{"collection":"philosophy-ethics","full_text_available":true,"graph_url":"https://unchartedknowledge.5gfusion.net/v2/api/page/gutenberg_4391/graph","html_url":"https://unchartedknowledge.5gfusion.net/v2/page/gutenberg_4391","id":"gutenberg_4391","license":"Public Domain (US)","rights_basis":"gutenberg_metadata_copyright_false","source":"gutenberg","source_url":"https://www.gutenberg.org/ebooks/4391","summary":null,"tags":["Category: Philosophy & Ethics","Philosophy"],"text":"SELECTIONS FROM THE PRINCIPLES OF PHILOSOPHY\nOF\nRENE DESCARTES\n(1596-1650)\n\nTRANSLATED BY\nJOHN VEITCH, LL. D.\nLATE PROFESSOR OF LOGIC AND RHETORIC IN THE UNIVERSITY OF GLASGOW\n\n\n\n\nFrom the Publisher's Preface.\n\nThe present volume contains a reprint of the preface and the first\npart of the Principles of Philosophy, together with selections from\nthe second, third and fourth parts of that work, corresponding to\nthe extracts in the French edition of Gamier, are also given, as\nwell as an appendix containing part of Descartes' reply to the\nSecond Objections (viz., his formal demonstrations of the existence\nof Deity). The translation is based on the original Latin edition of\nthe Principles, published in 1644.\n\nThe work had been translated into French during Descartes' lifetime,\nand personally revised and corrected by him, the French text is\nevidently deserving of the same consideration as the Latin\noriginals, and consequently, the additions and variations of the\nFrench version have also been given--the additions being put in\nsquare brackets in the text and the variations in the footnotes.\n\nA copy of the title-page of the original edition, as given in Dr. C.\nGuttler's work (Munich: C. H. Beck. 1901), are also reproduced in\nthe present volume.\n\n\n\n\nSELECTIONS FROM THE PRINCIPLES OF PHILOSOPHY\nOF DESCARTES\n\nTRANSLATED FROM THE LATIN AND COLLATED WITH THE FRENCH\n\n\n\n\nLETTER OF THE AUTHOR\n\nTO THE FRENCH TRANSLATOR OF THE PRINCIPLES OF PHILOSOPHY SERVING FOR\nA PREFACE.\n\nSir,--The version of my principles which you have been at pains to\nmake, is so elegant and finished as to lead me to expect that the\nwork will be more generally read in French than in Latin, and better\nunderstood. The only apprehension I entertain is lest the title\nshould deter some who have not been brought up to letters, or with\nwhom philosophy is in bad repute, because the kind they were taught\nhas proved unsatisfactory; and this makes me think that it will be\nuseful to add a preface to it for the purpose of showing what the\nMATTER of the work is, what END I had in view in writing it, and\nwhat UTILITY may be derived from it. But although it might be my\npart to write a preface of this nature, seeing I ought to know those\nparticulars better than any other person, I cannot nevertheless\nprevail upon myself to do anything more than merely to give a\nsummary of the chief points that fall, as I think, to be discussed\nin it: and I leave it to your discretion to present to the public\nsuch part of them as you shall judge proper.\n\nI should have desired, in the first place, to explain in it what\nphilosophy is, by commencing with the most common matters, as, for\nexample, that the word PHILOSOPHY signifies the study of wisdom, and\nthat by wisdom is to be understood not merely prudence in the\nmanagement of affairs, but a perfect knowledge of all that man can\nknow, as well for the conduct of his life as for the preservation of\nhis health and the discovery of all the arts, and that knowledge to\nsubserve these ends must necessarily be deduced from first causes;\nso that in order to study the acquisition of it (which is properly\ncalled philosophizing), we must commence with the investigation of\nthose first causes which are called PRINCIPLES. Now these principles\nmust possess TWO CONDITIONS: in the first place, they must be so\nclear and evident that the human mind, when it attentively considers\nthem, cannot doubt of their truth; in the second place, the\nknowledge of other things must be so dependent on them as that\nthough the principles themselves may indeed be known apart from what\ndepends on them, the latter cannot nevertheless be known apart from\nthe former. It will accordingly be necessary thereafter to endeavour\nso to deduce from those principles the knowledge of the things that\ndepend on them, as that there may be nothing in the whole series of\ndeductions which is not perfectly manifest. God is in truth the only\nbeing who is absolutely wise, that is, who possesses a perfect\nknowledge of all things; but we may say that men are more or less\nwise as their knowledge of the most important truths is greater or\nless. And I am confident that there is nothing, in what I have now\nsaid, in which all the learned do not concur.\n\nI should, in the next place, have proposed to consider the utility\nof philosophy, and at the same time have shown that, since it\nembraces all that the human mind can know, we ought to believe that\nit is by it we are distinguished from savages and barbarians, and\nthat the civilisation and culture of a nation is regulated by the\ndegree in which true philosophy nourishes in it, and, accordingly,\nthat to contain true philosophers is the highest privilege a state\ncan enjoy. Besides this, I should have shown that, as regards\nindividuals, it is not only useful for each man to have intercourse\nwith those who apply themselves to this study, but that it is\nincomparably better he should himself direct his attention to it;\njust as it is doubtless to be preferred that a man should make use\nof his own eyes to direct his steps, and enjoy by means of the same\nthe beauties of colour and light, than that he should blindly follow\nthe guidance of another; though the latter course is certainly\nbetter than to have the eyes closed with no guide except one's self.\nBut to live without philosophizing is in truth the same as keeping\nthe eyes closed without attempting to open them; and the pleasure of\nseeing all that sight discloses is not to be compared with the\nsatisfaction afforded by the discoveries of philosophy. And,\nfinally, this study is more imperatively requisite for the\nregulation of our manners, and for conducting us through life, than\nis the use of our eyes for directing our steps. The brutes, which\nhave only their bodies to conserve, are continually occupied in\nseeking sources of nourishment; but men, of whom the chief part is\nthe mind, ought to make the search after wisdom their principal\ncare, for wisdom is the true nourishment of the mind; and I feel\nassured, moreover, that there are very many who would not fail in\nthe search, if they would but hope for success in it, and knew the\ndegree of their capabilities for it. There is no mind, how ignoble\nsoever it be, which remains so firmly bound up in the objects of the\nsenses, as not sometime or other to turn itself away from them in\nthe aspiration after some higher good, although not knowing\nfrequently wherein that good consists. The greatest favourites of\nfortune--those who have health, honours, and riches in abundance--\nare not more exempt from aspirations of this nature than others;\nnay, I am persuaded that these are the persons who sigh the most\ndeeply after another good greater and more perfect still than any\nthey already possess. But the supreme good, considered by natural\nreason without the light of faith, is nothing more than the\nknowledge of truth through its first causes, in other words, the\nwisdom of which philosophy is the study. And, as all these\nparticulars are indisputably true, all that is required to gain\nassent to their truth is that they be well stated.\n\nBut as one is restrained from assenting to these doctrines by\nexperience, which shows that they who make pretensions to philosophy\nare often less wise and reasonable than others who never applied\nthemselves to the study, I should have here shortly explained\nwherein consists all the science we now possess, and what are the\ndegrees of wisdom at which we have arrived. The first degree\ncontains only notions so clear of themselves that they can be\nacquired without meditation; the second comprehends all that the\nexperience of the senses dictates; the third, that which the\nconversation of other men teaches us; to which may be added as the\nfourth, the reading, not of all books, but especially of such as\nhave been written by persons capable of conveying proper\ninstruction, for it is a species of conversation we hold with their\nauthors. And it seems to me that all the wisdom we in ordinary\npossess is acquired only in these four ways; for I do not class\ndivine revelation among them, because it does not conduct us by\ndegrees, but elevates us at once to an infallible faith.\n\nThere have been, indeed, in all ages great minds who endeavoured to\nfind a fifth road to wisdom, incomparably more sure and elevated\nthan the other four. The path they essayed was the search of first\ncauses and true principles, from which might be deduced the reasons\nof all that can be known by man; and it is to them the appellation\nof philosophers has been more especially accorded. I am not aware\nthat there is any one of them up to the present who has succeeded in\nthis enterprise. The first and chief whose writings we possess are\nPlato and Aristotle, between whom there was no difference, except\nthat the former, following in the footsteps of his master, Socrates,\ningenuously confessed that he had never yet been able to find\nanything certain, and that he was contented to write what seemed to\nhim probable, imagining, for this end, certain principles by which\nhe endeavoured to account for the other things. Aristotle, on the\nother hand, characterised by less candour, although for twenty years\nthe disciple of Plato, and with no principles beyond those of his\nmaster, completely reversed his mode of putting them, and proposed\nas true and certain what it is probable he himself never esteemed as\nsuch. But these two men had acquired much judgment and wisdom by the\nfour preceding means, qualities which raised their authority very\nhigh, so much so that those who succeeded them were willing rather\nto acquiesce in their opinions, than to seek better for themselves.\nThe chief question among their disciples, however, was as to whether\nwe ought to doubt of all things or hold some as certain,--a dispute\nwhich led them on both sides into extravagant errors; for a part of\nthose who were for doubt, extended it even to the actions of life,\nto the neglect of the most ordinary rules required for its conduct;\nthose, on the other hand, who maintained the doctrine of certainty,\nsupposing that it must depend upon the senses, trusted entirely to\nthem. To such an extent was this carried by Epicurus, that it is\nsaid he ventured to affirm, contrary to all the reasonings of the\nastronomers, that the sun is no larger than it appears.\n\nIt is a fault we may remark in most disputes, that, as truth is the\nmean between the two opinions that are upheld, each disputant\ndeparts from it in proportion to the degree in which he possesses\nthe spirit of contradiction. But the error of those who leant too\nmuch to the side of doubt, was not followed for any length of time,\nand that of the opposite party has been to some extent corrected by\nthe doctrine that the senses are deceitful in many instances.\nNevertheless, I do not know that this error was wholly removed by\nshowing that certitude is not in the senses, but in the\nunderstanding alone when it has clear perceptions; and that while we\nonly possess the knowledge which is acquired in the first four\ngrades of wisdom, we ought not to doubt of the things that appear to\nbe true in what regards the conduct of life, nor esteem them as so\ncertain that we cannot change our opinions regarding them, even\nthough constrained by the evidence of reason.\n\nFrom ignorance of this truth, or, if there was any one to whom it\nwas known, from neglect of it, the majority of those who in these\nlater ages aspired to be philosophers, blindly followed Aristotle,\nso that they frequently corrupted the sense of his writings, and\nattributed to him various opinions which he would not recognise as\nhis own were he now to return to the world; and those who did not\nfollow him, among whom are to be found many of the greatest minds,\ndid yet not escape being imbued with his opinions in their youth, as\nthese form the staple of instruction in the schools; and thus their\nminds were so preoccupied that they could not rise to the knowledge\nof true principles. And though I hold all the philosophers in\nesteem, and am unwilling to incur odium by my censure, I can adduce\na proof of my assertion, which I do not think any of them will\ngainsay, which is, that they all laid down as a principle what they\ndid not perfectly know. For example, I know none of them who did not\nsuppose that there was gravity in terrestrial bodies; but although\nexperience shows us very clearly that bodies we call heavy descend\ntowards the center of the earth, we do not, therefore, know the\nnature of gravity, that is, the cause or principle in virtue of\nwhich bodies descend, and we must derive our knowledge of it from\nsome other source. The same may be said of a vacuum and atoms, of\nheat and cold, of dryness and humidity, and of salt, sulphur, and\nmercury, and the other things of this sort which some have adopted\nas their principles. But no conclusion deduced from a principle\nwhich is not clear can be evident, even although the deduction be\nformally valid; and hence it follows that no reasonings based on\nsuch principles could lead them to the certain knowledge of any one\nthing, nor consequently advance them one step in the search after\nwisdom. And if they did discover any truth, this was due to one or\nother of the four means above mentioned. Notwithstanding this, I am\nin no degree desirous to lessen the honour which each of them can\njustly claim; I am only constrained to say, for the consolation of\nthose who have not given their attention to study, that just as in\ntravelling, when we turn our back upon the place to which we were\ngoing, we recede the farther from it in proportion as we proceed in\nthe new direction for a greater length of time and with greater\nspeed, so that, though we may be afterwards brought back to the\nright way, we cannot nevertheless arrive at the destined place as\nsoon as if we had not moved backwards at all; so in philosophy, when\nwe make use of false principles, we depart the farther from the\nknowledge of truth and wisdom exactly in proportion to the care with\nwhich we cultivate them, and apply ourselves to the deduction of\ndiverse consequences from them, thinking that we are philosophizing\nwell, while we are only departing the farther from the truth; from\nwhich it must be inferred that they who have learned the least of\nall that has been hitherto distinguished by the name of philosophy\nare the most fitted for the apprehension of truth.\n\nAfter making those matters clear, I should, in the next place, have\ndesired to set forth the grounds for holding that the true\nprinciples by which we may reach that highest degree of wisdom\nwherein consists the sovereign good of human life, are those I have\nproposed in this work; and two considerations alone are sufficient\nto establish this--the first of which is, that these principles are\nvery clear, and the second, that we can deduce all other truths from\nthem; for it is only these two conditions that are required in true\nprinciples. But I easily prove that they are very clear; firstly, by\na reference to the manner in which I found them, namely, by\nrejecting all propositions that were in the least doubtful, for it\nis certain that such as could not be rejected by this test when they\nwere attentively considered, are the most evident and clear which\nthe human mind can know. Thus by considering that he who strives to\ndoubt of all is unable nevertheless to doubt that he is while he\ndoubts, and that what reasons thus, in not being able to doubt of\nitself and doubting nevertheless of everything else, is not that\nwhich we call our body, but what we name our mind or thought, I have\ntaken the existence of this thought for the first principle, from\nwhich I very clearly deduced the following truths, namely, that\nthere is a God who is the author of all that is in the world, and\nwho, being the source of all truth, cannot have created our\nunderstanding of such a nature as to be deceived in the judgments it\nforms of the things of which it possesses a very clear and distinct\nperception. Those are all the principles of which I avail myself\ntouching immaterial or metaphysical objects, from which I most\nclearly deduce these other principles of physical or corporeal\nthings, namely, that there are bodies extended in length, breadth,\nand depth, which are of diverse figures and are moved in a variety\nof ways. Such are in sum the principles from which I deduce all\nother truths. The second circumstance that proves the clearness of\nthese principles is, that they have been known in all ages, and even\nreceived as true and indubitable by all men, with the exception only\nof the existence of God, which has been doubted by some, because\nthey attributed too much to the perceptions of the senses, and God\ncan neither be seen nor touched.\n\nBut, though all the truths which I class among my principles were\nknown at all times, and by all men, nevertheless, there has been no\none up to the present, who, so far as I know, has adopted them as\nprinciples of philosophy: in other words, as such that we can deduce\nfrom them the knowledge of whatever else is in the world. It\naccordingly now remains for me to prove that they are such; and it\nappears to me that I cannot better establish this than by the test\nof experience: in other words, by inviting readers to peruse the\nfollowing work. For, though I have not treated in it of all matters-\n-that being impossible--I think I have so explained all of which I\nhad occasion to treat, that they who read it attentively will have\nground for the persuasion that it is unnecessary to seek for any\nother principles than those I have given, in order to arrive at the\nmost exalted knowledge of which the mind of man is capable;\nespecially if, after the perusal of my writings, they take the\ntrouble to consider how many diverse questions are therein discussed\nand explained, and, referring to the writings of others, they see\nhow little probability there is in the reasons that are adduced in\nexplanation of the same questions by principles different from mine.\nAnd that they may the more easily undertake this, I might have said\nthat those imbued with my doctrines have much less difficulty in\ncomprehending the writings of others, and estimating their true\nvalue, than those who have not been so imbued; and this is precisely\nthe opposite of what I before said of such as commenced with the\nancient philosophy, namely, that the more they have studied it the\nless fit are they for rightly apprehending the truth.\n\nI should also have added a word of advice regarding the manner of\nreading this work, which is, that I should wish the reader at first\nto go over the whole of it, as he would a romance, without greatly\nstraining his attention, or tarrying at the difficulties he may\nperhaps meet with in it, with the view simply of knowing in general\nthe matters of which I treat; and that afterwards, if they seem to\nhim to merit a more careful examination, and he feel a desire to\nknow their causes, he may read it a second time, in order to observe\nthe connection of my reasonings; but that he must not then give it\nup in despair, although he may not everywhere sufficiently discover\nthe connection of the proof, or understand all the reasonings--it\nbeing only necessary to mark with a pen the places where the\ndifficulties occur, and continue to read without interruption to the\nend; then, if he does not grudge to take up the book a third time, I\nam confident he will find in a fresh perusal the solution of most of\nthe difficulties he will have marked before; and that, if any still\nremain, their solution will in the end be found in another reading.\n\nI have observed, on examining the natural constitutions of different\nminds, that there are hardly any so dull or slow of understanding as\nto be incapable of apprehending good opinions, or even of acquiring\nall the highest sciences, if they be but conducted along the right\nroad. And this can also be proved by reason; for, as the principles\nare clear, and as nothing ought to be deduced from them, unless most\nmanifest inferences, no one is so devoid of intelligence as to be\nunable to comprehend the conclusions that flow from them. But,\nbesides the entanglement of prejudices, from which no one is\nentirely exempt, although it is they who have been the most ardent\nstudents of the false sciences that receive the greatest detriment\nfrom them, it happens very generally that people of ordinary\ncapacity neglect to study from a conviction that they want ability,\nand that others, who are more ardent, press on too rapidly: whence\nit comes to pass that they frequently admit principles far from\nevident, and draw doubtful inferences from them. For this reason, I\nshould wish to assure those who are too distrustful of their own\nability that there is nothing in my writings which they may not\nentirely understand, if they only take the trouble to examine them;\nand I should wish, at the same time, to warn those of an opposite\ntendency that even the most superior minds will have need of much\ntime and attention to remark all I designed to embrace therein.\n\nAfter this, that I might lead men to understand the real design I\nhad in publishing them, I should have wished here to explain the\norder which it seems to me one ought to follow with the view of\ninstructing himself. In the first place, a man who has merely the\nvulgar and imperfect knowledge which can be acquired by the four\nmeans above explained, ought, before all else, to endeavour to form\nfor himself a code of morals, sufficient to regulate the actions of\nhis life, as well for the reason that this does not admit of delay\nas because it ought to be our first care to live well. In the next\nplace, he ought to study Logic, not that of the schools, for it is\nonly, properly speaking, a dialectic which teaches the mode of\nexpounding to others what we already know, or even of speaking much,\nwithout judgment, of what we do not know, by which means it corrupts\nrather than increases good sense--but the logic which teaches the\nright conduct of the reason with the view of discovering the truths\nof which we are ignorant; and, because it greatly depends on usage,\nit is desirable he should exercise himself for a length of time in\npractising its rules on easy and simple questions, as those of the\nmathematics. Then, when he has acquired some skill in discovering\nthe truth in these questions, he should commence to apply himself in\nearnest to true philosophy, of which the first part is Metaphysics,\ncontaining the principles of knowledge, among which is the\nexplication of the principal attributes of God, of the immateriality\nof the soul, and of all the clear and simple notions that are in us;\nthe second is Physics, in which, after finding the true principles\nof material things, we examine, in general, how the whole universe\nhas been framed; in the next place, we consider, in particular, the\nnature of the earth, and of all the bodies that are most generally\nfound upon it, as air, water, fire, the loadstone and other\nminerals. In the next place it is necessary also to examine singly\nthe nature of plants, of animals, and above all of man, in order\nthat we may thereafter be able to discover the other sciences that\nare useful to us. Thus, all Philosophy is like a tree, of which\nMetaphysics is the root, Physics the trunk, and all the other\nsciences the branches that grow out of this trunk, which are reduced\nto three principal, namely, Medicine, Mechanics, and Ethics. By the\nscience of Morals, I understand the highest and most perfect which,\npresupposing an entire knowledge of the other sciences, is the last\ndegree of wisdom.\n\nBut as it is not from the roots or the trunks of trees that we\ngather the fruit, but only from the extremities of their branches,\nso the principal utility of philosophy depends on the separate uses\nof its parts, which we can only learn last of all. But, though I am\nignorant of almost all these, the zeal I have always felt in\nendeavouring to be of service to the public, was the reason why I\npublished, some ten or twelve years ago, certain Essays on the\ndoctrines I thought I had acquired. The first part of these Essays\nwas a \"Discourse on the Method of rightly conducting the Reason, and\nseeking Truth in the Sciences,\" in which I gave a summary of the\nprincipal rules of logic, and also of an imperfect ethic, which a\nperson may follow provisionally so long as he does not know any\nbetter. The other parts were three treatises: the first of\nDioptrics, the second of Meteors, and the third of Geometry. In the\nDioptrics, I designed to show that we might proceed far enough in\nphilosophy as to arrive, by its means, at the knowledge of the arts\nthat are useful to life, because the invention of the telescope, of\nwhich I there gave an explanation, is one of the most difficult that\nhas ever been made. In the treatise of Meteors, I desired to exhibit\nthe difference that subsists between the philosophy I cultivate and\nthat taught in the schools, in which the same matters are usually\ndiscussed. In fine, in the Geometry, I professed to demonstrate that\nI had discovered many things that were before unknown, and thus\nafford ground for believing that we may still discover many others,\nwith the view of thus stimulating all to the investigation of truth.\nSince that period, anticipating the difficulty which many would\nexperience in apprehending the foundations of the Metaphysics, I\nendeavoured to explain the chief points of them in a book of\nMeditations, which is not in itself large, but the size of which has\nbeen increased, and the matter greatly illustrated, by the\nObjections which several very learned persons sent to me on occasion\nof it, and by the Replies which I made to them. At length, after it\nappeared to me that those preceding treatises had sufficiently\nprepared the minds of my readers for the Principles of Philosophy, I\nalso published it; and I have divided this work into four parts, the\nfirst of which contains the principles of human knowledge, and which\nmay be called the First Philosophy, or Metaphysics. That this part,\naccordingly, may be properly understood, it will be necessary to\nread beforehand the book of Meditations I wrote on the same subject.\nThe other three parts contain all that is most general in Physics,\nnamely, the explication of the first laws or principles of nature,\nand the way in which the heavens, the fixed stars, the planets,\ncomets, and generally the whole universe, were composed; in the next\nplace, the explication, in particular, of the nature of this earth,\nthe air, water, fire, the magnet, which are the bodies we most\ncommonly find everywhere around it, and of all the qualities we\nobserve in these bodies, as light, heat, gravity, and the like. In\nthis way, it seems to me, I have commenced the orderly explanation\nof the whole of philosophy, without omitting any of the matters that\nought to precede the last which I discussed. But to bring this\nundertaking to its conclusion, I ought hereafter to explain, in the\nsame manner, the nature of the other more particular bodies that are\non the earth, namely, minerals, plants, animals, and especially man;\nfinally, to treat thereafter with accuracy of Medicine, Ethics, and\nMechanics. I should require to do this in order to give to the world\na complete body of philosophy; and I do not yet feel myself so old,-\n-I do not so much distrust my strength, nor do I find myself so far\nremoved from the knowledge of what remains, as that I should not\ndare to undertake to complete this design, provided I were in a\nposition to make all the experiments which I should require for the\nbasis and verification of my reasonings. But seeing that would\ndemand a great expenditure, to which the resources of a private\nindividual like myself would not be adequate, unless aided by the\npublic, and as I have no ground to expect this aid, I believe that I\nought for the future to content myself with studying for my own\ninstruction, and posterity will excuse me if I fail hereafter to\nlabour for them.\n\nMeanwhile, that it may be seen wherein I think I have already\npromoted the general good, I will here mention the fruits that may\nbe gathered from my Principles. The first is the satisfaction which\nthe mind will experience on finding in the work many truths before\nunknown; for although frequently truth does not so greatly affect\nour imagination as falsity and fiction, because it seems less\nwonderful and is more simple, yet the gratification it affords is\nalways more durable and solid. The second fruit is, that in studying\nthese principles we will become accustomed by degrees to judge\nbetter of all the things we come in contact with, and thus be made\nwiser, in which respect the effect will be quite the opposite of the\ncommon philosophy, for we may easily remark in those we call pedants\nthat it renders them less capable of rightly exercising their reason\nthan they would have been if they had never known it. The third is,\nthat the truths which they contain, being highly clear and certain,\nwill take away all ground of dispute, and thus dispose men's minds\nto gentleness and concord; whereas the contrary is the effect of the\ncontroversies of the schools, which, as they insensibly render those\nwho are exercised in them more wrangling and opinionative, are\nperhaps the prime cause of the heresies and dissensions that now\nharass the world. The last and chief fruit of these Principles is,\nthat one will be able, by cultivating them, to discover many truths\nI myself have not unfolded, and thus passing by degrees from one to\nanother, to acquire in course of time a perfect knowledge of the\nwhole of philosophy, and to rise to the highest degree of wisdom.\nFor just as all the arts, though in their beginnings they are rude\nand imperfect, are yet gradually perfected by practice, from their\ncontaining at first something true, and whose effect experience\nevinces; so in philosophy, when we have true principles, we cannot\nfail by following them to meet sometimes with other truths; and we\ncould not better prove the falsity of those of Aristotle, than by\nsaying that men made no progress in knowledge by their means during\nthe many ages they prosecuted them.\n\nI well know that there are some men so precipitate and accustomed to\nuse so little circumspection in what they do, that, even with the\nmost solid foundations, they could not rear a firm superstructure;\nand as it is usually those who are the readiest to make books, they\nwould in a short time mar all that I have done, and introduce\nuncertainty and doubt into my manner of philosophizing, from which I\nhave carefully endeavoured to banish them, if people were to receive\ntheir writings as mine, or as representing my opinions. I had, not\nlong ago, some experience of this in one of those who were believed\ndesirous of following me the most closely, [Footnote: Regius; see La\nVie de M. Descartes, reduite en abrege (Baillet). Liv. vii., chap.\nvii.--T.] and one too of whom I had somewhere said that I had such\nconfidence in his genius as to believe that he adhered to no\nopinions which I should not be ready to avow as mine; for he last\nyear published a book entitled \"Fundamental Physics,\" in which,\nalthough he seems to have written nothing on the subject of Physics\nand Medicine which he did not take from my writings, as well from\nthose I have published as from another still imperfect on the nature\nof animals, which fell into his hands; nevertheless, because he has\ncopied them badly, and changed the order, and denied certain\nmetaphysical truths upon which all Physics ought to be based, I am\nobliged wholly to disavow his work, and here to request readers not\nto attribute to me any opinion unless they find it expressly stated\nin my own writings, and to receive no opinion as true, whether in my\nwritings or elsewhere, unless they see that it is very clearly\ndeduced from true principles. I well know, likewise, that many ages\nmay elapse ere all the truths deducible from these principles are\nevolved out of them, as well because the greater number of such as\nremain to be discovered depend on certain particular experiments\nthat never occur by chance, but which require to be investigated\nwith care and expense by men of the highest intelligence, as because\nit will hardly happen that the same persons who have the sagacity to\nmake a right use of them, will possess also the means of making\nthem, and also because the majority of the best minds have formed so\nlow an estimate of philosophy in general, from the imperfections\nthey have remarked in the kind in vogue up to the present time, that\nthey cannot apply themselves to the search after truth.\n\nBut, in conclusion, if the difference discernible between the\nprinciples in question and those of every other system, and the\ngreat array of truths deducible from them, lead them to discern the\nimportance of continuing the search after these truths, and to\nobserve the degree of wisdom, the perfection and felicity of life,\nto which they are fitted to conduct us, I venture to believe that\nthere will not be found one who is not ready to labour hard in so\nprofitable a study, or at least to favour and aid with all his might\nthose who shall devote themselves to it with success.\n\nThe height of my wishes is, that posterity may sometime behold the\nhappy issue of it, etc.\n\n\n\n\nTO THE MOST SERENE PRINCESS,\n\nELIZABETH, ELDEST DAUGHTER OF FREDERICK, KING OF BOHEMIA, COUNT\nPALATINE, AND ELECTOR OF THE SACRED ROMAN EMPIRE.\n\nMADAM,--The greatest advantage I have derived from the writings\nwhich I have already published, has arisen from my having, through\nmeans of them, become known to your Highness, and thus been\nprivileged to hold occasional converse with one in whom so many rare\nand estimable qualities are united, as to lead me to believe I\nshould do service to the public by proposing them as an example to\nposterity. It would ill become me to flatter, or to give expression\nto anything of which I had no certain knowledge, especially in the\nfirst pages of a work in which I aim at laying down the principles\nof truth. And the generous modesty that is conspicuous in all your\nactions, assures me that the frank and simple judgment of a man who\nonly writes what he believes will be more agreeable to you than the\nornate laudations of those who have studied the art of compliment.\nFor this reason, I will give insertion to nothing in this letter for\nwhich I have not the certainty both of experience and reason; and in\nthe exordium, as in the rest of the work, I will write only as\nbecomes a philosopher. There is a vast difference between real and\napparent virtues; and there is also a great discrepancy between\nthose real virtues that proceed from an accurate knowledge of the\ntruth, and such as are accompanied with ignorance or error. The\nvirtues I call apparent are only, properly speaking, vices, which,\nas they are less frequent than the vices that are opposed to them,\nand are farther removed from them than the intermediate virtues, are\nusually held in higher esteem than those virtues. Thus, because\nthose who fear dangers too much are more numerous than they who fear\nthem too little, temerity is frequently opposed to the vice of\ntimidity, and taken for a virtue, and is commonly more highly\nesteemed than true fortitude. Thus, also, the prodigal are in\nordinary more praised than the liberal; and none more easily acquire\na great reputation for piety than the superstitious and\nhypocritical. With regard to true virtues, these do not all proceed\nfrom true knowledge, for there are some that likewise spring from\ndefect or error; thus, simplicity is frequently the source of\ngoodness, fear of devotion, and despair of courage. The virtues that\nare thus accompanied with some imperfections differ from each other,\nand have received diverse appellations. But those pure and perfect\nvirtues that arise from the knowledge of good alone are all of the\nsame nature, and may be comprised under the single term wisdom. For,\nwhoever owns the firm and constant resolution of always using his\nreason as well as lies in his power, and in all his actions of doing\nwhat he judges to be best, is truly wise, as far as his nature\npermits; and by this alone he is just, courageous, temperate, and\npossesses all the other virtues, but so well balanced as that none\nof them appears more prominent than another: and for this reason,\nalthough they are much more perfect than the virtues that blaze\nforth through the mixture of some defect, yet, because the crowd\nthus observes them less, they are not usually extolled so highly.\nBesides, of the two things that are requisite for the wisdom thus\ndescribed, namely, the perception of the understanding and the\ndisposition of the will, it is only that which lies in the will\nwhich all men can possess equally, inasmuch as the understanding of\nsome is inferior to that of others. But although those who have only\nan inferior understanding may be as perfectly wise as their nature\npermits, and may render themselves highly acceptable to God by their\nvirtue, provided they preserve always a firm and constant resolution\nto do all that they shall judge to be right, and to omit nothing\nthat may lead them to the knowledge of the duties of which they are\nignorant; nevertheless, those who preserve a constant resolution of\nperforming the right, and are especially careful in instructing\nthemselves, and who possess also a highly perspicacious intellect,\narrive doubtless at a higher degree of wisdom than others; and I see\nthat these three particulars are found in great perfection in your\nHighness. For, in the first place, your desire of self-instruction\nis manifest, from the circumstance that neither the amusements of\nthe court, nor the accustomed mode of educating ladies, which\nordinarily condemns them to ignorance, have been sufficient to\nprevent you from studying with much care all that is best in the\narts and sciences; and the incomparable perspicacity of your\nintellect is evinced by this, that you penetrated the secrets of the\nsciences and acquired an accurate knowledge of them in a very short\nperiod. But of the vigour of your intellect I have a still stronger\nproof, and one peculiar to myself, in that I have never yet met any\none who understood so generally and so well as yourself all that is\ncontained in my writings. For there are several, even among men of\nthe highest intellect and learning, who find them very obscure. And\nI remark, in almost all those who are versant in Metaphysics, that\nthey are wholly disinclined from Geometry; and, on the other hand,\nthat the cultivators of Geometry have no ability for the\ninvestigations of the First Philosophy: insomuch that I can say with\ntruth I know but one mind, and that is your own, to which both\nstudies are alike congenial, and which I therefore, with propriety,\ndesignate incomparable. But what most of all enhances my admiration\nis, that so accurate and varied an acquaintance with the whole\ncircle of the sciences is not found in some aged doctor who has\nemployed many years in contemplation, but in a Princess still young,\nand whose countenance and years would more fitly represent one of\nthe Graces than a Muse or the sage Minerva. In conclusion, I not\nonly remark in your Highness all that is requisite on the part of\nthe mind to perfect and sublime wisdom, but also all that can be\nrequired on the part of the will or the manners, in which benignity\nand gentleness are so conjoined with majesty that, though fortune\nhas attacked you with continued injustice, it has failed either to\nirritate or crush you. And this constrains me to such veneration\nthat I not only think this work due to you, since it treats of\nphilosophy which is the study of wisdom, but likewise feel not more\nzeal for my reputation as a philosopher than pleasure in subscribing\nmyself,--\n\nOf your most Serene Highness, The most devoted servant,\n\nDESCARTES.\n\n\n\n\nPART I.\nOF THE PRINCIPLES OF HUMAN KNOWLEDGE.\n\n\n I. THAT in order to seek truth, it is necessary once in the course\nof our life, to doubt, as far as possible, of all things.\n\nAs we were at one time children, and as we formed various judgments\nregarding the objects presented to our senses, when as yet we had\nnot the entire use of our reason, numerous prejudices stand in the\nway of our arriving at the knowledge of truth; and of these it seems\nimpossible for us to rid ourselves, unless we undertake, once in our\nlifetime, to doubt of all those things in which we may discover even\nthe smallest suspicion of uncertainty.\n\n\n II. That we ought also to consider as false all that is doubtful.\n\nMoreover, it will be useful likewise to esteem as false the things\nof which we shall be able to doubt, that we may with greater\nclearness discover what possesses most certainty and is the easiest\nto know.\n\n\n III. That we ought not meanwhile to make use of doubt in the\nconduct of life.\n\nIn the meantime, it is to be observed that we are to avail ourselves\nof this general doubt only while engaged in the contemplation of\ntruth. For, as far as concerns the conduct of life, we are very\nfrequently obliged to follow opinions merely probable, or even\nsometimes, though of two courses of action we may not perceive more\nprobability in the one than in the other, to choose one or other,\nseeing the opportunity of acting would not unfrequently pass away\nbefore we could free ourselves from our doubts.\n\n\n IV. Why we may doubt of sensible things.\n\nAccordingly, since we now only design to apply ourselves to the\ninvestigation of truth, we will doubt, first, whether of all the\nthings that have ever fallen under our senses, or which we have ever\nimagined, any one really exist; in the first place, because we know\nby experience that the senses sometimes err, and it would be\nimprudent to trust too much to what has even once deceived us;\nsecondly, because in dreams we perpetually seem to perceive or\nimagine innumerable objects which have no existence. And to one who\nhas thus resolved upon a general doubt, there appear no marks by\nwhich he can with certainty distinguish sleep from the waking state.\n\n\n V. Why we may also doubt of mathematical demonstrations.\n\nWe will also doubt of the other things we have before held as most\ncertain, even of the demonstrations of mathematics, and of their\nprinciples which we have hitherto deemed self-evident; in the first\nplace, because we have sometimes seen men fall into error in such\nmatters, and admit as absolutely certain and self evident what to us\nappeared false, but chiefly because we have learnt that God who\ncreated us is all-powerful; for we do not yet know whether perhaps\nit was his will to create us so that we are always deceived, even in\nthe things we think we know best: since this does not appear more\nimpossible than our being occasionally deceived, which, however, as\nobservation teaches us, is the case. And if we suppose that an all-\npowerful God is not the author of our being, and that we exist of\nourselves or by some other means, still, the less powerful we\nsuppose our author to be, the greater reason will we have for\nbelieving that we are not so perfect as that we may not be\ncontinually deceived.\n\n\n VI. That we possess a free-will, by which we can withhold our\nassent from what is doubtful, and thus avoid error.\n\nBut meanwhile, whoever in the end may be the author of our being,\nand however powerful and deceitful he may be, we are nevertheless\nconscious of a freedom, by which we can refrain from admitting to a\nplace in our belief aught that is not manifestly certain and\nundoubted, and thus guard against ever being deceived.\n\n\n VII. That we cannot doubt of our existence while we doubt, and that\nthis is the first knowledge we acquire when we philosophize in\norder.\n\nWhile we thus reject all of which we can entertain the smallest\ndoubt, and even imagine that it is false, we easily indeed suppose\nthat there is neither God, nor sky, nor bodies, and that we\nourselves even have neither hands nor feet, nor, finally, a body;\nbut we cannot in the same way suppose that we are not while we doubt\nof the truth of these things; for there is a repugnance in\nconceiving that what thinks does not exist at the very time when it\nthinks. Accordingly, the knowledge, _I_ THINK, THEREFORE _I_ AM, is\nthe first and most certain that occurs to one who philosophizes\norderly.\n\n\n VIII. That we hence discover the distinction between the mind and\nthe body, or between a thinking and corporeal thing.\n\nAnd this is the best mode of discovering the nature of the mind, and\nits distinctness from the body: for examining what we are, while\nsupposing, as we now do, that there is nothing really existing apart\nfrom our thought, we clearly perceive that neither extension, nor\nfigure, nor local motion,[Footnote: Instead of \"local motion,\" the\nFrench has \"existence in any place.\"] nor anything similar that can\nbe attributed to body, pertains to our nature, and nothing save\nthought alone; and, consequently, that the notion we have of our\nmind precedes that of any corporeal thing, and is more certain,\nseeing we still doubt whether there is any body in existence, while\nwe already perceive that we think.\n\n\n IX. What thought (COGITATIO) is.\n\nBy the word thought, I understand all that which so takes place in\nus that we of ourselves are immediately conscious of it; and,\naccordingly, not only to understand (INTELLIGERE, ENTENDRE), to will\n(VELLE), to imagine (IMAGINARI), but even to perceive (SENTIRE,\nSENTIR), are here the same as to think (COGITARE, PENSER). For if I\nsay, I see, or, I walk, therefore I am; and if I understand by\nvision or walking the act of my eyes or of my limbs, which is the\nwork of the body, the conclusion is not absolutely certain, because,\nas is often the case in dreams, I may think that I see or walk,\nalthough I do not open my eyes or move from my place, and even,\nperhaps, although I have no body: but, if I mean the sensation\nitself, or consciousness of seeing or walking, the knowledge is\nmanifestly certain, because it is then referred to the mind, which\nalone perceives or is conscious that it sees or walks. [Footnote: In\nthe French, \"which alone has the power of perceiving, or of being\nconscious in any other way whatever.\"]\n\n\n X. That the notions which are simplest and self-evident, are\nobscured by logical definitions; and that such are not to be\nreckoned among the cognitions acquired by study, [but as born with\nus].\n\nI do not here explain several other terms which I have used, or\ndesign to use in the sequel, because their meaning seems to me\nsufficiently self-evident. And I frequently remarked that\nphilosophers erred in attempting to explain, by logical definitions,\nsuch truths as are most simple and self-evident; for they thus only\nrendered them more obscure. And when I said that the proposition,\n_I_ THINK, THEREFORE _I_ AM, is of all others the first and most\ncertain which occurs to one philosophizing orderly, I did not\ntherefore deny that it was necessary to know what thought,\nexistence, and certitude are, and the truth that, in order to think\nit is necessary to be, and the like; but, because these are the most\nsimple notions, and such as of themselves afford the knowledge of\nnothing existing, I did not judge it proper there to enumerate them.\n\n\n XI. How we can know our mind more clearly than our body.\n\nBut now that it may be discerned how the knowledge we have of the\nmind not only precedes, and has greater certainty, but is even\nclearer, than that we have of the body, it must be remarked, as a\nmatter that is highly manifest by the natural light, that to nothing\nno affections or qualities belong; and, accordingly, that where we\nobserve certain affections, there a thing or substance to which\nthese pertain, is necessarily found. The same light also shows us\nthat we know a thing or substance more clearly in proportion as we\ndiscover in it a greater number of qualities. Now, it is manifest\nthat we remark a greater number of qualities in our mind than in any\nother thing; for there is no occasion on which we know anything\nwhatever when we are not at the same time led with much greater\ncertainty to the knowledge of our own mind. For example, if I judge\nthat there is an earth because I touch or see it, on the same\nground, and with still greater reason, I must be persuaded that my\nmind exists; for it may be, perhaps, that I think I touch the earth\nwhile there is one in existence; but it is not possible that I\nshould so judge, and my mind which thus judges not exist; and the\nsame holds good of whatever object is presented to our mind.\n\n\n XII. How it happens that every one does not come equally to know\nthis.\n\nThose who have not philosophized in order have had other opinions on\nthis subject, because they never distinguished with sufficient care\nthe mind from the body. For, although they had no difficulty in\nbelieving that they themselves existed, and that they had a higher\nassurance of this than of any other thing, nevertheless, as they did\nnot observe that by THEMSELVES, they ought here to understand their\nMINDS alone [when the question related to metaphysical certainty];\nand since, on the contrary, they rather meant their bodies which\nthey saw with their eyes, touched with their hands, and to which\nthey erroneously attributed the faculty of perception, they were\nprevented from distinctly apprehending the nature of the mind.\n\n\n XIII. In what sense the knowledge of other things depends upon the\nknowledge of God.\n\nBut when the mind, which thus knows itself but is still in doubt as\nto all other things, looks around on all sides, with a view to the\nfarther extension of its knowledge, it first of all discovers within\nitself the ideas of many things; and while it simply contemplates\nthem, and neither affirms nor denies that there is anything beyond\nitself corresponding to them, it is in no danger of erring. The mind\nalso discovers certain common notions out of which it frames various\ndemonstrations that carry conviction to such a degree as to render\ndoubt of their truth impossible, so long as we give attention to\nthem. For example, the mind has within itself ideas of numbers and\nfigures, and it has likewise among its common notions the principle\nTHAT IF EQUALS BE ADDED TO EQUALS THE WHOLES WILL BE EQUAL and the\nlike; from which it is easy to demonstrate that the three angles of\na triangle are equal to two right angles, etc. Now, so long as we\nattend to the premises from which this conclusion and others similar\nto it were deduced, we feel assured of their truth; but, as the mind\ncannot always think of these with attention, when it has the\nremembrance of a conclusion without recollecting the order of its\ndeduction, and is uncertain whether the author of its being has\ncreated it of a nature that is liable to be deceived, even in what\nappears most evident, it perceives that there is just ground to\ndistrust the truth of such conclusions, and that it cannot possess\nany certain knowledge until it has discovered its author.\n\n\n XIV. That we may validly infer the existence of God from necessary\nexistence being comprised in the concept we have of him.\n\nWhen the mind afterwards reviews the different ideas that are in it,\nit discovers what is by far the chief among them--that of a Being\nomniscient, all-powerful, and absolutely perfect; and it observes\nthat in this idea there is contained not only possible and\ncontingent existence, as in the ideas of all other things which it\nclearly perceives, but existence absolutely necessary and eternal.\nAnd just as because, for example, the equality of its three angles\nto two right angles is necessarily comprised in the idea of a\ntriangle, the mind is firmly persuaded that the three angles of a\ntriangle are equal to two right angles; so, from its perceiving\nnecessary and eternal existence to be comprised in the idea which it\nhas of an all-perfect Being, it ought manifestly to conclude that\nthis all-perfect Being exists.\n\n\n XV. That necessary existence is not in the same way comprised in\nthe notions which we have of other things, but merely contingent\nexistence.\n\nThe mind will be still more certain of the truth of this conclusion,\nif it consider that it has no idea of any other thing in which it\ncan discover that necessary existence is contained; for, from this\ncircumstance alone, it will discern that the idea of an all-perfect\nBeing has not been framed by itself, and that it does not represent\na chimera, but a true and immutable nature, which must exist since\nit can only be conceived as necessarily existing.\n\n\n XVI. That prejudices hinder many from clearly knowing the necessity\nof the existence of God.\n\nOur mind would have no difficulty in assenting to this truth, if it\nwere, first of all, wholly free from prejudices; but as we have been\naccustomed to distinguish, in all other things, essence from\nexistence, and to imagine at will many ideas of things which neither\nare nor have been, it easily happens, when we do not steadily fix\nour thoughts on the contemplation of the all-perfect Being, that a\ndoubt arises as to whether the idea we have of him is not one of\nthose which we frame at pleasure, or at least of that class to whose\nessence existence does not pertain.\n\n\n XVII. That the greater objective (representative) perfection there\nis in our idea of a thing, the greater also must be the perfection\nof its cause.\n\nWhen we further reflect on the various ideas that are in us, it is\neasy to perceive that there is not much difference among them, when\nwe consider them simply as certain modes of thinking, but that they\nare widely different, considered in reference to the objects they\nrepresent; and that their causes must be so much the more perfect\naccording to the degree of objective perfection contained in them.\n[Footnote: \"as what they represent of their object has more\nperfection.\"--FRENCH.] For there is no difference between this and\nthe case of a person who has the idea of a machine, in the\nconstruction of which great skill is displayed, in which\ncircumstances we have a right to inquire how he came by this idea,\nwhether, for example, he somewhere saw such a machine constructed by\nanother, or whether he was so accurately taught the mechanical\nsciences, or is endowed with such force of genius, that he was able\nof himself to invent it, without having elsewhere seen anything like\nit; for all the ingenuity which is contained in the idea objectively\nonly, or as it were in a picture, must exist at least in its first\nand chief cause, whatever that may be, not only objectively or\nrepresentatively, but in truth formally or eminently.\n\n\n XVIII. That the existence of God may be again inferred from the\nabove.\n\nThus, because we discover in our minds the idea of God, or of an\nall-perfect Being, we have a right to inquire into the source whence\nwe derive it; and we will discover that the perfections it\nrepresents are so immense as to render it quite certain that we\ncould only derive it from an all-perfect Being; that is, from a God\nreally existing. For it is not only manifest by the natural light\nthat nothing cannot be the cause of anything whatever, and that the\nmore perfect cannot arise from the less perfect, so as to be thereby\nproduced as by its efficient and total cause, but also that it is\nimpossible we can have the idea or representation of anything\nwhatever, unless there be somewhere, either in us or out of us, an\noriginal which comprises, in reality, all the perfections that are\nthus represented to us; but, as we do not in any way find in\nourselves those absolute perfections of which we have the idea, we\nmust conclude that they exist in some nature different from ours,\nthat is, in God, or at least that they were once in him; and it most\nmanifestly follows [from their infinity] that they are still there.\n\n\n XIX. That, although we may not comprehend the nature of God, there\nis yet nothing which we know so clearly as his perfections.\n\nThis will appear sufficiently certain and manifest to those who have\nbeen accustomed to contemplate the idea of God, and to turn their\nthoughts to his infinite perfections; for, although we may not\ncomprehend them, because it is of the nature of the infinite not to\nbe comprehended by what is finite, we nevertheless conceive them\nmore clearly and distinctly than material objects, for this reason,\nthat, being simple, and unobscured by limits,[Footnote: After\nLIMITS, \"what of them we do conceive is much less confused. There\nis, besides, no speculation more calculated to aid in perfecting our\nunderstanding, and which is more important than this, inasmuch as\nthe consideration of an object that has no limits to its perfections\nfills us with satisfaction and assurance.\"-FRENCH.] they occupy our\nmind more fully.\n\n\n XX. That we are not the cause of ourselves, but that this is God,\nand consequently that there is a God.\n\nBut, because every one has not observed this, and because, when we\nhave an idea of any machine in which great skill is displayed, we\nusually know with sufficient accuracy the manner in which we\nobtained it, and as we cannot even recollect when the idea we have\nof a God was communicated to us by him, seeing it was always in our\nminds, it is still necessary that we should continue our review, and\nmake inquiry after our author, possessing, as we do, the idea of the\ninfinite perfections of a God: for it is in the highest degree\nevident by the natural light, that that which knows something more\nperfect than itself, is not the source of its own being, since it\nwould thus have given to itself all the perfections which it knows;\nand that, consequently, it could draw its origin from no other being\nthan from him who possesses in himself all those perfections, that\nis, from God.\n\n\n XXI. That the duration alone of our life is sufficient to\ndemonstrate the existence of God.\n\nThe truth of this demonstration will clearly appear, provided we\nconsider the nature of time, or the duration of things; for this is\nof such a kind that its parts are not mutually dependent, and never\nco-existent; and, accordingly, from the fact that we now are, it\ndoes not necessarily follow that we shall be a moment afterwards,\nunless some cause, viz., that which first produced us, shall, as it\nwere, continually reproduce us, that is, conserve us. For we easily\nunderstand that there is no power in us by which we can conserve\nourselves, and that the being who has so much power as to conserve\nus out of himself, must also by so much the greater reason conserve\nhimself, or rather stand in need of being conserved by no one\nwhatever, and, in fine, be God.\n\n\n XXII. That in knowing the existence of God, in the manner here\nexplained, we likewise know all his attributes, as far as they can\nbe known by the natural light alone.\n\nThere is the great advantage in proving the existence of God in this\nway, viz., by his idea, that we at the same time know what he is, as\nfar as the weakness of our nature allows; for, reflecting on the\nidea we have of him which is born with us, we perceive that he is\neternal, omniscient, omnipotent, the source of all goodness and\ntruth, creator of all things, and that, in fine, he has in himself\nall that in which we can clearly discover any infinite perfection or\ngood that is not limited by any imperfection.\n\n\n XXIII. That God is not corporeal, and does not perceive by means of\nsenses as we do, or will the evil of sin.\n\nFor there are indeed many things in the world that are to a certain\nextent imperfect or limited, though possessing also some perfection;\nand it is accordingly impossible that any such can be in God. Thus,\nlooking to corporeal nature,[Footnote: In the French, \"since\nextension constitutes the nature of body.\"] since divisibility is\nincluded in local extension, and this indicates imperfection, it is\ncertain that God is not body. And although in men it is to some\ndegree a perfection to be capable of perceiving by means of the\nsenses, nevertheless since in every sense there is passivity\n[Footnote: In the French, \"because our perceptions arise from\nimpressions made upon us from another source,\" i.e., than\nourselves.] which indicates dependency, we must conclude that God is\nin no manner possessed of senses, and that he only understands and\nwills, not, however, like us, by acts in any way distinct, but\nalways by an act that is one, identical, and the simplest possible,\nunderstands, wills, and operates all, that is, all things that in\nreality exist; for he does not will the evil of sin, seeing this is\nbut the negation of being.\n\n\n XXIV. That in passing from the knowledge of God to the knowledge of\nthe creatures, it is necessary to remember that our understanding is\nfinite, and the power of God infinite.\n\nBut as we know that God alone is the true cause of all that is or\ncan be, we will doubtless follow the best way of philosophizing, if,\nfrom the knowledge we have of God himself, we pass to the\nexplication of the things which he has created, and essay to deduce\nit from the notions that are naturally in our minds, for we will\nthus obtain the most perfect science, that is, the knowledge of\neffects through their causes. But that we may be able to make this\nattempt with sufficient security from error, we must use the\nprecaution to bear in mind as much as possible that God, who is the\nauthor of things, is infinite, while we are wholly finite.\n\n\n XXV. That we must believe all that God has revealed, although it\nmay surpass the reach of our faculties.\n\nThus, if perhaps God reveal to us or others, matters concerning\nhimself which surpass the natural powers of our mind, such as the\nmysteries of the incarnation and of the trinity, we will not refuse\nto believe them, although we may not clearly understand them; nor\nwill we be in any way surprised to find in the immensity of his\nnature, or even in what he has created, many things that exceed our\ncomprehension.\n\n\n XXVI. That it is not needful to enter into disputes [Footnote: \"to\nessay to comprehend the infinite.\"--FRENCH.] regarding the infinite,\nbut merely to hold all that in which we can find no limits as\nindefinite, such as the extension of the world, the divisibility of\nthe parts of matter, the number of the stars, etc.\n\nWe will thus never embarrass ourselves by disputes about the\ninfinite, seeing it would be absurd for us who are finite to\nundertake to determine anything regarding it, and thus as it were to\nlimit it by endeavouring to comprehend it. We will accordingly give\nourselves no concern to reply to those who demand whether the half\nof an infinite line is also infinite, and whether an infinite number\nis even or odd, and the like, because it is only such as imagine\ntheir minds to be infinite who seem bound to entertain questions of\nthis sort. And, for our part, looking to all those things in which\nin certain senses, we discover no limits, we will not, therefore,\naffirm that they are infinite, but will regard them simply as\nindefinite. Thus, because we cannot imagine extension so great that\nwe cannot still conceive greater, we will say that the magnitude of\npossible things is indefinite, and because a body cannot be divided\ninto parts so small that each of these may not be conceived as again\ndivided into others still smaller, let us regard quantity as\ndivisible into parts whose number is indefinite; and as we cannot\nimagine so many stars that it would seem impossible for God to\ncreate more, let us suppose that their number is indefinite, and so\nin other instances.\n\n\n XXVII. What difference there is between the indefinite and the\ninfinite.\n\nAnd we will call those things indefinite rather than infinite, with\nthe view of reserving to God alone the appellation of infinite; in\nthe first place, because not only do we discover in him alone no\nlimits on any side, but also because we positively conceive that he\nadmits of none; and in the second place, because we do not in the\nsame way positively conceive that other things are in every part\nunlimited, but merely negatively admit that their limits, if they\nhave any, cannot be discovered by us.\n\n\n XXVIII. That we must examine, not the final, but the efficient,\ncauses of created things.\n\nLikewise, finally, we will not seek reasons of natural things from\nthe end which God or nature proposed to himself in their creation\n(i. e., final causes), [Footnote: \"We will not stop to consider the\nends which God proposed to himself in the creation of the world, and\nwe will entirely reject from our philosophy the search of final\ncauses!\"--French.] for we ought not to presume so far as to think\nthat we are sharers in the counsels of Deity, but, considering him\nas the efficient cause of all things, let us endeavour to discover\nby the natural light [Footnote: \"Faculty of reasoning.\"--FRENCH.]\nwhich he has planted in us, applied to those of his attributes of\nwhich he has been willing we should have some knowledge, what must\nbe concluded regarding those effects we perceive by our senses;\nbearing in mind, however, what has been already said, that we must\nonly confide in this natural light so long as nothing contrary to\nits dictates is revealed by God himself. [Footnote: The last clause,\nbeginning \"bearing in mind.\" is omitted in the French.]\n\n\n XXIX. That God is not the cause of our errors.\n\nThe first attribute of God which here falls to be considered, is\nthat he is absolutely veracious and the source of all light, so that\nit is plainly repugnant for him to deceive us, or to be properly and\npositively the cause of the errors to which we are consciously\nsubject; for although the address to deceive seems to be some mark\nof subtlety of mind among men, yet without doubt the will to deceive\nonly proceeds from malice or from fear and weakness, and\nconsequently cannot be attributed to God.\n\n\n XXX. That consequently all which we clearly perceive is true, and\nthat we are thus delivered from the doubts above proposed.\n\nWhence it follows, that the light of nature, or faculty of knowledge\ngiven us by God, can never compass any object which is not true, in\nas far as it attains to a knowledge of it, that is, in as far as the\nobject is clearly and distinctly apprehended. For God would have\nmerited the appellation of a deceiver if he had given us this\nfaculty perverted, and such as might lead us to take falsity for\ntruth [when we used it aright]. Thus the highest doubt is removed,\nwhich arose from our ignorance on the point as to whether perhaps\nour nature was such that we might be deceived even in those things\nthat appear to us the most evident. The same principle ought also to\nbe of avail against all the other grounds of doubting that have been\nalready enumerated. For mathematical truths ought now to be above\nsuspicion, since these are of the clearest. And if we perceive\nanything by our senses, whether while awake or asleep, we will\neasily discover the truth provided we separate what there is of\nclear and distinct in the knowledge from what is obscure and\nconfused. There is no need that I should here say more on this\nsubject, since it has already received ample treatment in the\nmetaphysical Meditations; and what follows will serve to explain it\nstill more accurately.\n\n\n XXXI. That our errors are, in respect of God, merely negations,\nbut, in respect of ourselves, privations.\n\nBut as it happens that we frequently fall into error, although God\nis no deceiver, if we desire to inquire into the origin and cause of\nour errors, with a view to guard against them, it is necessary to\nobserve that they depend less on our understanding than on our will,\nand that they have no need of the actual concourse of God, in order\nto their production; so that, when considered in reference to God,\nthey are merely negations, but in reference to ourselves,\nprivations.\n\n\n XXXII. That there are only two modes of thinking in us, viz., the\nperception of the understanding and the action of the will.\n\nFor all the modes of thinking of which we are conscious may be\nreferred to two general classes, the one of which is the perception\nor operation of the understanding, and the other the volition or\noperation of the will. Thus, to perceive by the senses (SENTIRE), to\nimagine, and to conceive things purely intelligible, are only\ndifferent modes of perceiving (PERCIP IENDI); but to desire, to be\naverse from, to affirm, to deny, to doubt, are different modes of\nwilling.\n\n\n XXXIII. That we never err unless when we judge of something which\nwe do not sufficiently apprehend.\n\nWhen we apprehend anything we are in no danger of error, if we\nrefrain from judging of it in any way; and even when we have formed\na judgment regarding it, we would never fall into error, provided we\ngave our assent only to what we clearly and distinctly perceived;\nbut the reason why we are usually deceived, is that we judge without\npossessing an exact knowledge of that of which we judge.\n\n\n XXXIV. That the will as well as the understanding is required for\njudging.\n\nI admit that the understanding is necessary for judging, there being\nno room to suppose that we can judge of that which we in no way\napprehend; but the will also is required in order to our assenting\nto what we have in any degree perceived. It is not necessary,\nhowever, at least to form any judgment whatever, that we have an\nentire and perfect apprehension of a thing; for we may assent to\nmany things of which we have only a very obscure and confused\nknowledge.\n\n\n XXXV. That the will is of greater extension than the understanding,\nand is thus the source of our errors.\n\nFurther, the perception of the intellect extends only to the few\nthings that are presented to it, and is always very limited: the\nwill, on the other hand, may, in a certain sense, be said to be\ninfinite, because we observe nothing that can be the object of the\nwill of any other, even of the unlimited will of God, to which ours\ncannot also extend, so that we easily carry it beyond the objects we\nclearly perceive; and when we do this, it is not wonderful that we\nhappen to be deceived.\n\n\n XXXVI. That our errors cannot be imputed to God.\n\nBut although God has not given us an omniscient understanding, he is\nnot on this account to be considered in any wise the author of our\nerrors, for it is of the nature of created intellect to be finite,\nand of finite intellect not to embrace all things.\n\n\n XXXVII. That the chief perfection of man is his being able to act\nfreely or by will, and that it is this which renders him worthy of\npraise or blame.\n\nThat the will should be the more extensive is in harmony with its\nnature: and it is a high perfection in man to be able to act by\nmeans of it, that is, freely; and thus in a peculiar way to be the\nmaster of his own actions, and merit praise or blame. For self-\nacting machines are not commended because they perform with\nexactness all the movements for which they were adapted, seeing\ntheir motions are carried on necessarily; but the maker of them is\npraised on account of the exactness with which they were framed,\nbecause he did not act of necessity, but freely; and, on the same\nprinciple, we must attribute to ourselves something more on this\naccount, that when we embrace truth, we do so not of necessity, but\nfreely.\n\n\n XXXVIII. That error is a defect in our mode of acting, not in our\nnature; and that the faults of their subjects may be frequently\nattributed to other masters, but never to God.\n\nIt is true, that as often as we err, there is some defect in our\nmode of action or in the use of our liberty, but not in our nature,\nbecause this is always the same, whether our judgments be true or\nfalse. And although God could have given to us such perspicacity of\nintellect that we should never have erred, we have, notwithstanding,\nno right to demand this of him; for, although with us he who was\nable to prevent evil and did not is held guilty of it, God is not in\nthe same way to be reckoned responsible for our errors because he\nhad the power to prevent them, inasmuch as the dominion which some\nmen possess over others has been instituted for the purpose of\nenabling them to hinder those under them from doing evil, whereas\nthe dominion which God exercises over the universe is perfectly\nabsolute and free. For this reason we ought to thank him for the\ngoods he has given us, and not complain that he has not blessed us\nwith all which we know it was in his power to impart.\n\n\n XXXIX. That the liberty of our will is self-evident.\n\nFinally, it is so manifest that we possess a free will, capable of\ngiving or withholding its assent, that this truth must be reckoned\namong the first and most common notions which are born with us.\nThis, indeed, has already very clearly appeared, for when essaying\nto doubt of all things, we went so far as to suppose even that he\nwho created us employed his limitless power in deceiving us in every\nway, we were conscious nevertheless of being free to abstain from\nbelieving what was not in every respect certain and undoubted. But\nthat of which we are unable to doubt at such a time is as self-\nevident and clear as any thing we can ever know.\n\n\n XL. That it is likewise certain that God has fore-ordained all\nthings.\n\nBut because what we have already discovered of God, gives us the\nassurance that his power is so immense that we would sin in thinking\nourselves capable of ever doing anything which he had not ordained\nbeforehand, we should soon be embarrassed in great difficulties if\nwe undertook to harmonise the pre-ordination of God with the freedom\nof our will, and endeavoured to comprehend both truths at once.\n\n\n XLI. How the freedom of our will may be reconciled with the Divine\npre-ordination.\n\nBut, in place of this, we will be free from these embarrassments if\nwe recollect that our mind is limited, while the power of God, by\nwhich he not only knew from all eternity what is or can be, but also\nwilled and pre-ordained it, is infinite. It thus happens that we\npossess sufficient intelligence to know clearly and distinctly that\nthis power is in God, but not enough to comprehend how he leaves the\nfree actions of men indeterminate} and, on the other hand, we have\nsuch consciousness of the liberty and indifference which exists in\nourselves, that there is nothing we more clearly or perfectly\ncomprehend: [so that the omnipotence of God ought not to keep us\nfrom believing it]. For it would be absurd to doubt of that of which\nwe are fully conscious, and which we experience as existing in\nourselves, because we do not comprehend another matter which, from\nits very nature, we know to be incomprehensible.\n\n\n XLII. How, although we never will to err, it is nevertheless by our\nwill that we do err.\n\nBut now since we know that all our errors depend upon our will, and\nas no one wishes to deceive himself, it may seem wonderful that\nthere is any error in our judgments at all. It is necessary to\nremark, however, that there is a great difference between willing to\nbe deceived, and willing to yield assent to opinions in which it\nhappens that error is found. For though there is no one who\nexpressly wishes to fall into error, we will yet hardly find any one\nwho is not ready to assent to things in which, unknown to himself,\nerror lurks; and it even frequently happens that it is the desire\nitself of following after truth that leads those not fully aware of\nthe order in which it ought to be sought for, to pass judgment on\nmatters of which they have no adequate knowledge, and thus to fall\ninto error.\n\n\n XLIII. That we shall never err if we give our assent only to what\nwe clearly and distinctly perceive.\n\nBut it is certain we will never admit falsity for truth, so long as\nwe judge only of that which we clearly and distinctly perceive;\nbecause, as God is no deceiver, the faculty of knowledge which he\nhas given us cannot be fallacious, nor, for the same reason, the\nfaculty of will, when we do not extend it beyond the objects we\nclearly know. And even although this truth could not be established\nby reasoning, the minds of all have been so impressed by nature as\nspontaneously to assent to whatever is clearly perceived, and to\nexperience an impossibility to doubt of its truth.\n\n\n XLIV. That we uniformly judge improperly when we assent to what we\ndo not clearly perceive, although our judgment may chance to be\ntrue; and that it is frequently our memory which deceives us by\nleading us to believe that certain things were formerly sufficiently\nunderstood by us.\n\nIt is likewise certain that, when we approve of any reason which we\ndo not apprehend, we are either deceived, or, if we stumble on the\ntruth, it is only by chance, and thus we can never possess the\nassurance that we are not in error. I confess it seldom happens that\nwe judge of a thing when we have observed we do not apprehend it,\nbecause it is a dictate of the natural light never to judge of what\nwe do not know. But we most frequently err in this, that we presume\nupon a past knowledge of much to which we give our assent, as to\nsomething treasured up in the memory, and perfectly known to us;\nwhereas, in truth, we have no such knowledge.\n\n\n XLV. What constitutes clear and distinct perception.\n\nThere are indeed a great many persons who, through their whole\nlifetime, never perceive anything in a way necessary for judging of\nit properly; for the knowledge upon which we can establish a certain\nand indubitable judgment must be not only clear, but also, distinct.\nI call that clear which is present and manifest to the mind giving\nattention to it, just as we are said clearly to see objects when,\nbeing present to the eye looking on, they stimulate it with\nsufficient force. and it is disposed to regard them; but the\ndistinct is that which is so precise and different from all other\nobjects as to comprehend in itself only what is clear. [Footnote:\n\"what appears manifestly to him who considers it as he ought.\"--\nFRENCH.]\n\n\n XLVI. It is shown, from the example of pain, that a perception may\nbe clear without being distinct, but that it cannot be distinct\nunless it is clear.\n\nFor example, when any one feels intense pain, the knowledge which he\nhas of this pain is very clear, but it is not always distinct; for\nmen usually confound it with the obscure judgment they form\nregarding its nature, and think that there is in the suffering part\nsomething similar to the sensation of pain of which they are alone\nconscious. And thus perception may be clear without being distinct,\nbut it can never be distinct without likewise being clear.\n\n\n XLVII. That, to correct the prejudices of our early years, we must\nconsider what is clear in each of our simple [Footnote: \"first.\"--\nFRENCH.] notions.\n\nAnd, indeed, in our early years, the mind was so immersed in the\nbody, that, although it perceived many things with sufficient\nclearness, it yet knew nothing distinctly; and since even at that\ntime we exercised our judgment in many matters, numerous prejudices\nwere thus contracted, which, by the majority, are never afterwards\nlaid aside. But that we may now be in a position to get rid of\nthese, I will here briefly enumerate all the simple notions of which\nour thoughts are composed, and distinguish in each what is clear\nfrom what is obscure, or fitted to lead into error.\n\n\n XLVIII. That all the objects of our knowledge are to be regarded\neither (1) as things or the affections of things: or (2) as eternal\ntruths; with the enumeration of things.\n\nWhatever objects fall under our knowledge we consider either as\nthings or the affections of things,[Footnote: Things and the\naffections of things are (in the French) equivalent to \"what has\nsome (i.e., a REAL) existence,\" as opposed to the class of \"eternal\ntruths,\" which have merely an IDEAL existence.] or as eternal truths\npossessing no existence beyond our thought. Of the first class the\nmost general are substance, duration, order, number, and perhaps\nalso some others, which notions apply to all the kinds of things. I\ndo not, however, recognise more than two highest kinds (SUMMA\nGENERA) of things; the first of intellectual things, or such as have\nthe power of thinking, including mind or thinking substance and its\nproperties; the second, of material things, embracing extended\nsubstance, or body and its properties. Perception, volition, and all\nmodes as well of knowing as of willing, are related to thinking\nsubstance; on the other hand, to extended substance we refer\nmagnitude, or extension in length, breadth, and depth, figure,\nmotion, situation, divisibility of parts themselves, and the like.\nThere are, however, besides these, certain things of which we have\nan internal experience that ought not to be referred either to the\nmind of itself, or to the body alone, but to the close and intimate\nunion between them, as will hereafter be shown in its place. Of this\nclass are the appetites of hunger and thirst, etc., and also the\nemotions or passions of the mind which are not exclusively mental\naffections, as the emotions of anger, joy, sadness, love, etc.; and,\nfinally, all the sensations, as of pain, titillation, light and\ncolours, sounds, smells, tastes, heat, hardness, and the other\ntactile qualities.\n\n\n XLIX. That the eternal truths cannot be thus enumerated, but that\nthis is not necessary.\n\nWhat I have already enumerated we are to regard as things, or the\nqualities or modes of things. We now come to speak of eternal\ntruths. When we apprehend that it is impossible a thing can arise\nfrom nothing, this proposition, EX NIHILO NIHIL FIT, is not\nconsidered as somewhat existing, or as the mode of a thing, but as\nan eternal truth having its seat in our mind, and is called a common\nnotion or axiom. Of this class are the following:--It is impossible\nthe same thing can at once be and not be; what is done cannot be\nundone; he who thinks must exist while he thinks; and innumerable\nothers, the whole of which it is indeed difficult to enumerate, but\nthis is not necessary, since, if blinded by no prejudices, we cannot\nfail to know them when the occasion of thinking them occurs.\n\n\n L. That these truths are clearly perceived, but not equally by all\nmen, on account of prejudices.\n\nAnd, indeed, with regard to these common notions, it is not to be\ndoubted that they can be clearly and distinctly known, for otherwise\nthey would not merit this appellation: as, in truth, some of them\nare not, with respect to all men, equally deserving of the name,\nbecause they are not equally admitted by all: not, however, from\nthis reason, as I think, that the faculty of knowledge of one man\nextends farther than that of another, but rather because these\ncommon notions are opposed to the prejudices of some, who, on this\naccount, are not able readily to embrace them, even although others,\nwho are free from those prejudices, apprehend them with the greatest\nclearness.\n\n\n LI. What substance is, and that the term is not applicable to God\nand the creatures in the same sense.\n\nBut with regard to what we consider as things or the modes of\nthings, it is worth while to examine each of them by itself. By\nsubstance we can conceive nothing else than a thing which exists in\nsuch a way as to stand in need of nothing beyond itself in order to\nits existence. And, in truth, there can be conceived but one\nsubstance which is absolutely independent, and that is God. We\nperceive that all other things can exist only by help of the\nconcourse of God. And, accordingly, the term substance does not\napply to God and the creatures UNIVOCALLY, to adopt a term familiar\nin the schools; that is, no signification of this word can be\ndistinctly understood which is common to God and them.\n\n\n LII. That the term is applicable univocally to the mind and the\nbody, and how substance itself is known.\n\nCreated substances, however, whether corporeal or thinking, may be\nconceived under this common concept; for these are things which, in\norder to their existence, stand in need of nothing but the concourse\nof God. But yet substance cannot be first discovered merely from its\nbeing a thing which exists independently, for existence by itself is\nnot observed by us. We easily, however, discover substance itself\nfrom any attribute of it, by this common notion, that of nothing\nthere are no attributes, properties, or qualities: for, from\nperceiving that some attribute is present, we infer that some\nexisting thing or substance to which it may be attributed is also of\nnecessity present.\n\n\n LIII. That of every substance there is one principal attribute, as\nthinking of the mind, extension of the body.\n\nBut, although any attribute is sufficient to lead us to the\nknowledge of substance, there is, however, one principal property of\nevery substance, which constitutes its nature or essence, and upon\nwhich all the others depend. Thus, extension in length, breadth, and\ndepth, constitutes the nature of corporeal substance; and thought\nthe nature of thinking substance. For every other thing that can be\nattributed to body, presupposes extension, and is only some mode of\nan extended thing; as all the properties we discover in the mind are\nonly diverse modes of thinking. Thus, for example, we cannot\nconceive figure unless in something extended, nor motion unless in\nextended space, nor imagination, sensation, or will, unless in a\nthinking thing. But, on the other hand, we can conceive extension\nwithout figure or motion, and thought without imagination or\nsensation, and so of the others; as is clear to any one who attends\nto these matters.\n\n\n LIV. How we may have clear and distinct notions of the substance\nwhich thinks, of that which is corporeal, and of God.\n\nAnd thus we may easily have two clear and distinct notions or ideas,\nthe one of created substance, which thinks, the other of corporeal\nsubstance, provided we carefully distinguish all the attributes of\nthought from those of extension. We may also have a clear and\ndistinct idea of an uncreated and independent thinking substance,\nthat is, of God, provided we do not suppose that this idea\nadequately represents to us all that is in God, and do not mix up\nwith it anything fictitious, but attend simply to the characters\nthat are comprised in the notion we have of him, and which we\nclearly know to belong to the nature of an absolutely perfect Being.\nFor no one can deny that there is in us such an idea of God, without\ngroundlessly supposing that there is no knowledge of God at all in\nthe human mind.\n\n\n LV. How duration, order, and number may be also distinctly\nconceived.\n\nWe will also have most distinct conceptions of duration, order, and\nnumber, if, in place of mixing up with our notions of them that\nwhich properly belongs to the concept of substance, we merely think\nthat the duration of a thing is a mode under which we conceive this\nthing, in so far as it continues to exist; and, in like manner, that\norder and number are not in reality different from things disposed\nin order and numbered, but only modes under which we diversely\nconsider these things.\n\n\n LVI. What are modes, qualities, attributes.\n\nAnd, indeed, we here understand by modes the same with what we\nelsewhere designate attributes or qualities. But when we consider\nsubstance as affected or varied by them, we use the term modes; when\nfrom this variation it may be denominated of such a kind, we adopt\nthe term qualities [to designate the different modes which cause it\nto be so named]; and, finally, when we simply regard these modes as\nin the substance, we call them attributes. Accordingly, since God\nmust be conceived as superior to change, it is not proper to say\nthat there are modes or qualities in him, but simply attributes; and\neven in created things that which is found in them always in the\nsame mode, as existence and duration in the thing which exists and\nendures, ought to be called attribute and not mode or quality.\n\n\n LVII. That some attributes exist in the things to which they are\nattributed, and others only in our thought; and what duration and\ntime are.\n\nOf these attributes or modes there are some which exist in the\nthings themselves, and others that have only an existence in our\nthought; thus, for example, time, which we distinguish from duration\ntaken in its generality, and call the measure of motion, is only a\ncertain mode under which we think duration itself, for we do not\nindeed conceive the duration of things that are moved to be\ndifferent from the duration of things that are not moved: as is\nevident from this, that if two bodies are in motion for an hour, the\none moving quickly and the other slowly, we do not reckon more time\nin the one than in the other, although there may be much more motion\nin the one of the bodies than in the other. But that we may\ncomprehend the duration of all things under a common measure, we\ncompare their duration with that of the greatest and most regular\nmotions that give rise to years and days, and which we call time;\nhence what is so designated is nothing superadded to duration, taken\nin its generality, but a mode of thinking.\n\n\n LVIII. That number and all universals are only modes of thought.\n\nIn the same way number, when it is not considered as in created\nthings, but merely in the abstract or in general, is only a mode of\nthinking; and the same is true of all those general ideas we call\nuniversals.\n\n\n LIX. How universals are formed; and what are the five common, viz.,\ngenus, species, difference, property, and accident.\n\nUniversals arise merely from our making use of one and the same idea\nin thinking of all individual objects between which there subsists a\ncertain likeness; and when we comprehend all the objects represented\nby this idea under one name, this term likewise becomes universal.\nFor example, when we see two stones, and do not regard their nature\nfarther than to remark that there are two of them, we form the idea\nof a certain number, which we call the binary; and when we\nafterwards see two birds or two trees, and merely take notice of\nthem so far as to observe that there are two of them, we again take\nup the same idea as before, which is, accordingly, universal; and we\nlikewise give to this number the same universal appellation of\nbinary. In the same way, when we consider a figure of three sides,\nwe form a certain idea, which we call the idea of a triangle, and we\nafterwards make use of it as the universal to represent to our mind\nall other figures of three sides. But when we remark more\nparticularly that of figures of three sides, some have a right angle\nand others not, we form the universal idea of a right-angled\ntriangle, which being related to the preceding as more general, may\nbe called species; and the right angle the universal difference by\nwhich right-angled triangles are distinguished from all others; and\nfarther, because the square of the side which sustains the right\nangle is equal to the squares of the other two sides, and because\nthis property belongs only to this species of triangles, we may call\nit the universal property of the species. Finally, if we suppose\nthat of these triangles some are moved and others not, this will be\ntheir universal accident; and, accordingly, we commonly reckon five\nuniversals, viz., genus, species, difference, property, accident.\n\n\n LX. Of distinctions; and first of the real.\n\nBut number in things themselves arises from the distinction there is\nbetween them: and distinction is threefold, viz., real, modal, and\nof reason. The real properly subsists between two or more\nsubstances; and it is sufficient to assure us that two substances\nare really mutually distinct, if only we are able clearly and\ndistinctly to conceive the one of them without the other. For the\nknowledge we have of God renders it certain that he can effect all\nthat of which we have a distinct idea: wherefore, since we have now,\nfor example, the idea of an extended and corporeal substance, though\nwe as yet do not know with certainty whether any such thing is\nreally existent, nevertheless, merely because we have the idea of\nit, we may be assured that such may exist; and, if it really exists,\nthat every part which we can determine by thought must be really\ndistinct from the other parts of the same substance. In the same\nway, since every one is conscious that he thinks, and that he in\nthought can exclude from himself every other substance, whether\nthinking or extended, it is certain that each of us thus considered\nis really distinct from every other thinking and corporeal\nsubstance. And although we suppose that God united a body to a soul\nso closely that it was impossible to form a more intimate union, and\nthus made a composite whole, the two substances would remain really\ndistinct, notwithstanding this union; for with whatever tie God\nconnected them, he was not able to rid himself of the power he\npossessed of separating them, or of conserving the one apart from\nthe other, and the things which God can separate or conserve\nseparately are really distinct.\n\n\n LXI. Of the modal distinction.\n\nThere are two kinds of modal distinctions, viz., that between the\nmode properly so-called and the substance of which it is a mode, and\nthat between two modes of the same substance. Of the former we have\nan example in this, that we can clearly apprehend substance apart\nfrom the mode which we say differs from it; while, on the other\nhand, we cannot conceive this mode without conceiving the substance\nitself. There is, for example, a modal distinction between figure or\nmotion and corporeal substance in which both exist; there is a\nsimilar distinction between affirmation or recollection and the\nmind. Of the latter kind we have an illustration in our ability to\nrecognise the one of two modes apart from the other, as figure apart\nfrom motion, and motion apart from figure; though we cannot think of\neither the one or the other without thinking of the common substance\nin which they adhere. If, for example, a stone is moved, and is\nwithal square, we can, indeed, conceive its square figure without\nits motion, and reciprocally its motion without its square figure;\nbut we can conceive neither this motion nor this figure apart from\nthe substance of the stone. As for the distinction according to\nwhich the mode of one substance is different from another substance,\nor from the mode of another substance, as the motion of one body is\ndifferent from another body or from the mind, or as motion is\ndifferent from doubt, it seems to me that it should be called real\nrather than modal, because these modes cannot be clearly conceived\napart from the really distinct substances of which they are the\nmodes.\n\n\n LXII. Of the distinction of reason (logical distinction).\n\nFinally, the distinction of reason is that between a substance and\nsome one of its attributes, without which it is impossible, however,\nwe can have a distinct conception of the substance itself; or\nbetween two such attributes of a common substance, the one of which\nwe essay to think without the other. This distinction is manifest\nfrom our inability to form a clear and distinct idea of such\nsubstance, if we separate from it such attribute; or to have a clear\nperception of the one of two such attributes if we separate it from\nthe other. For example, because any substance which ceases to endure\nceases also to exist, duration is not distinct from substance except\nin thought (RATIONE); and in general all the modes of thinking which\nwe consider as in objects differ only in thought, as well from the\nobjects of which they are thought as from each other in a common\nobject.[Footnote: \"and generally all the attributes that lead us to\nentertain different thoughts of the same thing, such as, for\nexample, the extension of body and its property of divisibility, do\nnot differ from the body which is to us the object of them, or from\neach other, unless as we sometimes confusedly think the one without\nthinking the other.\"--FRENCH.] It occurs, indeed, to me that I have\nelsewhere classed this kind of distinction with the modal (viz.,\ntowards the end of the Reply to the First Objections to the\nMeditations on the First Philosophy); but there it was only\nnecessary to treat of these distinctions generally, and it was\nsufficient for my purpose at that time simply to distinguish both of\nthem from the real.\n\n\n LXIII. How thought and extension may be distinctly known, as\nconstituting, the one the nature of mind, the other that of body.\n\nThought and extension may be regarded as constituting the natures of\nintelligent and corporeal substance; and then they must not be\notherwise conceived than as the thinking and extended substances\nthemselves, that is, as mind and body, which in this way are\nconceived with the greatest clearness and distinctness. Moreover, we\nmore easily conceive extended or thinking substance than substance\nby itself, or with the omission of its thinking or extension. For\nthere is some difficulty in abstracting the notion of substance from\nthe notions of thinking and extension, which, in truth, are only\ndiverse in thought itself (i.e., logically different); and a concept\nis not more distinct because it comprehends fewer properties, but\nbecause we accurately distinguish what is comprehended in it from\nall other notions.\n\n\n LXIV. How these may likewise be distinctly conceived as modes of\nsubstance.\n\nThought and extension may be also considered as modes of substance;\nin as far, namely, as the same mind may have many different\nthoughts, and the same body, with its size unchanged, may be\nextended in several diverse ways, at one time more in length and\nless in breadth or depth, and at another time more in breadth and\nless in length; and then they are modally distinguished from\nsubstance, and can be conceived not less clearly and distinctly,\nprovided they be not regarded as substances or things separated from\nothers, but simply as modes of things. For by regarding them as in\nthe substances of which they are the modes, we distinguish them from\nthese substances, and take them for what in truth they are: whereas,\non the other hand, if we wish to consider them apart from the\nsubstances in which they are, we should by this itself regard them\nas self-subsisting things, and thus confound the ideas of mode and\nsubstance.\n\n\n LXV. How we may likewise know their modes.\n\nIn the same way we will best apprehend the diverse modes of thought,\nas intellection, imagination, recollection, volition, etc., and also\nthe diverse modes of extension, or those that belong to extension,\nas all figures, the situation of parts and their motions, provided\nwe consider them simply as modes of the things in which they are;\nand motion as far as it is concerned, provided we think merely of\nlocomotion, without seeking to know the force that produces it, and\nwhich nevertheless I will essay to explain in its own place.\n\n\n LXVI. How our sensations, affections, and appetites may be clearly\nknown, although we are frequently wrong in our judgments regarding\nthem.\n\nThere remain our sensations, affections, and appetites, of which we\nmay also have a clear knowledge, if we take care to comprehend in\nthe judgments we form of them only that which is precisely contained\nin our perception of them, and of which we are immediately\nconscious. There is, however, great difficulty in observing this, at\nleast in respect of sensations; because we have all, without\nexception, from our youth judged that all the things we perceived by\nour senses had an existence beyond our thought, and that they were\nentirely similar to the sensations, that is, perceptions, we had of\nthem. Thus when, for example, we saw a certain colour, we thought we\nsaw something occupying a place out of us, and which was entirely\nsimilar to that idea of colour we were then conscious of; and from\nthe habit of judging in this way, we seemed to see this so clearly\nand distinctly that we esteemed it (i.e., the externality of the\ncolour) certain and indubitable.\n\n\n LXVII. That we are frequently deceived in our judgments regarding\npain itself.\n\nThe same prejudice has place in all our other sensations, even in\nthose of titillation and pain. For though we are not in the habit of\nbelieving that there exist out of us objects that resemble\ntitillation and pain, we do not nevertheless consider these\nsensations as in the mind alone, or in our perception, but as in the\nhand, or foot, or some other part of our body. There is no reason,\nhowever, to constrain us to believe that the pain, for example,\nwhich we feel, as it were, in the foot is something out of the mind\nexisting in the foot, or that the light which we see, as it were, in\nthe sun exists in the sun as it is in us. Both these beliefs are\nprejudices of our early years, as will clearly appear in the sequel.\n\n\n LXVIII. How in these things what we clearly conceive is to be\ndistinguished from that in which we may be deceived.\n\nBut that we may distinguish what is clear in our sensations from\nwhat is obscure, we ought most carefully to observe that we possess\na clear and distinct knowledge of pain, colour, and other things of\nthis sort, when we consider them simply as sensations or thoughts;\nbut that, when they are judged to be certain things subsisting\nbeyond our mind, we are wholly unable to form any conception of\nthem. Indeed, when any one tells us that he sees colour in a body or\nfeels pain in one of his limbs, this is exactly the same as if he\nsaid that he there saw or felt something of the nature of which he\nwas entirely ignorant, or that he did not know what he saw or felt.\nFor although, when less attentively examining his thoughts, a person\nmay easily persuade himself that he has some knowledge of it, since\nhe supposes that there is something resembling that sensation of\ncolour or of pain of which he is conscious; yet, if he reflects on\nwhat the sensation of colour or pain represents to him as existing\nin a coloured body or in a wounded member, he will find that of such\nhe has absolutely no knowledge.\n\n\n LXIX. That magnitude, figure, etc., are known far differently from\ncolour, pain, etc.\n\nWhat we have said above will be more manifest; especially if we\nconsider that size in the body perceived, figure, motion (at least\nlocal, for philosophers by fancying other kinds of motion have\nrendered its nature less intelligible to themselves), the situation\nof parts, duration, number, and those other properties which, as we\nhave already said, we clearly perceive in all bodies, are known by\nus in a way altogether different from that in which we know what\ncolour is in the same body, or pain, smell, taste, or any other of\nthose properties which I have said above must be referred to the\nsenses. For although when we see a body we are not less assured of\nits existence from its appearing figured than from its appearing\ncoloured,[Footnote: \"by the colour we perceive on occasion of it.\"--\nFRENCH.] we yet know with far greater clearness its property of\nfigure than its colour.\n\n\n LXX. That we may judge of sensible things in two ways, by the one\nof which we avoid error, by the other fall into it.\n\nIt is thus manifest that to say we perceive colours in objects is in\nreality equivalent to saying we perceive something in objects and\nare yet ignorant of what it is, except as that which determines in\nus a certain highly vivid and clear sensation, which we call the\nsensation of colours. There is, however, very great diversity in the\nmanner of judging: for so long as we simply judge that there is an\nunknown something in objects (that is, in things such as they are,\nfrom which the sensation reached us), so far are we from falling\ninto error that, on the contrary, we thus rather provide against it,\nfor we are less apt to judge rashly of a thing which we observe we\ndo not know. But when we think we perceive colours in objects,\nalthough we are in reality ignorant of what we then denominate\ncolour, and are unable to conceive any resemblance between the\ncolour we suppose to be in objects, and that of which we are\nconscious in sensation, yet because we do not observe this, or\nbecause there are in objects several properties, as size, figure,\nnumber, etc., which, as we clearly know, exist, or may exist in them\nas they are perceived by our senses or conceived by our\nunderstanding, we easily glide into the error of holding that what\nis called colour in objects is something entirely resembling the\ncolour we perceive, and thereafter of supposing that we have a clear\nperception of what is in no way perceived by us.\n\n\n LXXI. That the chief cause of our errors is to be found in the\nprejudices of our childhood.\n\nAnd here we may notice the first and chief cause of our errors. In\nearly life the mind was so closely bound to the body that it\nattended to nothing beyond the thoughts by which it perceived the\nobjects that made impression on the body; nor as yet did it refer\nthese thoughts to anything existing beyond itself, but simply felt\npain when the body was hurt, or pleasure when anything beneficial to\nthe body occurred, or if the body was so highly affected that it was\nneither greatly benefited nor hurt, the mind experienced the\nsensations we call tastes, smells, sounds, heat, cold, light,\ncolours, and the like, which in truth are representative of nothing\nexisting out of our mind, and which vary according to the\ndiversities of the parts and modes in which the body is affected.\n[Footnote: \"which vary according to the diversities of the movements\nthat pass from all parts of our body to the part of the brain to\nwhich it (the mind) is closely joined and united.\"--FRENCH.] The\nmind at the same time also perceived magnitudes, figures, motions,\nand the like, which were not presented to it as sensations but as\nthings or the modes of things existing, or at least capable of\nexisting out of thought, although it did not yet observe this\ndifference between these two kinds of perceptions. And afterwards\nwhen the machine of the body, which has been so fabricated by nature\nthat it can of its own inherent power move itself in various ways,\nby turning itself at random on every side, followed after what was\nuseful and avoided what was detrimental; the mind, which was closely\nconnected with it, reflecting on the objects it pursued or avoided,\nremarked, for the first time, that they existed out of itself, and\nnot only attributed to them magnitudes, figures, motions, and the\nlike, which it apprehended either as things or as the modes of\nthings, but, in addition, attributed to them tastes, odours, and the\nother ideas of that sort, the sensations of which were caused by\nitself; [Footnote: \"which it perceived on occasion of them\" (i.e.,\nof external objects).--FRENCH.] and as it only considered other\nobjects in so far as they were useful to the body, in which it was\nimmersed, it judged that there was greater or less reality in each\nobject, according as the impressions it caused on the body were more\nor less powerful. Hence arose the belief that there was more\nsubstance or body in rocks and metals than in air or water, because\nthe mind perceived in them more hardness and weight. Moreover, the\nair was thought to be merely nothing so long as we experienced no\nagitation of it by the wind, or did not feel it hot or cold. And\nbecause the stars gave hardly more light than the slender flames of\ncandles, we supposed that each star was but of this size. Again,\nsince the mind did not observe that the earth moved on its axis, or\nthat its superficies was curved like that of a globe, it was on that\naccount more ready to judge the earth immovable and its surface\nflat. And our mind has been imbued from our infancy with a thousand\nother prejudices of the same sort which afterwards in our youth we\nforgot we had accepted without sufficient examination, and admitted\nas possessed of the highest truth and clearness, as if they had been\nknown by means of our senses, or implanted in us by nature.\n\n\n LXXII. That the second cause of our errors is that we cannot forget\nthese prejudices.\n\nAnd although now in our mature years, when the mind, being no longer\nwholly subject to the body, is not in the habit of referring all\nthings to it, but also seeks to discover the truth of things\nconsidered in themselves, we observe the falsehood of a great many\nof the judgments we had before formed; yet we experience a\ndifficulty in expunging them from our memory, and, so long as they\nremain there, they give rise to various errors. Thus, for example,\nsince from our earliest years we imagined the stars to be of very\nsmall size, we find it highly difficult to rid ourselves of this\nimagination, although assured by plain astronomical reasons that\nthey are of the greatest,--so prevailing is the power of\npreconceived opinion.\n\n\n LXXIII. The third cause is, that we become fatigued by attending to\nthose objects which are not present to the senses; and that we are\nthus accustomed to judge of these not from present perception but\nfrom pre-conceived opinion.\n\nBesides, our mind cannot attend to any object without at length\nexperiencing some pain and fatigue; and of all objects it has the\ngreatest difficulty in attending to those which are present neither\nto the senses nor to the imagination: whether for the reason that\nthis is natural to it from its union with the body, or because in\nour early years, being occupied merely with perceptions and\nimaginations, it has become more familiar with, and acquired greater\nfacility in thinking in those modes than in any other. Hence it also\nhappens that many are unable to conceive any substance except what\nis imaginable and corporeal, and even sensible. For they are\nignorant of the circumstance, that those objects alone are\nimaginable which consist in extension, motion, and figure, while\nthere are many others besides these that are intelligible; and they\npersuade themselves that nothing can subsist but body, and, finally,\nthat there is no body which is not sensible. And since in truth we\nperceive no object such as it is by sense alone [but only by our\nreason exercised upon sensible objects], as will hereafter be\nclearly shown, it thus happens that the majority during life\nperceive nothing unless in a confused way.\n\n\n LXXIV. The fourth source of our errors is, that we attach our\nthoughts to words which do not express them with accuracy.\n\nFinally, since for the use of speech we attach all our conceptions\nto words by which to express them, and commit to memory our thoughts\nin connection with these terms, and as we afterwards find it more\neasy to recall the words than the things signified by them, we can\nscarcely conceive anything with such distinctness as to separate\nentirely what we conceive from the words that were selected to\nexpress it. On this account the majority attend to words rather than\nto things; and thus very frequently assent to terms without\nattaching to them any meaning, either because they think they once\nunderstood them, or imagine they received them from others by whom\nthey were correctly understood. This, however, is not the place to\ntreat of this matter in detail, seeing the nature of the human body\nhas not yet been expounded, nor the existence even of body\nestablished; enough, nevertheless, appears to have been said to\nenable one to distinguish such of our conceptions as are clear and\ndistinct from those that are obscure and confused.\n\n\n LXXV. Summary of what must be observed in order to philosophize\ncorrectly.\n\nWherefore if we would philosophize in earnest, and give ourselves to\nthe search after all the truths we are capable of knowing, we must,\nin the first place, lay aside our prejudices; in other words, we\nmust take care scrupulously to withhold our assent from the opinions\nwe have formerly admitted, until upon new examination we discover\nthat they are true. We must, in the next place, make an orderly\nreview of the notions we have in our minds, and hold as true all and\nonly those which we will clearly and distinctly apprehend. In this\nway we will observe, first of all, that we exist in so far as it is\nour nature to think, and at the same time that there is a God upon\nwhom we depend; and after considering his attributes we will be able\nto investigate the truth of all other things, since God is the cause\nof them. Besides the notions we have of God and of our mind, we will\nlikewise find that we possess the knowledge of many propositions\nwhich are eternally true, as, for example, that nothing cannot be\nthe cause of anything, etc. We will farther discover in our minds\nthe knowledge of a corporeal or extended nature that may be moved,\ndivided, etc., and also of certain sensations that affect us, as of\npain, colours, tastes, etc., although we do not yet know the cause\nof our being so affected; and, comparing what we have now learne'd,\nby examining those things in their order, with our former confused\nknowledge of them, we will acquire the habit of forming clear and\ndistinct conceptions of all the objects we are capable of knowing.\nIn these few precepts seem to me to be comprised the most general\nand important principles of human knowledge.\n\n\n LXXVI. That we ought to prefer the Divine authority to our\nperception; [Footnote: \"reasonings.\"--FRENCH]. but that, apart from\nthings revealed, we ought to assent to nothing that we do not\nclearly apprehend.\n\nAbove all, we must impress on our memory the infallible rule, that\nwhat God has revealed is incomparably more certain than anything\nelse; and that, we ought to submit our belief to the Divine\nauthority rather than to our own judgment, even although perhaps the\nlight of reason should, with the greatest clearness and evidence,\nappear to suggest to us something contrary to what is revealed. But\nin things regarding which there is no revelation, it is by no means\nconsistent with the character of a philosopher to accept as true\nwhat he has not ascertained to be such, and to trust more to the\nsenses, in other words, to the inconsiderate judgments of childhood\nthan to the dictates of mature reason.\n\n\n\n\nPART II.\nOF THE PRINCIPLES OF MATERIAL THINGS.\n\n\nI. The grounds on which the existence of material things may be\nknown with certainty.\n\nAlthough we are all sufficiently persuaded of the existence of\nmaterial things, yet, since this was before called in question by\nus, and since we reckoned the persuasion of their existence as among\nthe prejudices of our childhood, it is now necessary for us to\ninvestigate the grounds on which this truth may be known with\ncertainty. In the first place, then, it cannot be doubted that every\nperception we have comes to us from some object different from our\nmind; for it is not in our power to cause ourselves to experience\none perception rather than another, the perception being entirely\ndependent on the object which affects our senses. It may, indeed, be\nmatter of inquiry whether that object be God, or something different\nfrom God; but because we perceive, or rather, stimulated by sense,\nclearly and distinctly apprehend, certain matter extended in length,\nbreadth, and thickness, the various parts of which have different\nfigures and motions, and give rise to the sensation we have of\ncolours, smells, pain, etc., God would, without question, deserve to\nbe regarded as a deceiver, if he directly and of himself presented\nto our mind the idea of this extended matter, or merely caused it to\nbe presented to us by some object which possessed neither extension,\nfigure, nor motion. For we clearly conceive this matter as entirely\ndistinct from God, and from ourselves, or our mind; and appear even\nclearly to discern that the idea of it is formed in us on occasion\nof objects existing out of our minds, to which it is in every\nrespect similar. But since God cannot deceive us, for this is\nrepugnant to his nature, as has been already remarked, we must\nunhesitatingly conclude that there exists a certain object extended\nin length, breadth, and thickness, and possessing all those\nproperties which we clearly apprehend to belong to what is extended.\nAnd this extended substance is what we call body or matter.\n\n\n II. How we likewise know that the human body is closely connected\nwith the mind.\n\nWe ought also to conclude that a certain body is more closely united\nto our mind than any other, because we clearly observe that pain and\nother sensations affect us without our foreseeing them; and these,\nthe mind is conscious, do not arise from itself alone, nor pertain\nto it, in so far as it is a thing which thinks, but only in so far\nas it is united to another thing extended and movable, which is\ncalled the human body. But this is not the place to treat in detail\nof this matter.\n\n\n III. That the perceptions of the senses do not teach us what is in\nreality in things, but what is beneficial of hurtful to the\ncomposite whole of mind and body.\n\nIt will be sufficient to remark that the perceptions of the senses\nare merely to be referred to this intimate union of the human body\nand mind, and that they usually make us aware of what, in external\nobjects, may be useful or adverse to this union, but do not present\nto us these objects as they are in themselves, unless occasionally\nand by accident. For, after this observation, we will without\ndifficulty lay aside the prejudices of the senses, and will have\nrecourse to our understanding alone on this question by reflecting\ncarefully on the ideas implanted in it by nature.\n\n\n IV. That the nature of body consists not in weight hardness, colour\nand the like, but in extension alone.\n\nIn this way we will discern that the nature of matter or body,\nconsidered in general, does not consist in its being hard, or\nponderous, or coloured, or that which affects our senses in any\nother way, but simply in its being a substance extended in length,\nbreadth, and depth. For with respect to hardness, we know nothing of\nit by sense farther than that the parts of hard bodies resist the\nmotion of our hands on coming into contact with them; but if every\ntime our hands moved towards any part, all the bodies in that place\nreceded as quickly as our hands approached, we should never feel\nhardness; and yet we have no reason to believe that bodies which\nmight thus recede would on this account lose that which makes them\nbodies. The nature of body does not, therefore, consist in hardness.\nIn the same way, it may be shown that weight, colour, and all the\nother qualities of this sort, which are perceived in corporeal\nmatter, may be taken from it, itself meanwhile remaining entire: it\nthus follows that the nature of body depends on none of these.\n\n\n V. That the truth regarding the nature of body is obscured by the\nopinions respecting rarefaction and a vacuum with which we are pre-\noccupied.\n\nThere still remain two causes to prevent its being fully admitted\nthat the true nature of body consists in extension alone. The first\nis the prevalent opinion, that most bodies admit of being so\nrarefied and condensed that, when rarefied, they have greater\nextension than when condensed; and some even have subtilized to such\na degree as to make a distinction between the substance of body and\nits quantity, and between quantity itself and extension. The second\ncause is this, that where we conceive only extension in length,\nbreadth, and depth, we are not in the habit of saying that body is\nthere, but only space and further void space, which the generality\nbelieve to be a mere negation.\n\n\n VI. In what way rarefaction takes place.\n\nBut with regard to rarefaction and condensation, whoever gives his\nattention to his own thoughts, and admits nothing of which he is not\nclearly conscious, will not suppose that there is anything in those\nprocesses further than a change of figure in the body rarefied or\ncondensed: so that, in other words, rare bodies are those between\nthe parts of which there are numerous distances filled with other\nbodies; and dense bodies, on the other hand, those whose parts\napproaching each other, either diminish these distances or take them\nwholly away, in the latter of which cases the body is rendered\nabsolutely dense. The body, however, when condensed, has not,\ntherefore, less extension than when the parts embrace a greater\nspace, owing to their removal from each other, and their dispersion\ninto branches. For we ought not to attribute to it the extension of\nthe pores or distances which its parts do not occupy when it is\nrarefied, but to the other bodies that fill these interstices; just\nas when we see a sponge full of water or any other liquid, we do not\nsuppose that each part of the sponge has on this account greater\nextension than when compressed and dry, but only that its pores are\nwider, and therefore that the body is diffused over a larger space.\n\n\n VII. That rarefaction cannot be intelligibly explained unless in\nthe way here proposed.\n\nAnd indeed I am unable to discover the force of the reasons which\nhave induced some to say that rarefaction is the result of the\naugmentation of the quantity of body, rather than to explain it on\nthe principle exemplified in the case of a sponge. For although when\nair or water is rarefied we do not see any of the pores that are\nrendered large, or the new body that is added to occupy them, it is\nyet less agreeable to reason to suppose something that is\nunintelligible for the purpose of giving a verbal and merely\napparent explanation of the rarefaction of bodies, than to conclude,\nbecause of their rarefaction, that there are pores or distances\nbetween the parts which are increased in size, and filled with some\nnew body. Nor ought we to refrain from assenting to this\nexplanation, because we perceive this new body by none of our\nsenses, for there is no reason which obliges us to believe that we\nshould perceive by our senses all the bodies in existence. And we\nsee that it is very easy to explain rarefaction in this manner, but\nimpossible in any other; for, in fine, there would be, as appears to\nme, a manifest contradiction in supposing that any body was\nincreased by a quantity or extension which it had not before,\nwithout the addition to it of a new extended substance, in other\nwords, of another body, because it is impossible to conceive any\naddition of extension or quantity to a thing without supposing the\naddition of a substance having quantity or extension, as will more\nclearly appear from what follows.\n\n\n VIII. That quantity and number differ only in thought (RATIONE)\nfrom that which has quantity and is numbered.\n\nFor quantity differs from extended substance, and number from what\nis numbered, not in reality but merely in our thought; so that, for\nexample, we may consider the whole nature of a corporeal substance\nwhich is comprised in a space of ten feet, although we do not attend\nto this measure of ten feet, for the obvious reason that the thing\nconceived is of the same nature in any part of that space as in the\nwhole; and, on the other hand, we can conceive the number ten, as\nalso a continuous quantity of ten feet, without thinking of this\ndeterminate substance, because the concept of the number ten is\nmanifestly the same whether we consider a number of ten feet or ten\nof anything else; and we can conceive a continuous quantity of ten\nfeet without thinking of this or that determinate substance,\nalthough we cannot conceive it without some extended substance of\nwhich it is the quantity. It is in reality, however, impossible that\nany, even the least part, of such quantity or extension, can be\ntaken away, without the retrenchment at the same time of as much of\nthe substance, nor, on the other hand, can we lessen the substance,\nwithout at the same time taking as much from the quantity or\nextension.\n\n\n IX. That corporeal substance, when distinguished from its quantity,\nis confusedly conceived as something incorporeal.\n\nAlthough perhaps some express themselves otherwise on this matter, I\nam nevertheless convinced that they do not think differently from\nwhat I have now said: for when they distinguish (corporeal)\nsubstance from extension or quantity, they either mean nothing by\nthe word (corporeal) substance, or they form in their minds merely a\nconfused idea of incorporeal substance, which they falsely attribute\nto corporeal, and leave to extension the true idea of this corporeal\nsubstance; which extension they call an accident, but with such\nimpropriety as to make it easy to discover that their words are not\nin harmony with their thoughts.\n\n\n X. What space or internal place is.\n\nSpace or internal place, and the corporeal substance which is\ncomprised in it, are not different in reality, but merely in the\nmode in which they are wont to be conceived by us. For, in truth,\nthe same extension in length, breadth, and depth, which constitutes\nspace, constitutes body; and the difference between them lies only\nin this, that in body we consider extension as particular, and\nconceive it to change with the body; whereas in space we attribute\nto extension a generic unity, so that after taking from a certain\nspace the body which occupied it, we do not suppose that we have at\nthe same time removed the extension of the space, because it appears\nto us that the same extension remains there so long as it is of the\nsame magnitude and figure, and preserves the same situation in\nrespect to certain bodies around it, by means of which we determine\nthis space.\n\n\n XI. How space is not in reality different from corporeal substance.\n\nAnd indeed it will be easy to discern that it is the same extension\nwhich constitutes the nature of body as of space, and that these two\nthings are mutually diverse only as the nature of the genus and\nspecies differs from that of the individual, provided we reflect on\nthe idea we have of any body, taking a stone for example, and reject\nall that is not essential to the nature of body. In the first place,\nthen, hardness may be rejected, because if the stone were liquefied\nor reduced to powder, it would no longer possess hardness, and yet\nwould not cease to be a body; colour also may be thrown out of\naccount, because we have frequently seen stones so transparent as to\nhave no colour; again, we may reject weight, because we have the\ncase of fire, which, though very light, is still a body; and,\nfinally, we may reject cold, heat, and all the other qualities of\nthis sort, either because they are not considered as in the stone,\nor because, with the change of these qualities, the stone is not\nsupposed to have lost the nature of body. After this examination we\nwill find that nothing remains in the idea of body, except that it\nis something extended in length, breadth, and depth; and this\nsomething is comprised in our idea of space, not only of that which\nis full of body, but even of what is called void space.\n\n\n XII. How space differs from body in our mode of conceiving it.\n\nThere is, however, some difference between them in the mode of\nconception; for if we remove a stone from the space or place in\nwhich it was, we conceive that its extension also is taken away,\nbecause we regard this as particular, and inseparable from the stone\nitself: but meanwhile we suppose that the same extension of place in\nwhich this stone was remains, although the place of the stone be\noccupied by wood, water, air, or by any other body, or be even\nsupposed vacant, because we now consider extension in general, and\nthink that the same is common to stones, wood, water, air, and other\nbodies, and even to a vacuum itself, if there is any such thing,\nprovided it be of the same magnitude and figure as before, and\npreserve the same situation among the external bodies which\ndetermine this space.\n\n\n XIII. What external place is.\n\nThe reason of which is, that the words place and space signify\nnothing really different from body which is said to be in place, but\nmerely designate its magnitude, figure, and situation among other\nbodies. For it is necessary, in order to determine this situation,\nto regard certain other bodies which we consider as immovable; and,\naccording as we look to different bodies, we may see that the same\nthing at the same time does and does not change place. For example,\nwhen a vessel is being carried out to sea, a person sitting at the\nstern may be said to remain always in one place, if we look to the\nparts of the vessel, since with respect to these he preserves the\nsame situation; and on the other hand, if regard be had to the\nneighbouring shores, the same person will seem to be perpetually\nchanging place, seeing he is constantly receding from one shore and\napproaching another. And besides, if we suppose that the earth\nmoves, and that it makes precisely as much way from west to east as\nthe vessel from east to west, we will again say that the person at\nthe stern does not change his place, because this place will be\ndetermined by certain immovable points which we imagine to be in the\nheavens. But if at length we are persuaded that there are no points\nreally immovable in the universe, as will hereafter be shown to be\nprobable, we will thence conclude that nothing has a permanent place\nunless in so far as it is fixed by our thought.\n\n\n XIV. Wherein place and space differ.\n\nThe terms place and space, however, differ in signification, because\nplace more expressly designates situation than magnitude or figure,\nwhile, on the other hand, we think of the latter when we speak of\nspace. For we frequently say that a thing succeeds to the place of\nanother, although it be not exactly of the same magnitude or figure;\nbut we do not therefore admit that it occupies the same space as the\nother; and when the situation is changed we say that the place also\nis changed, although there are the same magnitude and figure as\nbefore: so that when we say that a thing is in a particular place,\nwe mean merely that it is situated in a determinate way in respect\nof certain other objects; and when we add that it occupies such a\nspace or place, we understand besides that it is of such determinate\nmagnitude and figure as exactly to fill this space.\n\n\n XV. How external place is rightly taken for the superficies of the\nsurrounding body.\n\nAnd thus we never indeed distinguish space from extension in length,\nbreadth, and depth; we sometimes, however, consider place as in the\nthing placed, and at other times as out of it. Internal place indeed\ndiffers in no way from space; but external place may be taken for\nthe superficies that immediately surrounds the thing placed. It\nought to be remarked that by superficies we do not here understand\nany part of the surrounding body, but only the boundary between the\nsurrounding and surrounded bodies, which is nothing more than a\nmode; or at least that we speak of superficies in general which is\nno part of one body rather than another, but is always considered\nthe same, provided it retain the same magnitude and figure. For\nalthough the whole surrounding body with its superficies were\nchanged, it would not be supposed that the body which was surrounded\nby it had therefore changed its place, if it meanwhile preserved the\nsame situation with respect to the other bodies that are regarded as\nimmovable. Thus, if we suppose that a boat is carried in one\ndirection by the current of a stream, and impelled by the wind in\nthe opposite with an equal force, so that its situation with respect\nto the banks is not changed, we will readily admit that it remains\nin the same place, although the whole superficies which surrounds it\nis incessantly changing.\n\n\n XVI. That a vacuum or space in which there is absolutely no body is\nrepugnant to reason.\n\nWith regard to a vacuum, in the philosophical sense of the term,\nthat is, a space in which there is no substance, it is evident that\nsuch does not exist, seeing the extension of space or internal place\nis not different from that of body. For since from this alone, that\na body has extension in length, breadth, and depth, we have reason\nto conclude that it is a substance, it being absolutely\ncontradictory that nothing should possess extension, we ought to\nform a similar inference regarding the space which is supposed void,\nviz., that since there is extension in it there is necessarily also\nsubstance.\n\n\n XVII. That a vacuum in the ordinary use of the term does not\nexclude all body.\n\nAnd, in truth, by the term vacuum in its common use, we do not mean\na place or space in which there is absolutely nothing, but only a\nplace in which there is none of those things we presume ought to be\nthere. Thus, because a pitcher is made to hold water, it is said to\nbe empty when it is merely filled with air; or if there are no fish\nin a fish-pond, we say there is nothing in it, although it be full\nof water; thus a vessel is said to be empty, when, in place of the\nmerchandise which it was designed to carry, it is loaded with sand\nonly, to enable it to resist the violence of the wind; and, finally,\nit is in the same sense that we say space is void when it contains\nnothing sensible, although it contain created and self-subsisting\nmatter; for we are not in the habit of considering the bodies near\nus, unless in so far as they cause in our organs of sense,\nimpressions strong enough to enable us to perceive them. And if, in\nplace of keeping in mind what ought to be understood by these terms\na vacuum and nothing, we afterwards suppose that in the space we\ncalled a vacuum, there is not only no sensible object, but no object\nat all, we will fall into the same error as if, because a pitcher in\nwhich there is nothing but air, is, in common speech, said to be\nempty, we were therefore to judge that the air contained in it is\nnot a substance (RES SUBSISTENS).\n\n\n XVIII. How the prejudice of an absolute vacuum is to be corrected.\n\nWe have almost all fallen into this error from the earliest age,\nfor, observing that there is no necessary connection between a\nvessel and the body it contains, we thought that God at least could\ntake from a vessel the body which occupied it, without it being\nnecessary that any other should be put in the place of the one\nremoved. But that we may be able now to correct this false opinion,\nit is necessary to remark that there is in truth no connection\nbetween the vessel and the particular body which it contains, but\nthat there is an absolutely necessary connection between the concave\nfigure of the vessel and the extension considered generally which\nmust be comprised in this cavity; so that it is not more\ncontradictory to conceive a mountain without a valley than such a\ncavity without the extension it contains, or this extension apart\nfrom an extended substance, for, as we have often said, of nothing\nthere can be no extension. And accordingly, if it be asked what\nwould happen were God to remove from a vessel all the body contained\nin it, without permitting another body to occupy its place, the\nanswer must be that the sides of the vessel would thus come into\nproximity with each other. For two bodies must touch each other when\nthere is nothing between them, and it is manifestly contradictory\nfor two bodies to be apart, in other words, that there should be a\ndistance between them, and this distance yet be nothing; for all\ndistance is a mode of extension, and cannot therefore exist without\nan extended substance.\n\n\n XIX. That this confirms what was said of rarefaction.\n\nAfter we have thus remarked that the nature of corporeal substance\nconsists only in its being an extended thing, and that its extension\nis not different from that which we attribute to space, however\nempty, it is easy to discover the impossibility of any one of its\nparts in any way whatsoever occupying more space at one time than at\nanother, and thus of being otherwise rarefied than in the way\nexplained above; and it is easy to perceive also that there cannot\nbe more matter or body in a vessel when it is filled with lead or\ngold, or any other body however heavy and hard, than when it but\ncontains air and is supposed to be empty: for the quantity of the\nparts of which a body is composed does not depend on their weight or\nhardness, but only on the extension, which is always equal in the\nsame vase.\n\n\n XX. That from this the non-existence of atoms may likewise be\ndemonstrated.\n\nWe likewise discover that there cannot exist any atoms or parts of\nmatter that are of their own nature indivisible. For however small\nwe suppose these parts to be, yet because they are necessarily\nextended, we are always able in thought to divide any one of them\ninto two or more smaller parts, and may accordingly admit their\ndivisibility. For there is nothing we can divide in thought which we\ndo not thereby recognize to be divisible; and, therefore, were we to\njudge it indivisible our judgment would not be in harmony with the\nknowledge we have of the thing; and although we should even suppose\nthat God had reduced any particle of matter to a smallness so\nextreme that it did not admit of being further divided, it would\nnevertheless be improperly styled indivisible, for though God had\nrendered the particle so small that it was not in the power of any\ncreature to divide it, he could not however deprive himself of the\nability to do so, since it is absolutely impossible for him to\nlessen his own omnipotence, as was before observed. Wherefore,\nabsolutely speaking, the smallest extended particle is always\ndivisible, since it is such of its very nature.\n\n\n XXI. It is thus also demonstrated that the extension of the world\nis indefinite.\n\nWe further discover that this world or the whole (universitas) of\ncorporeal substance, is extended without limit, for wherever we fix\na limit, we still not only imagine beyond it spaces indefinitely\nextended, but perceive these to be truly imaginable, in other words,\nto be in reality such as we imagine them; so that they contain in\nthem corporeal substance indefinitely extended, for, as has been\nalready shown at length, the idea of extension which we conceive in\nany space whatever is plainly identical with the idea of corporeal\nsubstance.\n\n\n XXII. It also follows that the matter of the heavens and earth is\nthe same, and that there cannot be a plurality of worlds.\n\nAnd it may also be easily inferred from all this that the earth and\nheavens are made of the same matter; and that even although there\nwere an infinity of worlds, they would all be composed of this\nmatter; from which it follows that a plurality of worlds is\nimpossible, because we clearly conceive that the matter whose nature\nconsists only in its being an extended substance, already wholly\noccupies all the imaginable spaces where these other worlds could\nalone be, and we cannot find in ourselves the idea of any other\nmatter.\n\n\n XXIII. That all the variety of matter, or the diversity of its\nforms, depends on motion.\n\nThere is therefore but one kind of matter in the whole universe, and\nthis we know only by its being extended. All the properties we\ndistinctly perceive to belong to it are reducible to its capacity of\nbeing divided and moved according to its parts; and accordingly it\nis capable of all those affections which we perceive can arise from\nthe motion of its parts. For the partition of matter in thought\nmakes no change in it; but all variation of it, or diversity of\nform, depends on motion. The philosophers even seem universally to\nhave observed this, for they said that nature was the principle of\nmotion and rest, and by nature they understood that by which all\ncorporeal things become such as they are found in experience.\n\n\n XXIV. What motion is, taking the term in its common use.\n\nBut motion (viz., local, for I can conceive no other kind of motion,\nand therefore I do not think we ought to suppose there is any other\nin nature), in the ordinary sense of the term, is nothing more than\nthe action by which a body passes from one place to another. And\njust as we have remarked above that the same thing may be said to\nchange and not to change place at the same time, so also we may say\nthat the same thing is at the same time moved and not moved. Thus,\nfor example, a person seated in a vessel which is setting sail,\nthinks he is in motion if he look to the shore that he has left, and\nconsider it as fixed; but not if he regard the ship itself, among\nthe parts of which he preserves always the same situation. Moreover,\nbecause we are accustomed to suppose that there is no motion without\naction, and that in rest there is the cessation of action, the\nperson thus seated is more properly said to be at rest than in\nmotion, seeing he is not conscious of being in action.\n\n\n XXV. What motion is properly so called.\n\nBut if, instead of occupying ourselves with that which has no\nfoundation, unless in ordinary usage, we desire to know what ought\nto be understood by motion according to the truth of the thing, we\nmay say, in order to give it a determinate nature, that it is THE\nTRANSPORTING OF ONE PART OF MATTER OR OF ONE BODY FROM THE VICINITY\nOF THOSE BODIES THAT ARE IN IMMEDIATE CONTACT WITH IT, OR WHICH WE\nREGARD AS AT REST, to the vicinity of other bodies. By a body as a\npart of matter, I understand all that which is transferred together,\nalthough it be perhaps composed of several parts, which in\nthemselves have other motions; and I say that it is the transporting\nand not the force or action which transports, with the view of\nshowing that motion is always in the movable thing, not in that\nwhich moves; for it seems to me that we are not accustomed to\ndistinguish these two things with sufficient accuracy. Farther, I\nunderstand that it is a mode of the movable thing, and not a\nsubstance, just as figure is a property of the thing figured, and\nrepose of that which is at rest.\n\n\n\n\nPART III.\nOF THE VISIBLE WORLD.\n\n\n I. That we cannot think too highly of the works of God.\n\nHaving now ascertained certain principles of material things, which\nwere sought, not by the prejudices of the senses, but by the light\nof reason, and which thus possess so great evidence that we cannot\ndoubt of their truth, it remains for us to consider whether from\nthese alone we can deduce the explication of all the phenomena of\nnature. We will commence with those phenomena that are of the\ngreatest generality, and upon which the others depend, as, for\nexample, with the general structure of this whole visible world. But\nin order to our philosophizing aright regarding this, two things are\nfirst of all to be observed. The first is, that we should ever bear\nin mind the infinity of the power and goodness of God, that we may\nnot fear falling into error by imagining his works to be too great,\nbeautiful, and perfect, but that we may, on the contrary, take care\nlest, by supposing limits to them of which we have no certain\nknowledge, we appear to think less highly than we ought of the power\nof God.\n\n II. That we ought to beware lest, in our presumption, we imagine\nthat the ends which God proposed to himself in the creation of the\nworld are understood by us.\n\nThe second is, that we should beware of presuming too highly of\nourselves, as it seems we should do if we supposed certain limits to\nthe world, without being assured of their existence either by\nnatural reasons or by divine revelation, as if the power of our\nthought extended beyond what God has in reality made; but likewise\nstill more if we persuaded ourselves that all things were created by\nGod for us only, or if we merely supposed that we could comprehend\nby the power of our intellect the ends which God proposed to himself\nin creating the universe.\n\n III. In what sense it may be said that all things were created for\nthe sake of man.\n\nFor although, as far as regards morals, it may be a pious thought to\nbelieve that God made all things for us, seeing we may thus be\nincited to greater gratitude and love toward him; and although it is\neven in some sense true, because there is no created thing of which\nwe cannot make some use, if it be only that of exercising our mind\nin considering it, and honouring God on account of it, it is yet by\nno means probable that all things were created for us in this way\nthat God had no other end in their creation; and this supposition\nwould be plainly ridiculous and inept in physical reasoning, for we\ndo not doubt but that many things exist, or formerly existed and\nhave now ceased to be, which were never seen or known by man, and\nwere never of use to him.\n\n\n\n\nPART IV.\nOF THE EARTH.\n\n\n CLXXXVIII. Of what is to be borrowed from disquisitions on animals\nand man to advance the knowledge of material objects.\n\nI should add nothing farther to this the Fourth Part of the\nPrinciples of Philosophy, did I purpose carrying out my original\ndesign of writing a Fifth and Sixth Part, the one treating of things\npossessed of life, that is, animals and plants, and the other of\nman. But because I have not yet acquired sufficient knowledge of all\nthe matters of which I should desire to treat in these two last\nparts, and do not know whether I shall ever have sufficient leisure\nto finish them, I will here subjoin a few things regarding the\nobjects of our senses, that I may not, for the sake of the latter,\ndelay too long the publication of the former parts, or of what may\nbe desiderated in them, which I might have reserved for explanation\nin those others: for I have hitherto described this earth, and\ngenerally the whole visible world, as if it were merely a machine in\nwhich there was nothing at all to consider except the figures and\nmotions of its parts, whereas our senses present to us many other\nthings, for example colours, smells, sounds, and the like, of which,\nif I did not speak at all, it would be thought I had omitted the\nexplication of the majority of the objects that are in nature.\n\n\n CLXXXIX. What perception (SENSUS) is, and how we perceive.\n\nWe must know, therefore, that although the human soul is united to\nthe whole body, it has, nevertheless, its principal seat in the\nbrain, where alone it not only understands and imagines, but also\nperceives; and this by the medium of the nerves, which are extended\nlike threads from the brain to all the other members, with which\nthey are so connected that we can hardly touch any one of them\nwithout moving the extremities of some of the nerves spread over it;\nand this motion passes to the other extremities of those nerves\nwhich are collected in the brain round the seat of the soul,\n[Footnote: *** FOOTNOTE NOT VISIBLE IN PAGE IMAGE (#98, Text p 195)]\nas I have already explained with sufficient minuteness in the fourth\nchapter of the Dioptrics. But the movements which are thus excited\nin the brain by the nerves variously affect the soul or mind, which\nis intimately conjoined with the brain, according to the diversity\nof the motions themselves. And the diverse affections of the mind or\nthoughts that immediately arise from these motions, are called\nperceptions of the senses (SENSUUM PERCEPTIONES), or, as we commonly\nspeak, sensations (SENSUS).\n\n\n CXC. Of the distinction of the senses; and, first, of the internal,\nthat is, of the affections of the mind (passions), and the natural\nappetites.\n\nThe varieties of these sensations depend, firstly, on the diversity\nof the nerves themselves, and, secondly, of the movements that are\nmade in each nerve. We have not, however, as many different senses\nas there are nerves. We can distinguish but seven principal classes\nof nerves, of which two belong to the internal, and the other five\nto the external senses. The nerves which extend to the stomach, the\noesophagus, the fauces, and the other internal parts that are\nsubservient to our natural wants, constitute one of our internal\nsenses. This is called the natural appetite (APPETITUS NATURALIS).\nThe other internal sense, which embraces all the emotions\n(COMMOTIONES) of the mind or passions, and affections, as joy,\nsadness, love, hate, and the like, depends upon the nerves which\nextend to the heart and the parts about the heart, and are\nexceedingly small; for, by way of example, when the blood happens to\nbe pure and well tempered, so that it dilates in the heart more\nreadily and strongly than usual, this so enlarges and moves the\nsmall nerves scattered around the orifices, that there is thence a\ncorresponding movement in the brain, which affects the mind with a\ncertain natural feeling of joy; and as often as these same nerves\nare moved in the same way, although this is by other causes, they\nexcite in our mind the same feeling (sensus, sentiment). Thus, the\nimagination of the enjoyment of a good does not contain in itself\nthe feeling of joy, but it causes the animal spirits to pass from\nthe brain to the muscles in which these nerves are inserted; and\nthus dilating the orifices of the heart, it also causes these small\nnerves to move in the way appointed by nature to afford the\nsensation of joy. Thus, when we receive news, the mind first of all\njudges of it, and if the news be good, it rejoices with that\nintellectual joy (GAUDIUM INTELLECTUALE) which is independent of any\nemotion (COMMOTIO) of the body, and which the Stoics did not deny to\ntheir wise man [although they supposed him exempt from all passion].\nBut as soon as this joy passes from the understanding to the\nimagination, the spirits flow from the brain to the muscles that are\nabout the heart, and there excite the motion of the small nerves, by\nmeans of which another motion is caused in the brain, which affects\nthe mind with the sensation of animal joy (LAETITIA ANIMALIS). On\nthe same principle, when the blood is so thick that it flows but\nsparingly into the ventricles of the heart, and is not there\nsufficiently dilated, it excites in the same nerves a motion quite\ndifferent from the preceding, which, communicated to the brain,\ngives to the mind the sensation of sadness, although the mind itself\nis perhaps ignorant of the cause of its sadness. And all the other\ncauses which move these nerves in the same way may also give to the\nmind the same sensation. But the other movements of the same nerves\nproduce other effects, as the feelings of love, hate, fear, anger,\netc., as far as they are merely affections or passions of the mind;\nin other words, as far as they are confused thoughts which the mind\nhas not from itself alone, but from its being closely joined to the\nbody, from which it receives impressions; for there is the widest\ndifference between these passions and the distinct thoughts which we\nhave of what ought to be loved, or chosen, or shunned, etc.,\n[although these are often enough found together]. The natural\nappetites, as hunger, thirst, and the others, are likewise\nsensations excited in the mind by means of the nerves of the\nstomach, fauces, and other parts, and are entirely different from\nthe will which we have to eat, drink, [and to do all that which we\nthink proper for the conservation of our body]; but, because this\nwill or appetition almost always accompanies them, they are\ntherefore named appetites.\n\n\n CXCI. Of the external senses; and first of touch.\n\nWe commonly reckon the external senses five in number, because there\nare as many different kinds of objects which move the nerves and\ntheir organs, and an equal number of kinds of confused thoughts\nexcited in the soul by these emotions. In the first place, the\nnerves terminating in the skin of the whole body can be touched\nthrough this medium by any terrene objects whatever, and moved by\nthese wholes, in one way by their hardness, in another by their\ngravity, in a third by their heat, in a fourth by their humidity,\netc.--and in as many diverse modes as they are either moved or\nhindered from their ordinary motion, to that extent are diverse\nsensations excited in the mind, from which a corresponding number of\ntactile qualities derive their appellations. Besides this, when\nthese nerves are moved a little more powerfully than usual, but not\nnevertheless to the degree by which our body is in any way hurt,\nthere thus arises a sensation of titillation, which is naturally\nagreeable to the mind, because it testifies to it of the powers of\nthe body with which it is joined, [in that the latter can suffer the\naction causing this titillation, without being hurt]. But if this\naction be strong enough to hurt our body in any way, this gives to\nour mind the sensation of pain. And we thus see why corporeal\npleasure and pain, although sensations of quite an opposite\ncharacter, arise nevertheless from causes nearly alike.\n\n\n CXCII. Of taste.\n\nIn the second place, the other nerves scattered over the tongue and\nthe parts in its vicinity are diversely moved by the particles of\nthe same bodies, separated from each other and floating in the\nsaliva in the mouth, and thus cause sensations of diverse tastes\naccording to the diversity of figure in these particles. [Footnote:\nIn the French this section begins, \"Taste, after touch the grossest\nof the senses,\" etc.]\n\n\n CXCIII. Of smell.\n\nThirdly, two nerves also or appendages of the brain, for they do not\ngo beyond the limits of the skull, are moved by the particles of\nterrestrial bodies, separated and flying in the air, not indeed by\nall particles indifferently, but by those only that are sufficiently\nsubtle and penetrating to enter the pores of the bone we call the\nspongy, when drawn into the nostrils, and thus to reach the nerves.\nFrom the different motions of these particles arise the sensations\nof the different smells.\n\n\n CXCIV. Of hearing.\n\nFourthly, there are two nerves within the ears, so attached to three\nsmall bones that are mutually sustaining, and the first of which\nrests on the small membrane that covers the cavity we call the\ntympanum of the ear, that all the diverse vibrations which the\nsurrounding air communicates to this membrane are transmitted to the\nmind by these nerves, and these vibrations give rise, according to\ntheir diversity, to the sensations of the different sounds.\n\n\n CXCV. Of sight.\n\nFinally, the extremities of the optic nerves, composing the coat in\nthe eyes called the retina, are not moved by the air nor by any\nterrestrial object, but only by the globules of the second element,\nwhence we have the sense of light and colours: as I have already at\nsufficient length explained in the Dioptrics and treatise of\nMeteors. [Footnote: In the French this section begins, \"Finally,\nsight is the most subtle of all the senses,\" etc.]\n\n\n CXCVI. That the soul perceives only in so far as it is in the\nbrain.\n\nIt is clearly established, however, that the soul does not perceive\nin so far as it is in each member of the body, but only in so far as\nit is in the brain, where the nerves by their movements convey to it\nthe diverse actions of the external objects that touch the parts of\nthe body in which they are inserted. For, in the first place, there\nare various maladies, which, though they affect the brain alone, yet\nbring disorder upon, or deprive us altogether of the use of, our\nsenses, just as sleep, which affects the brain only, and yet takes\nfrom us daily during a great part of our time the faculty of\nperception, which afterwards in our waking state is restored to us.\nThe second proof is, that though there be no disease in the brain,\n[or in the members in which the organs of the external senses are],\nit is nevertheless sufficient to take away sensation from the part\nof the body where the nerves terminate, if only the movement of one\nof the nerves that extend from the brain to these members be\nobstructed in any part of the distance that is between the two. And\nthe last proof is, that we sometimes feel pain as if in certain of\nour members, the cause of which, however, is not in these members\nwhere it is felt, but somewhere nearer the brain, through which the\nnerves pass that give to the mind the sensation of it. I could\nestablish this fact by innumerable experiments; I will here,\nhowever, merely refer to one of them. A girl suffering from a bad\nulcer in the hand, had her eyes bandaged whenever the surgeon came\nto visit her, not being able to bear the sight of the dressing of\nthe sore; and, the gangrene having spread, after the expiry of a few\ndays the arm was amputated from the elbow [without the girl's\nknowledge]; linen cloths tied one above the other were substituted\nin place of the part amputated, so that she remained for some time\nwithout knowing that the operation had been performed, and meanwhile\nshe complained of feeling various pains, sometimes in one finger of\nthe hand that was cut off, and sometimes in another. The only\nexplanation of this is, that the nerves which before stretched\ndownwards from the brain to the hand, and then terminated in the arm\nclose to the elbow, were there moved in the same way as they\nrequired to be moved before in the hand for the purpose of\nimpressing on the mind residing in the brain the sensation of pain\nin this or that finger. [And this clearly shows that the pain of the\nhand is not felt by the mind in so far as it is in the hand, but in\nso far as it is in the brain.]\n\n\n CXCVII. That the nature of the mind is such that from the motion\nalone of body the various sensations can be excited in it.\n\nIn the next place, it can be proved that our mind is of such a\nnature that the motions of the body alone are sufficient to excite\nin it all sorts of thoughts, without it being necessary that these\nshould in any way resemble the motions which give rise to them, and\nespecially that these motions can excite in it those confused\nthoughts called sensations (SENSUS, SENSATIONES). For we see that\nwords, whether uttered by the voice or merely written, excite in our\nminds all kinds of thoughts and emotions. On the same paper, with\nthe same pen and ink, by merely moving the point of the pen over the\npaper in a particular way, we can trace letters that will raise in\nthe minds of our readers the thoughts of combats, tempests, or the\nfuries, and the passions of indignation and sorrow; in place of\nwhich, if the pen be moved in another way hardly different from the\nformer, this slight change will cause thoughts widely different from\nthe above, such as those of repose, peace, pleasantness, and the\nquite opposite passions of love and joy. Some one will perhaps\nobject that writing and speech do not immediately excite in the mind\nany passions, or imaginations of things different from the letters\nand sounds, but afford simply the knowledge of these, on occasion of\nwhich the mind, understanding the signification of the words,\nafterwards excites in itself the imaginations and passions that\ncorrespond to the words. But what will be said of the sensations of\npain and titillation? The motion merely of a sword cutting a part of\nour skin causes pain, [but does not on that account make us aware of\nthe motion or figure of the sword]. And it is certain that this\nsensation of pain is not less different from the motion that causes\nit, or from that of the part of our body which the sword cuts, than\nare the sensations we have of colour, sound, odour, or taste. On\nthis ground we may conclude that our mind is of such a nature that\nthe motions alone of certain bodies can also easily excite in it all\nthe other sensations, as the motion of a sword excites in it the\nsensation of pain.\n\n\n CXCVIII. That by our senses we know nothing of external objects\nbeyond their figure [or situation], magnitude, and motion.\n\nBesides, we observe no such difference between the nerves as to lead\nus to judge that one set of them convey to the brain from the organs\nof the external senses anything different from another, or that\nanything at all reaches the brain besides the local motion of the\nnerves themselves. And we see that local motion alone causes in us\nnot only the sensation of titillation and of pain, but also of light\nand sounds. For if we receive a blow on the eye of sufficient force\nto cause the vibration of the stroke to reach the retina, we see\nnumerous sparks of fire, which, nevertheless, are not out of our\neye; and when we stop our ear with our finger, we hear a humming\nsound, the cause of which can only proceed from the agitation of the\nair that is shut up within it. Finally, we frequently observe that\nheat [hardness, weight], and the other sensible qualities, as far as\nthey are in objects, and also the forms of those bodies that are\npurely material, as, for example, the forms of fire, are produced in\nthem by the motion of certain other bodies, and that these in their\nturn likewise produce other motions in other bodies. And we can\neasily conceive how the motion of one body may be caused by that of\nanother, and diversified by the size, figure, and situation of its\nparts, but we are wholly unable to conceive how these same things\n(viz., size, figure, and motion), can produce something else of a\nnature entirely different from themselves, as, for example, those\nsubstantial forms and real qualities which many philosophers suppose\nto be in bodies; nor likewise can we conceive how these qualities or\nforms possess force to cause motions in other bodies. But since we\nknow, from the nature of our soul, that the diverse motions of body\nare sufficient to produce in it all the sensations which it has, and\nsince we learn from experience that several of its sensations are in\nreality caused by such motions, while we do not discover that\nanything besides these motions ever passes from the organs of the\nexternal senses to the brain, we have reason to conclude that we in\nno way likewise apprehend that in external objects, which we call\nlight, colour, smell, taste, sound, heat or cold, and the other\ntactile qualities, or that which we call their substantial forms,\nunless as the various dispositions of these objects which have the\npower of moving our nerves in various ways. [Footnote: \"the diverse\nfigures, situations, magnitudes, and motions of their parts.\"--\nFrench.]\n\n\n CXCIX. That there is no phenomenon of nature whose explanation has\nbeen omitted in this treatise.\n\nAnd thus it may be gathered, from an enumeration that is easily\nmade, that there is no phenomenon of nature whose explanation has\nbeen omitted in this treatise; for beyond what is perceived by the\nsenses, there is nothing that can be considered a phenomenon of\nnature. But leaving out of account motion, magnitude, figure, [and\nthe situation of the parts of each body], which I have explained as\nthey exist in body, we perceive nothing out of us by our senses\nexcept light, colours, smells, tastes, sounds, and the tactile\nqualities; and these I have recently shown to be nothing more, at\nleast so far as they are known to us, than certain dispositions of\nthe objects, consisting in magnitude, figure, and motion.\n\n\n CC. That this treatise contains no principles which are not\nuniversally received; and that this philosophy is not new, but of\nall others the most ancient and common.\n\nBut I am desirous also that it should be observed that, though I\nhave here endeavoured to give an explanation of the whole nature of\nmaterial things, I have nevertheless made use of no principle which\nwas not received and approved by Aristotle, and by the other\nphilosophers of all ages; so that this philosophy, so far from being\nnew, is of all others the most ancient and common: for I have in\ntruth merely considered the figure, motion, and magnitude of bodies,\nand examined what must follow from their mutual concourse on the\nprinciples of mechanics, which are confirmed by certain and daily\nexperience. But no one ever doubted that bodies are moved, and that\nthey are of various sizes and figures, according to the diversity of\nwhich their motions also vary, and that from mutual collision those\nsomewhat greater than others are divided into many smaller, and thus\nchange figure. We have experience of the truth of this, not merely\nby a single sense, but by several, as touch, sight, and hearing: we\nalso distinctly imagine and understand it. This cannot be said of\nany of the other things that fall under our senses, as colours,\nsounds, and the like; for each of these affects but one of our\nsenses, and merely impresses upon our imagination a confused image\nof itself, affording our understanding no distinct knowledge of what\nit is.\n\n\n CCI. That sensible bodies are composed of insensible particles.\n\nBut I allow many particles in each body that are perceived by none\nof our senses, and this will not perhaps be approved of by those who\ntake the senses for the measure of the knowable. [We greatly wrong\nhuman reason, however, as appears to me, if we suppose that it does\nnot go beyond the eye-sight]; for no one can doubt that there are\nbodies so small as not to be perceptible by any of our senses,\nprovided he only consider what is each moment added to those bodies\nthat are being increased little by little, and what is taken from\nthose that are diminished in the same way. A tree increases daily,\nand it is impossible to conceive how it becomes greater than it was\nbefore, unless we at the same time conceive that some body is added\nto it. But who ever observed by the senses those small bodies that\nare in one day added to a tree while growing? Among the philosophers\nat least, those who hold that quantity is indefinitely divisible,\nought to admit that in the division the parts may become so small as\nto be wholly imperceptible. And indeed it ought not to be a matter\nof surprise, that we are unable to perceive very minute bodies; for\nthe nerves that must be moved by objects to cause perception are not\nthemselves very minute, but are like small cords, being composed of\na quantity of smaller fibres, and thus the most minute bodies are\nnot capable of moving them. Nor do I think that any one who makes\nuse of his reason will deny that we philosophize with much greater\ntruth when we judge of what takes place in those small bodies which\nare imperceptible from their minuteness only, after the analogy of\nwhat we see occurring in those we do perceive, [and in this way\nexplain all that is in nature, as I have essayed to do in this\ntreatise], than when we give an explanation of the same things by\ninventing I know not what novelties, that have no relation to the\nthings we actually perceive, [as first matter, substantial forms,\nand all that grand array of qualities which many are in the habit of\nsupposing, each of which is more difficult to comprehend than all\nthat is professed to be explained by means of them].\n\n\n CCII. That the philosophy of Democritus is not less different from\nours than from the common. [Footnote: \"that of Aristotle or the\nothers.\"--French.]\n\nBut it may be said that Democritus also supposed certain corpuscles\nthat were of various figures, sizes, and motions, from the heaping\ntogether and mutual concourse of which all sensible bodies arose;\nand, nevertheless, his mode of philosophizing is commonly rejected\nby all. To this I reply that the philosophy of Democritus was never\nrejected by any one, because he allowed the existence of bodies\nsmaller than those we perceive, and attributed to them diverse\nsizes, figures, and motions, for no one can doubt that there are in\nreality such, as we have already shown; but it was rejected, in the\nfirst place, because he supposed that these corpuscles were\nindivisible, on which ground I also reject it; in the second place,\nbecause he imagined there was a vacuum about them, which I show to\nbe impossible; thirdly, because he attributed gravity to these\nbodies, of which I deny the existence in any body, in so far as a\nbody is considered by itself, because it is a quality that depends\non the relations of situation and motion which several bodies bear\nto each other; and, finally, because he has not explained in\nparticular how all things arose from the concourse of corpuscles\nalone, or, if he gave this explanation with regard to a few of them,\nhis whole reasoning was far from being coherent, [or such as would\nwarrant us in extending the same explanation to the whole of\nnature]. This, at least, is the verdict we must give regarding his\nphilosophy, if we may judge of his opinions from what has been\nhanded down to us in writing. I leave it to others to determine\nwhether the philosophy I profess possesses a valid coherency, [and\nwhether on its principles we can make the requisite number of\ndeductions; and, inasmuch as the consideration of figure, magnitude,\nand motion has been admitted by Aristotle and by all the others, as\nwell as by Democritus, and since I reject all that the latter has\nsupposed, with this single exception, while I reject generally all\nthat has been supposed by the others, it is plain that this mode of\nphilosophizing has no more affinity with that of Democritus than of\nany other particular sect].\n\n\n CCIII. How we may arrive at the knowledge of the figures,\n[magnitudes], and motions of the insensible particles of bodies.\n\nBut, since I assign determinate figures, magnitudes, and motions to\nthe insensible particles of bodies, as if I had seen them, whereas I\nadmit that they do not fall under the senses, some one will perhaps\ndemand how I have come by my knowledge of them. [To this I reply,\nthat I first considered in general all the clear and distinct\nnotions of material things that are to be found in our\nunderstanding, and that, finding no others except those of figures,\nmagnitudes, and motions, and of the rules according to which these\nthree things can be diversified by each other, which rules are the\nprinciples of geometry and mechanics, I judged that all the\nknowledge man can have of nature must of necessity be drawn from\nthis source; because all the other notions we have of sensible\nthings, as confused and obscure, can be of no avail in affording us\nthe knowledge of anything out of ourselves, but must serve rather to\nimpede it]. Thereupon, taking as my ground of inference the simplest\nand best known of the principles that have been implanted in our\nminds by nature, I considered the chief differences that could\npossibly subsist between the magnitudes, and figures, and situations\nof bodies insensible on account of their smallness alone, and what\nsensible effects could be produced by their various modes of coming\ninto contact; and afterwards, when I found like effects in the\nbodies that we perceive by our senses, I judged that they could have\nbeen thus produced, especially since no other mode of explaining\nthem could be devised. And in this matter the example of several\nbodies made by art was of great service to me: for I recognize no\ndifference between these and natural bodies beyond this, that the\neffects of machines depend for the most part on the agency of\ncertain instruments, which, as they must bear some proportion to the\nhands of those who make them, are always so large that their figures\nand motions can be seen; in place of which, the effects of natural\nbodies almost always depend upon certain organs so minute as to\nescape our senses. And it is certain that all the rules of mechanics\nbelong also to physics, of which it is a part or species, [so that\nall that is artificial is withal natural]: for it is not less\nnatural for a clock, made of the requisite number of wheels, to mark\nthe hours, than for a tree, which has sprung from this or that seed,\nto produce the fruit peculiar to it. Accordingly, just as those who\nare familiar with automata, when they are informed of the use of a\nmachine, and see some of its parts, easily infer from these the way\nin which the others, that are not seen by them, are made; so from\nconsidering the sensible effects and parts of natural bodies, I have\nessayed to determine the character of their causes and insensible\nparts.\n\n\n CCIV. That, touching the things which our senses do not perceive,\nit is sufficient to explain how they can be, [and that this is all\nthat Aristotle has essayed].\n\nBut here some one will perhaps reply, that although I have supposed\ncauses which could produce all natural objects, we ought not on this\naccount to conclude that they were produced by these causes; for,\njust as the same artisan can make two clocks, which, though they\nboth equally well indicate the time, and are not different in\noutward appearance, have nevertheless nothing resembling in the\ncomposition of their wheels; so doubtless the Supreme Maker of\nthings has an infinity of diverse means at his disposal, by each of\nwhich he could have made all the things of this world to appear as\nwe see them, without it being possible for the human mind to know\nwhich of all these means he chose to employ. I most freely concede\nthis; and I believe that I have done all that was required, if the\ncauses I have assigned are such that their effects accurately\ncorrespond to all the phenomena of nature, without determining\nwhether it is by these or by others that they are actually produced.\nAnd it will be sufficient for the use of life to know the causes\nthus imagined, for medicine, mechanics, and in general all the arts\nto which the knowledge of physics is of service, have for their end\nonly those effects that are sensible, and that are accordingly to be\nreckoned among the phenomena of nature. [Footnote: \"have for their\nend only to apply certain sensible bodies to each other in such a\nway that, in the course of natural causes, certain sensible effects\nmay be produced; and we will be able to accomplish this quite as\nwell by considering the series of certain causes thus imagined,\nalthough false, as if they were the true, since this series is\nsupposed similar as far as regards sensible effects.\"-French.]\n\nAnd lest it should be supposed that Aristotle did, or professed to\ndo, anything more than this, it ought to be remembered that he\nhimself expressly says, at the commencement of the seventh chapter\nof the first book of the Meteorologies, that, with regard to things\nwhich are not manifest to the senses, he thinks to adduce sufficient\nreasons and demonstrations of them, if he only shows that they may\nbe such as he explains them. [Footnote: words in Greek]\n\n\n CCV. That nevertheless there is a moral certainty that all the\nthings of this world are such as has been here shown they may be.\n\nBut nevertheless, that I may not wrong the truth by supposing it\nless certain than it is, I will here distinguish two kinds of\ncertitude. The first is called moral, that is, a certainty\nsufficient for the conduct of life, though, if we look to the\nabsolute power of God, what is morally certain may be false. [Thus,\nthose who never visited Rome do not doubt that it is a city of\nItaly, though it might be that all from whom they got their\ninformation were deceived]. Again, if any one, wishing to decipher a\nletter written in Latin characters that are not placed in regular\norder, bethinks himself of reading a B wherever an A is found, and a\nC wherever there is a B, and thus of substituting in place of each\nletter the one which follows it in the order of the alphabet, and if\nby this means he finds that there are certain Latin words composed\nof these, he will not doubt that the true meaning of the writing is\ncontained in these words, although he may discover this only by\nconjecture, and although it is possible that the writer of it did\nnot arrange the letters on this principle of alphabetical order, but\non some other, and thus concealed another meaning in it: for this is\nso improbable [especially when the cipher contains a number of\nwords] as to seem incredible. But they who observe how many things\nregarding the magnet, fire, and the fabric of the whole world, are\nhere deduced from a very small number of principles, though they\ndeemed that I had taken them up at random and without grounds, will\nyet perhaps acknowledge that it could hardly happen that so many\nthings should cohere if these principles were false.\n\n\n CCVI. That we possess even more than a moral certainty of it.\n\nBesides, there are some, even among natural, things which we judge\nto be absolutely certain. [Absolute certainty arises when we judge\nthat it is impossible a thing can be otherwise than as we think it].\nThis certainty is founded on the metaphysical ground, that, as God\nis supremely good and the source of all truth, the faculty of\ndistinguishing truth from error which he gave us, cannot be\nfallacious so long as we use it aright, and distinctly perceive\nanything by it. Of this character are the demonstrations of\nmathematics, the knowledge that material things exist, and the clear\nreasonings that are formed regarding them. The results I have given\nin this treatise will perhaps be admitted to a place in the class of\ntruths that are absolutely certain, if it be considered that they\nare deduced in a continuous series from the first and most\nelementary principles of human knowledge; especially if it be\nsufficiently understood that we can perceive no external objects\nunless some local motion be caused by them in our nerves, and that\nsuch motion cannot be caused by the fixed stars, owing to their\ngreat distance from us, unless a motion be also produced in them and\nin the whole heavens lying between them and us: for these points\nbeing admitted, all the others, at least the more general doctrines\nwhich I have advanced regarding the world or earth [e. g., the\nfluidity of the heavens, Part III., Section XLVI.], will appear to\nbe almost the only possible explanations of the phenomena they\npresent.\n\n\n CCVII. That, however, I submit all my opinions to the authority of\nthe church.\n\nNevertheless, lest I should presume too far, I affirm nothing, but\nsubmit all these my opinions to the authority of the church and the\njudgment of the more sage; and I desire no one to believe anything I\nmay have said, unless he is constrained to admit it by the force and\nevidence of reason.","title":"Selections from the Principles of Philosophy","tradition":"philosophy-ethics","translated_text":null,"word_count":31383}