We're talking about materialism, the idea that our mental life emerges from our physical brain. If you're listening closely, if you're thinking about this, I hope you acknowledged that this is an odd and unnatural view. I don't expect you to believe it, at least not at first. And in fact, for the most part, people are far more attracted to the doctrine called "Dualism." Dualism is an idea that's been found in just about every religion and every philosophy. It's made explicit in Plato, for instance. But I think the most thoughtful and articulate defender of dualism was the philosopher, Rene Descartes. Descartes believed that animals were material things. He thought that the doctrine of materialism was correct about non-human animals. "But humans are different," Descartes argued. For humans, there's a duality. We possess two sorts of things. We are composed of two sorts of things. We are in part material, but we're also in part spiritual, separate, mental, psychological. In some way that doesn't reduce to the material. He made two arguments for this, and they're both reasonably good arguments, at least quite persuasive at his time, and have persuaded many people and continue to persuade many people. The first arguments for a non-material nature is that humans are capable of doing things that no machine, no material entity ever could. So, it might surprise you to hear this, but Descartes in the 17th century was familiar with robots. He knew about the French Royal Gardens, which is like a 17th century Disneyland or Euro Disney, which had robots that react when you approach them or when you step on certain stones. For instance, you might approach Diana, and then Neptune would jump out from the bushes holding a trident. This was done not of electricity, but with water. So, Descartes knew about these robots, and Descartes asked, "Well, maybe we're such things, maybe we're just machines responding to the environment." And he said that we can't be. He said maybe animals, non-human animals can be, but human behavior is far more complicated, and variegated, and subtle to be explained in such simple ways. We'll return to this point later on in the course when we talk about Noam Chomsky and Noam Chomsky's critique of behaviorism, which argued that basically humans respond in a relatively reflexive way to environmental stimuli. Descartes along with Chomsky said, "That can't be. Our behavior's far too complicated for that. So, we can't be machines." His second argument is probably better now, and it's based on intuition. And his claim was we don't feel like bodies. So, to put it more technically, he applied what was called a method of doubt. He asked the question, "What do we know for sure, and what can we question?" So, for instance, you might believe you were born in such and so place. You could be wrong. You could be deceived. You might believe that the Earth is thousands or millions of years old. But maybe the Earth was created 100 years ago and all the memories that your grandparents have of the past were just manufactured. You might believe, said Descartes, that you live in a world of things, that you're sitting on a chair or there's a wall in front of you or there's a computer near your hands. But Descartes observe that we often believe such things when we're in dreams, but weren't mistaken. He observed that people who are mentally ill, or were deranged in some way, might have such beliefs, but don't be mistaken. So, you could be wrong that there's a physical world around you. You could be wrong that there is a body that you have. This is an ancient concern of course, but it's best articulated in the movie, The Matrix, which maintains that we think we're running around in the physical world, but actually, with the lucky exception of our heroes like Neo and Trinity, we're actually just plugged into some sort of system. Another version of this is that we're brains in a vat. If you were a brain, just the brain sitting in a vat with electrical wires stimulating your experiences, you couldn't help. Maybe you are such things. Modern-day philosophers for instance, will argue that there's an excellent chance that we are simulations, we computer simulations. So, Descartes and people following Descartes said, "There's a lot we can't be sure of. The things that we are seemingly most confident about in real world can't be shaken." But Descartes said, "There's one thing you can't doubt. You can't doubt your own consciousness. You can't doubt your own existence." The famous line is, "I think, therefore I am." And spelling out this intuition, building from the fact you could doubt that you have a body, but you can't doubt that you have a mind. Descartes wrote, "I knew that I was a substance the whole essence or nature of which is to think, and that for its existence there is no need of any place, nor does it dependent in a material thing.. that is to say, the soul by which I am what I am, is entirely distinct from body." So, that's a philosophical case for dualism. But as I said, dualism is also emerged out of common sense. Think about how you describe your body. You describe your body's if you possess it. My arm, my heart, my body, my brain, as if it's something separate from you that you have. Or consider your intuitions about personal identity. So, typically, as people age, their consciousness follows their body. So, I get 10 years older, my mind 10 years older, my brain is 10 years older, it all connects together, but we easily accept at least infection that people can hop from one body to another. There are many comedies that involve body switching, body swamps. There are movies that involve somebody going to sleep one morning as one person and waking up as another. We understand they're fiction, they aren't real. But they make sense to us. There's an intuitive rationale to this. We don't walk out of the theory and say, "I am totally confused what happened there." Rather, at least with our naive conception of the self, we accept that least of the possibility, that you can hop from one body to another. None of this is limited to modern-day movies, the most famous short story of history by Franz Kafka begins with the sentence, "As Gregor Samsa awoke one morning from uneasy dreams, he found himself transformed in his bed into a gigantic insect." Metamorphosis involves that transformation and along before that in Ulysses the characters are transformed. Some of the characters are transformed by an evil witch into pigs. It's non of you took to people and turn them into pigs rather it's much worse. They put them in the body of pigs. As the passage goes, "They had the head and voice, and bristles, and body of swine; but their minds remained unchanged as before. So they were penned there, weeping." Our conception that bodies and cells are separate, allows us to accept idea you had many people inhabiting one body. This is how many people think about multiple personality disorder, something we'll get to quite later on the course. It's also at the root of a view that many people; both religious and non-religious hold, which is the idea of demonic possession. Your body can be taken over by somebody else. Another manifestation of dualism, is you could believe in intelligent beings without bodies. If mind and body are separate it raises the possibility you could have one without the other. Plainly you got to have bodies without minds. That's what a corpse is. But the argument goes you could also have minds without bodies. This is for instance what many people think about gods or angels. Which are the immaterial beings that can think, that can observe, that can act, but they don't have physical bodies in the same sense that we do. Finally, and maybe most important for people, the idea that of dualism, the idea you are not your physical body, raises what must be for many and incredibly appealing consequence, which is that you can survive the destruction of the body. In fact, if you ask most people; religious and non-religious, what will happen after you body is destroyed? The answer is not well, I'm dead then, that's it. It's the end of things. But rather the belief is that you can live on. Maybe you'll end up in some spirit world, maybe you will ascend to heaven, if you're unlucky maybe will descend to hell. Maybe you'll occupy some other body as an reincarnation. But the idea is that the destruction of your body need not be the destruction of you because you are not your body. All of these beliefs, the beliefs about personal identity, the beliefs about life after death, about the existence of supernatural beings. About God. All rest at least to some extent, on a dualist perspective. So, materialism, which says dualism is just playing wrong is an audacious view, and should be treated as such. You shouldn't just shrug and write it down. You should grapple with it, you should worry about it. You should either be grudgingly accepted or fight against it. So, why are modern-day psychologists and neuroscientists so confident that dualism is mistaken? Well, there are a few problems with it. One is that it simply doesn't help us explain certain things that need to be explained. Appealing to an immaterial world to an immaterial soul seems to dock certain questions that really do deserve an answer. So, throughout this course we'll ask questions like, how do we learn language? What do we find sexually attractive? How does memory work? These are questions about ourselves, about our minds. To say, "Oh, it all happens some immaterial realm", leaves us hopeless when it comes to answering them. The second concern is that at the time, Descartes was correct, to infer from the limitations of material things physical things, that we probably are not physical things. But by now we have a much better understanding what physical things can do which makes it entirely possible for many of us that we are set things. So, I'm thinking for instance of computers and robots. For Descartes, the idea that a physical thing can do something as complicated as play a game of chess would seem ludicrous. But now of course we know that physical things and if you're looking at a computer you are looking at such a physical thing, can do exactly that. They can understand language, they could recognize objects, they could store things in memory, they can make inferences, and so on. Now, for some of these things, they don't do it anywhere near as well as people do. So, when we talk about language development for instance we see that, a two-year-old child uses and understands language better than any computer around. So, we need to bear that in mind. But still, it's no longer nuts to say that physical thing can do all of the rich and psychologically diverse and psychologically complicated things that people do. Which means that we have to take seriously the claim that we are in fact such physical things. The final consideration is that there's tremendous evidence that the brain is in fact the roots of mental life. So, put aside all that philosophical abstract, arguments, there's just tons of direct evidence. To some extent that direct evidence has always been there. You don't have to be born in the 20th or 21st century to appreciate that getting hit in the head could affect your consciousness and your memory. To appreciate that diseases like syphilis can lead to disruption of the will and of consciousness. Alzheimer's can rob you of your rationality. That coffee and alcohol can inflame the passions. It just is so evident in everyday life that if physical events that affect the brain can affect ourselves, suggesting that at the very least, our mental life is intimately connected to the brain. Over recent years something else has happened, which is we've developed technologies that allow us to look directly into the brain. Look at the brains activation, and infer from patterns of the brain activation what people are thinking. So, very crudely, you can put somebody into a scanner, an fMRI scanner, and you could tell whether or not are thinking about language, or music, or sex. The technology is increasing. There is such a point that is not implausible that for some of you by the time you're listening to this, we can put a sleeping person under fMRI scanner, and know from neural patterns of neural firings, know what they're dreaming. All of this I think it is very difficult to keep this in mind, and hold on to the view of dualism. I think materialism however uncomfortable, however unpalatable is a view that the science forces us to adopt.