Meditations on First Philosophy

To the most wise and distinguished men, the Dean and Doctors of the Sacred Faculty of Theology of Paris, René Descartes sends greetings.note

So just a cause moves me to offer you this work, and I am confident that you too will have so just a cause for taking up its defense once you understand the plan of my undertaking, that I can recommend it here in no better way than by saying briefly what I have aimed at in it.

I have always thought that two questions, concerning God and the soul, are chief among those that ought to be demonstrated with the help of philosophy rather than of theology. For although it is enough for us who are believers to accept by faith that the human soul does not perish with the body, and that God exists, it certainly seems that unbelievers cannot be persuaded of any religion, or even of hardly any moral virtue, unless these two things are first proved to them by natural reason. And since in this life greater rewards are often held out for vices than for virtues, few would prefer what is right to what is useful if they neither feared God nor expected another life.

As for the soul, many have judged that its nature 3 cannot easily be investigated, and some have even dared to say that human reasoning persuades us that it perishes together with the body, and that the contrary is held by faith alone. But since the Lateran Council held under Leo X, in its eighth session, condemns these people, and expressly commands Christian philosophers to refute their arguments and to prove the truth as far as they are able, I have not hesitated to undertake this as well.note

Further, I know that most impious people refuse to believe that God exists and that the human mind is distinct from the body for no other reason than that, as they say, no one has so far been able to demonstrate these two things. I do not agree with them in the least. On the contrary, I think that nearly all the reasons which great men have brought forward on these questions have the force of demonstration when they are properly understood, and I can hardly persuade myself that any can be given which have not already been discovered by others. Nevertheless, I think nothing more useful can be accomplished in philosophy than to seek out carefully, once and for all, the best of them, and to set them forth so precisely and clearly that from now on it will be established for everyone that they are demonstrations.

Whatever I have been able to accomplish is contained entirely in this treatise. Not that I have tried to collect in it all the various reasons that could be brought forward to prove the same things; that does not seem worth the effort except where no single reason is certain enough. Rather, I have pursued only the first and principal ones, and in such a way that I would now venture to put them forward as most certain and most evident demonstrations. I will add, too, that they are such that I do not think any path lies open to human ingenuity by which better ones could ever be found. For the urgency of the cause, and the glory of God, to which this whole work is directed, compel me here to speak somewhat more freely of my own work than is my custom.

And so, whatever my reasons may be worth, since they belong to philosophy, I do not expect to accomplish much of value with their help unless you assist me with your patronage. But the opinion of your Faculty is so deeply fixed in everyone’s mind, and the name of the Sorbonne carries such authority, that not only in matters of faith has no body, after the sacred councils, ever been trusted as much as yours, but also in human philosophy nowhere is there thought to be greater insight and soundness, or greater integrity and wisdom in delivering judgments. I therefore have no doubt that if you would deign to take such care of this work—first, by correcting it

I touched briefly on the questions of God and the human mind some time ago, in the Discourse on the Method of Rightly Conducting Reason and Seeking Truth in the Sciences, published in French in 1637. My aim there was not to treat them thoroughly, but only to give a taste of them, and to learn from readers’ judgments how they should be treated afterward. For they seemed to me of such importance that I judged they ought to be dealt with more than once. And the path I follow in explaining them is so little trodden, and so far from common use, that I did not think it useful to teach it at greater length in a work written in French and to be read by everyone indiscriminately, lest those of weaker talent too might believe that they ought to set out on it.note

But when I had asked there that anyone who found something in my writings worthy of criticism should kindly let me know, no objections worth noting were raised against what I had touched on concerning these questions, except two. I will reply to these briefly here, before undertaking a more exact explanation of the questions themselves.

The first is this: from the fact that the human mind, when turned 8 in on itself, does not perceive itself to be anything other than a thinking thing, it does not follow that its nature or essence consists only in its being a thinking thing, in such a way that the word “only” excludes everything else that might perhaps also be said to belong to the nature of the soul. To this objection I reply that there too I did not mean to exclude those things in the order of the truth of the matter itself (which I was not then dealing with), but only in the order of my perception. The meaning was that I knew nothing at all that I knew to belong to my essence except that I was a thinking thing, or a thing having in itself the faculty of thinking.

The second is that from the fact that I have within me the idea of a thing more perfect than I am, it does not follow that the idea itself is more perfect than I am, and much less that what is represented by that idea exists. But I reply that there is an ambiguity here in the word “idea.” It can be taken either materially, for an operation of the intellect, in which sense it cannot be said to be more perfect than I am; or objectively, for the thing represented by that operation, and this thing, even if it is not supposed to exist outside the intellect, can nevertheless be more perfect than I am by reason of its essence. But how, from the mere fact that there is in me the idea of a thing more perfect than I am, it follows that this thing really exists will be explained at length in what follows.

I have also seen two fairly long writings, but in them it was not so much my reasons on these matters as my conclusions that were attacked, with arguments borrowed from atheist 9 commonplaces. Arguments of that kind can have no force with those who understand my reasons; and the judgments of many people are so perverse and weak that they are more persuaded by opinions accepted first, however false and contrary to reason, than by a true and solid refutation of them heard later. So I do not wish to reply to them here, lest I should first have to report them.

Now, having once made some trial of people’s judgments, I here take up again the same questions about God and the human mind, and at the same time undertake to treat the beginnings of the whole of first philosophy—but in such a way that I expect no applause from the crowd and no great number of readers. Indeed, I advise no one to read these things except those who are able and willing to meditate seriously with me and to withdraw their minds from the senses, and at the same time from all preconceived opinions; and I know well enough that very few such people are to be found. As for those who, not caring to grasp the order and connection of my reasons, busy themselves with quibbling over individual clauses, as 10 many are in the habit of doing, they will get little profit from reading this work. Although they may perhaps find occasion for cavilling in many places, they will not easily raise any objection that is pressing or deserves a reply.

But since I do not promise even the others that I will satisfy them on every point at first sight, and I do not presume so far as to trust that I can foresee everything that will seem difficult to anyone, I will first set out in the Meditations the very thoughts by whose help I seem to myself to have reached a certain and evident knowledge of the truth, so as to find out whether I can perhaps persuade others by the same reasons that persuaded me. After that I will reply to the objections of several men outstanding in talent and learning, to whom these Meditations were sent for examination before they went to press. For they raised objections numerous and varied enough that I venture to hope that nothing, at least of any importance, will easily occur to others that they have not already touched on.

In the First Meditation, the reasons are set out for which we can doubt all things, especially material things—so long, that is, as we have no other foundations for the sciences than those we have had until now. Although the usefulness of so extensive a doubt is not apparent at first sight, it is in fact very great: it frees us from all preconceived opinions and lays down the easiest path for withdrawing the mind from the senses; and finally, it makes it impossible for us to doubt any further the things we later discover to be true.

In the Second, the mind, using its own freedom, supposes that none of the things exist about whose existence it can have even the slightest doubt, and notices that it cannot be that it does not itself exist meanwhile. This too is of the greatest usefulness, since in this way the mind easily distinguishes what belongs to itself, that is, to an intellectual nature, and what belongs to the body. But since some people will perhaps expect arguments for the immortality of the soul in that place, I think I should warn them here 13 that I have tried to write nothing that I could not demonstrate precisely. So I could follow no order other than the one customary among geometers: namely, to set out first everything on which the proposition in question depends, before concluding anything about it.

In the Third Meditation I have explained my principal argument for proving the existence of God at sufficient length, as it seems to me. However, since I wished to lead my readers’ minds as far as possible away from the senses, I chose not to use any comparisons drawn from corporeal things there, and so many obscurities may perhaps remain. These, I hope, will be entirely removed later in the replies to the objections—among others, the question of how the idea of a supremely perfect being, which is in us,

In the Fourth, it is proved that everything we perceive clearly and distinctly is true, and at the same time it is explained what the nature of falsity consists in. These things must necessarily be known, both to confirm what precedes and to understand what remains. (But it should be noted meanwhile that the discussion there is in no way about sin, or the error committed in pursuing good and evil, but only about the error that occurs in distinguishing true from false. Nor are matters considered that pertain to faith or to the conduct of life, but only speculative truths, known solely by the help of the natural light.)

In the Fifth, besides an explanation of corporeal nature taken in general, the existence of God is also demonstrated by a new argument—though here again some difficulties may perhaps arise, which will be resolved later in the reply to the objections. And finally it is shown in what sense it is true that the certainty even of geometrical demonstrations depends on the knowledge of God.

In the Sixth, finally, understanding is separated from imagination; the marks of the distinctions are described; it is proved that the mind is really distinct from the body, and yet shown to be so closely joined to it that it forms a single thing with it; all the errors that commonly arise from the senses are surveyed; the ways in which they can be avoided are set out; and finally all the reasons from which the existence of material things can be concluded are presented. This is not because I thought them very useful for proving what they 16 prove—namely, that there really is a world, that human beings have bodies, and the like, which no one of sound mind has ever seriously doubted—but because, in considering them, one recognizes that they are neither as firm nor as clear as those by which we arrive at knowledge of our own mind and of God; so that these latter are the most certain and most evident of all that can be known by human ingenuity.

Some years ago now I noticed how many false things I had accepted as true in my youth, and how doubtful everything was that I had since built on them; and so I saw that once in my life everything had to be torn down completely and begun anew from the first foundations, if I ever wanted to establish anything firm and lasting in the sciences. But the task seemed enormous, and I kept waiting for an age so mature that no later one would be better suited to taking up learning. For that reason I delayed so long that from now on I would be at fault if I used up in deliberating the time that remains for acting. So today, at the right moment, I have freed my mind from all 18 cares, I have secured for myself untroubled leisure, I withdraw alone, and at last I will devote myself seriously and freely to this general overthrow of my opinions.

For this, however, it will not be necessary to show that they are all false, which I might perhaps never manage. Since reason already persuades me that I should withhold assent no less carefully from things that are not entirely certain and indubitable than from those that are obviously false, it will be enough, for rejecting all of them, if I find some reason for doubt in each. Nor, for that reason, will I need to go through them one by one, which would be an endless task. Since anything built on foundations collapses of its own accord once they are undermined, I will go straight for the principles on which everything I once believed rested.

Whatever I have accepted up to now as most true, I have received either from the senses or through the senses. But I have found that these sometimes deceive, and it is prudent never to trust completely those who have deceived us even once.

But perhaps, although the senses sometimes deceive us about things that are very small or far away, there are many other things about which there can be no doubt at all, even though they are drawn from the same source: for example, that I am here, sitting by the fire, wearing a winter gown, handling this paper, and the like. And how could it be denied that these very hands and this whole body are mine? Unless perhaps I were to compare myself with some madmen or other, 19 whose brains are so disordered by a stubborn vapor from black bile that they constantly insist that they are kings when they are paupers, or that they are dressed in purple when they are naked, or that they have heads made of clay, or that they are entirely gourds, or made of glass. But such people are insane, and I would seem no less mad myself if I took them as a model for myself.

Well then, suppose we are dreaming, and these particulars are not true—that we open our eyes, move our heads, stretch out our hands—and suppose that perhaps we do not even have such hands, or such a body at all. Still, it must surely be admitted that the things seen in sleep are like painted images, which could only have been fashioned in the likeness of true things; and so at least these general things—eyes, head, hands, and the whole body—exist as things that are not imaginary but true.

Of this kind seem to be corporeal nature in general and its extension; the shape of extended things; their quantity, that is, their size and number; the place in which they exist, the time through which they endure, and the like.

So perhaps we will not be wrong to conclude from this that physics, astronomy, medicine, and all the other disciplines that depend on the consideration of composite things are indeed doubtful, but that arithmetic, geometry, and others of that kind, which deal only with the simplest and most general things and care little whether these exist in nature or not, contain something certain and indubitable. For whether I am awake or asleep, two and three added together make five, and a square has no more than four sides; and it does not seem possible that such transparent truths should fall under suspicion of falsity.

Yet there is fixed in my mind a certain long-standing opinion that there is a God who can do everything, and by whom I was created such as I am. How do I know that he has not brought it about that there is no earth at all, no sky, no extended thing, no shape, no size, no place, and yet that all these things seem to me to exist just as they do now? Indeed, just as I sometimes judge that others err about things they think they know most perfectly, how do I know that he has not brought it about that I am deceived every time I add two and three, or count the sides of a square, or do something even easier, if anything easier can be imagined?

There may perhaps be some who would rather deny that there is any God so powerful than believe that everything else is uncertain. But let us not argue with them, and let us grant that all this about God is fiction. Whether they suppose that I have come to be what I am by fate, or by chance, or by a continuous series of events, or in any other way, since being deceived and erring seem to be a kind of imperfection, the less powerful they make the author of my origin, the more probable it will be that I am so imperfect as to be always deceived.

But it is not enough to have noticed this; I must take care to remember it. For my habitual opinions keep coming back, and they take hold of my credulity, which is bound to them, as it were, by long use and the right of familiarity, almost even against my will. Nor will I ever break the habit of assenting to them and trusting them, so long as I suppose them to be what they really are: doubtful in a certain way, as has just been shown, but nonetheless highly probable, and such that it is much more reasonable to believe them than to deny them. For this reason, I think I will not do badly if I turn my will completely in the opposite direction and deceive myself, pretending for a while that they are wholly false and imaginary, until at last, with the weights of preconceived opinion balanced on both sides, as it were, no bad habit any longer twists my judgment away from the correct perception of things.

Yesterday’s meditation has thrown me into such doubts that I can no longer forget them, and yet I do not see how they are to be resolved. It is as if I had suddenly fallen into a deep whirlpool: I am so tossed about that I can neither plant my foot on the bottom nor swim up to the surface. Still, I will make the effort and try once more the same path I set out on yesterday. That is, I will set aside everything that admits even the slightest doubt, just as if I had found it to be wholly false. And I will keep going until I know something certain—or, if nothing else, until I at least know for certain that nothing is certain. Archimedes asked for nothing but one point that was firm and immovable, in order to move the whole earth from its place. So too great things are to be hoped for if I find even the least thing that is certain and unshakable.

I suppose, then, that everything I see is false. I believe that none of the things my lying memory represents to me has ever existed. I have no senses at all. Body, shape, extension, motion, and place are chimeras. What, then, will be true? Perhaps just this one thing: that nothing is certain.

But how do I know that there is not something distinct from all the things I have just listed, about which there is not even the slightest occasion for doubt? Is there not some God, or whatever I may call him, who puts these very thoughts into me? But why should I think so, when I myself may perhaps be their author? Am I not, then, at least something? But I have already denied that I have any senses or any body. Still, I hesitate; for what 25 follows from that? Am I so bound to a body and senses that I cannot be without them? But I have persuaded myself that there is nothing at all in the world—no sky, no earth, no minds, no bodies. Did I not, then, also persuade myself that I do not exist? No: surely I existed, if I persuaded myself of something. But there is some deceiver or other, supremely powerful, supremely cunning, who is deliberately deceiving me all the time.

But I do not yet understand well enough who this I is that now necessarily exists. So from here on I must take care not to carelessly take something else in place of myself, and so go astray even in the knowledge that I maintain is the most certain and evident of all. I will therefore meditate afresh on what I once believed myself to be, before I fell into these thoughts. From this I will then subtract whatever could be weakened even slightly by the reasons already brought forward, so that in the end precisely what is certain and unshakable, and only that, remains.

What, then, did I formerly think I was? A man, of course. But what is a man? Shall I say a rational animal? No, because then I would have to ask what an animal is, and what rational is, and so from one question I would slide into several harder ones. Nor do I now have so much spare time that I would want to waste it on subtleties of that kind. Instead I will attend here to what used to occur to my thought spontaneously 26 and with nature as my guide, whenever I considered what I was. First, it occurred to me that I had a face, hands, arms, and this whole machine of limbs, such as can be seen even in a corpse, which I referred to by the name “body.” It occurred to me, moreover, that I was nourished, that I walked, sensed, and thought; and these actions I attributed to the soul.

But what now, when I suppose that some deceiver, supremely powerful and, if I may say so, malicious, has deliberately deceived me in everything, as far as he could? Can I affirm that I have even the least of all the things that I have just said belong to the nature 27 of body? I attend, I think, I turn it over; nothing comes to mind. I grow tired of repeating the same things in vain. What about the things I attributed to the soul? Being nourished, or walking? Since I now have no body, these too are nothing but fictions. Sensing? This too surely does not happen without a body; and in dreams I have seemed to sense a great many things that I later realized I had not sensed. Thinking? Here I find it: it is thought. This alone cannot be torn away from me. I am, I exist; that is certain. But for how long?

What else? I will imagine. I am not that framework of limbs called the human body. Nor am I some thin air infused into those limbs—not a wind, not a fire, not a vapor, not a breath, not anything I invent for myself; for I have supposed that these things are nothing. The supposition stands: nevertheless I am still something. Yet might it perhaps turn out that these very things which I suppose to be nothing, because they are unknown to me, are in truth no different from the I that I know? I do not know; I am not arguing about that now. I can pass judgment only on things that are known to me. I know that I exist; I am asking who this I is that I know. It is quite certain that knowledge of this I, taken precisely in this way, does not depend on things that I do not yet know to exist 28 —and so not on any of the things that I invent in imagination.

That is certainly quite a lot, if all of it belongs to me. But why should it not? Am I not the very one who now doubts almost everything, who nonetheless understands something, who affirms that this one thing is true and denies the rest, who desires to know more, who does not want to be deceived, who imagines many things even against my will, and who also notices many things as if they came from the senses? Even if I am always asleep, 29 and even if the one who created me is deceiving me as far as he can, which of these is not just as true as that I exist? Which of them is distinct from my thought? Which of them can be said to be separate from myself? For that it is I who doubt, who understand, who will, is so obvious that nothing occurs to me by which it could be explained more evidently.

From all this I am indeed beginning to know somewhat better who I am. But it still seems to me—and I cannot keep from thinking—that corporeal things, whose images are formed by thought and which the senses themselves explore, are known much more distinctly than this part of me, whatever it is, that does not come under the imagination. Yet it is surely strange that things I notice to be doubtful, unknown, and foreign to me should be grasped by me more distinctly than what is true, what is known—than, in short, myself. But I see what is going on: my mind enjoys wandering, and will not yet allow itself to be confined within the bounds of truth. Very well, then: let us once more give it the loosest possible 30 reins, so that when, a little later, they are drawn back at the right moment, it will more readily allow itself to be governed.

Perhaps it was what I now think: namely, that the wax itself was not that sweetness of honey, nor that fragrance of flowers, nor that whiteness, nor that shape, nor that sound, but a body that a little while ago appeared to me perceptible in those ways, and now in different ones. But what exactly is this thing that I imagine in this way? Let us attend 31 and, removing whatever does not belong to the wax, see what is left: nothing other than something extended, flexible, and changeable. But what is this “flexible” and “changeable”? Is it that I imagine that this wax can be changed from a round shape to a square one, or from that to a triangular one? Not at all. For I grasp that it is capable of countless changes of this kind, yet I cannot run through countless changes by imagining them; so this grasp is not accomplished by the faculty of imagining. What about “extended”? Is not even its extension unknown?

Meanwhile I am amazed at how prone my mind is to errors. For although I am considering these things silently within myself and without 32 speaking, I nonetheless get stuck on words themselves and am nearly deceived by ordinary ways of speaking. For we say that we see the wax itself, if it is there, not that we judge it to be there from its color or shape. From this I would at once conclude that the wax is therefore known by the eye’s vision, and not by an inspection of the mind alone—had I not just now happened to look out of the window at people passing in the street. Of them, too, I say, no less customarily than of the wax, that I see them. But what do I see besides hats and coats, under which there might be automata? Yet I judge that they are people. And so what I thought I was seeing with my eyes, I in fact grasp solely by the faculty of judging, which is in my mind.

But someone who wants to be wiser than the crowd should be ashamed to have looked for grounds for doubt in the forms of speech the crowd has invented. So let us go on, and consider whether I perceived what the wax was more perfectly and more evidently when I first looked at it and believed that I knew it by the external sense itself, or at least by the common sense, as they call it—that is, by the imaginative power—or rather now, after I have investigated more carefully both what it is and how it is known. Surely it would be foolish to doubt this. For what was there in my first perception that was distinct? What was there that any animal could not apparently have had? But when I distinguish the wax from its external forms and consider it naked, as if its clothes had been stripped off, then, although there may still be error in my judgment, I really cannot perceive it in this way without a human mind. 33note

But what am I to say about this mind itself, that is, about myself? For as yet I admit nothing to be in me except a mind. What, I ask, of me, who seem to perceive this wax so distinctly? Do I not know myself not only much more truly and much more certainly, but also much more distinctly and evidently? For if I judge that the wax exists from the fact that I see it, it certainly follows much more evidently, from this very fact that I see it, that I myself exist. For it may be that what I see is not really wax; it may be that I do not even have eyes with which anything is seen. But it is quite impossible, when I see, or (which I am not now distinguishing) when I think I see, that I myself who am thinking should not be something.

And look: at last I have come back of my own accord to where 34 I wanted to be. For I now know that bodies themselves are perceived, properly speaking, not by the senses or by the faculty of imagining but by the intellect alone, and that they are perceived not because they are touched or seen but only because they are understood. So I plainly recognize that nothing can be perceived by me more easily or more evidently than my own mind. But since the habit of an old opinion cannot be laid aside so quickly, I would like to pause here, so that by lengthy meditation this new knowledge may be fixed more deeply in my memory.

I will now close my eyes, stop my ears, and call away all my senses. I will even erase from my thought all images of corporeal things—or at least, since that can hardly be done, I will regard them as empty and false and count them as nothing. And by talking with myself alone and looking more deeply into myself, I will try gradually to make myself better known and more familiar to myself. I am a thinking thing: that is, a thing that doubts, affirms, denies, understands a few things, is ignorant of many, wills, refuses, and also imagines and senses. For as I noted before, even though the things I sense or imagine may perhaps be nothing outside me, still I am certain that those modes of thinking which I call sensations and imaginations, 35 insofar as they are simply modes of thinking, are in me.

With these few words I have reviewed everything I truly know, or at least everything I have so far noticed that I know. Now I will look around more carefully to see whether there may be other things in me that I have not yet considered. I am certain that I am a thinking thing. Do I not therefore also know what is required for me to be certain of anything? In this first knowledge there is nothing but a certain clear and distinct perception of what I affirm. This would certainly not be enough to make me certain of the truth of the matter if it could ever happen that something I perceived so clearly and distinctly was false. And so I now seem able to lay down as a general rule that whatever I perceive very clearly and distinctly is true.

Yet I previously accepted as wholly certain and evident many things that I later found to be doubtful. What were these, then? The earth, the sky, the stars, and all the other things I took in through the senses. But what did I clearly perceive about them? Only that the ideas, or thoughts, of such things were present to my mind. And even now I do not deny that those ideas are in me. But there was something else that I used to affirm, and that, through the habit of believing it, I thought I perceived clearly, though in fact I did not perceive it: namely, that there were certain things outside me from which those ideas proceeded and which they wholly resembled. And this was where I was either mistaken or, at any rate, if I was judging truly, that did not come about through the strength of my perception.

What, then? When I was considering something very simple and easy in arithmetic or geometry, 36 such as that two and three added together make five, or the like, did I not at least see these things clearly enough to affirm that they were true? Indeed, the only reason I later judged that they should be doubted was that it occurred to me that some God could perhaps have given me a nature such that I was deceived even about the things that seemed most evident. But whenever this preconceived opinion about the supreme power of God comes to mind, I cannot help admitting that, if he wished, it would be easy for him to make me go wrong even in the things I think I see most evidently with the eyes of the mind.

But now order seems to require that I first 37 divide all my thoughts into definite kinds, and ask in which of them truth or falsity properly lies. Some of them are like images of things, and to these alone the name “idea” properly applies: as when I think of a man, or a chimera, or the sky, or an angel, or God. Others have certain other forms in addition. When I will, when I fear, when I affirm, when I deny, I always apprehend some thing as the subject of my thought, but I also take in with my thought something more than the likeness of that thing. Of these, some are called volitions, or emotions, and others judgments.

Now as far as ideas are concerned, if they are considered solely in themselves and I do not refer them to anything else, they cannot, properly speaking, be false; for whether I imagine a goat or a chimera, it is no less true that I imagine the one than the other. Nor is there any falsity to fear in the will itself or in the emotions; for although I may desire wicked things, or even things that exist nowhere, it is still true that I desire them. So only judgments remain, and in them I must take care not to be deceived.

Of these ideas, some seem to me innate, some adventitious, 38 and some made by me myself. For my understanding what a thing is, what truth is, what thought is, seems to come from nowhere else than my own nature. But my now hearing a noise, seeing the sun, feeling the fire—these I have so far judged to proceed from certain things located outside me. And finally, sirens, hippogriffs, and the like are invented by me. Or perhaps I can even think that they are all adventitious, or all innate, or all made by me; for I have not yet clearly seen their true origin.note

But here I must chiefly ask, concerning the ideas that I consider as derived from things existing outside me, what reason leads me to think they resemble those things. Well, I seem to have been taught so by nature. And besides, I find by experience that they do not depend on my will, and hence not on me myself; for they often present themselves even against my will. Right now, for instance, whether I want to or not, I feel heat, and so I think that this sensation, or idea of heat, comes to me from a thing distinct from me, namely from the heat of the fire I am sitting by. And nothing is more obvious than for me to judge from this that the thing sends into me its own likeness rather than anything else.

Whether these reasons are firm enough, I will now see. When I say here that I have been taught so by nature, I mean only that I am carried by a certain spontaneous impulse to believe it, not that it is shown to me to be true by some natural light. These two things differ a great deal. For whatever is shown to me by the natural light—for instance, that from the fact that I doubt it follows that I exist, and the like—can in no way be doubtful, because there can be no other faculty that I trust as much as that light, and that could teach me that these things 39 are not true. But as for natural impulses, I have often judged in the past that they pushed me toward the worse side when it was a matter of choosing the good, and I do not see why I should trust them any more in any other matter.

Next, even though those ideas do not depend on my will, it does not follow that they necessarily proceed from things located outside me. For just as the impulses I was speaking of a moment ago, though they are in me, nonetheless seem to be distinct from my will, so perhaps there is also some other faculty in me, not yet well enough known to me, that produces these ideas—just as it has always seemed up to now that they are formed in me while I dream, without any help from external things.

And finally, even if they did proceed from things distinct from me, it does not follow that they must resemble those things. On the contrary, in many cases I think I have often found a great discrepancy. For example, I find in myself two different ideas of the sun. One, drawn as it were from the senses, and to be counted above all among the ideas I regard as adventitious, makes the sun appear very small to me. The other, derived from the reasonings of astronomy—that is, elicited from certain notions innate in me, or made by me in some other way—shows it to be several times larger than the earth. Certainly both cannot resemble the same sun existing outside me; and reason persuades me that the one which seems to have flowed most directly from the sun itself is the one that least resembles it.

All this shows clearly enough that until now I have believed, not 40 from any certain judgment, but only from some blind impulse, that there exist certain things distinct from me which send their ideas or images into me through the sense organs or in some other way.

But yet another way occurs to me of inquiring whether any of the things whose ideas are in me exist outside me. Insofar as these ideas are simply modes of thinking, I recognize no inequality among them, and they all seem to proceed from me in the same way. But insofar as one represents one thing and another represents another, it is clear that they differ greatly from one another. For undoubtedly the ideas that present substances to me are something more and, so to speak, contain more objective reality in themselves than those that represent only modes, or accidents. And again, the idea by which I understand a supreme God—eternal, infinite, omniscient, omnipotent, and creator of all things that exist besides himself—certainly has more objective reality in it than the ideas by which finite substances are presented.

Now it is manifest by the natural light that there must be at least as much in the efficient and total cause as in the effect of that same cause. For where, I ask, could the effect get its reality, if not from the cause? And how could the cause give it that reality, unless it also had it? From this it follows both that something cannot come from nothing, and also that what is more perfect—that is, what contains 41 more reality in itself—cannot come from what is less perfect. And this is plainly true not only of those effects whose reality is actual or formal, but also of ideas, in which only objective reality is considered.

Nor should I suspect that, since the reality I consider in my ideas is only objective, it is not 42 necessary for the same reality to be formally in the causes of those ideas, but that it is enough if it is in them objectively as well. For just as this objective mode of being belongs to ideas by their very nature, so the formal mode of being belongs to the causes of ideas—at least to the first and principal ones—by their nature. And although one idea may perhaps arise from another, there can be no infinite regress here; eventually we must arrive at some first idea, whose cause is like an archetype, in which all the reality that is in the idea only objectively is contained formally.

The longer and more carefully I examine all this, the more clearly and distinctly I recognize that it is true. But what, in the end, shall I conclude from it? This: if the objective reality of any one of my ideas is so great that I am certain it is not in me either formally or eminently, and hence that I myself cannot be the cause of that idea, then it necessarily follows that I am not alone in the world, but that some other thing, which is the cause of that idea, also exists. But if no such idea is found in me, I will have no argument at all to make me certain of the existence of any thing distinct from myself. For I have looked around most carefully, and so far I have been able to find no other.

Now among these ideas of mine, besides the one that presents me to myself, about which there can be no difficulty 43 here, there is one that represents God, others that represent corporeal and inanimate things, others angels, others animals, and finally others that represent other human beings like myself.

As for the ideas that present other human beings, or animals, or angels, I easily understand that they could be put together from the ideas I have of myself, of corporeal things, and of God, even if there were no human beings besides me in the world, and no animals, and no angels.

As for the ideas of corporeal things, there is nothing in them so great that it seems it could not have come from me myself. For if I look into them more deeply, and examine each one in the way I examined the idea of the wax yesterday, I notice that there are only very few things in them that I perceive clearly and distinctly: namely, size, or extension in length, breadth, and depth; shape, which arises from the bounding of that extension; position, which the various shaped things have relative to one another; and motion, or change of that position. To these can be added substance, duration, and number. But everything else—light and colors, sounds, smells, tastes, heat and cold, and the other tactile qualities—I think of only in a very confused and obscure way, so much so that I do not even know whether they are true or false, that is, whether the ideas I have of them are ideas of things or of non-things.

For these ideas I certainly need not posit any author distinct from myself. For if they are false, that is, if they represent no things, I know by the natural light that they come from nothing—that is, that they are in me only because something is lacking in my nature, which is not wholly perfect. If, on the other hand, they are true, then since they present so little reality to me that I cannot even distinguish it from a non-thing, I do not see why they could not come from me myself.

Of the things that are clear and distinct in the ideas of corporeal things, some I seem to have been able to borrow from the idea of myself: namely substance, duration, number, and anything else of that kind. For when I think that a stone is a substance, or a thing capable of existing by itself, and likewise that I am a substance, then although I conceive of myself as a thinking thing and not an extended one, and of the stone as an extended thing and not a thinking one, so that the two concepts differ enormously, they nevertheless seem to agree in the respect of being substance. Likewise, when I perceive that I exist now, and recall that I have also existed for some time before, and when I have various thoughts whose number I understand, I acquire 45 the ideas of duration and number, which I can then transfer to any other things whatever.

So there remains only the idea of God, in which I must consider whether there is anything that could not have come from me myself. By the name “God” I understand a certain substance that is infinite, independent, supremely intelligent, supremely powerful, and by which both I myself and everything else that exists—if anything else does exist—was created. All these attributes are such that the more carefully I attend to them, the less it seems possible that they came from me alone. And so, from what has been said, it must be concluded that God necessarily exists.

For although the idea of substance is in me by the very fact that I am a substance, it would not on that account be the idea of an infinite substance, since I am finite, unless it came from some substance that really was infinite.

Nor should I think that I perceive the infinite not through a true idea but only by negating the finite, as I perceive rest and darkness by negating motion and light. On the contrary, I clearly understand that there is more reality in an infinite substance than in a finite one, and hence that my perception of the infinite is in some way prior in me to my perception of the finite—that is, my perception of God to that of myself. For how could I understand that I doubt, that I 46 desire—that is, that something is lacking in me, and that I am not wholly perfect—if there were in me no idea of a more perfect being, by comparison with which I recognized my defects?

Nor can it be said that this idea of God is perhaps materially false, and so could come from nothing, as I noted a little earlier about the ideas of heat and cold and the like. On the contrary, since it is supremely clear and distinct, and contains more objective reality than any other, no idea is truer in itself, and none is less open to the suspicion of falsity. This idea of a supremely perfect and infinite being is, I say, supremely true. For although one might perhaps pretend that such a being does not exist, one cannot pretend that its idea presents nothing real to me, as I said earlier about the idea of cold. It is also supremely clear and distinct; for whatever I perceive clearly and distinctly that is real and true, and that implies some perfection, is wholly contained in it.

But perhaps I am something greater than I myself understand, and all the perfections I attribute to God are in some way in me potentially, even if they do not yet 47 show themselves and are not brought into actuality. For I already experience my knowledge gradually increasing; and I do not see what prevents it from increasing more and more to infinity, nor why, with my knowledge thus increased, I could not by its means acquire all the other perfections of God; nor, finally, why the potential for these perfections, if it is already in me, would not suffice to produce the idea of them.

But none of this can be so. First, even if it is true that my knowledge increases by degrees, and that there are many things in me potentially that are not yet actual, none of this pertains to the idea of God, in which there is nothing at all that is merely potential; indeed, this very fact—increasing by degrees—is the surest sign of imperfection. Moreover, even if my knowledge always increases more and more, I nevertheless understand that it will never on that account be actually infinite, because it will never reach a point where it is incapable of further increase. But I judge God to be actually infinite in such a way that nothing can be added to his perfection. And finally, I perceive that the objective being of an idea cannot be produced by merely potential being, which, properly speaking, is nothing, but only by actual or formal being.

Certainly there is nothing in all this that is not manifest by the natural light to anyone who attends carefully. But when I attend less, and the images of sensible things blind the mind’s eye, I do not so easily remember why the idea of a being more perfect than I must necessarily come from some being that really is more perfect. So I would like to inquire 48 further whether I myself, who have this idea, could exist if no such being existed.

From what, then, would I derive my existence? From myself, of course, or from my parents, or from any other things less perfect than God; for nothing more perfect than God, or even as perfect, can be thought or imagined.

Yet if I derived my existence from myself, I would not doubt, or wish for anything, or lack anything at all; for I would have given myself all the perfections of which there is any idea in me, and so I would myself be God. Nor should I think that the things I lack might perhaps be harder to acquire than those already in me. On the contrary, it is plain that it would have been far harder for me—that is, a thinking thing or substance—to emerge out of nothing than to acquire knowledge of the many things I do not know, since such knowledge is only an accident of that substance.

Nor do I escape the force of these arguments if I suppose that perhaps I have always existed as I do now, as if it followed from this that no author of my existence need be sought. For since the whole span of a life can be divided into 49 countless parts, each of which in no way depends on the others, it does not follow from the fact that I existed a little while ago that I must exist now, unless some cause as it were creates me again at this moment—that is, preserves me. For it is clear to anyone who attends to the nature of time that exactly the same power and action are needed to preserve any thing at each moment of its duration as would be needed to create it anew if it did not yet exist. So that preservation differs from creation only in the way we think of it is also one of the things that are manifest by the natural light.

So I must now ask myself whether I have some power by which I can bring it about that I, who exist now, will also exist a little while from now. For since I am nothing but a thinking thing—or at least, since I am now dealing precisely with only that part of me which is a thinking thing—if there were any such power in me, I would undoubtedly be aware of it. But I experience that there is none, and from this very fact I know most evidently that I depend on some being distinct from me.

But perhaps that being is not God, and I was produced either by my parents or by some other causes less perfect than God. No: as I have already said, it is clear that there must be at least as much in the cause as there is in the effect. And therefore, since I am a thinking thing and have in me some idea of God, whatever cause of me is finally assigned, it must be admitted that it too is a thinking thing and has the idea of all the perfections I attribute to God. And about that cause it can be asked in turn whether it derives its existence from itself or from another. If from itself, it is clear from what has been said that it is itself God; for 50 since it has the power of existing through itself, it undoubtedly also has the power of actually possessing all the perfections of which it has an idea in itself, that is, all those I conceive to be in God.

For it is clear enough that there can be no infinite regress here, especially since I am dealing here not only with the cause that once produced me, but most of all with the cause that preserves me at the present time.

Nor can it be supposed that several partial causes perhaps worked together to make me, and that I received the idea of one of the perfections I attribute to God from one cause, and the idea of another from another, so that all those perfections are indeed found somewhere in the universe, but not all joined together in some single being who would be God. On the contrary, the unity, simplicity, or inseparability of all the things that are in God is one of the chief perfections I understand to be in him. And certainly the idea of this unity of all his perfections could not have been placed in me by any cause from which I did not also get the ideas of the other perfections; for that cause could not have made me understand them as joined together and inseparable unless it had at the same time made me recognize what they were.

Finally, as for my parents, even if everything I have ever believed about them is true, it is certainly not they who preserve me, nor did they in any way make me insofar as I am a thinking thing. They only placed certain dispositions in the matter in which I have judged that I—that is, the mind, which alone I now 51 take to be myself—reside. So there can be no difficulty about them here. Rather, it must simply be concluded that from the mere fact that I exist, and that there is in me an idea of a most perfect being, that is, of God, it is most evidently demonstrated that God also exists.

It remains only for me to examine how I received this idea from God. For I did not draw it from the senses, nor has it ever come to me unexpectedly, as the ideas of sensible things usually do when those things strike, or seem to strike, the external organs of the senses. Nor was it made up by me, for I plainly cannot take anything away from it or add anything to it. And so it remains that it is innate in me, just as the idea of myself is also innate in me.

But before I examine this more carefully, and at the same time inquire into other truths that can be gathered from it, I would like to pause here for a while in the contemplation of God himself, to weigh his attributes within myself, and to gaze upon, wonder at, and adore the beauty of this immense light, so far as the eye of my clouded ingenuity can bear it. For just as we believe by faith that the supreme happiness of the next life consists in this contemplation of the divine majesty alone, so we now experience that from this same contemplation, though far less perfect, we can derive the greatest pleasure of which we are capable in this life.

In these past days I have so accustomed myself to withdrawing my mind from the senses, and I have so carefully observed that there are very few 53 things that are truly perceived about corporeal things, while much more is known about the human mind, and still much more about God, that I now turn my thought without any difficulty away from imaginable things to things that are purely intelligible and separated from all matter. And indeed I have a much more distinct idea of the human mind, insofar as it is a thinking thing, not extended in length, breadth, and depth, and having nothing else of body about it, than I have of any corporeal thing.

To begin with, I recognize that it is impossible for him ever to deceive me. For in all trickery or deception some imperfection is found; and although being able to deceive may seem to be some sign of cleverness or power, wanting to deceive undoubtedly bears witness either to malice or to weakness, and so cannot apply to God.

Next, I experience that there is in me a certain faculty of judging, which, like everything else that is in me, 54 I certainly received from God. And since he does not wish to deceive me, he surely did not give me a faculty such that I could ever err while using it correctly.

No doubt would remain on this matter, except that it seems to follow that I can therefore never err. For if whatever is in me I have from God, and he has not given me any faculty of erring, it seems I can never err.

Yet this is still not wholly satisfactory. For error is not 55 a pure negation, but a privation, or lack, of some knowledge that ought in some way to be in me. And when I attend to the nature of God, it does not seem possible that he should have placed in me some faculty that is not perfect of its kind, or that lacks some perfection due to it. For if the more skilled the craftsman, the more perfect the works that come from him, what can have been made by that supreme maker of all things that is not complete in every respect? Nor is there any doubt that God could have created me such that I would never be deceived; nor is there any doubt that he always wills what is best. Is it better, then, that I be deceived than not?

As I weigh these things more attentively, it occurs to me first that I should not be surprised if God does some things whose reasons I do not understand; nor should I doubt his existence on the grounds that I perhaps find other things of which I do not comprehend why or how he made them. For since I now know that my nature is very weak and limited, while the nature of God is immense, incomprehensible, and infinite, I also know well enough from this that he can do countless things whose causes I do not know. And for this reason alone I consider that the whole class of causes customarily sought from the end is of no use in physical matters; for I do not think I can investigate the ends of God without rashness.note

It also occurs to me that whenever we inquire whether the works of God are perfect, we should consider not some single creature in isolation but the whole universe of things. For what might perhaps rightly seem very 56 imperfect if it existed alone is most perfect when regarded as having the role of a part in the world. And although, since I resolved to doubt everything, I have so far known with certainty that nothing exists except myself and God, still, since I have become aware of God’s immense power, I cannot deny that many other things have been made by him, or at least could be made, so that I would have the role of a part in the universe of things.

Next, coming closer to myself and investigating what sort of thing my errors are (for they alone point to some imperfection in me), I notice that they depend on two causes working together: namely, on the faculty of knowing that is in me, and on the faculty of choosing, or freedom of choice—that is, on the intellect and at the same time on the will.

From these considerations I perceive that the cause of my errors is not the power of willing, which I have from God, considered in itself, for it is very ample and perfect of its kind. Nor is it the power of understanding: for whatever I understand, since I have from God the ability to understand it, I doubtless understand rightly, and I cannot possibly be deceived in it. Where, then, do my errors come from? Surely from this alone: that since the will extends more widely than the intellect, I do not keep it within the same limits, but extend it even to things I do not understand. Since it is indifferent to these, it easily turns aside from the true and the good; and so I both am deceived and sin.

For example, when I was examining these past days whether anything in the world existed, and noticed that from the very fact that I was examining this it evidently followed that I existed, I could not help judging that what I understood so clearly was true. Not that I was compelled to this by any 59 external force, but because a great light in the intellect was followed by a great inclination in the will; and so I believed it all the more spontaneously and freely the less indifferent I was to it.

Indeed, this indifference extends not only to things of which the intellect knows nothing at all, but in general to everything that the intellect does not know plainly enough at the very time when the will is deliberating about it. For however probable the conjectures that draw me in one direction, the mere knowledge that they are only conjectures, and not certain and indubitable reasons, is enough to push my assent the opposite way. I have had ample experience of this in these past days, when I supposed to be wholly false all the things I had previously believed most firmly to be true, for this one reason: that I had found they could in some way be doubted.

But when I do not perceive clearly and distinctly enough what is true, it is clear that if I refrain from making a judgment I act rightly and am not deceived. But if I either affirm or deny, then I do not use my freedom of choice rightly. And 60 if I turn to the side that is false, I shall plainly be deceived; if I embrace the other, I shall indeed hit on the truth by chance, but I shall not on that account be free of blame, since it is manifest by the natural light that the perception of the intellect must always precede the determination of the will. And in this incorrect use of free choice lies the privation that constitutes the form of error: the privation, I say, lies in the operation itself insofar as it proceeds from me, but not in the faculty I received from God, nor even in the operation insofar as it depends on him.note

For I have no cause to complain that God did not give me a greater power of understanding, or a greater natural light, than he did; for it belongs to the nature of a finite intellect not to understand many things, and to the nature of a created intellect to be finite. Rather, I have reason to thank him, who never owed me anything, for what he has bestowed—not to think that he has deprived me of the things he did not give, or taken them away from me.

Nor have I cause to complain that he gave me a will that extends more widely than the intellect. For since the will consists in one thing only, as if in something indivisible, its nature does not seem to allow anything to be taken away from it. And surely the ampler it is, the greater the thanks I owe to its giver.

Nor, finally, should I complain that God concurs with me in eliciting those acts of will, or those judgments, in which I am deceived. For those acts are wholly true and good insofar as they depend on God; and there is in a way greater perfection in me in being able to elicit them than if I could not. But the privation, in which alone the formal 61 character of falsity and fault consists, needs no concurrence from God, because it is not a thing; and when it is referred to him as its cause, it should be called not a privation but only a negation.

Moreover, even if I cannot abstain from errors in the first way, which depends on an evident perception of everything I must deliberate about, I can still do so in the other way, which depends only 62 on my remembering to refrain from judging whenever the truth of a matter is not plain. For although I experience in myself the weakness of not being able always to keep my attention fixed on one and the same piece of knowledge, I can nonetheless, by attentive and often repeated meditation, bring it about that I recall it whenever need requires, and so acquire a kind of habit of not erring.

Since the greatest and chief perfection of a human being consists in this, I think I have gained no small amount from today’s meditation, in having investigated the cause of error and falsity. And surely there can be no cause other than the one I have explained. For whenever I restrain the will in making judgments so that it extends only to what the intellect presents to it clearly and distinctly, it is quite impossible for me to err. For every clear and distinct perception is undoubtedly something, and so cannot come from nothing, but necessarily has God as its author—God, I say, that supremely perfect being, whom it is contradictory to suppose a deceiver. Therefore it is undoubtedly true.

Many things remain for me to investigate about God’s attributes, and many about the nature of myself, that is, of my mind. But perhaps I will take these up again another time. Now (having noticed what to guard against and what to do to attain the truth) nothing seems more urgent than to try to emerge from the doubts into which I fell in the preceding days, and to see whether anything certain can be had concerning material things.

And indeed, before I inquire whether any such things exist outside me, I must consider the ideas of them, insofar as they are in my thought, and see which of them are distinct and which confused.

Well, then: I distinctly imagine quantity—what philosophers commonly call continuous quantity—or rather the extension of this quantity, or better of the quantified thing, in length, breadth, and depth. I count various parts in it. To these parts I assign any sizes, shapes, positions, and local motions whatever, and to these motions any durations whatever.note

Not only are these things, considered thus in general, plainly known and transparent to me; in addition, by attending, I perceive countless particulars about shapes, number, motion, and the like, whose truth is so evident 64 and so in accord with my nature that, when I first discover them, I seem not so much to be learning something new as to be recalling what I already knew before, or to be noticing for the first time things that had long been in me, though I had not previously turned my mind’s gaze to them.

And what I think most needs to be considered here is this: I find in myself countless ideas of certain things which, even if they perhaps exist nowhere outside me, still cannot be said to be nothing. And although in a sense I think them at will, they are not invented by me, but have their own true and immutable natures.

Nor is it to the point if I say that this idea of a triangle perhaps came to me from external things through the sense organs, since I have sometimes seen bodies having a triangular shape. For I can think up countless other shapes of which there can be no suspicion that they ever reached me through the senses, and yet 65 I can demonstrate various properties of them, no less than of the triangle. And these are all certainly true, since I know them clearly; and therefore they are something, not merely nothing. For it is evident that whatever is true is something; and I have already amply demonstrated that everything I know clearly is true.

Admittedly, this is not entirely transparent at first sight, but has a certain look of a sophism. For since I am accustomed in all other things to distinguish existence from essence, I easily persuade myself that existence can also be separated from the essence of God, and so that God can be thought of as not existing. But when I attend more carefully it becomes manifest that existence can no more be separated from the essence of God than the equality of its three angles to two right angles can be separated from the essence of a triangle, or the idea of a valley from the idea of a mountain. So it is no less contradictory to think of God (that is, a supremely perfect being) lacking existence (that is, lacking some perfection) than to think of a mountain lacking a valley.

And yet, even granting that I cannot think of God except as existing, just as I cannot think of a mountain without a valley, still, just as it does not follow from my thinking of a mountain with a valley that there is any mountain in the world, so it does not seem to follow from my thinking of God as existing that God exists. For my thought imposes no necessity on things; and just as I may imagine a winged horse although no horse has wings, so perhaps I can attach existence to God although no God exists.

No—this is where the sophism lies. From the fact that I cannot think of a mountain except with a valley, it does not follow that a mountain and a valley exist anywhere, but only that a mountain 67 and a valley, whether they exist or not, cannot be separated from each other. But from the fact that I cannot think of God except as existing, it follows that existence is inseparable from God, and hence that he really exists. Not that my thought brings this about, or imposes any necessity on any thing; on the contrary, the necessity of the thing itself, namely of God’s existence, determines me to think this. For I am not free to think of God without existence (that is, a supremely perfect being without supreme perfection), as I am free to imagine a horse with or without wings.

Nor should it be said here that it is indeed necessary for me to posit that God exists once I have posited that he has all perfections, since existence is one of them, but that the first positing was not necessary—just as it is not necessary for me to think that all four-sided figures can be inscribed in a circle, but given that I do think this, I will have to admit that a rhombus can be inscribed in a circle, which is plainly false.

But whatever method of proof I use in the end, it always comes back to this: only what I perceive clearly and distinctly fully persuades me. And indeed, of the things I perceive in this way, although some are obvious to everyone while others are discovered only by those who look more closely and investigate diligently, nevertheless once the latter have been discovered they are judged no less certain than the former. Thus, although in a right 69 triangle it is not as readily apparent that the square on the base is equal to the squares on the sides as that the base is subtended by its greatest angle, the former is no less believed once it has been seen.

And although I needed attentive consideration to perceive this very thing, now I am not only as certain of it as of anything else that seems most certain, but I also notice that the certainty of all other things depends on it in such a way that without it nothing could ever be perfectly known.

For although I am of such a nature that, as long as I perceive something very clearly and distinctly, I cannot help believing it to be true, I am also of such a nature that I cannot always fix my mind’s gaze on the same thing so as to perceive it clearly; and the memory of a judgment previously made often comes back when I am no longer attending to the reasons for which I made it. So other reasons can be brought forward which, if I did not know God, would easily dislodge me from that opinion; and so I would never have true and certain knowledge of anything, but only shifting and changeable opinions.

But once I have perceived that God exists, since I have at the same time also understood that everything else depends on him and that he is not a deceiver, and have gathered from this that everything I perceive clearly and distinctly is necessarily true, then—even if I no longer attend to the reasons for which I judged it true, provided only that I remember having seen it clearly and distinctly—no contrary reason can be brought forward that would drive me to doubt it; instead, I have true and certain knowledge of it. And not only of this, but also of everything else I remember having once demonstrated, such as the truths of geometry and the like. For what will now be raised against me? That I was made such that I am often deceived? But I now know that I cannot be deceived in things I understand transparently. That at other times I took many things as true and certain that I later found to be false?

And so I plainly see that the certainty and truth of all knowledge depends on the knowledge of the true God alone, so that before I knew him I could not have known anything else perfectly. But now countless things can be plainly known and certain to me, both about God himself and other intellectual things, and also about the whole of that corporeal nature which is the object of pure mathematics.

It remains for me to examine whether material things exist. And indeed I already know at least that they can exist, insofar as they are the object of pure mathematics, since I perceive them clearly and distinctly. For there is no doubt that God is capable of bringing about everything that I am capable of perceiving in this way; and I have never judged that something could not be done by him except on the ground that it would be contradictory for me to perceive it distinctly. Further, from the faculty of imagination, which I find I use when I am occupied with these material things, it seems to follow that they exist. For when I consider more attentively what imagination is, 72 it appears to be nothing other than a certain application of the cognitive faculty to a body that is intimately present to it, and hence existing.

To make this plain, I first examine the difference between imagination and pure understanding. For example, when I imagine a triangle, I not only understand that it is a figure bounded by three lines, but at the same time I also look upon these three lines as present with the eye of the mind; and this is what I call imagining. But if I want to think about a chiliagon, I certainly understand that it is a figure consisting of a thousand sides just as well as I understand that a triangle is a figure consisting of three; but I do not imagine those thousand sides in the same way, or look upon them as present.note

In addition, I consider that this power of imagining that is in me, insofar as it differs from the power of understanding, is not required for my own essence, that is, for the essence of my mind. For even if it were absent from me, I would doubtless remain the same one I now am. From this it seems to follow that it depends on some thing different from me.

But I am accustomed to imagine many other things besides that corporeal nature which is the object of pure mathematics—such as colors, sounds, tastes, pain, and the like—but none so distinctly. And since I perceive these better by the senses, from which they seem to have reached the imagination with the help of memory, then in order to deal with them more conveniently I must by the same token deal with the senses as well, and see whether, from the things perceived by this mode of thinking that I call sensing, I can obtain some certain argument for the existence of corporeal things.

And first I will go back over in my mind what the things were that I previously thought were true, as perceived by the senses, and for what reasons I thought so. Next I will also weigh the reasons for which I later called these same things into doubt. And finally I will consider what I ought now to believe about them.

First, then, I sensed that I had a head, hands, feet, and the other limbs that make up that body which I regarded as a part of me, or perhaps even as the whole of me. And I sensed that this body was situated among many other bodies, by which it could be affected in various beneficial or harmful ways; and I measured the beneficial ones by a certain sensation of pleasure, and the harmful ones by a sensation of pain. Besides pain and pleasure, I also sensed in myself hunger, thirst, and other appetites of this kind; and likewise certain bodily inclinations toward cheerfulness, toward sadness, toward anger, and other similar emotions. And outside me, besides the extension of bodies, and their shapes and 75 motions, I also sensed in them hardness and heat and other tactile qualities; and in addition light, and colors, and smells, and tastes, and sounds, by whose variety I distinguished the sky, the earth, the seas, and the other bodies from one another.

Later, however, many experiences gradually undermined all the trust I had placed in the senses. Sometimes towers that had looked round from a distance appeared square from close up; and very large statues standing on their tops did not look large to someone viewing them from the ground. In countless other such cases I found that the judgments of the external senses were mistaken. And not only of the external senses, but of the internal 77 ones too. For what can be more internal than pain? Yet I had sometimes heard from people who had had a leg or an arm cut off that they still occasionally seemed to feel pain in the part of the body they no longer had. And so it seemed that even in my own case it was not entirely certain that a particular limb was hurting me, even though I felt pain in it.

But now that I am beginning to know myself and the author of my origin better, I do not think I should rashly 78 accept everything I seem to get from the senses; but neither should I call everything into doubt.

First, I know that everything I clearly and distinctly understand can be made by God just as I understand it. So it is enough that I can clearly and distinctly understand one thing without another for me to be certain that the one is different from the other, since they can be separated, at least by God; and it makes no difference by what power this is done for them to be judged different. Accordingly, from the very fact that I know that I exist, and that meanwhile I notice nothing else whatever belonging to my nature or essence except this alone, that I am a thinking thing, I rightly conclude that my essence consists in this one thing: that I am a thinking thing.

Further, I find in myself faculties for certain special modes of thinking, namely the faculties of imagining and sensing. I can clearly and distinctly understand myself as a whole without them, but not, conversely, them without me—that is, without an understanding substance in which they inhere. For their formal concept includes some understanding; and from this I perceive that they are distinguished from me as modes are from a thing. I also recognize certain other faculties, such as those of changing place, taking on various shapes, and the like. These, no more than the preceding ones, can be understood without 79 some substance in which they inhere, and so they cannot exist without one either. But it is evident that these, if they do exist, must inhere in a corporeal or extended substance, not an understanding one, since their clear and distinct concept contains some extension, but no understanding whatever.

As for the other things, which are either merely particular—for example, that the sun is of such-and-such a size or shape, and so on—or less clearly understood, such as light, sound, pain, and the like: although they are very doubtful and uncertain, still the very fact that God is not a deceiver, and that it is therefore impossible for any falsity to be found in my opinions unless there is also some faculty in me, given by God, for correcting it, offers me a sure hope of reaching the truth even in these matters.

Now there is nothing that this nature teaches me more explicitly than that I have a body, which is in a bad way when I feel pain, which needs food or drink when I suffer hunger or thirst, and so on. So I ought not to doubt that there is some truth in this. 81

I am also taught by nature that various other bodies exist around my body, some of which I should pursue and others avoid. And certainly, from the fact that I sense widely differing colors, sounds, smells, tastes, heat, hardness, and the like, I rightly conclude that in the bodies from which these various sense perceptions come there are some variations corresponding to them, even if perhaps not resembling them. And from the fact that some of these perceptions are pleasant to me and others unpleasant, it is entirely certain that my body—or rather, I as a whole, insofar as I am composed of body and mind—can be affected in various beneficial and harmful ways by the bodies around it. 82

But there are many other things which, although I seem to have been taught them by nature, I have in fact received not from nature but from a certain habit of judging thoughtlessly, and so they may easily be false. For example: that any space in which there is nothing at all to stimulate my senses is empty; that in a hot body, for instance, there is something exactly like the idea of heat that is in me; that in a white or green body there is the same whiteness or greenness that I sense, and in a bitter or sweet one the same taste, and so on; that stars and towers and any other distant bodies have only the size and shape they display to my senses; and other things of this kind.

I have already seen well enough how, despite the goodness of God, it happens that my judgments are false. But a new difficulty arises here concerning the very things that nature presents to me as to be pursued or avoided, and also concerning the internal senses, in which I seem to have detected errors: as when someone, deceived by the pleasant taste of some food, swallows poison hidden inside it. 84 But in that case, of course, he is driven by nature only to desire the thing in which the pleasant taste lies, not the poison, of which his nature is quite ignorant. Nothing can be concluded from this except that this nature is not omniscient. And that is not surprising: since a human being is a limited thing, the only perfection that belongs to him is a limited one.

But we quite often go wrong even in the things toward which nature drives us, as when sick people desire drink or food that will harm them shortly afterward. It might perhaps be said here that they go wrong because their nature is corrupted. But this does not remove the difficulty, since a sick man is no less truly a creature of God than a healthy one; and so it seems no less contradictory that he should have a deceptive nature from God.

And certainly, with regard to a body suffering from dropsy, it may be only an extrinsic denomination when its nature is said to be corrupted because it has a dry throat and yet does not need drink. But with regard to the composite—that is, the mind united to such a body—it is not a mere denomination but a true error of nature that it is thirsty when drink will harm it. So it remains to inquire here how the goodness of God does not prevent nature, taken in this sense, from being deceptive.

The first thing I notice here is that there is a great difference between mind and body, in that body is by its nature always divisible, whereas the mind is entirely 86 indivisible. For certainly, when I consider the mind—that is, myself insofar as I am only a thinking thing—I can distinguish no parts in myself, but understand myself to be a thing that is entirely one and whole. And although the whole mind seems to be united to the whole body, yet if a foot or an arm or any other part of the body is cut off, I know that nothing has thereby been taken away from the mind. Nor can the faculties of willing, sensing, understanding, and so on be called its parts, since it is one and the same mind that wills, that senses, that understands.

Next I notice that the mind is not affected immediately by all parts of the body, but only by the brain, or perhaps even by just one small part of it—namely, the part in which the “common sense” is said to be. Whenever this part is disposed in the same way, it presents the same thing to the mind, even if the other parts of the body are meanwhile in various different conditions. Countless experiments prove this, and there is no need to review them here.

I notice, further, that the nature of body is such that no part of it can be moved by another part some distance away without its also being possible for it to be moved in the same way by any of the parts in between, even if the more distant part does nothing. For example, in a cord A, B, C, D, if its far end D is pulled, the first part A will move in just the same way as it could also be moved if one of the intermediate parts, B or C, were pulled and the end D stayed still.

Finally, I notice that each of the motions that occur in the part of the brain that immediately affects the mind brings it only one particular sensation. Given this, nothing better can be devised than that it should bring the one which, of all those it could bring, is most conducive, and most often conducive, to the preservation of a healthy human being. And experience testifies that all the sensations nature has given us are of this kind; and so nothing at all is found in them that does not testify to the power and goodness of God.

From all this it is entirely evident that, despite the immense goodness of God, the nature of a human being, as composed of mind and body, cannot but be deceptive at times. For suppose some cause—not in the foot, but in any of the other parts through which the nerves stretch from the foot to the brain, or even in the brain itself—sets up exactly the same motion that is usually set up when the foot is injured. Then pain will be felt as if in the foot, and the senses will naturally be deceived. For that same motion in the brain can only ever bring the same sensation to the mind; and it usually arises much more often from a cause that injures the foot than from one existing elsewhere. So it is reasonable 89 that it should always present to the mind a pain in the foot rather than in some other part.

This consideration is of the greatest help, not only for noticing all the errors to which my nature is liable, but also for being able to correct or avoid them easily. For I know that in matters concerning the body’s welfare all the senses indicate what is true much more often than what is false; and I can almost always use several of them to examine the same thing, and in addition my memory, which connects present things with past ones, and my intellect, which has now seen all the causes of error. So I should no longer fear that what the senses present to me every day is false. Instead, the hyperbolic doubts of the past few days should be dismissed as laughable.