In Our Time - Cogito Ergo Sum

Episode Date: April 28, 2011

Melvyn Bragg and his guests discuss one of the most famous statements in philosophy: "Cogito ergo sum".In his Discourse on the Method, published in 1637, the French polymath Rene Descartes wrote a sentence which remains familiar today even to many people who have never heard of him. "I think", he wrote, "therefore I exist". Although the statement was made in French, it has become better known in its Latin translation; and philosophers ever since have referred to it as the Cogito Argument.In his first Meditation, published ten years after the Discourse, Descartes went even further. He asserted the need to demolish everything completely and start right again from the foundations, arguing, for instance, that information from the senses cannot be trusted. The only thing he could be sure of was this: because he was thinking, he must exist. This simple idea continues to stir up enormous interest and has attracted comment from thinkers from Hobbes to Nietzsche and Sartre. With:Susan JamesProfessor of Philosophy at Birkbeck College, University of LondonJohn CottinghamProfessor Emeritus of Philosophy at the University of Reading and Professorial Research Fellow at Heythrop College, University of LondonStephen MulhallProfessor of Philosophy at the University of Oxford.Producer: Thomas Morris.

Thanks for downloading the In Our Time podcast. For more details about In Our Time and for our terms of use, please go to BBC.co.com.uk forward slash radio 4. I hope you enjoy the program. Hello, there are a few sentences in the history of philosophy that have become as famous as their authors. The unexamined life is not worth living, said Socrates in the 5th century BC. Man is born free, wrote Rousseau, two millennia later, but everywhere he is in change. Pithier still is Nietzsche's statement, God is dead. But perhaps the best known saying in the history of philosophy

is one usually quoted in Latin, cogito ergo sum. I think, therefore I am. This statement first appeared in 1637, in a work by the French philosopher René Descartes. Despite its simplicity, it's the starting point for an entire system of thought. Today, Descartes' cogito argument

is commonly regarded as one of the foundations of modern philosophy. But what does this apparently unsublishing? Unassuming sentence mean, and why does it still provoke criticism and comment almost 400 years after it was written? With me to discuss Descartes in his statement, Cogito Ergo-Sum are Susan James, Professor of Philosophy, Birkbeck College University of London, John Cottingham, Professor Emeritus of Philosophy at the University of Reading, and professorial research fellow at Haythrop College University of London, and Stephen Mulhall, Professor of Philosophy at the University of Oxford.

Susan James, we've called this programme Cogito Ergo-Sum, but that's not, how it started. Could you tell us what Descartes actually did write and what you think it means? Well, Descartes first used this phrase in passing in the work that he published in 1637 called the Discourse on Method of rightly conducting one's reason and seeking the truth in the sciences. And that was a work he wrote in French, and there he wrote, I think, don't I'mui. That was translated into Latin as cogito ergo sum. I think, therefore I am.

So this is the origin of this phrase, and there I think that Descartes presents it as what he calls the first principle of philosophy, the first metaphysical principle of philosophy. Later on, in a work that he publishes in 1641, the meditations, he then begins to spell out the argument that he's summarising there, and that's, I guess, what we'll be discussing.

Could you give a some idea of his background, particularly his education? Descartes was born in Tours, in France, and he went to a sort of grand school, the Jesuit College of La Flesche, where a college which was reputed for providing very sound and solid education. And there Descartes studied grammar, Latin and Greek, and rhetoric,

mainly studying speeches of classical authors. He studied mathematics and he studied philosophy. He seems to have been a pretty good student. And after he'd finished school, he went to study law at the University of Poitier briefly. Because in spite of his father's wishes that he should become a lawyer, he went off to be a soldier.

And in Holland, where he joined an army, he came into contact with a famous mathematician, Begman, and began to produce really original and creative work in geometry and algebra. He's in his early 20s at this stage. He's in his early 20s, that's right. And this is the beginning, I think, of Descartes's intellectual project. It's his fascination with the sort of clear method that he develops for solving mathematical problems,

that first of all entrances him, as it were, and that he then gradually turns into a more ambitious programme for developing an account of the whole of the sciences, as it were, an explanatory system that will explain the whole of nature. His health has been described as fragile, and in this severe Jesuit school, he was allowed to stay in bed until 10 o'clock reading enormous number of books while the others had to get a goodness-noose,

It was probably 3 o'clock in the morning, whatever it was. And yet he joined the army. That seems to be rather strange. It does seem to be rather strange, and it's not clear to me really why Descartes was so keen to join the army, except that it was a way to travel, and he used this as joining one army after another as a means to travel. And his health was frail.

It seems quite likely that after he left school, he had some sort of breakdown. And highly vivid mental episodes are very very very very... important part of his intellectual career. John Cottingham, what was the intellectual environment in which we grew up outside the school? He had a rigorous education by the sign of it, he covered everything that the best educated young boys covered in those days in that part of Europe. What was around him? What was the context?

Well, the dominant system which he would have imbibed was scholasticism, which had really been going for several centuries. This was a kind of fusion. of the ideas of Aristotle, based on Aristotelian principles, worked and elaborated so as to be consistent with the Bible and with Christian doctrine. And it had various features. Perhaps one of the most important was that each subject was in a sense separate.

It had its own methods and standards of precision, as Aristotle himself originally said. It was also qualitative. That's to say, things were explained, things behaved the way they did because of certain real qualities they possessed. For example, things fell to the ground because of the quality of gravitas or heaviness. Now, Descartes, though he imbibed this system, had the thought, Susan has mentioned his early mathematical work,

had the thought that actually that wasn't really very valuable. as an explanation, that instead you ought to look for quantitative explanations, that things behaved the way they did because of their size and shape and motion. So he started to react against the qualitative views of the scholastics. And then also the scholastic system was largely purposive. Things were explained as moving towards a goal or purpose. And again, Descartes reacted against this and thought instead that we should search for mechanical explanations.

At that time, when he was a youth, we had Copernicus and the heliocentric notion of the known universe, as it were, and Galileo doing his experience. Was he excited by these men and what they were doing? Very much so. When he was still a schoolboy out to the flesh, Galileo's discoveries of the moons of Jupiter were published. And

that really was the first clear experimental confirmation that the earth was not the centre of the universe, as had previously been thought. It was the first confirmation of the Copernican view, which was about

a few decades before Descartes was born. So it was a time of change. Have we any evidence as to how he reacted when he read about that, and what he did as a consequence of that? Well, there was a poem performed at the school to celebrate this great new discovery

and it's possible that Descartes himself may have been involved in the recitation of this poem. In 1619, when he was 23, he had three powerful dreams which seemed to be very important to him and very important in the formation of the way he regarded the way the world worked. Could you tell us about them and what importance he drew from? them. Yes, he spent, this was in November 1619 when he was travelling as a gentleman soldier,

as has been mentioned. He was in southern Germany and spent the whole day shut up in a stove heated room, a Pauel, as he describes it in the discourse. And he had three very vivid dreams. The first one involved a very strong wind, almost a hurricane, which pushed him around and frightened him severely. He took refuge in a chapel and met someone who presented him with a fruit, which he thought was a melon from a foreign country. Then the second dream was very quick. It involved a big bang, a thunder clap and sparks. And then in the third dream, which is the most complicated, there was a series of books. First, there was a Latin poem which began. with the line, what part in life shall I follow.

And then a motto of Pythagoras appeared, the Greek geometer. And then finally, an encyclopedia, an unfinished encyclopedia, which he took to represent all the sciences connected together. Stephen Mulho, what did he draw from these dreams and from his previous education? This is not so much a turning point, but a point that can be marked. Well, I think one of the things that he drew, and Susan mentioned earlier, was the idea of the essential unity or continuity of human knowledge. I mean, one image that he uses famously in certain contexts is that of, as it were, a tree, the tree of human knowledge. With metaphysics, first philosophy as the roots, physics as the trunk, and all the other sciences as the branches.

So on the one hand, he seems to think that there is a fundamental unity in the whole. system of human knowledge, and so it must be possible in principle to articulate those various bodies of knowledge as forming part of a fundamental unity. And yet, there is a certain kind of hierarchy built into that image. Physics gets a certain kind of priority in relation to the other natural sciences, and in turn, metaphysics, first philosophy, has a certain priority over physics. So what Descartes is committing himself to, and perhaps this is what the image of the encyclopedia in the third dream was interpreted by him as meaning, he was interested in developing that project of a certain kind of unity of human knowledge. But I think another aspect of the context that John was sketching in was all so fundamental to his sense of how to go about developing that project. If one thinks about first philosophy or metaphysics

as the kind of root of the whole enterprise, that on which everything else has to be built, then one needs some way of establishing genuinely foundational, genuinely reliable knowledge. And the reliability of that knowledge can then be transmitted through the rest of the edifice, if you like. And the method that Descartes uses, as we'll talk about in more detail,

is that of skepticism, a kind of methodical down. And I think one of the reasons that was such a fundamental idea in the context of the time is one of the implications of the new modern science, natural sciences, as it was being developed. This was not just a kind of radical break with Aristotelian ways of understanding nature, where the quantitative became primary as opposed to the qualitative, but it was also one which revealed and was certainly beginning to reveal to those who understood what was going on at the cutting edge, as it were,

that the kind of vision of the world and one's place in it that is delivered to us naturally through the senses is fundamentally unreliable. Can you take us to the book, Stephen Mulholl, in 1637 they published a work known as the Discourse on the Method. What is this method, and is this a life project he's embarking on? Well, it's certainly a conception of method that he cleaves to throughout his intellectual career. But in fact, if one looks at the rules that are supposed to encapsulate or crystallize

the method, they're not on the face of it hugely exciting. There are four of them, and three of them have to do with the principles such as the following, that one should break down the problems or the areas that one's trying to study into the simplest possible parts, that one should build from the simple to the complex, and that one should try to make sure that the chain of reasoning that goes from the simple to the complex is as exhaustive and comprehensive as possible. All of that doesn't sound terribly exciting, certainly from our perspective. The first principle is the one that turns out to be much more fruitful and radical than it might look. According to the first rule of this method, Descartes says that one should

only rely upon that which one clearly and distinctly perceives to be true. And that turns out to be the core of the method that gets much more systematically articulated in the meditations. Susan James, it's also the first time here that he uses what became the non-as-a-cogito argument. What does he mean by it? Well, the cogito argument is something that Descartes takes over and adapts from Augustine. So it's something that most of his contemporaries are quite familiar with. And in its simplest form, it's the idea that when you're thinking something, when you're doubting something, you know that you're doubting it. Now, in the discourse, which is the text that Stephen was talking about, Descartes doesn't elaborate on this idea at all.

It's only later in the context of the meditations that he explains what use he's going to make. make of this claim. And that's in the context of the so-called radical doubt that he develops in the first part of the meditations. So you think it's almost incidental in this work, the first work, before we get the meditation? I don't think it's exactly incidental. I think it's offered, he says that he's offering

just a few metaphysical conclusions in this work to give his readers the idea that the method that he is developing there can be used and applied to first philosophy to metaphysics. And I think one of the reasons it's so briefly sketched is that the discourse on method was presented originally as an introduction to three other, as it were, essays or texts, which were about optics, meteorology, and geometry. So as it were, there's a part of the discourse on method

which tells you about the first philosophy, the roots of the tree, if you like. But it also sketches in his... conception of physics, and then it sketches in various implications of that conception for other natural sciences like biology and zoology. So what you get in the discourse is a certain kind of sketch of the whole of the tree, whereas what happens in the meditations is that he has the room to expand upon his conception of the roots, I think it's fascinating how he banked his philosophy up on so much science and was so quickly got to the number of things. John Cottingham, the idea developed in a work which Susan referred to, the meditations.

What does he set out to do in that book? Yes. To find something stable and secure, you had to demolish the whole lot and start again right from the foundations. That's what he says in the opening of the first meditation. There's six meditations, one for each day of the week, perhaps modeled a bit on the spiritual exercises of the Jesuits who brought him up. And it starts with these ways of of doubt. You push doubt to the limit to see if anything survives. So he starts

by doubting the senses, our basic source of knowledge, even the five senses. They can sometimes deceive us and we shouldn't trust what's sometimes deceived us. Can you give us some specific example? Well, elsewhere he mentions the

stick in water it looks bent, but really it's straight. Well, but really in water it's bent. I mean, another example he gives is the sun and the moon. They look roughly the same size, but actually, of course, the sun is enormously bigger. So if you rely on critically, uncritically on vision, you can be led astray. But then he says, wait a minute, here I am sitting by the fire in my winter dressing gown. Surely that's so certain that I couldn't be wrong.

but then he reasons no because sometimes I've had very vivid dreams and thought that something like this was going on only to find I was sleep in bed and then he broadens the doubt to think well maybe the whole of life might be a dream maybe all the whole external world all the images are just beamed into my mind

by a malicious demon bent on deceiving me this is the extremity of doubt But then he comes out of that into certainty because he reasons, even if I'm being deceived, even if I'm doubting, I must still be here in some sense to do the doubting. So I at least must exist. So as he phrases it in the meditations, sum existo. I am, I exist, that is certain, as long as I'm thinking it

or putting it forward in my mind. Do you want to develop that, how this cogito ego sums of Existro actually saves him or rides him through the dance? Well, it's, you know, as John says, he's going down, down, down, down, and it looks as though the whole project is really about to founder on the rocks.

If he's going to rescue himself, he's got to find something that isn't doubtful. And the cogito is meant to serve this. purpose, but it's a very, very small Archimedean point, as it were, from which to move the world, because as Descartes points out, what he can be sure of, it's only that as he's having a thought, he knows that he's having it. As I'm remembering that I was walking down the street, I know that I'm having this thought of remembering myself walking down the street. of course I don't know whether it's true that I was walking down the street

or as I'm doubting whether my hands are in front of me, I am aware of myself having that doubt and I'm thinking that thought. So as long as I'm thinking some thought or other, then I know that I exist. But it seems that at this stage, all I know about myself at the most is that I'm this kind of succession of momentary thoughts. Yes, I mean, there's nothing certain about my thinking. I could stop thinking any time. I could stop existing at any time.

But what is certain is that as long as I am actually engaged in this reflection, I must exist. Nothing can make me not exist as long as I'm thinking. So it's a very momentary, tiny, flickering candle of certainty, which could go out at any minute. And I think that's why the question of the function of the ergo in the Cogato Ergo Sum formulation is so fascinating and so hard to pin down. Because what's kind of coming out already is that there's a certain kind of performative aspect to the argument,

if it is an argument, that's being presented to us. The force of the conclusion is only going to, as it were, have an impact on us insofar as we are actually engaged in the process of, reflection that delivers that conclusion. And that kind of connects with a bigger issue, which is that as arguments go, Cogato-U-Gosum looks like a very peculiar kind of argument, or certainly would have at the time. I mean, the kind of canonical example that philosophers always offer of argument structure is involves Socrates, as you might expect.

You know, all men are mortal. Socrates is a man, therefore Socrates is mortal. you only get to the conclusion because you have two other claims, two premises, from which the conclusion follows. So when someone tells you cogito ergo sum, you naturally start looking for what the premises might be. And usually, at least in the form of a syllogistic argument, one premise isn't enough. You can't just have cogito. There must be some more general major premise in the background, one might think, such that everything that thinks, exists. Then if you can say, I'm thinking, it would follow that you exist. But that can't be the right way of understanding the argument because it would involve Descartes assuming the truth of the

general premise when he's precisely got himself right down to the roots at which the force of the evil demon hypothesis is supposed to prevent you from assuming the general truth of any. Do you want to come in? Susan, first of all. In fact, Descartes says, doesn't he, in the replies to his objectors, that this isn't really the way he wants one to take the argument. He says, of course, you can present this stuff in a kind of logical form once you know it. But that's not the order of discovery. The order of discovery is that you perceive with a simple intuition of the mind, I am, I exist. And that's, as it were, how you get started.

I think he was aware that all sorts of elaborate syllogisms and arguments could be rolled out and the sort of things he'd learned at school. But this is different. This is something each person has to do for themselves. In fact, he says in an introduction, I don't want to have anything to do with anyone who's not prepared to follow me along this path and meditate for themselves. So the title of Meditations is no accident. It's something each person has to do for themselves.

How important is proof of the existence of God to Descartes' argument? Well, he's got to get out of this tiny flickering candle of subjective certainty to something bigger, something more systematic, to know it, to a whole system of knowledge. He can't do it just on his own. And the way in which God underpins it, I think, is this, that once he's aware of himself as existing, he's immediately aware of his imperfection, of himself as finite.

There are many things he doesn't know, many things he can't do. And yet he has a sense of the infinite, of something infinitely greater than himself. So he has the idea, against the sense of himself as finite, he has the idea of this infinite being. And this idea he reasons

couldn't have been created by him from his own resources and therefore must have been put in his mind by God as he puts it like the mark of the craftsman stamped on his work kind of trademark. And once God's in the picture, then we get something good and benevolent and he can then reason that his mind is a reliable instrument as he puts it in an interview a reliable man

mind was God's gift to me. And once he knows he's got a reliable mind, then he can get going and build his new system of science. But does he believe that's a god or reason his way to God, Susan? Well, probably both, I think. I mean, it seems to me that what he gives

as proofs of God are not tremendously convincing as theological proofs, and indeed none of his contemporaries seem to be content with them. it's almost as though Descartes is sort of indulged, well, he's engaged on a kind of exploration of his ideas

and the process of meditation is one of, as we're becoming more clear about ideas that Descartes takes it actually are already innate in your mind, they're already there. And so what you're doing is uncovering them or finding them. And so he's sort of finding his idea of God. Can I say with you for a moment, His arguments raise the question of the relationship between the mind and the body.

Can you tell us what that means for Descartes? Well, we've seen that the cogito shows you that you're capable of thinking, and also Descartes argues capable of a variety of kinds of thinking. You can have volitions and perceptions and memories and so on. a thing that thinks is what you are at this point in the story and a thing that thinks Descartes says is what we call a mind so we're beginning to learn something about the mind and as Stephen said we have this kind of clear and distinct idea

of this mind as something that exists and we can now begin to explore it So that licenses Descartes to sort of look into his mind, as it were, and see what other ideas he finds hanging around in it. One of the ideas he finds is God, as John just explained. But another of the ideas he finds is his idea of physical bodies. And so he now asks himself, all right, well, what kind of really clear and indubitable idea do I have can I uncover of a body? and he says, well, the normal thing would be to say that as well, a body is something that you know through its sensory properties.

But I'm putting all that aside because I've got all that under doubt. What I do know about a body for sure is that in order to be a body, it must have certain essential properties, which Descartes calls extension or extendedness. Roughly speaking, it must have shape and size. so it's got these quantifiable properties of shape and size. So Descartes thinks now he knows clearly and distinctly what a body is. He's got two clear and distinct ideas, one of his mind as something fundamentally thinking,

the other of his body as fundamentally extended. And he's now in a position to see that he also, he argues, that these are distinct, that as it were, there's nothing in his idea of a mind which depends on his idea of a body and there's nothing in his idea of a body which, as a word, depends on the existence of a mind.

And through the argument of the meditation, Descartes arrives at the conclusion that these are distinct substances, distinct kinds of things, each of them absolutely fundamental. And so now he's done

something quite dramatic really. which is that he's generated a conception of body, a quantifiable conception of body that can be the basis of physical science and a quite separate idea of a mind which is just something that thinks. And you have to remember that this is against a background of an Aristotelian notion

of a mind or soul, which has all sorts of capacities other than thinking. Did this argument, John Cottingham, help his larger philosophical project. Was it a key? Well, certainly the idea of extension that Sue has mentioned was crucial. Extension, that's to say, length, breadth, height, the three dimensions. This forms the basis for geometry

and therefore in Descartes' way of thinking for physics. So physics really becomes a comprehensive system which will include all the particles in the universe, not just planets, stars, earth, stones, rocks, trees, plants, the whole lot can all be described, he thinks, in terms of geometrical properties of extension, except consciousness, thought. So although he's a great unifier,

he has this wonderful vision of a geometrical unified system of physics, the world of thought and consciousness is left on one side is not able to be quantified and measured. And that's the project he leaves us with in a way, kind of unfinished project. Everything can be subsumed under geometrical physics except for thought and consciousness. Stephen, it seems to be slightly odd,

very much an outsider and very much a sort of beginner, that having in his mathematics got down to particles and said it does come down his particles, that he switches entirely. It's a different thing altogether, the mind. Although it's inside the body and helps the body to function and maybe functions the body, it is a distinct thing. Were some of his contemporaries eager to challenge him on that from the beginning?

What were the arguments against? Was that one of the arguments against? Well, I suppose in the context of the meditations, it's very clear that this sense of a fundamental essential distinctness between mind and body comes out of the application of the method of skeptical doubt, because if, as it were, the mind's manifestation of itself as thinking is immune to that doubt, but it is possible for the meditator to doubt the existence of everything external to the present moment of consciousness, then it looks as if you can conceive of yourself as existing in an entirely non-material way,

in a conception of the world in which there is no material body that is yours or is you, So that, in a sense, is a radical consequence of the application of his method. But in another sense, there's a way in which this sense of mind and body in its essential distinctness fits into broader cultural contexts, particularly theological ones. Because what it suggests is that if the mind is essentially immaterial, then a belief in the immortality of the soul is entirely consistent with the basic principles of first philosophy. Matter is the kind of thing that decays and decomposes because it's extended. It's divisible.

Something which is essentially non-material is indivisible. So what you get is a conception of the mind, which is entirely consonant with the conception of the soul as being of the essence of the human individual. And to that extent, it feeds into the kind of continuing affection and loyalty that Descartes always showed to the church. But there's the Cartesian circle. with Antoine Arna's objections, how did they... The worry about the Cartesian Circle goes back to this question about the function of God in the system

as Descartes presents it in the meditations. And John was explaining a little earlier that part of what's going on there is that God gives us a reason to treat not just our senses but our reason, perceptions of rationality as generally reliable. So the way Descartes presents the situation is that one has the certainty of the cogato. One perceives the truth of the cogito by means of clear and distinct perception, the exercise of reason.

And because one knows that God exists, God is the guarantor of the general liability of clear and distinct perceptions. So God shows us that we can trust in these perceptions of the mind. The objection, the worry that's encompassed in the idea of there being something circular here, is on what basis do we believe in God's existence, if not the fact that we clearly and distinctly perceive the truth of the arguments Descartes offers for that belief? But it's God who's supposed to underwrite the validity of that general criterion for truthfulness.

Yeah, another way of putting this, in addition to the cogitoe which we've talked about, there's an earlier formulation which comes in a book of his called The Rules for the Direction of the Mind, which is sum ergo deus est. I am, therefore, God exists. And the circle arises because Descartes clearly wants to move from himself to God, but to reason from himself to God,

he needs to trust the reasoning process of some sort. And how is he going to do that, unless, as it were, he knows God is there in the first place guaranteeing the reliability of his reasoning. So it looks as if the whole thing is a, a vicious circle. Can we see how it was received, Susan James, talking about how, for example, Hobbes received this argument on Spinoza. If you could give us some indication in the time of office.

A big pair. Well, Hobbes is one of the people who is invited to write objections to the meditations, and Descartes replies to them. Hobbes is a materialist and picks Descartes up on the cogito argument in particular and raises the question of what this eye is that's doing the thinking.

Descartes says, it's a mind. But Hobbes says you say it's a mind, but how can you be sure that as well that's all it is? Maybe it's also a body. And actually Hobbes seems to think that it must be a body

because only bodies can be as it were the subjects that are capable of having thoughts predicated of them. Descartes points out quite reasonably that Hobbes is sort of begging the question there. But nonetheless there is a problem

that I think many of Descartes' contemporaries are very interested in, which is what exactly this cogito argument establishes about who this eye is. On the one hand, is it a body? On the other hand,

is it even a mind? Is it anything so, as it were, unified, is it just this kind of flickering in an out of sequence of thoughts that John mentioned before? Is it even something that you can attach a first person to? Maybe he should say we are thinking. Is it...

Well, as Nietzsche said, it is thinking. It is thinking, exactly. Or even only thinking is going on. You know, as it were, sort of subjectless thinking. So there are a lot of problems here about this and Descartes' contemporaries are pretty a cute lot that they're onto them

To move on from his contemporaries can you give us some idea of other reactions John I've got names down in Heidegger Nietzsche and so on just as the centuries rolled through and this remark of his and this philosophy of his was taken seriously

even when it was dismissed seriously it seems to be in a fairly foundational notion yes well as the centuries row on, there's a lot of emphasis on subjectivity, that the movement we know as existentialism lays a lot of stress on the individual awareness of the subject and the idea that the subject's got to somehow construct reality from him or herself. And that, in a way, is Descartes' starting point. So in a sense, they're inheriting that Cartesian starting point of the individual

existing self and starting philosophy from there. But the difference, I think, is that when you get on to Nietzsche and Sartre, too, you mentioned, you've got Descartes but without God. You've got the whole thing depending on just the individual thinker, meditating and wondering what's going on. Whereas with Descartes, you've got this radical subjective reflection, but against the background of a, as Stephen mentioned, of a firm belief. traditional belief in the source, the infinite source of his being God. So the moderns are very different, I think, although they see Descartes as their ancestor. Sartre is a particularly good

example of that, I think, because on the one hand, he's wholly explicit about his indebtedness to Descartes. He thinks that any project of philosophical system building has to begin with the truth of subjectivity. But he offers what seemed like a really minor tweak to the validity of the cogato and the conception of the mind that Descartes generates from it, that just utterly explodes the Cartesian system as Descartes would have understood it, because Sartre kind of points out two things. First of all, he says that Descartes's argument trades on the assumption that whenever one is in a state of consciousness, one is also and simultaneously explicitly aware of being in that state. And Sartre says that that, in fact, isn't all right.

the case. What is true, what is necessarily true about the mind is that one is capable of reflecting on the state one is in, but it's not true that one is always explicitly aware of that state, simultaneous with being in that state. So that creates a certain kind of problem which Sartre summarizes by saying the cogato is not reflective but pre-reflective. Being capable of reflecting on oneself is essential to subjectivity, but it's not true that it's always explicit. And that means that Descartes can't assume that whatever state of consciousness one is in, one is simultaneously necessarily aware of being in that state. And without that assumption, the Cogartor argument, however one parses it, is not going to work in the way that Descartes thought he did. The other problem

that Sartre raises is that when one does activate that reflective capacity and does take one's state of consciousness as an object of reflection, then one is no longer in that state of consciousness. Suppose I'm, to use one of Sartre's examples, in a state of warfare in which cigarettes are rationed and I'm desperately counting the cigarettes in my case to see when I've got enough left to last to the end of the month. Well, when I'm focused entirely on that task, then there's no explicit reflective awareness of what I'm doing on my part. But if someone comes along the street and asks me what I'm doing, I can perfectly well immediately tell them. And the moment I move into that state of reflecting on what I was doing,

namely counting the cigarettes, I'm no longer counting them. I'm now in a different state of consciousness, which has as its object not the cigarettes in the case, but myself in the past, counting those cigarettes. So the move from pre-reflection to reflection is also a change in the state of consciousness. and that means that time intervenes between being in that state of awareness and being reflectively aware of being in that state.

So the subject enters time. Yes, I'm thinking, just to add in fairness to Descartes, I think we've been talking today about very transparent thoughts or conscious acts like Cogito Ogo-Sum. But in his later work, Descartes acknowledged that there's a lot of other stuff, notably passions and emotions,

love, hate, fear and stuff. which are much more complicated and where we don't have such immediate, transparent awareness of all the implications of what's going on inside it. Myna, Susan, is Descartes still someone that contemporary philosophers take seriously work with? Enormously, I think. I think that Descartes keeps on resurfacing in a fascinating way and sort of kind of a chameleon, one of these great chameleons

that's constantly putting on new dresses. I suppose that the cogito continues to be sort of at the root of contemporary work on the nature of self-consciousness. And Descartes also has recently become, I suppose, much more a figure studied for his work on the passions and the relationship and these kind of more obscure relationships between mind and body that John just alluded to. Well, thank you very much, Susan James, Stephen Mulholl, John Cottinger. and next week we'll be talking about the origins of Sharia, Islamic Law, and thank you for listening. If you've enjoyed this Radio 4 podcast,

why not try others, such as Thinking Aloud, where Laurie Taylor discusses the latest social science research. To find out more, visit bbc.co.com.uk forward slash radio four.