Rene Descartes?argues that, while most of life is uncertain, he can prove?without a shadow of a doubt?that he exists.? What pro

Discourse on the Method of Rightly Conducting one’s Reason and Seeking Truth in the Sciences

René Descartes

Copyright © 2010–2015 All rights reserved. Jonathan Bennett

[Brackets] enclose editorial explanations. Small ·dots· enclose material that has been added, but can be read as though it were part of the original text. Occasional •bullets, and also indenting of passages that are not quotations, are meant as aids to grasping the structure of a sentence or a thought. Every four-point ellipsis . . . . indicates the omission of a brief passage that seems to present more difficulty than it is worth. Given this work’s full title, you can see that it is wrong to call it, for short, ‘Discourse on Method’ with no ‘the’.

First launched: June 2005 Last amended: November 2007

Discourse on the Method René Descartes Part 4

Part 4

I don’t know whether I should tell you of the first meditations that I had there, for they are perhaps too metaphysical [here = ‘abstract’] and uncommon for everyone’s taste. But I have to report on them if you are to judge whether the foundations I have chosen are firm enough. I had long been aware that in practical life one sometimes has to act on opinions that one knows to be quite uncertain just as if they were unquestionably •true (I remarked on this above). But now that I wanted to devote myself solely to the search for truth, I thought I needed to do the exact opposite—to reject as if it were absolutely •false everything regarding which I could

imagine the least doubt, so as to see whether this left me with anything entirely indubitable to believe. Thus,

•I chose to suppose that nothing was such as our senses led us to imagine,

because our senses sometimes deceive us. Also, •I rejected as unsound all the arguments I had pre- viously taken as demonstrative [= ‘absolutely rigorous’] proofs,

because some men make mistakes in reasoning, even in the simplest questions in geometry, and commit logical fallacies; and I judged that I was as open to this as anyone else. Lastly,

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•I decided to pretend that everything that had ever entered my mind was no more true than the illusions of my dreams,

because all the mental states we are in while awake can also occur while we sleep ·and dream·, without having any truth in them. But no sooner had I embarked on this project than I noticed that while I was trying in this way to think everything to be false it had to be the case that •I, who was thinking this, was •something. And observing that this truth

I am thinking, therefore I exist

was so firm and sure that not even the most extravagant suppositions of the sceptics could shake it, I decided that I could accept it without scruple as the first principle of the philosophy I was seeking. [This ‘first principle’ could be (1) ‘I exist’ or (2) the connection between ‘I am thinking’ and ‘I exist’—the

uncertainty in this version echoes that in Descartes’s French.]

Then I looked carefully into what I was. I saw that while I could pretend that I had no body and that there was no world and no place for me to be in, I still couldn’t pretend that I didn’t exist. I saw on the contrary that from the mere fact that I thought about doubting the truth of other things, it followed quite evidently and certainly that I existed; whereas if I had merely stopped thinking altogether [here = ‘stopped being in any conscious mental state’], even if everything else I had ever imagined had been true, I ·would have· had no reason to believe that I existed. This taught me that I was a substance whose whole essence or nature is simply to think [here = ‘to be in conscious mental states’], and which doesn’t need any place, or depend on any material thing, in order to exist. Accordingly this me—this soul that makes me what I am—•is entirely distinct from the body, •is easier to know than the body, and •would still be just what it is even if the body didn’t exist.

After that I considered in general what is needed for a proposition to be true and certain: I had just found one that I knew was true and certain, I thought that I ought also to know what this certainty consists in. I observed that the proposition ‘I am thinking, therefore I exist’ has nothing about it to assure me that I am speaking the truth ·when I assert it· except that I see very clearly that in order to think it is necessary to exist. This convinced me that I could take it as a general rule that the things we conceive very vividly and very clearly are all true; but ·this isn’t as powerfully simple a rule as you might think, because· there is some difficulty in telling which conceptions are really clear.

Next, I reflected on the fact that I was doubting, and that consequently I wasn’t wholly perfect (for I saw clearly that it is a greater perfection to know than to doubt). This led me to the question:

Where did I get my ability to think of something more perfect than I am?

and I drew the obvious conclusion that this ability had to come from—·had to be caused by·—something that was in fact more perfect than me. ·To explain why I reached that conclusion, I should first explain why· I wasn’t exercised about such questions as

Where did I get my ability to think of the heavens, the earth, light, heat (and so on)?

It was because I saw nothing in those thoughts that seemed to make them superior to me, ·i.e. more perfect than I am·; and ·that opened the door to a pair of possible explanations for my ability to have them·. (1) If the thoughts in question were true, they could depend on—·i.e. come from·—some perfection in my own nature. (2) If they weren’t true, I could have derived them from •nothingness – meaning that they could be in me because I had some •defect. But neither of these explanations could hold for the idea of a being more

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perfect than me. For it was obviously impossible (2) to get this from nothingness; and I couldn’t have (1) derived it from myself, because the proposition

(1) Something resulted from and depends on something less perfect than it is

is just as contradictory as (2) Something resulted from nothingness.

So the only possibility left was that the idea had been put into me by •something that truly was more perfect than I was, •something indeed having every perfection of which I could have any idea, that is—to explain myself in one word—by •God. To this I added that since I knew of some perfections that I didn’t myself have, I wasn’t the only being that existed. . . .,and there had to be some other more perfect being on which I depended and from which I had acquired everything that I had. For if I had existed alone, not depending on anything else, so that my meagre ration of perfections had come from myself, then by that same line of reasoning

•I could have derived from myself all the remaining perfections that I knew I lacked,

and thus •I could myself have been infinite, eternal, unchanging, omniscient, omnipotent;

in short, •I could have had all the perfections that I had been able to discover in God.

[What follows starts with the word Car = ‘For’. Descartes seems to be promising a reason for what he has just said, but the promise isn’t kept.] For, according to the arguments I have just presented: in order to know as much of God’s nature as my nature allows me to know, all I needed was to consider, for each property of which I had some idea, whether having it was a perfection or not; and I was sure that God doesn’t have any of the

properties that indicate any imperfection, but that he does have all the others. Thus I saw that God could not have doubt, inconstancy, sadness and the like, since I myself would have been very glad to be free from them, ·which shows that they are imperfections·. Furthermore, I had ideas of many perceptible bodies (even if I was dreaming, and everything that I saw or imagined was false, I still couldn’t deny that the ideas of bodies were in my mind). But since I had already recognized very clearly in my own case that intellectual nature is distinct from bodily nature, and as I observed that

•if a thing is composed ·of simpler elements· in any way, that shows that it is dependent on something else,

and that •dependence is obviously a defect,

I concluded that •it couldn’t be a perfection in God to be composed of these two natures—·the intellectual and the bodily·— and consequently that he was not composed of them;

and also that if there were any bodies in the world, or any intelligences or other natures that weren’t wholly perfect, their being must depend on God’s power in such a way that they couldn’t stay in existence for a single moment without him.

After that, I wanted to seek other truths: I took up the subject-matter of geometry, which I conceived of as •a continuous body, or •a space indefinitely extended in length, breadth and height or depth, and divisible into different parts that can have various shapes and sizes, and can be moved and swapped around in all sorts of way (geometers assume that their subject-matter has all these properties). I went through some of their simpler proofs, and noted that it’s because we conceive them as evident [= ‘obviously true’] that

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we all regard them as utterly certain. I noted also that these demonstrations gave no assurance—none—of the existence of their subject-matter. For example, I saw that given a triangle its three angles of must equal two right angles; but I saw nothing assuring me that there are any triangles in the world. In contrast with that, when I returned to the scrutiny of the idea I had of a perfect being, I found that

this idea of a perfect being included existence in the same way as—or even more evidently than—

the idea of a triangle includes the equality of its three angles to two right angles

or the idea of a sphere includes the equidistance from the centre of all the points on the surface.

Thus I concluded that the existence of this perfect being, God, is at least as certain as any geometrical proof.

Why are many people convinced that there is some diffi- culty in knowing God, and even in knowing what their soul is? It’s because they never raise their minds above things that can be perceived by the senses: they are so used to •thinking of things only in the way that is specially suited to material things, namely by •imagining ·or picturing· them, that they regard as unintelligible ·or •unthinkable· anything that they can’t •imagine. This shows up in the fact that even the scholastic philosophers take it as a maxim that there is nothing in the intellect that wasn’t previously in the senses; ·which leads people to find God and the soul problematic, be- cause· it is certain that the ideas of God and of the soul have never been ‘in the senses’! Trying to •understand these ideas through one’s •imagination strikes me as being like trying to •hear sounds or smell odours through •the use of one’s eyes. ·Actually, trying-to-understand-through-imagination is even more absurd than trying-to-hear-or-smell-with-the- eyes, because· there is this difference: the sense of sight

gives us as much assurance of the reality of its objects as do the senses of smell and hearing, whereas our imagination and our senses could never assure us of anything without the aid of our understanding.

Finally, if you are still not really convinced of the existence of God and of your soul by the arguments I have presented, I tell you this: everything else of which you may think you are •more sure—such as your having a body, there being stars and an earth, and the like—is •less certain. For although we have enough certainty for everyday practical purposes about these things, so that it seems wild and irresponsible to call them in question, nevertheless when it is a question of metaphysical certainty we have to admit that there are good reasons for not being entirely sure about them. We need only observe that in sleep we may imagine that we have a different body and see different stars and a different earth, without any of these things being real. ·This is a reason for having some uncertainty about the existence of our body, the stars, and so on·, because: how do we know that the mental states that come to us in dreams are any more false than the others, seeing that they are often just as lively and sharp? Let the best minds study this question as much as they like, I don’t think they’ll be able to give any reason that removes this doubt unless they presuppose the existence of God. For, in the first place, what I took just now as a rule, namely that whatever we conceive very vividly and clearly is true, is assured only because •God exists and •is a perfect being, and because •everything in us comes from him. It follows that our ideas or notions, being real things that get from God everything that is vivid and clear in them, must be true in every respect in which they are vivid and clear. So if we quite often have ideas containing some falsity, this can only be because there is something confused and shadowy in them; for their confusion etc. is something they share

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with nothingness, which means that they are in us in this confused state only because we aren’t completely perfect. And it is evident that it’s just as contradictory to suppose that falsity or imperfection as such should come from God as to suppose that truth or perfection should come from nothingness. But if we didn’t know that everything real and true within us comes from a perfect and infinite being, then, however vivid and clear our ideas were, we would have no reason to be sure that they had the perfection of being true.

But once the knowledge of God and the soul has made us certain of this rule, it is easy to recognize that the things we imagine in dreams shouldn’t make us doubt the truth of the experiences we have when awake. For if someone happened even in sleep to have some very clear idea (if, say, a ·dreaming· geometer devised some new proof), his being asleep wouldn’t prevent the idea from being true. The commonest error of our dreams consists in their representing various objects to us in the same way as our external senses do; but it doesn’t matter—·i.e. it doesn’t imply anything specially about dreams·—that this may lead us to doubt the truth of such ideas, for often they can also mislead us without our being asleep; for example, people with jaundice

see everything as yellow, and stars or other very distant bodies appear to us much smaller than they are. For after all, whether we are awake or asleep, we ought never to let ourselves be convinced except by the evidentness of our reason. Note that I say ‘our reason’, not ‘our imagination’ or ‘our senses’. Even though we •have a vividly open view of the sun, we mustn’t judge on that account that it is only as large as we see it; and we can clearly •imagine a lion’s head on a goat’s body without having to conclude from this that a chimera exists in the world. For reason doesn’t insist that what we thus •see or •imagine is true. But it does insist that all our ideas or notions must have some foundation of truth; for otherwise it wouldn’t be possible that God, who is all-perfect and all-truthful, should have placed them in us. Now, sometimes our imaginings in sleep are at least as lively and detailed as in waking life, but our reasonings when we are asleep are never so evident or complete as when we are awake; so reason also insists that, since our thoughts can’t all be true because we aren’t perfect, what truth they do possess must inevitably be found in the thoughts we have when awake, rather than in our dreams.

Part 5

I would like to go on with this, and present the whole chain of other •truths that I deduced from these first ones. But this would involve me in discussing here many questions that are being debated among the learned, and I don’t want to get into those quarrels. [This presumably refers to Descartes’s views in physics, which contradicted the Aristotelian physics that was

still dominant in the universities.] So I think it will be better if I

don’t follow my inclination and merely say in general what •those other truths are, and leave it to wiser heads to decide whether it would be useful for the public to be told about them in more detail. I have always stuck by my resolve •not to assume any principles except the one I have just used to demonstrate the existence of God and of the soul, and •not to accept anything as true unless it struck me as more open

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and more certain than the demonstrations of the geometers once seemed to be. And yet I venture to say that ·even under those constraints· it didn’t take me long to satisfy myself regarding all the chief difficulties usually discussed in philosophy. And I discovered certain laws that God has established in nature; he has implanted notions of these laws in our minds, in such a way that after adequate reflection we can’t doubt that the laws are exactly observed in everything that exists or occurs in the world. Moreover, by considering what follows from these laws I have discovered (it seems to me) many truths that are more useful and important than anything I had previously learned or even hoped to learn.

I tried to explain the most important of these truths in a treatise that certain considerations prevent me from publishing, and I know of no better way to make them known than by summarizing its contents. [Descartes’s treatise The World was completed in about 1632—five years before the present work. His

reasons for not publishing it are given starting on page 26.] I had planned to include in that work everything I thought I knew about the nature of material things at the time when I was poised to start writing it, ·but that turned out to be too much to tackle all at once·. A painter can’t represent all the different sides of a solid body equally well on his flat canvas, and so he chooses one principal side, sets it facing the light, and shades the others so that they are seen only in the course of looking at the favoured side. Well, in just the same way, fearing that I couldn’t put into my discourse everything that I wanted to, ·I started by (so to speak) letting daylight shine on just •one face of it; specifically·, I undertook merely to expound quite fully what I understood about •light, and then, as the occasions arose, ·to let the shaded sides of my object (so to speak) enter the picture, one at a time. That is·, I planned to add something about •the sun and fixed stars, because almost all light comes from them; about

•the heavens, because they transmit light; about •planets, comets and the earth, because they reflect light; about •the bodies on this planet, because they are either coloured or transparent or luminous, and finally about •man, because it is he who sees light. But I wanted to keep these matters still somewhat in the shadows, so as to be free to say what I thought about them without having to follow or to refute the opinions of the learned. My plan for doing this was to leave •our world wholly to the learned folk to argue about, and to speak solely about what would be the case in •a new world that would exist if

God now •created somewhere in imaginary spaces enough matter to compose a world; variously and randomly •agitated the different parts of this matter so as to create as confused a chaos as any poets could dream up; and then did nothing but •allow nature to unfold in accordance with the laws he had established.

·I shall sketch what I did with this supposition, in seven episodes·. (1) I described this matter, giving an account of it that I tried—successfully, it seems to me—to make as openly plain and intelligible as anything except what I have just said about God and the soul. ·As part of this search for clarity·, I explicitly stipulated that this matter had none of those ‘forms’ or ‘qualities’ that the scholastics argue about; allowed it to have only properties that our mind knows so naturally that no-one could even pretend not to. (2) I showed what the laws of nature were [= ‘are’?], and arguing solely from the infinite perfections of God I tried to demonstrate all those laws that might have been called into question, and to show that they are such that even if God created many worlds there couldn’t have been any in which these laws didn’t hold. (3) I then showed how •these laws had the result that most of the matter of this chaos had to resolve itself

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into a certain orderly arrangement that made it resemble our heavens [here = ‘sky’]; and how at the same time •some of the parts of matter had to form an earth, some to form planets and comets, and yet other parts to form a sun and fixed stars. (4) And here I spread myself on the subject of light, explaining at some length •the nature of the light that had to be present in the sun and the stars, •how from there it travelled instantaneously across the immense distances of the heavens, and •how it bounced off the planets and comets towards the earth. (5) To this I added many points about the substance, position, movement and all the various qualities of these heavens and stars; and I thought I took this far enough to show that any features observed in the heavens and stars of our world would—or at least could—also be features of the ·imaginary· world I was describing. (6) I went on from there to speak of the earth in particular: •how, although I had explicitly stipulated that God had put no gravity into the matter of which it was formed, all its parts nevertheless tended exactly towards its centre; •how, there being water and air on the earth’s surface, the lay-out of the heavens and heavenly bodies and especially the moon had to cause an ebb and flow exactly like that of our tides, and also an east-to-west current of both water and air like the one we observe between the tropics; •how mountains, seas, springs and rivers could be formed naturally there, and •how metals could appear in mines, plants grow in fields, and generally •how all the bodies we call ‘mixed’ or ‘composite’ could come into being there. (7) Among other things, I worked hard to get out into the open and fully understood everything about the nature of fire, because as far I know it’s the world’s only source of light other than the stars. Thus I showed •how fire is formed, •how it is fuelled, •how sometimes it gives off heat but no light, and sometimes light without heat; •how it can produce different colours and other qualities in different

bodies; •how it melts some bodies and hardens others; •how it can consume almost all bodies, or turn them into ashes and smoke; and finally •how it can through the sheer power of its action turn these ashes into glass. I took special pleasure in describing the formation of glass, because it seems to me as wonderful a transmutation as any in nature.

Still, I didn’t mean to infer from all this that our world was created in the way I had been describing, for it is much more likely that from the beginning God made our world just as it had to be. But if we think of material things as developing gradually out of chaos, their nature is easier to grasp than if we considered them only in their ·present· completed form. And there is nothing wrong with believing that God could have brought them about in that manner, starting with chaos, establishing the laws of nature, and then allowing nature to develop in a normal way in accordance with those laws. In particular, that belief doesn’t malign the miracle of God’s creation of the world. It is certain—and theologians generally agree—that God’s activity in now preserving the world is just the same as his earlier activity of creating it, ·so the ‘miracle of creation’ is with us in full strength even now, whether or not the material world began in chaos·.

[A long tradition, going back to Plato, held that plants are special in having ‘vegetative souls’, lower animals in also having ‘sensitive souls’,

and humans in having ‘rational souls’ as well as the other two. In

this paragraph, Descartes describes a thought-experiment concerning

a possible living human body which he takes not to be equipped with a

rational soul or any substitute for one; he tacitly rules out the other kinds

of soul as well, but allows that something in this human body—namely,

fire in the heart—might play the role that earlier thinkers assigned to

the vegetative and sensitive souls.] Moving on from •inanimate bodies and •plants, I describe •animals and in particular •men. But I didn’t yet know enough to speak of human bodies in the same way as I did of the other things—that is,

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by demonstrating effects from causes, and showing how and from what seeds nature must produce them. So I ·settled for a second supposition, comparable with my supposition of a chaotic material world. Specifically, I· supposed that God formed the body of a man exactly like yours or mine both in outward shape and in the internal lay-out of its organs, making it out of nothing but the matter that I had described and not at first putting into it any rational soul or anything else to function as a vegetative or sensitive soul, except for his kindling in the human body’s heart one of those fires without light that I had already explained, and whose nature I understood to be just the same as that of the fire that heats hay when it has been stored while wet. . . . And when I looked into what functions could occur in such a body I found precisely the ones that can occur in us without our thinking of them and hence without any co-operation from our soul—i.e. from that part of us, distinct from the body, whose nature is as I have pointed out simply to think. These functions are just the ones in which animals without reason may be said to resemble us. But I could find ·in my supposed living human body· none of the functions that we have only because we are men, the ones that depend on thought; though these all turned up later on, once I had supposed God to create a rational soul and join it to this body in a certain way that I described.

So that you can see how I went about doing this, I shall give my explanation of the movement of the heart and the arteries. [The next few pages—making nearly half of Part 5—are devoted to the circulation of the blood, and the function of the heart. They are of only historical interest, and are omitted here, except for three isolated fragments which help to convey the intellectual tone of the whole passage. [In the second of the three, the phrase ‘mathematical demonstrations’ means

merely ‘explanations conducted in terms of materialistic mechanism’.

Descartes isn’t claiming to have done this work a priori; he is well aware

that it is thoroughly empirical.]] •To readers who don’t know any anatomy: before going on, please arrange to observe someone dissecting the heart of some large animal with lungs (for such a heart is in all respects enough like that of a man), and get him to show you its two chambers or cavities. . . . •Those who don’t know the force of mathematical demonstrations and aren’t used to distinguishing true reasons from mere prob- abilities may be tempted to reject this explanation without examining it. To head them off, I would advise them that the movement I have just explained follows purely from

the layout of the organs of the heart, which can be seen with the naked eye, the heat in the heart, which can be felt with the fingers, and the nature of the blood, which can be discovered empirically;

and it follows just as necessarily from those three elements as does the movement of a clock from the force, position, and shape of its counterweights and wheels. . . . •An English physician—·William Harvey·—must be praised for having made the break-through on this subject. He is the first to teach that at the extremities of the arteries there are many small passages through which the blood they receive from the heart enters the small branches of the veins, from there going immediately back to the heart, so that its course is nothing but a perpetual circulation.

[Two technical terms in this paragraph: ‘animal spirits’ is the name for a supposed superfine fluid which acts as the body’s hydraulic system.

The ‘common sense’ was a supposed department of the mind in which

inputs from different senses come together and are organized in relation

to one another.] I had explained all these matters in enough detail in the treatise I had previously intended to publish. And then I had showed •how the nerves and muscles of the human body must be structured if the animal spirits inside them are to convey enough force to move its limbs. . . .; •what

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changes must occur in the brain as causes of waking, sleep and dreams; •how light, sounds, smells, tastes, heat and the other qualities of external objects can imprint various ideas on the brain through the mediation of the senses; •how hunger, thirst, and the other internal passions can also send their ideas there. And I explained which part of the brain must be ·identified with various supposed mental faculties—specifically, which part of the brain must be· taken to be the •‘common sense’, where these ideas are received; the •memory, which preserves them; and the •ima

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