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       PART I. OF THE PRINCIPLES OF HUMAN KNOWLEDGE
       I. THAT in order to seek truth, it is necessary once in the course
       of our life, to doubt, as far as possible, of all things.
       As we were at one time children, and as we formed various judgments
       regarding the objects presented to our senses, when as yet we had
       not the entire use of our reason, numerous prejudices stand in the
       way of our arriving at the knowledge of truth; and of these it seems
       impossible for us to rid ourselves, unless we undertake, once in our
       lifetime, to doubt of all those things in which we may discover even
       the smallest suspicion of uncertainty.
       II. That we ought also to consider as false all that is doubtful.
       Moreover, it will be useful likewise to esteem as false the things
       of which we shall be able to doubt, that we may with greater
       clearness discover what possesses most certainty and is the easiest
       to know.
       III. That we ought not meanwhile to make use of doubt in the
       conduct of life.
       In the meantime, it is to be observed that we are to avail ourselves
       of this general doubt only while engaged in the contemplation of
       truth. For, as far as concerns the conduct of life, we are very
       frequently obliged to follow opinions merely probable, or even
       sometimes, though of two courses of action we may not perceive more
       probability in the one than in the other, to choose one or other,
       seeing the opportunity of acting would not unfrequently pass away
       before we could free ourselves from our doubts.
       IV. Why we may doubt of sensible things.
       Accordingly, since we now only design to apply ourselves to the
       investigation of truth, we will doubt, first, whether of all the
       things that have ever fallen under our senses, or which we have ever
       imagined, any one really exist; in the first place, because we know
       by experience that the senses sometimes err, and it would be
       imprudent to trust too much to what has even once deceived us;
       secondly, because in dreams we perpetually seem to perceive or
       imagine innumerable objects which have no existence. And to one who
       has thus resolved upon a general doubt, there appear no marks by
       which he can with certainty distinguish sleep from the waking state.
       V. Why we may also doubt of mathematical demonstrations.
       We will also doubt of the other things we have before held as most
       certain, even of the demonstrations of mathematics, and of their
       principles which we have hitherto deemed self-evident; in the first
       place, because we have sometimes seen men fall into error in such
       matters, and admit as absolutely certain and self evident what to us
       appeared false, but chiefly because we have learnt that God who
       created us is all-powerful; for we do not yet know whether perhaps
       it was his will to create us so that we are always deceived, even in
       the things we think we know best: since this does not appear more
       impossible than our being occasionally deceived, which, however, as
       observation teaches us, is the case. And if we suppose that an all-
       powerful God is not the author of our being, and that we exist of
       ourselves or by some other means, still, the less powerful we
       suppose our author to be, the greater reason will we have for
       believing that we are not so perfect as that we may not be
       continually deceived.
       VI. That we possess a free-will, by which we can withhold our
       assent from what is doubtful, and thus avoid error.
       But meanwhile, whoever in the end may be the author of our being,
       and however powerful and deceitful he may be, we are nevertheless
       conscious of a freedom, by which we can refrain from admitting to a
       place in our belief aught that is not manifestly certain and
       undoubted, and thus guard against ever being deceived.
       VII. That we cannot doubt of our existence while we doubt, and that
       this is the first knowledge we acquire when we philosophize in
       order.
       While we thus reject all of which we can entertain the smallest
       doubt, and even imagine that it is false, we easily indeed suppose
       that there is neither God, nor sky, nor bodies, and that we
       ourselves even have neither hands nor feet, nor, finally, a body;
       but we cannot in the same way suppose that we are not while we doubt
       of the truth of these things; for there is a repugnance in
       conceiving that what thinks does not exist at the very time when it
       thinks. Accordingly, the knowledge, _I_ THINK, THEREFORE _I_ AM, is
       the first and most certain that occurs to one who philosophizes
       orderly.
       VIII. That we hence discover the distinction between the mind and
       the body, or between a thinking and corporeal thing.
       And this is the best mode of discovering the nature of the mind, and
       its distinctness from the body: for examining what we are, while
       supposing, as we now do, that there is nothing really existing apart
       from our thought, we clearly perceive that neither extension, nor
       figure, nor local motion,[Footnote: Instead of "local motion," the
       French has "existence in any place."] nor anything similar that can
       be attributed to body, pertains to our nature, and nothing save
       thought alone; and, consequently, that the notion we have of our
       mind precedes that of any corporeal thing, and is more certain,
       seeing we still doubt whether there is any body in existence, while
       we already perceive that we think.
       IX. What thought (COGITATIO) is.
       By the word thought, I understand all that which so takes place in
       us that we of ourselves are immediately conscious of it; and,
       accordingly, not only to understand (INTELLIGERE, ENTENDRE), to will
       (VELLE), to imagine (IMAGINARI), but even to perceive (SENTIRE,
       SENTIR), are here the same as to think (COGITARE, PENSER). For if I
       say, I see, or, I walk, therefore I am; and if I understand by
       vision or walking the act of my eyes or of my limbs, which is the
       work of the body, the conclusion is not absolutely certain, because,
       as is often the case in dreams, I may think that I see or walk,
       although I do not open my eyes or move from my place, and even,
       perhaps, although I have no body: but, if I mean the sensation
       itself, or consciousness of seeing or walking, the knowledge is
       manifestly certain, because it is then referred to the mind, which
       alone perceives or is conscious that it sees or walks. [Footnote: In
       the French, "which alone has the power of perceiving, or of being
       conscious in any other way whatever."]
       X. That the notions which are simplest and self-evident, are
       obscured by logical definitions; and that such are not to be
       reckoned among the cognitions acquired by study, [but as born with
       us].
       I do not here explain several other terms which I have used, or
       design to use in the sequel, because their meaning seems to me
       sufficiently self-evident. And I frequently remarked that
       philosophers erred in attempting to explain, by logical definitions,
       such truths as are most simple and self-evident; for they thus only
       rendered them more obscure. And when I said that the proposition,
       _I_ THINK, THEREFORE _I_ AM, is of all others the first and most
       certain which occurs to one philosophizing orderly, I did not
       therefore deny that it was necessary to know what thought,
       existence, and certitude are, and the truth that, in order to think
       it is necessary to be, and the like; but, because these are the most
       simple notions, and such as of themselves afford the knowledge of
       nothing existing, I did not judge it proper there to enumerate them.
       XI. How we can know our mind more clearly than our body.
       But now that it may be discerned how the knowledge we have of the
       mind not only precedes, and has greater certainty, but is even
       clearer, than that we have of the body, it must be remarked, as a
       matter that is highly manifest by the natural light, that to nothing
       no affections or qualities belong; and, accordingly, that where we
       observe certain affections, there a thing or substance to which
       these pertain, is necessarily found. The same light also shows us
       that we know a thing or substance more clearly in proportion as we
       discover in it a greater number of qualities. Now, it is manifest
       that we remark a greater number of qualities in our mind than in any
       other thing; for there is no occasion on which we know anything
       whatever when we are not at the same time led with much greater
       certainty to the knowledge of our own mind. For example, if I judge
       that there is an earth because I touch or see it, on the same
       ground, and with still greater reason, I must be persuaded that my
       mind exists; for it may be, perhaps, that I think I touch the earth
       while there is one in existence; but it is not possible that I
       should so judge, and my mind which thus judges not exist; and the
       same holds good of whatever object is presented to our mind.
       XII. How it happens that every one does not come equally to know
       this.
       Those who have not philosophized in order have had other opinions on
       this subject, because they never distinguished with sufficient care
       the mind from the body. For, although they had no difficulty in
       believing that they themselves existed, and that they had a higher
       assurance of this than of any other thing, nevertheless, as they did
       not observe that by THEMSELVES, they ought here to understand their
       MINDS alone [when the question related to metaphysical certainty];
       and since, on the contrary, they rather meant their bodies which
       they saw with their eyes, touched with their hands, and to which
       they erroneously attributed the faculty of perception, they were
       prevented from distinctly apprehending the nature of the mind.
       XIII. In what sense the knowledge of other things depends upon the
       knowledge of God.
       But when the mind, which thus knows itself but is still in doubt as
       to all other things, looks around on all sides, with a view to the
       farther extension of its knowledge, it first of all discovers within
       itself the ideas of many things; and while it simply contemplates
       them, and neither affirms nor denies that there is anything beyond
       itself corresponding to them, it is in no danger of erring. The mind
       also discovers certain common notions out of which it frames various
       demonstrations that carry conviction to such a degree as to render
       doubt of their truth impossible, so long as we give attention to
       them. For example, the mind has within itself ideas of numbers and
       figures, and it has likewise among its common notions the principle
       THAT IF EQUALS BE ADDED TO EQUALS THE WHOLES WILL BE EQUAL and the
       like; from which it is easy to demonstrate that the three angles of
       a triangle are equal to two right angles, etc. Now, so long as we
       attend to the premises from which this conclusion and others similar
       to it were deduced, we feel assured of their truth; but, as the mind
       cannot always think of these with attention, when it has the
       remembrance of a conclusion without recollecting the order of its
       deduction, and is uncertain whether the author of its being has
       created it of a nature that is liable to be deceived, even in what
       appears most evident, it perceives that there is just ground to
       distrust the truth of such conclusions, and that it cannot possess
       any certain knowledge until it has discovered its author.
       XIV. That we may validly infer the existence of God from necessary
       existence being comprised in the concept we have of him.
       When the mind afterwards reviews the different ideas that are in it,
       it discovers what is by far the chief among them--that of a Being
       omniscient, all-powerful, and absolutely perfect; and it observes
       that in this idea there is contained not only possible and
       contingent existence, as in the ideas of all other things which it
       clearly perceives, but existence absolutely necessary and eternal.
       And just as because, for example, the equality of its three angles
       to two right angles is necessarily comprised in the idea of a
       triangle, the mind is firmly persuaded that the three angles of a
       triangle are equal to two right angles; so, from its perceiving
       necessary and eternal existence to be comprised in the idea which it
       has of an all-perfect Being, it ought manifestly to conclude that
       this all-perfect Being exists.
       XV. That necessary existence is not in the same way comprised in
       the notions which we have of other things, but merely contingent
       existence.
       The mind will be still more certain of the truth of this conclusion,
       if it consider that it has no idea of any other thing in which it
       can discover that necessary existence is contained; for, from this
       circumstance alone, it will discern that the idea of an all-perfect
       Being has not been framed by itself, and that it does not represent
       a chimera, but a true and immutable nature, which must exist since
       it can only be conceived as necessarily existing.
       XVI. That prejudices hinder many from clearly knowing the necessity
       of the existence of God.
       Our mind would have no difficulty in assenting to this truth, if it
       were, first of all, wholly free from prejudices; but as we have been
       accustomed to distinguish, in all other things, essence from
       existence, and to imagine at will many ideas of things which neither
       are nor have been, it easily happens, when we do not steadily fix
       our thoughts on the contemplation of the all-perfect Being, that a
       doubt arises as to whether the idea we have of him is not one of
       those which we frame at pleasure, or at least of that class to whose
       essence existence does not pertain.
       XVII. That the greater objective (representative) perfection there
       is in our idea of a thing, the greater also must be the perfection
       of its cause.
       When we further reflect on the various ideas that are in us, it is
       easy to perceive that there is not much difference among them, when
       we consider them simply as certain modes of thinking, but that they
       are widely different, considered in reference to the objects they
       represent; and that their causes must be so much the more perfect
       according to the degree of objective perfection contained in them.
       [Footnote: "as what they represent of their object has more
       perfection."--FRENCH.] For there is no difference between this and
       the case of a person who has the idea of a machine, in the
       construction of which great skill is displayed, in which
       circumstances we have a right to inquire how he came by this idea,
       whether, for example, he somewhere saw such a machine constructed by
       another, or whether he was so accurately taught the mechanical
       sciences, or is endowed with such force of genius, that he was able
       of himself to invent it, without having elsewhere seen anything like
       it; for all the ingenuity which is contained in the idea objectively
       only, or as it were in a picture, must exist at least in its first
       and chief cause, whatever that may be, not only objectively or
       representatively, but in truth formally or eminently.
       XVIII. That the existence of God may be again inferred from the
       above.
       Thus, because we discover in our minds the idea of God, or of an
       all-perfect Being, we have a right to inquire into the source whence
       we derive it; and we will discover that the perfections it
       represents are so immense as to render it quite certain that we
       could only derive it from an all-perfect Being; that is, from a God
       really existing. For it is not only manifest by the natural light
       that nothing cannot be the cause of anything whatever, and that the
       more perfect cannot arise from the less perfect, so as to be thereby
       produced as by its efficient and total cause, but also that it is
       impossible we can have the idea or representation of anything
       whatever, unless there be somewhere, either in us or out of us, an
       original which comprises, in reality, all the perfections that are
       thus represented to us; but, as we do not in any way find in
       ourselves those absolute perfections of which we have the idea, we
       must conclude that they exist in some nature different from ours,
       that is, in God, or at least that they were once in him; and it most
       manifestly follows [from their infinity] that they are still there.
       XIX. That, although we may not comprehend the nature of God, there
       is yet nothing which we know so clearly as his perfections.
       This will appear sufficiently certain and manifest to those who have
       been accustomed to contemplate the idea of God, and to turn their
       thoughts to his infinite perfections; for, although we may not
       comprehend them, because it is of the nature of the infinite not to
       be comprehended by what is finite, we nevertheless conceive them
       more clearly and distinctly than material objects, for this reason,
       that, being simple, and unobscured by limits,[Footnote: After
       LIMITS, "what of them we do conceive is much less confused. There
       is, besides, no speculation more calculated to aid in perfecting our
       understanding, and which is more important than this, inasmuch as
       the consideration of an object that has no limits to its perfections
       fills us with satisfaction and assurance."-FRENCH.] they occupy our
       mind more fully.
       XX. That we are not the cause of ourselves, but that this is God,
       and consequently that there is a God.
       But, because every one has not observed this, and because, when we
       have an idea of any machine in which great skill is displayed, we
       usually know with sufficient accuracy the manner in which we
       obtained it, and as we cannot even recollect when the idea we have
       of a God was communicated to us by him, seeing it was always in our
       minds, it is still necessary that we should continue our review, and
       make inquiry after our author, possessing, as we do, the idea of the
       infinite perfections of a God: for it is in the highest degree
       evident by the natural light, that that which knows something more
       perfect than itself, is not the source of its own being, since it
       would thus have given to itself all the perfections which it knows;
       and that, consequently, it could draw its origin from no other being
       than from him who possesses in himself all those perfections, that
       is, from God.
       XXI. That the duration alone of our life is sufficient to
       demonstrate the existence of God.
       The truth of this demonstration will clearly appear, provided we
       consider the nature of time, or the duration of things; for this is
       of such a kind that its parts are not mutually dependent, and never
       co-existent; and, accordingly, from the fact that we now are, it
       does not necessarily follow that we shall be a moment afterwards,
       unless some cause, viz., that which first produced us, shall, as it
       were, continually reproduce us, that is, conserve us. For we easily
       understand that there is no power in us by which we can conserve
       ourselves, and that the being who has so much power as to conserve
       us out of himself, must also by so much the greater reason conserve
       himself, or rather stand in need of being conserved by no one
       whatever, and, in fine, be God.
       XXII. That in knowing the existence of God, in the manner here
       explained, we likewise know all his attributes, as far as they can
       be known by the natural light alone.
       There is the great advantage in proving the existence of God in this
       way, viz., by his idea, that we at the same time know what he is, as
       far as the weakness of our nature allows; for, reflecting on the
       idea we have of him which is born with us, we perceive that he is
       eternal, omniscient, omnipotent, the source of all goodness and
       truth, creator of all things, and that, in fine, he has in himself
       all that in which we can clearly discover any infinite perfection or
       good that is not limited by any imperfection.
       XXIII. That God is not corporeal, and does not perceive by means of
       senses as we do, or will the evil of sin.
       For there are indeed many things in the world that are to a certain
       extent imperfect or limited, though possessing also some perfection;
       and it is accordingly impossible that any such can be in God. Thus,
       looking to corporeal nature,[Footnote: In the French, "since
       extension constitutes the nature of body."] since divisibility is
       included in local extension, and this indicates imperfection, it is
       certain that God is not body. And although in men it is to some
       degree a perfection to be capable of perceiving by means of the
       senses, nevertheless since in every sense there is passivity
       [Footnote: In the French, "because our perceptions arise from
       impressions made upon us from another source," i.e., than
       ourselves.] which indicates dependency, we must conclude that God is
       in no manner possessed of senses, and that he only understands and
       wills, not, however, like us, by acts in any way distinct, but
       always by an act that is one, identical, and the simplest possible,
       understands, wills, and operates all, that is, all things that in
       reality exist; for he does not will the evil of sin, seeing this is
       but the negation of being.
       XXIV. That in passing from the knowledge of God to the knowledge of
       the creatures, it is necessary to remember that our understanding is
       finite, and the power of God infinite.
       But as we know that God alone is the true cause of all that is or
       can be, we will doubtless follow the best way of philosophizing, if,
       from the knowledge we have of God himself, we pass to the
       explication of the things which he has created, and essay to deduce
       it from the notions that are naturally in our minds, for we will
       thus obtain the most perfect science, that is, the knowledge of
       effects through their causes. But that we may be able to make this
       attempt with sufficient security from error, we must use the
       precaution to bear in mind as much as possible that God, who is the
       author of things, is infinite, while we are wholly finite.
       XXV. That we must believe all that God has revealed, although it
       may surpass the reach of our faculties.
       Thus, if perhaps God reveal to us or others, matters concerning
       himself which surpass the natural powers of our mind, such as the
       mysteries of the incarnation and of the trinity, we will not refuse
       to believe them, although we may not clearly understand them; nor
       will we be in any way surprised to find in the immensity of his
       nature, or even in what he has created, many things that exceed our
       comprehension.
       XXVI. That it is not needful to enter into disputes [Footnote: "to
       essay to comprehend the infinite."--FRENCH.] regarding the infinite,
       but merely to hold all that in which we can find no limits as
       indefinite, such as the extension of the world, the divisibility of
       the parts of matter, the number of the stars, etc.
       We will thus never embarrass ourselves by disputes about the
       infinite, seeing it would be absurd for us who are finite to
       undertake to determine anything regarding it, and thus as it were to
       limit it by endeavouring to comprehend it. We will accordingly give
       ourselves no concern to reply to those who demand whether the half
       of an infinite line is also infinite, and whether an infinite number
       is even or odd, and the like, because it is only such as imagine
       their minds to be infinite who seem bound to entertain questions of
       this sort. And, for our part, looking to all those things in which
       in certain senses, we discover no limits, we will not, therefore,
       affirm that they are infinite, but will regard them simply as
       indefinite. Thus, because we cannot imagine extension so great that
       we cannot still conceive greater, we will say that the magnitude of
       possible things is indefinite, and because a body cannot be divided
       into parts so small that each of these may not be conceived as again
       divided into others still smaller, let us regard quantity as
       divisible into parts whose number is indefinite; and as we cannot
       imagine so many stars that it would seem impossible for God to
       create more, let us suppose that their number is indefinite, and so
       in other instances.
       XXVII. What difference there is between the indefinite and the
       infinite.
       And we will call those things indefinite rather than infinite, with
       the view of reserving to God alone the appellation of infinite; in
       the first place, because not only do we discover in him alone no
       limits on any side, but also because we positively conceive that he
       admits of none; and in the second place, because we do not in the
       same way positively conceive that other things are in every part
       unlimited, but merely negatively admit that their limits, if they
       have any, cannot be discovered by us.
       XXVIII. That we must examine, not the final, but the efficient,
       causes of created things.
       Likewise, finally, we will not seek reasons of natural things from
       the end which God or nature proposed to himself in their creation
       (i. e., final causes), [Footnote: "We will not stop to consider the
       ends which God proposed to himself in the creation of the world, and
       we will entirely reject from our philosophy the search of final
       causes!"--French.] for we ought not to presume so far as to think
       that we are sharers in the counsels of Deity, but, considering him
       as the efficient cause of all things, let us endeavour to discover
       by the natural light [Footnote: "Faculty of reasoning."--FRENCH.]
       which he has planted in us, applied to those of his attributes of
       which he has been willing we should have some knowledge, what must
       be concluded regarding those effects we perceive by our senses;
       bearing in mind, however, what has been already said, that we must
       only confide in this natural light so long as nothing contrary to
       its dictates is revealed by God himself. [Footnote: The last clause,
       beginning "bearing in mind." is omitted in the French.]
       XXIX. That God is not the cause of our errors.
       The first attribute of God which here falls to be considered, is
       that he is absolutely veracious and the source of all light, so that
       it is plainly repugnant for him to deceive us, or to be properly and
       positively the cause of the errors to which we are consciously
       subject; for although the address to deceive seems to be some mark
       of subtlety of mind among men, yet without doubt the will to deceive
       only proceeds from malice or from fear and weakness, and
       consequently cannot be attributed to God.
       XXX. That consequently all which we clearly perceive is true, and
       that we are thus delivered from the doubts above proposed.
       Whence it follows, that the light of nature, or faculty of knowledge
       given us by God, can never compass any object which is not true, in
       as far as it attains to a knowledge of it, that is, in as far as the
       object is clearly and distinctly apprehended. For God would have
       merited the appellation of a deceiver if he had given us this
       faculty perverted, and such as might lead us to take falsity for
       truth [when we used it aright]. Thus the highest doubt is removed,
       which arose from our ignorance on the point as to whether perhaps
       our nature was such that we might be deceived even in those things
       that appear to us the most evident. The same principle ought also to
       be of avail against all the other grounds of doubting that have been
       already enumerated. For mathematical truths ought now to be above
       suspicion, since these are of the clearest. And if we perceive
       anything by our senses, whether while awake or asleep, we will
       easily discover the truth provided we separate what there is of
       clear and distinct in the knowledge from what is obscure and
       confused. There is no need that I should here say more on this
       subject, since it has already received ample treatment in the
       metaphysical Meditations; and what follows will serve to explain it
       still more accurately.
       XXXI. That our errors are, in respect of God, merely negations,
       but, in respect of ourselves, privations.
       But as it happens that we frequently fall into error, although God
       is no deceiver, if we desire to inquire into the origin and cause of
       our errors, with a view to guard against them, it is necessary to
       observe that they depend less on our understanding than on our will,
       and that they have no need of the actual concourse of God, in order
       to their production; so that, when considered in reference to God,
       they are merely negations, but in reference to ourselves,
       privations.
       XXXII. That there are only two modes of thinking in us, viz., the
       perception of the understanding and the action of the will.
       For all the modes of thinking of which we are conscious may be
       referred to two general classes, the one of which is the perception
       or operation of the understanding, and the other the volition or
       operation of the will. Thus, to perceive by the senses (SENTIRE), to
       imagine, and to conceive things purely intelligible, are only
       different modes of perceiving (PERCIP IENDI); but to desire, to be
       averse from, to affirm, to deny, to doubt, are different modes of
       willing.
       XXXIII. That we never err unless when we judge of something which
       we do not sufficiently apprehend.
       When we apprehend anything we are in no danger of error, if we
       refrain from judging of it in any way; and even when we have formed
       a judgment regarding it, we would never fall into error, provided we
       gave our assent only to what we clearly and distinctly perceived;
       but the reason why we are usually deceived, is that we judge without
       possessing an exact knowledge of that of which we judge.
       XXXIV. That the will as well as the understanding is required for
       judging.
       I admit that the understanding is necessary for judging, there being
       no room to suppose that we can judge of that which we in no way
       apprehend; but the will also is required in order to our assenting
       to what we have in any degree perceived. It is not necessary,
       however, at least to form any judgment whatever, that we have an
       entire and perfect apprehension of a thing; for we may assent to
       many things of which we have only a very obscure and confused
       knowledge.
       XXXV. That the will is of greater extension than the understanding,
       and is thus the source of our errors.
       Further, the perception of the intellect extends only to the few
       things that are presented to it, and is always very limited: the
       will, on the other hand, may, in a certain sense, be said to be
       infinite, because we observe nothing that can be the object of the
       will of any other, even of the unlimited will of God, to which ours
       cannot also extend, so that we easily carry it beyond the objects we
       clearly perceive; and when we do this, it is not wonderful that we
       happen to be deceived.
       XXXVI. That our errors cannot be imputed to God.
       But although God has not given us an omniscient understanding, he is
       not on this account to be considered in any wise the author of our
       errors, for it is of the nature of created intellect to be finite,
       and of finite intellect not to embrace all things.
       XXXVII. That the chief perfection of man is his being able to act
       freely or by will, and that it is this which renders him worthy of
       praise or blame.
       That the will should be the more extensive is in harmony with its
       nature: and it is a high perfection in man to be able to act by
       means of it, that is, freely; and thus in a peculiar way to be the
       master of his own actions, and merit praise or blame. For self-
       acting machines are not commended because they perform with
       exactness all the movements for which they were adapted, seeing
       their motions are carried on necessarily; but the maker of them is
       praised on account of the exactness with which they were framed,
       because he did not act of necessity, but freely; and, on the same
       principle, we must attribute to ourselves something more on this
       account, that when we embrace truth, we do so not of necessity, but
       freely.
       XXXVIII. That error is a defect in our mode of acting, not in our
       nature; and that the faults of their subjects may be frequently
       attributed to other masters, but never to God.
       It is true, that as often as we err, there is some defect in our
       mode of action or in the use of our liberty, but not in our nature,
       because this is always the same, whether our judgments be true or
       false. And although God could have given to us such perspicacity of
       intellect that we should never have erred, we have, notwithstanding,
       no right to demand this of him; for, although with us he who was
       able to prevent evil and did not is held guilty of it, God is not in
       the same way to be reckoned responsible for our errors because he
       had the power to prevent them, inasmuch as the dominion which some
       men possess over others has been instituted for the purpose of
       enabling them to hinder those under them from doing evil, whereas
       the dominion which God exercises over the universe is perfectly
       absolute and free. For this reason we ought to thank him for the
       goods he has given us, and not complain that he has not blessed us
       with all which we know it was in his power to impart.
       XXXIX. That the liberty of our will is self-evident.
       Finally, it is so manifest that we possess a free will, capable of
       giving or withholding its assent, that this truth must be reckoned
       among the first and most common notions which are born with us.
       This, indeed, has already very clearly appeared, for when essaying
       to doubt of all things, we went so far as to suppose even that he
       who created us employed his limitless power in deceiving us in every
       way, we were conscious nevertheless of being free to abstain from
       believing what was not in every respect certain and undoubted. Bat
       that of which we are unable to doubt at such a time is as self-
       evident and clear as any thing we can ever know.
       XL. That it is likewise certain that God has fore-ordained all
       things.
       But because what we have already discovered of God, gives us the
       assurance that his power is so immense that we would sin in thinking
       ourselves capable of ever doing anything which he had not ordained
       beforehand, we should soon be embarrassed in great difficulties if
       we undertook to harmonise the pre-ordination of God with the freedom
       of our will, and endeavoured to comprehend both truths at once.
       XLI. How the freedom of our will may be reconciled with the Divine
       pre-ordination.
       But, in place of this, we will be free from these embarrassments if
       we recollect that our mind is limited, while the power of God, by
       which he not only knew from all eternity what is or can be, but also
       willed and pre-ordained it, is infinite. It thus happens that we
       possess sufficient intelligence to know clearly and distinctly that
       this power is in God, but not enough to comprehend how he leaves the
       free actions of men indeterminate} and, on the other hand, we have
       such consciousness of the liberty and indifference which exists in
       ourselves, that there is nothing we more clearly or perfectly
       comprehend: [so that the omnipotence of God ought not to keep us
       from believing it]. For it would be absurd to doubt of that of which
       we are fully conscious, and which we experience as existing in
       ourselves, because we do not comprehend another matter which, from
       its very nature, we know to be incomprehensible.
       XLII. How, although we never will to err, it is nevertheless by our
       will that we do err.
       But now since we know that all our errors depend upon our will, and
       as no one wishes to deceive himself, it may seem wonderful that
       there is any error in our judgments at all. It is necessary to
       remark, however, that there is a great difference between willing to
       be deceived, and willing to yield assent to opinions in which it
       happens that error is found. For though there is no one who
       expressly wishes to fall into error, we will yet hardly find any one
       who is not ready to assent to things in which, unknown to himself,
       error lurks; and it even frequently happens that it is the desire
       itself of following after truth that leads those not fully aware of
       the order in which it ought to be sought for, to pass judgment on
       matters of which they have no adequate knowledge, and thus to fall
       into error.
       XLIII. That we shall never err if we give our assent only to what
       we clearly and distinctly perceive.
       But it is certain we will never admit falsity for truth, so long as
       we judge only of that which we clearly and distinctly perceive;
       because, as God is no deceiver, the faculty of knowledge which he
       has given us cannot be fallacious, nor, for the same reason, the
       faculty of will, when we do not extend it beyond the objects we
       clearly know. And even although this truth could not be established
       by reasoning, the minds of all have been so impressed by nature as
       spontaneously to assent to whatever is clearly perceived, and to
       experience an impossibility to doubt of its truth.
       XLIV. That we uniformly judge improperly when we assent to what we
       do not clearly perceive, although our judgment may chance to be
       true; and that it is frequently our memory which deceives us by
       leading us to believe that certain things were formerly sufficiently
       understood by us.
       It is likewise certain that, when we approve of any reason which we
       do not apprehend, we are either deceived, or, if we stumble on the
       truth, it is only by chance, and thus we can never possess the
       assurance that we are not in error. I confess it seldom happens that
       we judge of a thing when we have observed we do not apprehend it,
       because it is a dictate of the natural light never to judge of what
       we do not know. But we most frequently err in this, that we presume
       upon a past knowledge of much to which we give our assent, as to
       something treasured up in the memory, and perfectly known to us;
       whereas, in truth, we have no such knowledge.
       XLV. What constitutes clear and distinct perception.
       There are indeed a great many persons who, through their whole
       lifetime, never perceive anything in a way necessary for judging of
       it properly; for the knowledge upon which we can establish a certain
       and indubitable judgment must be not only clear, but also, distinct.
       I call that clear which is present and manifest to the mind giving
       attention to it, just as we are said clearly to see objects when,
       being present to the eye looking on, they stimulate it with
       sufficient force. and it is disposed to regard them; but the
       distinct is that which is so precise and different from all other
       objects as to comprehend in itself only what is clear. [Footnote:
       "what appears manifestly to him who considers it as he ought."--
       FRENCH.]
       XLVI. It is shown, from the example of pain, that a perception may
       be clear without being distinct, but that it cannot be distinct
       unless it is clear.
       For example, when any one feels intense pain, the knowledge which he
       has of this pain is very clear, but it is not always distinct; for
       men usually confound it with the obscure judgment they form
       regarding its nature, and think that there is in the suffering part
       something similar to the sensation of pain of which they are alone
       conscious. And thus perception may be clear without being distinct,
       but it can never be distinct without likewise being clear.
       XLVII. That, to correct the prejudices of our early years, we must
       consider what is clear in each of our simple [Footnote: "first."--
       FRENCH.] notions.
       And, indeed, in our early years, the mind was so immersed in the
       body, that, although it perceived many things with sufficient
       clearness, it yet knew nothing distinctly; and since even at that
       time we exercised our judgment in many matters, numerous prejudices
       were thus contracted, which, by the majority, are never afterwards
       laid aside. But that we may now be in a position to get rid of
       these, I will here briefly enumerate all the simple notions of which
       our thoughts are composed, and distinguish in each what is clear
       from what is obscure, or fitted to lead into error.
       XLVIII. That all the objects of our knowledge are to be regarded
       either (1) as things or the affections of things: or (2) as eternal
       truths; with the enumeration of things.
       Whatever objects fall under our knowledge we consider either as
       things or the affections of things,[Footnote: Things and the
       affections of things are (in the French) equivalent to "what has
       some (i.e., a REAL) existence," as opposed to the class of "eternal
       truths," which have merely an IDEAL existence.] or as eternal truths
       possessing no existence beyond our thought. Of the first class the
       most general are substance, duration, order, number, and perhaps
       also some others, which notions apply to all the kinds of things. I
       do not, however, recognise more than two highest kinds (SUMMA
       GENERA) of things; the first of intellectual things, or such as have
       the power of thinking, including mind or thinking substance and its
       properties; the second, of material things, embracing extended
       substance, or body and its properties. Perception, volition, and all
       modes as well of knowing as of willing, are related to thinking
       substance; on the other hand, to extended substance we refer
       magnitude, or extension in length, breadth, and depth, figure,
       motion, situation, divisibility of parts themselves, and the like.
       There are, however, besides these, certain things of which we have
       an internal experience that ought not to be referred either to the
       mind of itself, or to the body alone, but to the close and intimate
       union between them, as will hereafter be shown in its place. Of this
       class are the appetites of hunger and thirst, etc., and also the
       emotions or passions of the mind which are not exclusively mental
       affections, as the emotions of anger, joy, sadness, love, etc.; and,
       finally, all the sensations, as of pain, titillation, light and
       colours, sounds, smells, tastes, heat, hardness, and the other
       tactile qualities.
       XLIX. That the eternal truths cannot be thus enumerated, but that
       this is not necessary.
       What I have already enumerated we are to regard as things, or the
       qualities or modes of things. We now come to speak of eternal
       truths. When we apprehend that it is impossible a thing can arise
       from nothing, this proposition, EX NIHILO NIHIL FIT, is not
       considered as somewhat existing, or as the mode of a thing, but as
       an eternal truth having its seat in our mind, and is called a common
       notion or axiom. Of this class are the following:--It is impossible
       the same thing can at once be and not be; what is done cannot be
       undone; he who thinks must exist while he thinks; and innumerable
       others, the whole of which it is indeed difficult to enumerate, but
       this is not necessary, since, if blinded by no prejudices, we cannot
       fail to know them when the occasion of thinking them occurs.
       L. That these truths are clearly perceived, but not equally by all
       men, on account of prejudices.
       And, indeed, with regard to these common notions, it is not to be
       doubted that they can be clearly and distinctly known, for otherwise
       they would not merit this appellation: as, in truth, some of them
       are not, with respect to all men, equally deserving of the name,
       because they are not equally admitted by all: not, however, from
       this reason, as I think, that the faculty of knowledge of one man
       extends farther than that of another, but rather because these
       common notions are opposed to the prejudices of some, who, on this
       account, are not able readily to embrace them, even although others,
       who are free from those prejudices, apprehend them with the greatest
       clearness.
       LI. What substance is, and that the term is not applicable to God
       and the creatures in the same sense.
       But with regard to what we consider as things or the modes of
       things, it is worth while to examine each of them by itself. By
       substance we can conceive nothing else than a thing which exists in
       such a way as to stand in need of nothing beyond itself in order to
       its existence. And, in truth, there can be conceived but one
       substance which is absolutely independent, and that is God. We
       perceive that all other things can exist only by help of the
       concourse of God. And, accordingly, the term substance does not
       apply to God and the creatures UNIVOCALLY, to adopt a term familiar
       in the schools; that is, no signification of this word can be
       distinctly understood which is common to God and them.
       LII. That the term is applicable univocally to the mind and the
       body, and how substance itself is known.
       Created substances, however, whether corporeal or thinking, may be
       conceived under this common concept; for these are things which, in
       order to their existence, stand in need of nothing but the concourse
       of God. But yet substance cannot be first discovered merely from its
       being a thing which exists independently, for existence by itself is
       not observed by us. We easily, however, discover substance itself
       from any attribute of it, by this common notion, that of nothing
       there are no attributes, properties, or qualities: for, from
       perceiving that some attribute is present, we infer that some
       existing thing or substance to which it may be attributed is also of
       necessity present.
       LIII. That of every substance there is one principal attribute, as
       thinking of the mind, extension of the body.
       But, although any attribute is sufficient to lead us to the
       knowledge of substance, there is, however, one principal property of
       every substance, which constitutes its nature or essence, and upon
       which all the others depend. Thus, extension in length, breadth, and
       depth, constitutes the nature of corporeal substance; and thought
       the nature of thinking substance. For every other thing that can be
       attributed to body, presupposes extension, and is only some mode of
       an extended thing; as all the properties we discover in the mind are
       only diverse modes of thinking. Thus, for example, we cannot
       conceive figure unless in something extended, nor motion unless in
       extended space, nor imagination, sensation, or will, unless in a
       thinking thing. But, on the other hand, we can conceive extension
       without figure or motion, and thought without imagination or
       sensation, and so of the others; as is clear to any one who attends
       to these matters.
       LIV. How we may have clear and distinct notions of the substance
       which thinks, of that which is corporeal, and of God.
       And thus we may easily have two clear and distinct notions or ideas,
       the one of created substance, which thinks, the other of corporeal
       substance, provided we carefully distinguish all the attributes of
       thought from those of extension. We may also have a clear and
       distinct idea of an uncreated and independent thinking substance,
       that is, of God, provided we do not suppose that this idea
       adequately represents to us all that is in God, and do not mix up
       with it anything fictitious, but attend simply to the characters
       that are comprised in the notion we have of him, and which we
       clearly know to belong to the nature of an absolutely perfect Being.
       For no one can deny that there is in us such an idea of God, without
       groundlessly supposing that there is no knowledge of God at all in
       the human mind.
       LV. How duration, order, and number may be also distinctly
       conceived.
       We will also have most distinct conceptions of duration, order, and
       number, if, in place of mixing up with our notions of them that
       which properly belongs to the concept of substance, we merely think
       that the duration of a thing is a mode under which we conceive this
       thing, in so far as it continues to exist; and, in like manner, that
       order and number are not in reality different from things disposed
       in order and numbered, but only modes under which we diversely
       consider these things.
       LVI. What are modes, qualities, attributes.
       And, indeed, we here understand by modes the same with what we
       elsewhere designate attributes or qualities. But when we consider
       substance as affected or varied by them, we use the term modes; when
       from this variation it may be denominated of such a kind, we adopt
       the term qualities [to designate the different modes which cause it
       to be so named]; and, finally, when we simply regard these modes as
       in the substance, we call them attributes. Accordingly, since God
       must be conceived as superior to change, it is not proper to say
       that there are modes or qualities in him, but simply attributes; and
       even in created things that which is found in them always in the
       same mode, as existence and duration in the thing which exists and
       endures, ought to be called attribute and not mode or quality.
       LVII. That some attributes exist in the things to which they are
       attributed, and others only in our thought; and what duration and
       time are.
       Of these attributes or modes there are some which exist in the
       things themselves, and others that have only an existence in our
       thought; thus, for example, time, which we distinguish from duration
       taken in its generality, and call the measure of motion, is only a
       certain mode under which we think duration itself, for we do not
       indeed conceive the duration of things that are moved to be
       different from the duration of things that are not moved: as is
       evident from this, that if two bodies are in motion for an hour, the
       one moving quickly and the other slowly, we do not reckon more time
       in the one than in the other, although there may be much more motion
       in the one of the bodies than in the other. But that we may
       comprehend the duration of all things under a common measure, we
       compare their duration with that of the greatest and most regular
       motions that give rise to years and days, and which we call time;
       hence what is so designated is nothing superadded to duration, taken
       in its generality, but a mode of thinking.
       LVIII. That number and all universals are only modes of thought.
       In the same way number, when it is not considered as in created
       things, but merely in the abstract or in general, is only a mode of
       thinking; and the same is true of all those general ideas we call
       universals.
       LIX. How universals are formed; and what are the five common, viz.,
       genus, species, difference, property, and accident.
       Universals arise merely from our making use of one and the same idea
       in thinking of all individual objects between which there subsists a
       certain likeness; and when we comprehend all the objects represented
       by this idea under one name, this term likewise becomes universal.
       For example, when we see two stones, and do not regard their nature
       farther than to remark that there are two of them, we form the idea
       of a certain number, which we call the binary; and when we
       afterwards see two birds or two trees, and merely take notice of
       them so far as to observe that there are two of them, we again take
       up the same idea as before, which is, accordingly, universal; and we
       likewise give to this number the same universal appellation of
       binary. In the same way, when we consider a figure of three sides,
       we form a certain idea, which we call the idea of a triangle, and we
       afterwards make use of it as the universal to represent to our mind
       all other figures of three sides. But when we remark more
       particularly that of figures of three sides, some have a right angle
       and others not, we form the universal idea of a right-angled
       triangle, which being related to the preceding as more general, may
       be called species; and the right angle the universal difference by
       which right-angled triangles are distinguished from all others; and
       farther, because the square of the side which sustains the right
       angle is equal to the squares of the other two sides, and because
       this property belongs only to this species of triangles, we may call
       it the universal property of the species. Finally, if we suppose
       that of these triangles some are moved and others not, this will be
       their universal accident; and, accordingly, we commonly reckon five
       universals, viz., genus, species, difference, property, accident.
       LX. Of distinctions; and first of the real.
       But number in things themselves arises from the distinction there is
       between them: and distinction is threefold, viz., real, modal, and
       of reason. The real properly subsists between two or more
       substances; and it is sufficient to assure us that two substances
       are really mutually distinct, if only we are able clearly and
       distinctly to conceive the one of them without the other. For the
       knowledge we have of God renders it certain that he can effect all
       that of which we have a distinct idea: wherefore, since we have now,
       for example, the idea of an extended and corporeal substance, though
       we as yet do not know with certainty whether any such thing is
       really existent, nevertheless, merely because we have the idea of
       it, we may be assured that such may exist; and, if it really exists,
       that every part which we can determine by thought must be really
       distinct from the other parts of the same substance. In the same
       way, since every one is conscious that he thinks, and that he in
       thought can exclude from himself every other substance, whether
       thinking or extended, it is certain that each of us thus considered
       is really distinct from every other thinking and corporeal
       substance. And although we suppose that God united a body to a soul
       so closely that it was impossible to form a more intimate union, and
       thus made a composite whole, the two substances would remain really
       distinct, notwithstanding this union; for with whatever tie God
       connected them, he was not able to rid himself of the power he
       possessed of separating them, or of conserving the one apart from
       the other, and the things which God can separate or conserve
       separately are really distinct.
       LXI. Of the modal distinction.
       There are two kinds of modal distinctions, viz., that between the
       mode properly so-called and the substance of which it is a mode, and
       that between two modes of the same substance. Of the former we have
       an example in this, that we can clearly apprehend substance apart
       from the mode which we say differs from it; while, on the other
       hand, we cannot conceive this mode without conceiving the substance
       itself. There is, for example, a modal distinction between figure or
       motion and corporeal substance in which both exist; there is a
       similar distinction between affirmation or recollection and the
       mind. Of the latter kind we have an illustration in our ability to
       recognise the one of two modes apart from the other, as figure apart
       from motion, and motion apart from figure; though we cannot think of
       either the one or the other without thinking of the common substance
       in which they adhere. If, for example, a stone is moved, and is
       withal square, we can, indeed, conceive its square figure without
       its motion, and reciprocally its motion without its square figure;
       but we can conceive neither this motion nor this figure apart from
       the substance of the stone. As for the distinction according to
       which the mode of one substance is different from another substance,
       or from the mode of another substance, as the motion of one body is
       different from another body or from the mind, or as motion is
       different from doubt, it seems to me that it should be called real
       rather than modal, because these modes cannot be clearly conceived
       apart from the really distinct substances of which they are the
       modes.
       LXII. Of the distinction of reason (logical distinction).
       Finally, the distinction of reason is that between a substance and
       some one of its attributes, without which it is impossible, however,
       we can have a distinct conception of the substance itself; or
       between two such attributes of a common substance, the one of which
       we essay to think without the other. This distinction is manifest
       from our inability to form a clear and distinct idea of such
       substance, if we separate from it such attribute; or to have a clear
       perception of the one of two such attributes if we separate it from
       the other. For example, because any substance which ceases to endure
       ceases also to exist, duration is not distinct from substance except
       in thought (RATIONE); and in general all the modes of thinking which
       we consider as in objects differ only in thought, as well from the
       objects of which they are thought as from each other in a common
       object.[Footnote: "and generally all the attributes that lead us to
       entertain different thoughts of the same thing, such as, for
       example, the extension of body and its property of divisibility, do
       not differ from the body which is to us the object of them, or from
       each other, unless as we sometimes confusedly think the one without
       thinking the other."--FRENCH.] It occurs, indeed, to me that I have
       elsewhere classed this kind of distinction with the modal (viz.,
       towards the end of the Reply to the First Objections to the
       Meditations on the First Philosophy); but there it was only
       necessary to treat of these distinctions generally, and it was
       sufficient for my purpose at that time simply to distinguish both of
       them from the real.
       LXIII. How thought and extension may be distinctly known, as
       constituting, the one the nature of mind, the other that of body.
       Thought and extension may be regarded as constituting the natures of
       intelligent and corporeal substance; and then they must not be
       otherwise conceived than as the thinking and extended substances
       themselves, that is, as mind and body, which in this way are
       conceived with the greatest clearness and distinctness. Moreover, we
       more easily conceive extended or thinking substance than substance
       by itself, or with the omission of its thinking or extension. For
       there is some difficulty in abstracting the notion of substance from
       the notions of thinking and extension, which, in truth, are only
       diverse in thought itself (i.e., logically different); and a concept
       is not more distinct because it comprehends fewer properties, but
       because we accurately distinguish what is comprehended in it from
       all other notions.
       LXIV. How these may likewise be distinctly conceived as modes of
       substance.
       Thought and extension may be also considered as modes of substance;
       in as far, namely, as the same mind may have many different
       thoughts, and the same body, with its size unchanged, may be
       extended in several diverse ways, at one time more in length and
       less in breadth or depth, and at another time more in breadth and
       less in length; and then they are modally distinguished from
       substance, and can be conceived not less clearly and distinctly,
       provided they be not regarded as substances or things separated from
       others, but simply as modes of things. For by regarding them as in
       the substances of which they are the modes, we distinguish them from
       these substances, and take them for what in truth they are: whereas,
       on the other hand, if we wish to consider them apart from the
       substances in which they are, we should by this itself regard them
       as self-subsisting things, and thus confound the ideas of mode and
       substance.
       LXV. How we may likewise know their modes.
       In the same way we will best apprehend the diverse modes of thought,
       as intellection, imagination, recollection, volition, etc., and also
       the diverse modes of extension, or those that belong to extension,
       as all figures, the situation of parts and their motions, provided
       we consider them simply as modes of the things in which they are;
       and motion as far as it is concerned, provided we think merely of
       locomotion, without seeking to know the force that produces it, and
       which nevertheless I will essay to explain in its own place.
       LXVI. How our sensations, affections, and appetites may be clearly
       known, although we are frequently wrong in our judgments regarding
       them.
       There remain our sensations, affections, and appetites, of which we
       may also have a clear knowledge, if we take care to comprehend in
       the judgments we form of them only that which is precisely contained
       in our perception of them, and of which we are immediately
       conscious. There is, however, great difficulty in observing this, at
       least in respect of sensations; because we have all, without
       exception, from our youth judged that all the things we perceived by
       our senses had an existence beyond our thought, and that they were
       entirely similar to the sensations, that is, perceptions, we ad of
       them. Thus when, for example, we saw a certain colour, we thought we
       saw something occupying a place out of us, and which was entirely
       similar to that idea of colour we were then conscious of; and from
       the habit of judging in this way, we seemed to see this so clearly
       and distinctly that we esteemed it (i.e., the externality of the
       colour) certain and indubitable.
       LXVII. That we are frequently deceived in our judgments regarding
       pain itself.
       The same prejudice has place in all our other sensations, even in
       those of titillation and pain. For though we are not in the habit of
       believing that there exist out of us objects that resemble
       titillation and pain, we do not nevertheless consider these
       sensations as in the mind alone, or in our perception, but as in the
       hand, or foot, or some other part of our body. There is no reason,
       however, to constrain us to believe that the pain, for example,
       which we feel, as it were, in the foot is something out of the mind
       existing in the foot, or that the light which we see, as it were, in
       the sun exists in the sun as it is in us. Both these beliefs are
       prejudices of our early years, as will clearly appear in the sequel.
       LXVIII. How in these things what we clearly conceive is to be
       distinguished from that in which we may be deceived.
       But that we may distinguish what is clear in our sensations from
       what is obscure, we ought most carefully to observe that we possess
       a clear and distinct knowledge of pain, colour, and other things of
       this sort, when we consider them simply as sensations or thoughts;
       but that, when they are judged to be certain things subsisting
       beyond our mind, we are wholly unable to form any conception of
       them. Indeed, when any one tells us that he sees colour in a body or
       feels pain in one of his limbs, this is exactly the same as if he
       said that he there saw or felt something of the nature of which he
       was entirely ignorant, or that he did not know what he saw or felt.
       For although, when less attentively examining his thoughts, a person
       may easily persuade himself that he has some knowledge of it, since
       he supposes that there is something resembling that sensation of
       colour or of pain of which he is conscious; yet, if he reflects on
       what the sensation of colour or pain represents to him as existing
       in a coloured body or in a wounded member, he will find that of such
       he has absolutely no knowledge.
       LXIX. That magnitude, figure, etc., are known far differently from
       colour, pain, etc.
       What we have said above will be more manifest; especially if we
       consider that size in the body perceived, figure, motion (at least
       local, for philosophers by fancying other kinds of motion have
       rendered its nature less intelligible to themselves), the situation
       of parts, duration, number, and those other properties which, as we
       have already said, we clearly perceive in all bodies, are known by
       us in a way altogether different from that in which we know what
       colour is in the same body, or pain, smell, taste, or any other of
       those properties which I have said above must be referred to the
       senses. For although when we see a body we are not less assured of
       its existence from its appearing figured than from its appearing
       coloured,[Footnote: "by the colour we perceive on occasion of it."--
       FRENCH.] we yet know with far greater clearness its property of
       figure than its colour.
       LXX. That we may judge of sensible things in two ways, by the one
       of which we avoid error, by the other fall into it.
       It is thus manifest that to say we perceive colours in objects is in
       reality equivalent to saying we perceive something in objects and
       are yet ignorant of what it is, except as that which determines in
       us a certain highly vivid and clear sensation, which we call the
       sensation of colours. There is, however, very great diversity in the
       manner of judging: for so long as we simply judge that there is an
       unknown something in objects (that is, in things such as they are,
       from which the sensation reached us), so far are we from falling
       into error that, on the contrary, we thus rather provide against it,
       for we are less apt to judge rashly of a thing which we observe we
       do not know. But when we think we perceive colours in objects,
       although we are in reality ignorant of what we then denominate
       colour, and are unable to conceive any resemblance between the
       colour we suppose to be in objects, and that of which we are
       conscious in sensation, yet because we do not observe this, or
       because there are in objects several properties, as size, figure,
       number, etc., which, as we clearly know, exist, or may exist in them
       as they are perceived by our senses or conceived by our
       understanding, we easily glide into the error of holding that what
       is called colour in objects is something entirely resembling the
       colour we perceive, and thereafter of supposing that we have a clear
       perception of what is in no way perceived by us.
       LXXI. That the chief cause of our errors is to be found in the
       prejudices of our childhood.
       And here we may notice the first and chief cause of our errors. In
       early life the mind was so closely bound to the body that it
       attended to nothing beyond the thoughts by which it perceived the
       objects that made impression on the body; nor as yet did it refer
       these thoughts to anything existing beyond itself, but simply felt
       pain when the body was hurt, or pleasure when anything beneficial to
       the body occurred, or if the body was so highly affected that it was
       neither greatly benefited nor hurt, the mind experienced the
       sensations we call tastes, smells, sounds, heat, cold, light,
       colours, and the like, which in truth are representative of nothing
       existing out of our mind, and which vary according to the
       diversities of the parts and modes in which the body is affected.
       [Footnote: "which vary according to the diversities of the movements
       that pass from all parts of our body to the part of the brain to
       which it (the mind) is closely joined and united."--FRENCH.] The
       mind at the same time also perceived magnitudes, figures, motions,
       and the like, which were not presented to it as sensations but as
       things or the modes of things existing, or at least capable of
       existing out of thought, although it did not yet observe this
       difference between these two kinds of perceptions. And afterwards
       when the machine of the body, which has been so fabricated by nature
       that it can of its own inherent power move itself in various ways,
       by turning itself at random on every side, followed after what was
       useful and avoided what was detrimental; the mind, which was closely
       connected with it, reflecting on the objects it pursued or avoided,
       remarked, for the first time, that they existed out of itself, and
       not only attributed to them magnitudes, figures, motions, and the
       like, which it apprehended either as things or as the modes of
       things, but, in addition, attributed to them tastes, odours, and the
       other ideas of that sort, the sensations of which were caused by
       itself; [Footnote: "which it perceived on occasion of them" (i.e.,
       of external objects).--FRENCH.] and as it only considered other
       objects in so far as they were useful to the body, in which it was
       immersed, it judged that there was greater or less reality in each
       object, according as the impressions it caused on the body were more
       or less powerful. Hence arose the belief that there was more
       substance or body in rocks and metals than in air or water, because
       the mind perceived in them more hardness and weight. Moreover, the
       air was thought to be merely nothing so long as we experienced no
       agitation of it by the wind, or did not feel it hot or cold. And
       because the stars gave hardly more light than the slender flames of
       candles, we supposed that each star was but of this size. Again,
       since the mind did not observe that the earth moved on its axis, or
       that its superficies was curved like that of a globe, it was on that
       account more ready to judge the earth immovable and its surface
       flat. And our mind has been imbued from our infancy with a thousand
       other prejudices of the same sort which afterwards in our youth we
       forgot we had accepted without sufficient examination, and admitted
       as possessed of the highest truth and clearness, as if they had been
       known by means of our senses, or implanted in us by nature.
       LXXII. That the second cause of our errors is that we cannot forget
       these prejudices.
       And although now in our mature years, when the mind, being no longer
       wholly subject to the body, is not in the habit of referring all
       things to it, but also seeks to discover the truth of things
       considered in themselves, we observe the falsehood of a great many
       of the judgments we had before formed; yet we experience a
       difficulty in expunging them from our memory, and, so long as they
       remain there, they give rise to various errors. Thus, for example,
       since from our earliest years we imagined the stars to be of very
       small size, we find it highly difficult to rid ourselves of this
       imagination, although assured by plain astronomical reasons that
       they are of the greatest,--so prevailing is the power of
       preconceived opinion.
       LXXIII. The third cause is, that we become fatigued by attending to
       those objects which are not present to the senses; and that we are
       thus accustomed to judge of these not from present perception but
       from pre-conceived opinion.
       Besides, our mind cannot attend to any object without at length
       experiencing some pain and fatigue; and of all objects it has the
       greatest difficulty in attending to those which are present neither
       to the senses nor to the imagination: whether for the reason that
       this is natural to it from its union with the body, or because in
       our early years, being occupied merely with perceptions and
       imaginations, it has become more familiar with, and acquired greater
       facility in thinking in those modes than in any other. Hence it also
       happens that many are unable to conceive any substance except what
       is imaginable and corporeal, and even sensible. For they are
       ignorant of the circumstance, that those objects alone are
       imaginable which consist in extension, motion, and figure, while
       there are many others besides these that are intelligible; and they
       persuade themselves that nothing can subsist but body, and, finally,
       that there is no body which is not sensible. And since in truth we
       perceive no object such as it is by sense alone [but only by our
       reason exercised upon sensible objects], as will hereafter be
       clearly shown, it thus happens that the majority during life
       perceive nothing unless in a confused way.
       LXXIV. The fourth source of our errors is, that we attach our
       thoughts to words which do not express them with accuracy.
       Finally, since for the use of speech we attach all our conceptions
       to words by which to express them, and commit to memory our thoughts
       in connection with these terms, and as we afterwards find it more
       easy to recall the words than the things signified by them, we can
       scarcely conceive anything with such distinctness as to separate
       entirely what we conceive from the words that were selected to
       express it. On this account the majority attend to words rather than
       to things; and thus very frequently assent to terms without
       attaching to them any meaning, either because they think they once
       understood them, or imagine they received them from others by whom
       they were correctly understood. This, however, is not the place to
       treat of this matter in detail, seeing the nature of the human body
       has not yet been expounded, nor the existence even of body
       established; enough, nevertheless, appears to have been said to
       enable one to distinguish such of our conceptions as are clear and
       distinct from those that are obscure and confused.
       LXXV. Summary of what must be observed in order to philosophize
       correctly.
       Wherefore if we would philosophize in earnest, and give ourselves to
       the search after all the truths we are capable of knowing, we must,
       in the first place, lay aside our prejudices; in other words, we
       must take care scrupulously to withhold our assent from the opinions
       we have formerly admitted, until upon new examination we discover
       that they are true. We must, in the next place, make an orderly
       review of the notions we have in our minds, and hold as true all and
       only those which we will clearly and distinctly apprehend. In this
       way we will observe, first of all, that we exist in so far as it is
       our nature to think, and at the same time that there is a God upon
       whom we depend; and after considering his attributes we will be able
       to investigate the truth of all other things, since God is the cause
       of them. Besides the notions we have of God and of our mind, we will
       likewise find that we possess the knowledge of many propositions
       which are eternally true, as, for example, that nothing cannot be
       the cause of anything, etc. We will farther discover in our minds
       the knowledge of a corporeal or extended nature that may be moved,
       divided, etc., and also of certain sensations that affect us, as of
       pain, colours, tastes, etc., although we do not yet know the cause
       of our being so affected; and, comparing what we have now learne'd,
       by examining those things in their order, with our former confused
       knowledge of them, we will acquire the habit of forming clear and
       distinct conceptions of all the objects we are capable of knowing.
       In these few precepts seem to me to be comprised the most general
       and important principles of human knowledge.
       LXXVI. That we ought to prefer the Divine authority to our
       perception; [Footnote: "reasonings."--FRENCH]. but that, apart from
       things revealed, we ought to assent to nothing that we do not
       clearly apprehend.
       Above all, we must impress on our memory the infallible rule, that
       what God has revealed is incomparably more certain than anything
       else; and that, we ought to submit our belief to the Divine
       authority rather than to our own judgment, even although perhaps the
       light of reason should, with the greatest clearness and evidence,
       appear to suggest to us something contrary to what is revealed. But
       in things regarding which there is no revelation, it is by no means
       consistent with the character of a philosopher to accept as true
       what he has not ascertained to be such, and to trust more to the
       senses, in other words, to the inconsiderate judgments of childhood
       than to the dictates of mature reason. _

From the Publisher's Preface
PART I. OF THE PRINCIPLES OF HUMAN KNOWLEDGE
PART II. OF THE PRINCIPLES OF MATERIAL THINGS
PART III. OF THE VISIBLE WORLD
PART IV. OF THE EARTH