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Principles of Philosophy, The
From the Publisher's Preface
Rene Descartes
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       From the Publisher's Preface
       The present volume contains a reprint of the preface and the first
       part of the Principles of Philosophy, together with selections from
       the second, third and fourth parts of that work, corresponding to
       the extracts in the French edition of Gamier, are also given, as
       well as an appendix containing part of Descartes' reply to the
       Second Objections (viz., his formal demonstrations of the existence
       of Deity). The translation is based on the original Latin edition of
       the Principles, published in 1644.
       The work had been translated into French during Descartes' lifetime,
       and personally revised and corrected by him, the French text is
       evidently deserving of the same consideration as the Latin
       originals, and consequently, the additions and variations of the
       French version have also been given--the additions being put in
       square brackets in the text and the variations in the footnotes.
       A copy of the title-page of the original edition, as given in Dr. C.
       Guttler's work (Munich: C. H. Beck. 1901), are also reproduced in
       the present volume.
       SELECTIONS FROM THE PRINCIPLES OF PHILOSOPHY
       OF DESCARTES
       TRANSLATED FROM THE LATIN AND COLLATED WITH THE FRENCH
       LETTER OF THE AUTHOR
       TO THE FRENCH TRANSLATOR OF THE PRINCIPLES OF PHILOSOPHY SERVING FOR
       A PREFACE.
       Sir,--The version of my principles which you have been at pains to
       make, is so elegant and finished as to lead me to expect that the
       work will be more generally read in French than in Latin, and better
       understood. The only apprehension I entertain is lest the title
       should deter some who have not been brought up to letters, or with
       whom philosophy is in bad repute, because the kind they were taught
       has proved unsatisfactory; and this makes me think that it will be
       useful to add a preface to it for the purpose of showing what the
       MATTER of the work is, what END I had in view in writing it, and
       what UTILITY may be derived from it. But although it might be my
       part to write a preface of this nature, seeing I ought to know those
       particulars better than any other person, I cannot nevertheless
       prevail upon myself to do anything more than merely to give a
       summary of the chief points that fall, as I think, to be discussed
       in it: and I leave it to your discretion to present to the public
       such part of them as you shall judge proper.
       I should have desired, in the first place, to explain in it what
       philosophy is, by commencing with the most common matters, as, for
       example, that the word PHILOSOPHY signifies the study of wisdom, and
       that by wisdom is to be understood not merely prudence in the
       management of affairs, but a perfect knowledge of all that man can
       know, as well for the conduct of his life as for the preservation of
       his health and the discovery of all the arts, and that knowledge to
       subserve these ends must necessarily be deduced from first causes;
       so that in order to study the acquisition of it (which is properly
       called philosophizing), we must commence with the investigation of
       those first causes which are called PRINCIPLES. Now these principles
       must possess TWO CONDITIONS: in the first place, they must be so
       clear and evident that the human mind, when it attentively considers
       them, cannot doubt of their truth; in the second place, the
       knowledge of other things must be so dependent on them as that
       though the principles themselves may indeed be known apart from what
       depends on them, the latter cannot nevertheless be known apart from
       the former. It will accordingly be necessary thereafter to endeavour
       so to deduce from those principles the knowledge of the things that
       depend on them, as that there may be nothing in the whole series of
       deductions which is not perfectly manifest. God is in truth the only
       being who is absolutely wise, that is, who possesses a perfect
       knowledge of all things; but we may say that men are more or less
       wise as their knowledge of the most important truths is greater or
       less. And I am confident that there is nothing, in what I have now
       said, in which all the learned do not concur.
       I should, in the next place, have proposed to consider the utility
       of philosophy, and at the same time have shown that, since it
       embraces all that the human mind can know, we ought to believe that
       it is by it we are distinguished from savages and barbarians, and
       that the civilisation and culture of a nation is regulated by the
       degree in which true philosophy nourishes in it, and, accordingly,
       that to contain true philosophers is the highest privilege a state
       can enjoy. Besides this, I should have shown that, as regards
       individuals, it is not only useful for each man to have intercourse
       with those who apply themselves to this study, but that it is
       incomparably better he should himself direct his attention to it;
       just as it is doubtless to be preferred that a man should make use
       of his own eyes to direct his steps, and enjoy by means of the same
       the beauties of colour and light, than that he should blindly follow
       the guidance of another; though the latter course is certainly
       better than to have the eyes closed with no guide except one's self.
       But to live without philosophizing is in truth the same as keeping
       the eyes closed without attempting to open them; and the pleasure of
       seeing all that sight discloses is not to be compared with the
       satisfaction afforded by the discoveries of philosophy. And,
       finally, this study is more imperatively requisite for the
       regulation of our manners, and for conducting us through life, than
       is the use of our eyes for directing our steps. The brutes, which
       have only their bodies to conserve, are continually occupied in
       seeking sources of nourishment; but men, of whom the chief part is
       the mind, ought to make the search after wisdom their principal
       care, for wisdom is the true nourishment of the mind; and I feel
       assured, moreover, that there are very many who would not fail in
       the search, if they would but hope for success in it, and knew the
       degree of their capabilities for it. There is no mind, how ignoble
       soever it be, which remains so firmly bound up in the objects of the
       senses, as not sometime or other to turn itself away from them in
       the aspiration after some higher good, although not knowing
       frequently wherein that good consists. The greatest favourites of
       fortune--those who have health, honours, and riches in abundance--
       are not more exempt from aspirations of this nature than others;
       nay, I am persuaded that these are the persons who sigh the most
       deeply after another good greater and more perfect still than any
       they already possess. But the supreme good, considered by natural
       reason without the light of faith, is nothing more than the
       knowledge of truth through its first causes, in other words, the
       wisdom of which philosophy is the study. And, as all these
       particulars are indisputably true, all that is required to gain
       assent to their truth is that they be well stated.
       But as one is restrained from assenting to these doctrines by
       experience, which shows that they who make pretensions to philosophy
       are often less wise and reasonable than others who never applied
       themselves to the study, I should have here shortly explained
       wherein consists all the science we now possess, and what are the
       degrees of wisdom at which we have arrived. The first degree
       contains only notions so clear of themselves that they can be
       acquired without meditation; the second comprehends all that the
       experience of the senses dictates; the third, that which the
       conversation of other men teaches us; to which may be added as the
       fourth, the reading, not of all books, but especially of such as
       have been written by persons capable of conveying proper
       instruction, for it is a species of conversation we hold with their
       authors. And it seems to me that all the wisdom we in ordinary
       possess is acquired only in these four ways; for I do not class
       divine revelation among them, because it does not conduct us by
       degrees, but elevates us at once to an infallible faith.
       There have been, indeed, in all ages great minds who endeavoured to
       find a fifth road to wisdom, incomparably more sure and elevated
       than the other four. The path they essayed was the search of first
       causes and true principles, from which might be deduced the reasons
       of all that can be known by man; and it is to them the appellation
       of philosophers has been more especially accorded. I am not aware
       that there is any one of them up to the present who has succeeded in
       this enterprise. The first and chief whose writings we possess are
       Plato and Aristotle, between whom there was no difference, except
       that the former, following in the footsteps of his master, Socrates,
       ingenuously confessed that he had never yet been able to find
       anything certain, and that he was contented to write what seemed to
       him probable, imagining, for this end, certain principles by which
       he endeavoured to account for the other things. Aristotle, on the
       other hand, characterised by less candour, although for twenty years
       the disciple of Plato, and with no principles beyond those of his
       master, completely reversed his mode of putting them, and proposed
       as true and certain what it is probable he himself never esteemed as
       such. But these two men had acquired much judgment and wisdom by the
       four preceding means, qualities which raised their authority very
       high, so much so that those who succeeded them were willing rather
       to acquiesce in their opinions, than to seek better for themselves.
       The chief question among their disciples, however, was as to whether
       we ought to doubt of all things or hold some as certain,--a dispute
       which led them on both sides into extravagant errors; for a part of
       those who were for doubt, extended it even to the actions of life,
       to the neglect of the most ordinary rules required for its conduct;
       those, on the other hand, who maintained the doctrine of certainty,
       supposing that it must depend upon the senses, trusted entirely to
       them. To such an extent was this carried by Epicurus, that it is
       said he ventured to affirm, contrary to all the reasonings of the
       astronomers, that the sun is no larger than it appears.
       It is a fault we may remark in most disputes, that, as truth is the
       mean between the two opinions that are upheld, each disputant
       departs from it in proportion to the degree in which he possesses
       the spirit of contradiction. But the error of those who leant too
       much to the side of doubt, was not followed for any length of time,
       and that of the opposite party has been to some extent corrected by
       the doctrine that the senses are deceitful in many instances.
       Nevertheless, I do not know that this error was wholly removed by
       showing that certitude is not in the senses, but in the
       understanding alone when it has clear perceptions; and that while we
       only possess the knowledge which is acquired in the first four
       grades of wisdom, we ought not to doubt of the things that appear to
       be true in what regards the conduct of life, nor esteem them as so
       certain that we cannot change our opinions regarding them, even
       though constrained by the evidence of reason.
       From ignorance of this truth, or, if there was any one to whom it
       was known, from neglect of it, the majority of those who in these
       later ages aspired to be philosophers, blindly followed Aristotle,
       so that they frequently corrupted the sense of his writings, and
       attributed to him various opinions which he would not recognise as
       his own were he now to return to the world; and those who did not
       follow him, among whom are to be found many of the greatest minds,
       did yet not escape being imbued with his opinions in their youth, as
       these form the staple of instruction in the schools; and thus their
       minds were so preoccupied that they could not rise to the knowledge
       of true principles. And though I hold all the philosophers in
       esteem, and am unwilling to incur odium by my censure, I can adduce
       a proof of my assertion, which I do not think any of them will
       gainsay, which is, that they all laid down as a principle what they
       did not perfectly know. For example, I know none of them who did not
       suppose that there was gravity in terrestrial bodies; but although
       experience shows us very clearly that bodies we call heavy descend
       towards the center of the earth, we do not, therefore, know the
       nature of gravity, that is, the cause or principle in virtue of
       which bodies descend, and we must derive our knowledge of it from
       some other source. The same may be said of a vacuum and atoms, of
       heat and cold, of dryness and humidity, and of salt, sulphur, and
       mercury, and the other things of this sort which some have adopted
       as their principles. But no conclusion deduced from a principle
       which is not clear can be evident, even although the deduction be
       formally valid; and hence it follows that no reasonings based on
       such principles could lead them to the certain knowledge of any one
       thing, nor consequently advance them one step in the search after
       wisdom. And if they did discover any truth, this was due to one or
       other of the four means above mentioned. Notwithstanding this, I am
       in no degree desirous to lessen the honour which each of them can
       justly claim; I am only constrained to say, for the consolation of
       those who have not given their attention to study, that just as in
       travelling, when we turn our back upon the place to which we were
       going, we recede the farther from it in proportion as we proceed in
       the new direction for a greater length of time and with greater
       speed, so that, though we may be afterwards brought back to the
       right way, we cannot nevertheless arrive at the destined place as
       soon as if we had not moved backwards at all; so in philosophy, when
       we make use of false principles, we depart the farther from the
       knowledge of truth and wisdom exactly in proportion to the care with
       which we cultivate them, and apply ourselves to the deduction of
       diverse consequences from them, thinking that we are philosophizing
       well, while we are only departing the farther from the truth; from
       which it must be inferred that they who have learned the least of
       all that has been hitherto distinguished by the name of philosophy
       are the most fitted for the apprehension of truth.
       After making those matters clear, I should, in the next place, have
       desired to set forth the grounds for holding that the true
       principles by which we may reach that highest degree of wisdom
       wherein consists the sovereign good of human life, are those I have
       proposed in this work; and two considerations alone are sufficient
       to establish this--the first of which is, that these principles are
       very clear, and the second, that we can deduce all other truths from
       them; for it is only these two conditions that are required in true
       principles. But I easily prove that they are very clear; firstly, by
       a reference to the manner in which I found them, namely, by
       rejecting all propositions that were in the least doubtful, for it
       is certain that such as could not be rejected by this test when they
       were attentively considered, are the most evident and clear which
       the human mind can know. Thus by considering that he who strives to
       doubt of all is unable nevertheless to doubt that he is while he
       doubts, and that what reasons thus, in not being able to doubt of
       itself and doubting nevertheless of everything else, is not that
       which we call our body, but what we name our mind or thought, I have
       taken the existence of this thought for the first principle, from
       which I very clearly deduced the following truths, namely, that
       there is a God who is the author of all that is in the world, and
       who, being the source of all truth, cannot have created our
       understanding of such a nature as to be deceived in the judgments it
       forms of the things of which it possesses a very clear and distinct
       perception. Those are all the principles of which I avail myself
       touching immaterial or metaphysical objects, from which I most
       clearly deduce these other principles of physical or corporeal
       things, namely, that there are bodies extended in length, breadth,
       and depth, which are of diverse figures and are moved in a variety
       of ways. Such are in sum the principles from which I deduce all
       other truths. The second circumstance that proves the clearness of
       these principles is, that they have been known in all ages, and even
       received as true and indubitable by all men, with the exception only
       of the existence of God, which has been doubted by some, because
       they attributed too much to the perceptions of the senses, and God
       can neither be seen nor touched.
       But, though all the truths which I class among my principles were
       known at all times, and by all men, nevertheless, there has been no
       one up to the present, who, so far as I know, has adopted them as
       principles of philosophy: in other words, as such that we can deduce
       from them the knowledge of whatever else is in the world. It
       accordingly now remains for me to prove that they are such; and it
       appears to me that I cannot better establish this than by the test
       of experience: in other words, by inviting readers to peruse the
       following work. For, though I have not treated in it of all matters-
       -that being impossible--I think I have so explained all of which I
       had occasion to treat, that they who read it attentively will have
       ground for the persuasion that it is unnecessary to seek for any
       other principles than those I have given, in order to arrive at the
       most exalted knowledge of which the mind of man is capable;
       especially if, after the perusal of my writings, they take the
       trouble to consider how many diverse questions are therein discussed
       and explained, and, referring to the writings of others, they see
       how little probability there is in the reasons that are adduced in
       explanation of the same questions by principles different from mine.
       And that they may the more easily undertake this, I might have said
       that those imbued with my doctrines have much less difficulty in
       comprehending the writings of others, and estimating their true
       value, than those who have not been so imbued; and this is precisely
       the opposite of what I before said of such as commenced with the
       ancient philosophy, namely, that the more they have studied it the
       less fit are they for rightly apprehending the truth.
       I should also have added a word of advice regarding the manner of
       reading this work, which is, that I should wish the reader at first
       to go over the whole of it, as he would a romance, without greatly
       straining his attention, or tarrying at the difficulties he may
       perhaps meet with in it, with the view simply of knowing in general
       the matters of which I treat; and that afterwards, if they seem to
       him to merit a more careful examination, and he feel a desire to
       know their causes, he may read it a second time, in order to observe
       the connection of my reasonings; but that he must not then give it
       up in despair, although he may not everywhere sufficiently discover
       the connection of the proof, or understand all the reasonings--it
       being only necessary to mark with a pen the places where the
       difficulties occur, and continue to read without interruption to the
       end; then, if he does not grudge to take up the book a third time, I
       am confident he will find in a fresh perusal the solution of most of
       the difficulties he will have marked before; and that, if any still
       remain, their solution will in the end be found in another reading.
       I have observed, on examining the natural constitutions of different
       minds, that there are hardly any so dull or slow of understanding as
       to be incapable of apprehending good opinions, or even of acquiring
       all the highest sciences, if they be but conducted along the right
       road. And this can also be proved by reason; for, as the principles
       are clear, and as nothing ought to be deduced from them, unless most
       manifest inferences, no one is so devoid of intelligence as to be
       unable to comprehend the conclusions that flow from them. But,
       besides the entanglement of prejudices, from which no one is
       entirely exempt, although it is they who have been the most ardent
       students of the false sciences that receive the greatest detriment
       from them, it happens very generally that people of ordinary
       capacity neglect to study from a conviction that they want ability,
       and that others, who are more ardent, press on too rapidly: whence
       it comes to pass that they frequently admit principles far from
       evident, and draw doubtful inferences from them. For this reason, I
       should wish to assure those who are too distrustful of their own
       ability that there is nothing in my writings which they may not
       entirely understand, if they only take the trouble to examine them;
       and I should wish, at the same time, to warn those of an opposite
       tendency that even the most superior minds will have need of much
       time and attention to remark all I designed to embrace therein.
       After this, that I might lead men to understand the real design I
       had in publishing them, I should have wished here to explain the
       order which it seems to me one ought to follow with the view of
       instructing himself. In the first place, a man who has merely the
       vulgar and imperfect knowledge which can be acquired by the four
       means above explained, ought, before all else, to endeavour to form
       for himself a code of morals, sufficient to regulate the actions of
       his life, as well for the reason that this does not admit of delay
       as because it ought to be our first care to live well. In the next
       place, he ought to study Logic, not that of the schools, for it is
       only, properly speaking, a dialectic which teaches the mode of
       expounding to others what we already know, or even of speaking much,
       without judgment, of what we do not know, by which means it corrupts
       rather than increases good sense--but the logic which teaches the
       right conduct of the reason with the view of discovering the truths
       of which we are ignorant; and, because it greatly depends on usage,
       it is desirable he should exercise himself for a length of time in
       practising its rules on easy and simple questions, as those of the
       mathematics. Then, when he has acquired some skill in discovering
       the truth in these questions, he should commence to apply himself in
       earnest to true philosophy, of which the first part is Metaphysics,
       containing the principles of knowledge, among which is the
       explication of the principal attributes of God, of the immateriality
       of the soul, and of all the clear and simple notions that are in us;
       the second is Physics, in which, after finding the true principles
       of material things, we examine, in general, how the whole universe
       has been framed; in the next place, we consider, in particular, the
       nature of the earth, and of all the bodies that are most generally
       found upon it, as air, water, fire, the loadstone and other
       minerals. In the next place it is necessary also to examine singly
       the nature of plants, of animals, and above all of man, in order
       that we may thereafter be able to discover the other sciences that
       are useful to us. Thus, all Philosophy is like a tree, of which
       Metaphysics is the root, Physics the trunk, and all the other
       sciences the branches that grow out of this trunk, which are reduced
       to three principal, namely, Medicine, Mechanics, and Ethics. By the
       science of Morals, I understand the highest and most perfect which,
       presupposing an entire knowledge of the other sciences, is the last
       degree of wisdom.
       But as it is not from the roots or the trunks of trees that we
       gather the fruit, but only from the extremities of their branches,
       so the principal utility of philosophy depends on the separate uses
       of its parts, which we can only learn last of all. But, though I am
       ignorant of almost all these, the zeal I have always felt in
       endeavouring to be of service to the public, was the reason why I
       published, some ten or twelve years ago, certain Essays on the
       doctrines I thought I had acquired. The first part of these Essays
       was a "Discourse on the Method of rightly conducting the Reason, and
       seeking Truth in the Sciences," in which I gave a summary of the
       principal rules of logic, and also of an imperfect ethic, which a
       person may follow provisionally so long as he does not know any
       better. The other parts were three treatises: the first of
       Dioptrics, the second of Meteors, and the third of Geometry. In the
       Dioptrics, I designed to show that we might proceed far enough in
       philosophy as to arrive, by its means, at the knowledge of the arts
       that are useful to life, because the invention of the telescope, of
       which I there gave an explanation, is one of the most difficult that
       has ever been made. In the treatise of Meteors, I desired to exhibit
       the difference that subsists between the philosophy I cultivate and
       that taught in the schools, in which the same matters are usually
       discussed. In fine, in the Geometry, I professed to demonstrate that
       I had discovered many things that were before unknown, and thus
       afford ground for believing that we may still discover many others,
       with the view of thus stimulating all to the investigation of truth.
       Since that period, anticipating the difficulty which many would
       experience in apprehending the foundations of the Metaphysics, I
       endeavoured to explain the chief points of them in a book of
       Meditations, which is not in itself large, but the size of which has
       been increased, and the matter greatly illustrated, by the
       Objections which several very learned persons sent to me on occasion
       of it, and by the Replies which I made to them. At length, after it
       appeared to me that those preceding treatises had sufficiently
       prepared the minds of my readers for the Principles of Philosophy, I
       also published it; and I have divided this work into four parts, the
       first of which contains the principles of human knowledge, and which
       may be called the First Philosophy, or Metaphysics. That this part,
       accordingly, may be properly understood, it will be necessary to
       read beforehand the book of Meditations I wrote on the same subject.
       The other three parts contain all that is most general in Physics,
       namely, the explication of the first laws or principles of nature,
       and the way in which the heavens, the fixed stars, the planets,
       comets, and generally the whole universe, were composed; in the next
       place, the explication, in particular, of the nature of this earth,
       the air, water, fire, the magnet, which are the bodies we most
       commonly find everywhere around it, and of all the qualities we
       observe in these bodies, as light, heat, gravity, and the like. In
       this way, it seems to me, I have commenced the orderly explanation
       of the whole of philosophy, without omitting any of the matters that
       ought to precede the last which I discussed. But to bring this
       undertaking to its conclusion, I ought hereafter to explain, in the
       same manner, the nature of the other more particular bodies that are
       on the earth, namely, minerals, plants, animals, and especially man;
       finally, to treat thereafter with accuracy of Medicine, Ethics, and
       Mechanics. I should require to do this in order to give to the world
       a complete body of philosophy; and I do not yet feel myself so old,-
       -I do not so much distrust my strength, nor do I find myself so far
       removed from the knowledge of what remains, as that I should not
       dare to undertake to complete this design, provided I were in a
       position to make all the experiments which I should require for the
       basis and verification of my reasonings. But seeing that would
       demand a great expenditure, to which the resources of a private
       individual like myself would not be adequate, unless aided by the
       public, and as I have no ground to expect this aid, I believe that I
       ought for the future to content myself with studying for my own
       instruction, and posterity will excuse me if I fail hereafter to
       labour for them.
       Meanwhile, that it may be seen wherein I think I have already
       promoted the general good, I will here mention the fruits that may
       be gathered from my Principles. The first is the satisfaction which
       the mind will experience on finding in the work many truths before
       unknown; for although frequently truth does not so greatly affect
       our imagination as falsity and fiction, because it seems less
       wonderful and is more simple, yet the gratification it affords is
       always more durable and solid. The second fruit is, that in studying
       these principles we will become accustomed by degrees to judge
       better of all the things we come in contact with, and thus be made
       wiser, in which respect the effect will be quite the opposite of the
       common philosophy, for we may easily remark in those we call pedants
       that it renders them less capable of rightly exercising their reason
       than they would have been if they had never known it. The third is,
       that the truths which they contain, being highly clear and certain,
       will take away all ground of dispute, and thus dispose men's minds
       to gentleness and concord; whereas the contrary is the effect of the
       controversies of the schools, which, as they insensibly render those
       who are exercised in them more wrangling and opinionative, are
       perhaps the prime cause of the heresies and dissensions that now
       harass the world. The last and chief fruit of these Principles is,
       that one will be able, by cultivating them, to discover many truths
       I myself have not unfolded, and thus passing by degrees from one to
       another, to acquire in course of time a perfect knowledge of the
       whole of philosophy, and to rise to the highest degree of wisdom.
       For just as all the arts, though in their beginnings they are rude
       and imperfect, are yet gradually perfected by practice, from their
       containing at first something true, and whose effect experience
       evinces; so in philosophy, when we have true principles, we cannot
       fail by following them to meet sometimes with other truths; and we
       could not better prove the falsity of those of Aristotle, than by
       saying that men made no progress in knowledge by their means during
       the many ages they prosecuted them.
       I well know that there are some men so precipitate and accustomed to
       use so little circumspection in what they do, that, even with the
       most solid foundations, they could not rear a firm superstructure;
       and as it is usually those who are the readiest to make books, they
       would in a short time mar all that I have done, and introduce
       uncertainty and doubt into my manner of philosophizing, from which I
       have carefully endeavoured to banish them, if people were to receive
       their writings as mine, or as representing my opinions. I had, not
       long ago, some experience of this in one of those who were believed
       desirous of following me the most closely, [Footnote: Regius; see La
       Vie de M. Descartes, reduite en abrege (Baillet). Liv. vii., chap.
       vii.--T.] and one too of whom I had somewhere said that I had such
       confidence in his genius as to believe that he adhered to no
       opinions which I should not be ready to avow as mine; for he last
       year published a book entitled "Fundamental Physics," in which,
       although he seems to have written nothing on the subject of Physics
       and Medicine which he did not take from my writings, as well from
       those I have published as from another still imperfect on the nature
       of animals, which fell into his hands; nevertheless, because he has
       copied them badly, and changed the order, and denied certain
       metaphysical truths upon which all Physics ought to be based, I am
       obliged wholly to disavow his work, and here to request readers not
       to attribute to me any opinion unless they find it expressly stated
       in my own writings, and to receive no opinion as true, whether in my
       writings or elsewhere, unless they see that it is very clearly
       deduced from true principles. I well know, likewise, that many ages
       may elapse ere all the truths deducible from these principles are
       evolved out of them, as well because the greater number of such as
       remain to be discovered depend on certain particular experiments
       that never occur by chance, but which require to be investigated
       with care and expense by men of the highest intelligence, as because
       it will hardly happen that the same persons who have the sagacity to
       make a right use of them, will possess also the means of making
       them, and also because the majority of the best minds have formed so
       low an estimate of philosophy in general, from the imperfections
       they have remarked in the kind in vogue up to the present time, that
       they cannot apply themselves to the search after truth.
       But, in conclusion, if the difference discernible between the
       principles in question and those of every other system, and the
       great array of truths deducible from them, lead them to discern the
       importance of continuing the search after these truths, and to
       observe the degree of wisdom, the perfection and felicity of life,
       to which they are fitted to conduct us, I venture to believe that
       there will not be found one who is not ready to labour hard in so
       profitable a study, or at least to favour and aid with all his might
       those who shall devote themselves to it with success.
       The height of my wishes is, that posterity may sometime behold the
       happy issue of it, etc.
       TO THE MOST SERENE PRINCESS,
       ELIZABETH, ELDEST DAUGHTER OF FREDERICK, KING OF BOHEMIA, COUNT
       PALATINE, AND ELECTOR OF THE SACRED ROMAN EMPIRE.
       MADAM,--The greatest advantage I have derived from the writings
       which I have already published, has arisen from my having, through
       means of them, become known to your Highness, and thus been
       privileged to hold occasional converse with one in whom so many rare
       and estimable qualities are united, as to lead me to believe I
       should do service to the public by proposing them as an example to
       posterity. It would ill become me to flatter, or to give expression
       to anything of which I had no certain knowledge, especially in the
       first pages of a work in which I aim at laying down the principles
       of truth. And the generous modesty that is conspicuous in all your
       actions, assures me that the frank and simple judgment of a man who
       only writes what he believes will be more agreeable to you than the
       ornate laudations of those who have studied the art of compliment.
       For this reason, I will give insertion to nothing in this letter for
       which I have not the certainty both of experience and reason; and in
       the exordium, as in the rest of the work, I will write only as
       becomes a philosopher. There is a vast difference between real and
       apparent virtues; and there is also a great discrepancy between
       those real virtues that proceed from an accurate knowledge of the
       truth, and such as are accompanied with ignorance or error. The
       virtues I call apparent are only, properly speaking, vices, which,
       as they are less frequent than the vices that are opposed to them,
       and are farther removed from them than the intermediate virtues, are
       usually held in higher esteem than those virtues. Thus, because
       those who fear dangers too much are more numerous than they who fear
       them too little, temerity is frequently opposed to the vice of
       timidity, and taken for a virtue, and is commonly more highly
       esteemed than true fortitude. Thus, also, the prodigal are in
       ordinary more praised than the liberal; and none more easily acquire
       a great reputation for piety than the superstitious and
       hypocritical. With regard to true virtues, these do not all proceed
       from true knowledge, for there are some that likewise spring from
       defect or error; thus, simplicity is frequently the source of
       goodness, fear of devotion, and despair of courage. The virtues that
       are thus accompanied with some imperfections differ from each other,
       and have received diverse appellations. But those pure and perfect
       virtues that arise from the knowledge of good alone are all of the
       same nature, and may be comprised under the single term wisdom. For,
       whoever owns the firm and constant resolution of always using his
       reason as well as lies in his power, and in all his actions of doing
       what he judges to be best, is truly wise, as far as his nature
       permits; and by this alone he is just, courageous, temperate, and
       possesses all the other virtues, but so well balanced as that none
       of them appears more prominent than another: and for this reason,
       although they are much more perfect than the virtues that blaze
       forth through the mixture of some defect, yet, because the crowd
       thus observes them less, they are not usually extolled so highly.
       Besides, of the two things that are requisite for the wisdom thus
       described, namely, the perception of the understanding and the
       disposition of the will, it is only that which lies in the will
       which all men can possess equally, inasmuch as the understanding of
       some is inferior to that of others. But although those who have only
       an inferior understanding may be as perfectly wise as their nature
       permits, and may render themselves highly acceptable to God by their
       virtue, provided they preserve always a firm and constant resolution
       to do all that they shall judge to be right, and to omit nothing
       that may lead them to the knowledge of the duties of which they are
       ignorant; nevertheless, those who preserve a constant resolution of
       performing the right, and are especially careful in instructing
       themselves, and who possess also a highly perspicacious intellect,
       arrive doubtless at a higher degree of wisdom than others; and I see
       that these three particulars are found in great perfection in your
       Highness. For, in the first place, your desire of self-instruction
       is manifest, from the circumstance that neither the amusements of
       the court, nor the accustomed mode of educating ladies, which
       ordinarily condemns them to ignorance, have been sufficient to
       prevent you from studying with much care all that is best in the
       arts and sciences; and the incomparable perspicacity of your
       intellect is evinced by this, that you penetrated the secrets of the
       sciences and acquired an accurate knowledge of them in a very short
       period. But of the vigour of your intellect I have a still stronger
       proof, and one peculiar to myself, in that I have never yet met any
       one who understood so generally and so well as yourself all that is
       contained in my writings. For there are several, even among men of
       the highest intellect and learning, who find them very obscure. And
       I remark, in almost all those who are versant in Metaphysics, that
       they are wholly disinclined from Geometry; and, on the other hand,
       that the cultivators of Geometry have no ability for the
       investigations of the First Philosophy: insomuch that I can say with
       truth I know but one mind, and that is your own, to which both
       studies are alike congenial, and which I therefore, with propriety,
       designate incomparable. But what most of all enhances my admiration
       is, that so accurate and varied an acquaintance with the whole
       circle of the sciences is not found in some aged doctor who has
       employed many years in contemplation, but in a Princess still young,
       and whose countenance and years would more fitly represent one of
       the Graces than a Muse or the sage Minerva. In conclusion, I not
       only remark in your Highness all that is requisite on the part of
       the mind to perfect and sublime wisdom, but also all that can be
       required on the part of the will or the manners, in which benignity
       and gentleness are so conjoined with majesty that, though fortune
       has attacked you with continued injustice, it has failed either to
       irritate or crush you. And this constrains me to such veneration
       that I not only think this work due to you, since it treats of
       philosophy which is the study of wisdom, but likewise feel not more
       zeal for my reputation as a philosopher than pleasure in subscribing
       myself,--
       Of your most Serene Highness, The most devoted servant,
       DESCARTES. _