的东西时，使别人对它有更充分的理解；而且，既然许多人比一个人看得更清楚，还能引导那些现在开始利用我的原理的人，反过来用他们的发现来帮助我。但尽管我承认自己极容易犯错，几乎从不相信自己最初想到的念头，我对别人可能对我的观点提出的反对意见的经验，却使我不指望从中得到什么好处。因为我已经多次领教过别人的判断，既有我当作朋友的人的，也有一些我以为对我漠不关心的人的，甚至还有一些人的，我知道他们的恶意和嫉妒会促使他们努力去发现那些被偏爱遮住了、我的朋友们看不见的东西。但很少有人向我提出什么我自己完全忽略了的反对意见，除非是离题很远的东西；所以我从来没有遇到过一个批评我意见的人，在我看来不是比我自己更不严格，就是比我自己更不公正。此外，我也从来没有看到，学校里所进行的那些辩论揭示出过任何以前不知道的真理；因为在每个人都力求取胜的时候，每个人更多关心的是怎样充分利用那些仅仅似乎有理的东西，而不是权衡问题正反两方面的理由；那些长期做好律师的人，以后并不因此就成为更好的法官。

至于别人从我传达我的思想中能得到的好处，也不会很大；因为我还没有把这些思想推进到不需要再补充很多东西就能付诸实践的程度。我想我可以毫不自负地说，如果有谁能把它们推进到那一步，那必定是我自己，而不是别人：这并不是说世上没有许多心灵比我的高明得无可比拟，而是因为一样东西从别人那里学来，就不如自己发现时那样容易把握、那样能化为己有。在这个题目上，情况尤其是这样：我常常向一些很敏锐的人解释我的某些意见，我说的时候，他们似乎非常分明地理解了，可是当他们复述的时候，我注意到，他们几乎总是把这些意见改变到我再也不能承认是我的了。我顺便乐于借这个机会请求后人：凡不是我自己发表的东西，决不要凭传闻就相信它出自我；我对那些我们没有他们自己著作的古代哲学家被归于的种种荒诞之说，一点也不惊奇；不过我并不因此就认为他们的思想真的是荒谬的，因为他们是他们那个时代最有才能的人，我只认为这些思想是被错误地转述给我们的。因此可以看到，他们的门徒中几乎没有一个人超过了他们；我确信，今天亚里士多德最忠实的追随者，如果能有他那样多的关于自然的知识，即使条件是以后再也不能达到更高的程度，他们也会认为自己是幸福的。在这一点上，他们就像常春藤，从不力求爬得比支撑它的树更高，甚至常常爬到树顶以后又往下长；因为在我看来，有些人也在下沉，也就是说，使自己比放弃研究时还更不明智：他们不满足于知道他们的作者讲得明白易懂的一切，还想在他那里找到许多难题的答案，而他对这些难题一句话也没有说过，也许连想都没有想过。不过，他们这种哲学思考的方式，倒很适合那些才能在平庸以下的人；因为他们所用的那些区分和原理的晦涩，使他们能够对一切事情都说得那样自信，仿佛他们真的知道一样，并且能够对付最精明、最灵巧的人，为他们关于任何题目所说的一切辩护，而谁也不能证明他们错了。在这一点上，他们在我看来就像一个瞎子，为了和一个看得见的人平等地打斗，就把对方引到一个漆黑的山洞的深处：我可以说，这样的人巴不得我不发表我所使用的哲学原理；因为这些原理是最简单、最明显的一类，我发表它们，就差不多等于打开窗户，让白昼的光照进那些打斗者所下到的山洞里。但是，即使是较高明的人，也没有理由急于知道这些原理，因为如果他们所希望的是能够谈论一切事情，获得博学的名声，那么，满足于真理的外表，比寻求真理本身更容易达到他们的目的；真理的外表在各种事情上都不难找到，而真理本身只是慢慢地、而且只在某些领域里显露出来，当我们必须谈到别的领域时，它就迫使我们坦率地承认自己的无知。不过，如果他们宁愿认识少数几条真理，而不愿虚荣地显得样样都懂——这样的知识无疑是更可取的——如果他们愿意走一条与我类似的道路，那么，为此我并不需要再说什么，只要我在这篇谈话里已经说过的就够了。因为如果他们能比我取得更大的进步，他们就更能自己去发现我自信已经找到的一切；既然我从来都是按次序审察一切的，那么确定无疑的是，尚待发现的东西本身，比我已经能够找到的更困难、更深奥，而从我这里学到它，远不如自己去发现它那样令人满足。此外，他们先寻求容易的东西，然后慢慢地、一步一步地走向更困难的东西，由此养成的习惯，会比我的一切指教都更有益于他们。就我自己来说，我确信，如果我从青年时代起就被教给了后来我寻求其证明的所有那些真理，从而不费力地学到了它们，那么我也许永远不会知道这些以外的任何真理；至少，我永远不会养成那种习惯和那种熟练，我想我是有的：只要我投身于寻求，总能相应地发现新的真理。一句话，如果世上有什么工作，别人不能像开始它的人那样把它做好，那就是我正在做的这件工作。

诚然，就可能有助于这个目的的实验而言，一个人是不能胜任把它们全部做完的；但在这项工作中，除了他自己的手以外，他也不能有效地利用别人的手，除非是工匠或同类的人，他可以付给他们工钱，而获利的希望（这是一种非常有效的手段）能激励他们准确地完成交给他们的事。至于那些出于好奇或求知的愿望，也许自愿向他提供帮助的人，除了一般说来他们许诺的多于做到的，画出许多美好的计划而从来没有一个实现以外，他们无疑还会期望他用解释某些难题来报答他们的辛劳，或者至少用恭维话和无用的谈话来报答，而他在这上面花任何一点时间都不会不受损失。至于别人已经做过的实验，即使那些人愿意主动告诉他（那些把它们看作秘密的人是决不会这样做的），这些实验大多也夹杂着那么多的情节和多余的成分，要把真相从附带的东西里理出来是极其困难的；此外，他会发现几乎所有的实验都描述得很糟，甚至是假的（因为做实验的人只想在其中看到他们认为符合自己原理的事实），所以，即使在全部实验里有一些性质适合他的目的，它们的价值也抵不上挑选它们所必需的时间。所以，如果有这样一个人，我们确实知道他能作出最高级的、对公众最有用的发现；如果所有其他的人因此都急于用一切办法帮助他成功地实现他的计划，我看他们能为他做的，也只不过是帮助承担可能必需的实验的费用；此外，就是防止他的闲暇被任何人不合时宜的打扰所剥夺。但是，我既没有把自己看得那么高，愿意许诺什么非凡的东西，也没有沉溺于那样虚妄的想象，以为公众必定对我的计划很感兴趣；另一方面，我也没有一个卑贱到能从任何人那里接受一种可以认为我不配得的恩惠的灵魂。

这些考虑合在一起，就是我在过去三年里不愿发表手头那篇论著的原因，也是我甚至决心在生前不发表任何其他如此一般的、或者能使人理解我的物理学原理的论著的原因。但从那以后，又有两个别的理由起了作用，使我决定在这里附上一些具体的样品，向公众交代一下我的工作和计划。在这些考虑中，第一个是：如果我不这样做，许多知道我先前打算发表一些著作的人，可能会以为使我不发表的那些理由，比实际情况更不光彩；因为尽管我并不过分渴望荣誉，甚至，如果我敢这样说的话，就荣誉妨碍我所最看重的安宁而言，我是厌恶它的，但同时我也从来没有像隐瞒罪行那样隐瞒我的行动，也没有采取许多预防措施来使自己默默无闻；这一方面是因为我会认为这样的做法是对自己的不公，另一方面是因为它会使我产生某种不安，而这又会违背我所追求的完全的心灵宁静。既然我这样对名声或被遗忘都同样淡然，却仍不能阻止自己得到某种名声，我想我有责任尽力使自己至少不被人说坏话。决定我把这些哲学样品写下来的另一个理由是：我一天比一天更清楚地感到，由于缺少我所需要的无数实验，我自我教育的计划正受到拖延，而没有别人的帮助，我是不可能做这些实验的；我虽然并不那么自我恭维，指望公众会大力关心我的利益，却也不愿在我对自己应尽的责任上欠缺到这种地步，以致给我身后的人留下口实，有一天责备我说：要不是我太疏忽，没有让他们知道他们可以用什么方法来促进我的计划的实现，我本可以留给他们许多比现在完善得多的东西。

我想，我不难选出一些题材，它们既不会引起太多的争论，也不会迫使我阐述比我所愿意的更多的原理，却又足以清楚地显示我在各门学问中能做到什么、不能做到什么。我在这方面是否成功了，不该由我来说；我也不想由我自己来谈论我的著作，以免抢在别人的判断之前；但如果人们审察它们，我会很高兴；为了使人更愿意这样做，我请求一切对它们有反对意见的人，费心把意见寄给我的出版人，他会通知我，以便我努力同时附上我的答复；这样，读者同时看到两者，就更容易判断真理在哪一边；因为我决不承诺在任何情况下都作冗长的答复，只承诺：如果我确信自己错了，就完全坦率地承认错误；如果我看不出错误，就只简单地说明我认为为我所写的东西辩护所需要的话，不附加任何新题材的解释，免得必须无休止地从一件事转到另一件事。

如果我在《屈光学》和《气象学》开头所谈的某些事情，乍看起来令人不快，因为我把它们叫作假说，似乎对证明它们漠不关心，我就请求人们耐心而专注地把全书读完，我希望犹疑的人会从中得到满意；因为在我看来，这些论著中的推理是如此相互联系，以致后面的由作为它们原因的前面的来证明，而前面的又反过来由作为它们结果的后面的来证明。也不要以为我在这里犯了逻辑学家所说的循环论证的错误；因为既然经验使这些结果中的大多数极其确实，我用来推出它们的原因，与其说是用来证实它们的实在性，不如说是用来解释它们的存在；相反，倒是原因的实在性由结果的实在性来证实。我把它们叫作假说，也没有别的目的，只是要让人知道：我认为我能够从我已经阐述过的那些最初的真理中推出它们；但我又特意决定不这样做，以免某一类心灵借此在他们以为是我的原理的东西上建立起某种荒诞的哲学，而让我受责备。我指的是那样一些人：别人花了二十年才想透的东西，只要对他们说上两三句，他们就以为一天之内就能完全掌握；或者，他们越是精细敏捷，就越容易犯错，越不能看出真理。至于那些真正完全是我自己的意见，我并不因为它们新而为它们道歉——因为我相信，如果好好考虑它们的理由，就会发现它们那样简单，那样符合常识，比在同样题目上可能持有的任何其他意见都显得更不奇特、更不悖理；我甚至也不夸耀自己是其中任何一个意见的最早发现者，只说我之所以采纳它们，既不是因为别人持有过它们，也不是因为别人没有持有过它们，而只是因为理性使我确信它们是真的。

尽管工匠们也许不能立刻制造出《屈光学》中所解释的那项发明，我并不认为任何人有权因此就谴责它；因为要制造和调整我所描述的那些机器，不忽略最小的细节，需要技巧和练习，所以如果他们第一次尝试就成功了，我的惊奇不会亚于看到一个人只是因为面前摆着很好的乐谱，就在一天之内成了技艺娴熟的吉他手。如果说我用我国的语言法语写作，而不用我老师们的语言拉丁语，那是因为我期望，那些运用自己天然的、没有成见的理性的人，会比那些只信古人著作的人更能判断我的意见；至于那些把良知与研究的习惯结合起来的人，也是我唯一希望的评判者，我确信，他们不会偏爱拉丁语到这种地步，只因为我用通俗的语言来阐述我的推理，就拒绝倾听。

最后，我不愿在这里具体地谈我期望将来在各门学问中取得的进步，也不愿用任何我没有把握能够履行的诺言来约束自己对公众的义务；我只想说：我已经决心把我还能活着的时间，全部用于一件事，就是努力获得一些关于自然的知识，这种知识要能使我们从中推出比现在所用的更确实的医学规则；我的志趣与其他一切追求都如此相背，特别是与那些对一些人有用就不能不对另一些人有害的追求相背，以至于如果由于什么情况我被迫从事这样的追求，我不相信自己能够成功。我在这里公开声明这一点，尽管我很清楚，它不能为我在世上博得任何重视，而这一点我也丝毫不在意；比起那些可能给我世上最高职位的人，我将永远更感激那些使我能不受打扰地享受我的隐居生活的人。