Noam Chomsky on René Descartes

The modern scientific revolution, starting with Galileo, essentially, was aimed to construct a picture of the world that was mechanical, an idea that the world was a machine, a big, complicated machine made out of things like levers and gears and so on, which essentially could be constructed in principle by a master artisan. Of course, nobody's smart enough to do it, but it had that character. It's the kind of thing you could construct, like a huge clock or something like that. In fact, it was assumed it was constructed by a super artisan, better than any human artisan. But it was a mechanical device. That was called the mechanical philosophy. But remember, philosophy just meant science, so it was essentially the science of mechanics. Descartes was a major figure in advancing and developing the mechanical philosophy, the conception of the world as a machine. The idea was, from roughly Galileo on, to overcome the mystical character of neo-scholastic science, the reigning physics of the day, which held that the world was operated in terms of mystical forces. So if, say, a flower grows from a seed, that's because it has a vegetative force. And if something falls to the ground, it's because that's its natural place and where it wants to be. And if two things attract each other, it's because they have a sympathy. And if they repel one another, they have an antipathy. And if I see a cube, let's say, rotating in space, it's because the physical cube, the form of the cube rotating in space, flits through the air in some fashion and gets into my brain. And in my brain there's a cube rotating in space, so that's what I see. These are the kinds of conceptions of the physics of the day, the physics and physiology of the day. And the goal of the mechanical philosophy was to try to get rid of all that stuff and account for everything in terms of strictly mechanical principles that could be understood. The principles that we see when we see parts of a machine working and try to show that the whole world works like that. Well, Descartes made a lot of progress in this. He extended the mechanical philosophy, he thought he extended it, to the biological world, to a good part of human nature. So, for example, probably his most lasting scientific contributions, the ones that can really be restated in somewhat different forms today, had to do with his theory of vision. So he and other scientists of the day mocked the idea that the form of an object flits through the air and gets into your mind, that it's pure mysticism. It's got to be a mechanical interchange of some kind. And he had a theory of light which was mechanical and recognized that the retinal image, what's on your retina, is not the cube rotating in space. Or, let's say, if I look at the audience, I see people sitting around and so on, but that's not the retinal image. The retinal image is some complicated two-dimensional display which could be interpreted in all sorts of ways. Descartes recognized that what you see must be a construction of the mind, it has to come from the inside, in the terms that were used by later philosophers working on this. The sensory organs just provide the occasion for experience, which hits the sensory organs, provides the occasion for the mind to construct experience using its own internal resources, its own cognoscitive powers in terms of the day, which were understood to be innate, they had to be innate cognoscitive powers, properties of the mind, which somehow use the occasion of sense to create what you see, a cube rotating in space, people walking down the street, people sitting in front of me, whatever it may be. It was also understood, as I say, that this was innate. So, for example, Descartes was struck by the fact, he didn't do the experiments, but if he did the experiments, they would come out the way he imagined. Even Galileo didn't do most of the famous experiments, he mostly imagined them, the thought experiments. Some of them are physically impossible, in fact. Descartes did a thought experiment, which is undoubtedly correct. He asked, how is it that if you have an infant who has never seen a triangle, let's say, and suppose I were to draw a triangle on the blackboard and the infant were to look at it, what the infant would perceive is a triangle. But, in fact, what I drew is certainly not a triangle. I mean, it's some physical thing which couldn't possibly be a triangle. I mean, maybe two of the lines wouldn't quite come together, or one would be curved, or whatever. So why is it that the infant perceives a triangle, maybe a distorted triangle, and not a perfect image of exactly what it is? Why is that the case? And if you do experiments now, you find that is the case. Well, his conclusion was that it must be that the innate structure of the mind is based on principles like those of Euclidean geometry. And on the occasion of sense, the mind simply constructs a triangle, and whatever the sensory object is is seen as some distortion of what the mind constructs. And then he had theories of how the sensory image gets into the mind, which constructs those things and so on. Mechanical theories, which we wouldn't put in quite those terms today, but can be restated in modern terms without very dramatic change, apart from the mechanisms. All of this is quite plausible, and in fact apparently true in a modern reformulation, and modern neurophysiology and perceptual psychology is giving sharper accounts which are roughly of that kind. Descartes pursued this as far as he could. He wanted to see how far you could go in giving a hypothetical account of the way the world could be machined up to things like human sensation and perception. And he concluded that you could go quite a long way, but that some things were left out. What was left out primarily was acts of human will, which he said are our most noblest possession, the only thing that's truly human. So there was a lot of interest in those days in automata, just as there is today. The automata at that time were complicated devices that were made by master artisans and did all sorts of amazing things. And the question naturally arose, what's the difference between a human and an automaton if there is any? And Descartes argued that this is precisely where the difference would lie. In fact for him it was the difference between humans and automata, and also between humans and animals, which were automata. The difference lay in acts of will. So in the case of a machine, an automaton, if you set its parts in a certain arrangement and you have some external input, the machine is compelled to act in a certain fashion. It has no choice about the matter. It could be random, but it's either going to be random or determined. On the other hand, if you take a human being and its internal parts are arranged in a certain way and it has a certain sensory experience, it may be, as they put it, incited and inclined to act in a certain manner, but it's not compelled to do so. It could act in a different manner. So if somebody were to walk up here with an assault rifle or something and order everyone to stand up and say, you know, Heil Hitler or something, and if you took them seriously, it's very probable that everybody would do it. You'd be incited and inclined to do it. But we all know that there is a choice. You might decide to get killed, let's say, because you don't want to do it. And those things are not determined. There is no mechanistic determination of that. We know that as well as we know anything at all. And that is kind of irreducible, phenomenal knowledge, experience. And Descartes argued that that's the crucial difference between humans and animals. And certainly we have no reason to doubt that at the moment. But anyhow, that's the Cartesian argument. The most striking example that he offered was, in fact, language use. He pointed out that ordinary use of language, and I don't mean writing poetry or anything, just talking to your friends at a bus stop or whatever, ordinary use of language has a kind of creative aspect. It's unbounded. People are always saying new things that were never heard before in their experience or maybe in human history. They don't know that they're new. There's no way of knowing whether a sentence that you just heard is one you've heard before. It's impossible. So ordinary human interchange with language is constantly innovative and productive and unbounded, in fact. It's infinite in the technical sense. On the other hand, it's also undetermined. So you can't determine what a person is going to say on the basis of the situation that they're in or the arrangement of their internal organs. On the other hand, it's not random. So it's not caused by situations or internal states, but it's somehow appropriate to situations. It's coherent. Other people understand it. It evokes thoughts in other people, which they could have expressed that way themselves if they had had the thought. And maybe they do have the thought after they hear the expression. So this collection of properties of being unbounded, undetermined, uncaused, but appropriate to situations, coherent, evoking thoughts in others, and so on, that's a kind of creative aspect of language use. And Descartes argued that that's the striking difference between humans and automatons. There was a lot of interest in those days in trying to train, in asking whether you could construct an automaton or train an animal or whatever to act the way a human does. And most of the experiments turned on. They, again, weren't actually carried out, but most experiments in that period, even physics, weren't carried out. They were thought about. The experiments turned on this. So people would list the kinds of experimental techniques you might try to see if another object that looks like you has a mind like yours. And they're mostly language tests based on the creative aspect of language. Well, in order to deal with these apparent facts, and we have no reason to doubt that they're facts, in fact, they seem to be facts, in order to deal with that, Descartes had a problem. You couldn't incorporate this within the mechanical philosophy. It wasn't a matter of gears and levers and so on. So he was forced to invent a new principle, which is standard science, isn't it? If something isn't explained by the principles you have, you construct a new principle. The new principle is what he called the mind. So alongside a body, which works by mechanical principles, there's another principle, a kind of creative principle, that has other properties too, which is mind. That's the famous Cartesian dualism. So the world consists of body, and a special human characteristic, mind, which distinguishes humans from animals and automata, and turns on factors like these, and others, but primarily these. What was the fate of this doctrine? Here's where misunderstanding enters. The fate of this doctrine should be clearly understood. It was overthrown within a generation by Isaac Newton. But what Newton showed was that the theory of body was wrong. It didn't have anything to say about the theory of mind. That stayed unchanged. Newton showed that the world just isn't a machine. It works by mystical forces. That was an appalling discovery. Newton considered it a total absurdity, and to the end of his life tried to overcome it, but it was apparently true. The force of attraction does not involve contact. So I can, unbelievable as it is, move the moon by lifting my arm. And that's just the way the world works. It has mystical forces. As I say, Newton regarded this as a total absurdity. He was sharply condemned by the scientists of the day, the leading scientists of the day, for returning to neo-scholastic mysticism with occult forces, as they were called, that made the world work and showed that the world couldn't possibly be a machine. And these were unintelligible forces. We couldn't understand them. They were mysterious. Common sense tells us that I can only make something move by touching it, by being in contact with it in some fashion. But Newtonian physics said, no, that's not true. There's an occult force that allows you to make things move and that accounts for the terrestrial motion and the planetary motion and the tides and so on and so forth. Well, as I say, this was considered a total absurdity, but it was apparently true. And what it does is demolish the conception of body. It demolishes the idea that the world is a machine. It isn't. It has mystical forces. It's common these days to say, to ridicule, the Cartesian idea of the ghost in the machine, the mind's a ghost inside the machine. But that's misunderstanding. What was exercised was the machine, not the ghost. The ghost stayed where it was. It turned out the world was not a machine. There are no machines in the sense of our common sense understanding and the mechanical philosophy of the physics of the day. So that goal was undermined. It turns out the world is indeed unintelligible to us. We have to accept the existence of mystical forces. We can try to construct, develop an understanding of the principles, doctrines about them and so on, but they're not intelligible to human understanding and the mind stays where it was. This was, like I say, a kind of an outrageous discovery. Newton tried to overcome it to the end of his days. Well into the 20th century, physicists were still trying to construct some kind of mechanical conception of the universe. By now that's finally been abandoned totally, and people are accustomed to even more mystical notions like fields, which are mathematical objects, but still interact with one another. Electromagnetic forces. A conception of space and time, which eliminates any notion of solidity. In fact, all common sense is just gone. It's not even considered relevant at this point. Yes, the world is unintelligible to our common sense, but that's just the way it is. We do the best we can in trying to construct doctrines about it.