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  • Professor Paul Bloom: We're going to begin the class

  • proper, Introduction to Psychology, with a discussion

  • about the brain. And, in particular,

  • I want to lead off the class with an idea that the Nobel

  • Prize winning biologist, Francis Crick,

  • described as "The Astonishing Hypothesis."

  • And The Astonishing Hypothesis is summarized like this.

  • As he writes, The Astonishing Hypothesis is

  • that: You, your joys and your

  • sorrows, your memories and your ambitions, your sense of

  • personal identity and free will are in fact no more than the

  • behavior of a vast assembly of nerve cells and their associated

  • molecules. As Lewis Carroll's Alice might

  • have phrased it, "you're nothing but a pack of

  • neurons." It is fair to describe this as

  • astonishing. It is an odd and unnatural view

  • and I don't actually expect people to believe it at first.

  • It's an open question whether you'll believe it when this

  • class comes to an end, but I'd be surprised if many of

  • you believe it now. Most people don't.

  • Most people, in fact, hold a different view.

  • Most people are dualists. Now, dualism is a very

  • different doctrine. It's a doctrine that can be

  • found in every religion and in most philosophical systems

  • throughout history. It was very explicit in Plato,

  • for instance. But the most articulate and

  • well-known defender of dualism is the philosopher Rene

  • Descartes, and Rene Descartes explicitly

  • asked a question, "Are humans merely physical

  • machines, merely physical things?"

  • And he answered, "no." He agreed that animals are

  • machines. In fact, he called them "beast

  • machines" and said animals, nonhuman animals are merely

  • robots, but people are different.

  • There's a duality of people. Like animals,

  • we possess physical material bodies, but unlike animals,

  • what we are is not physical. We are immaterial souls that

  • possess physical bodies, that have physical bodies,

  • that reside in physical bodies, that connect to physical

  • bodies. So, this is known as dualism

  • because the claim is, for humans at least,

  • there are two separate things; there's our material bodies and

  • there's our immaterial minds. Now, Descartes made two

  • arguments for dualism. One argument involved

  • observations of a human action. So, Descartes lived in a fairly

  • sophisticated time, and his time did have robots.

  • These were not electrical robots, of course.

  • They were robots powered by hydraulics.

  • So, Descartes would walk around the French Royal Gardens and the

  • French Royal Gardens were set up like a seventeenth-century

  • Disneyland. They had these characters that

  • would operate according to water flow and so if you stepped on a

  • certain panel, a swordsman would jump out with

  • a sword. If you stepped somewhere else,

  • a bathing beauty would cover herself up behind some bushes.

  • And Descartes said, "Boy, these machines respond in

  • certain ways to certain actions so machines can do certain

  • things and, in fact," he says,

  • "our bodies work that way too. If you tap somebody on the

  • knee, your leg will jump out. Well, maybe that's what we are."

  • But Descartes said that can't be because there are things that

  • humans do that no machine could ever do.

  • Humans are not limited to reflexive action.

  • Rather, humans are capable of coordinated, creative,

  • spontaneous things. We can use language,

  • for instance, and sometimes my use of

  • language can be reflexive. Somebody says, "How are you?"

  • And I say, "I am fine. How are you?"

  • But sometimes I could say what I choose to be,

  • "How are you?" "Pretty damn good."

  • I can just choose. And machines,

  • Descartes argued, are incapable of that sort of

  • choice. Hence, we are not mere machines.

  • The second argument is, of course, quite famous and

  • this was the method. This he came to using the

  • method of doubt. So, he started asking himself

  • the question, "What can I be sure of?"

  • And he said, "Well, I believe there's a God,

  • but honestly, I can't be sure there's a God.

  • I believe I live in a rich country but maybe I've been

  • fooled." He even said,

  • "I believe I have had friends and family but maybe I am being

  • tricked. Maybe an evil demon,

  • for instance, has tricked me,

  • has deluded me into thinking I have experiences that aren't

  • real." And, of course,

  • the modern version of this is The Matrix.

  • The idea of The Matrix is explicitly built upon

  • Cartesian--Descartes' worries about an evil demon.

  • Maybe everything you're now experiencing is not real,

  • but rather is the product of some other, perhaps malevolent,

  • creature. Descartes, similarly,

  • could doubt he has a body. In fact, he noticed that madmen

  • sometimes believe they have extra limbs or they believe

  • they're of different sizes and shapes than they really are and

  • Descartes said, "How do I know I'm not crazy?

  • Crazy people don't think they're crazy so the fact that I

  • don't think I'm crazy doesn't mean I'm not crazy.

  • How do I know," Descartes said, "I'm not dreaming right now?"

  • But there is one thing, Descartes concluded,

  • that he cannot doubt, and the answer is he cannot

  • doubt that he is himself thinking.

  • That would be self-refuting. And so, Descartes used the

  • method of doubt to say there's something really different about

  • having a body that's always uncertain from having a mind.

  • And he used this argument as a way to support dualism,

  • as a way to support the idea that bodies and minds are

  • separate. And so he concluded,

  • "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 depend on any

  • material thing. That is to say,

  • the soul by which I am, when I am, is entirely distinct

  • from body." Now, I said before that this is

  • common sense and I want to illustrate the common sense

  • nature of this in a few ways. One thing is our dualism is

  • enmeshed in our language. So, we have a certain mode of

  • talking about things that we own or things that are close to us

  • my arm, my heart, my child,

  • my carbut we also extend that to my body and my brain.

  • We talk about owning our brains as if we're somehow separate

  • from them. Our dualism shows up in

  • intuitions about personal identity.

  • And what this means is that common sense tells us that

  • somebody can be the same person even if their body undergoes

  • radical and profound changes. The best examples of this are

  • fictional. So, we have no problem

  • understanding a movie where somebody goes to sleep as a

  • teenager and wakes up as Jennifer Garner,

  • as an older person. Now, nobody says,

  • "Oh, that's a documentary. I believe that thoroughly true"

  • but at the same time nobody, no adult, no teenager,

  • no child ever leaves and says, "I'm totally conceptually

  • confused." Rather, we follow the story.

  • We can also follow stories which involve more profound

  • transformations as when a man dies and is reborn into the body

  • of a child. Now, you might have different

  • views around--People around this room will have different views

  • as to whether reincarnation really exists,

  • but we can imagine it. We could imagine a person dying

  • and then reemerging in another body.

  • This is not Hollywood invention. One of the great short stories

  • of the last century begins with a sentence by Franz Kafka:

  • "As Gregor Samsa woke one morning from uneasy dreams,

  • he found himself transformed in his bed into a gigantic insect."

  • And again, Kafka invites us to imagine waking up into a body of

  • a cockroach and we can. This is also not modern.

  • Hundreds of years before the birth of Christ,

  • Homer described the fate of the companions of Odysseus who were

  • transformed by a witch into pigs.

  • Actually, that's not quite right.

  • She didn't turn them into pigs. She did something worse.

  • She stuck them in the bodies of pigs.

  • 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. And we are invited to imagine

  • the fate of again finding ourselves in the bodies of other

  • creatures and, if you can imagine this,

  • this is because you are imagining what you are as

  • separate from the body that you reside in.

  • We allow for the notion that many people can occupy one body.

  • This is a mainstay of some slapstick humor including the

  • classic movie, All of Me--Steve Martin

  • and Lily Tomlinhighly recommended.

  • But many people think this sort of thing really happens.

  • One analysis of multiple personality disorder is that you

  • have many people inside a single body fighting it out for

  • control. Now, we will discuss multiple

  • personality disorder towards the end of the semester and it turns

  • out things are a good deal more complicated than this,

  • but still my point isn't about how it really is but how we

  • think about it. Common sense tells us you could

  • have more than one person inside a single body.

  • This shows up in a different context involving exorcisms

  • where many belief systems allow for the idea that people's

  • behavior, particularly their evil or

  • irrational behavior, could be because something else

  • has taken over their bodies. Finally, most people around the

  • world, all religions and most people in most countries at most

  • times, believe that people can survive

  • the destruction of their bodies. Now, cultures differ according

  • to the fate of the body. Some cultures have the body

  • going to--sorry--the fate of the soul.

  • Some cultures have you going to Heaven or descending to Hell.

  • Others have you occupying another body.

  • Still, others have you occupying an amorphous spirit

  • world. But what they share is the idea

  • that what you are is separable from this physical thing you

  • carry around. And the physical thing that you

  • carry around can be destroyed while you live on.

  • These views are particularly common in the United States.

  • In one survey done in Chicago a few years ago,

  • people were asked their religion and then were asked

  • what would happen to them when they died.

  • Most people in the sample were Christian and about 96% of

  • Christians said, "When I die I'm going to go to

  • Heaven." Some of the sample was Jewish.

  • Now, Judaism is actually a religion with a less than clear

  • story about the afterlife. Still, most of the subjects who

  • identified themselves as Jewish said when they die they will go

  • to Heaven. Some of the sampled denied

  • having any religion at all--said they have no religion at all.

  • Still, when these people were asked what would happen when

  • they would die, most of them answered,

  • "I'm going to go to Heaven." So, dualism is emmeshed.

  • A lot rests on it but, as Crick points out;

  • the scientific consensus now is that dualism is wrong.

  • There is no "you" separable or separate from your body.

  • In particular, there is no "you" separable

  • from your brain. To put it the way cognitive

  • scientists and psychologists and neuroscientists like to put it,

  • "the mind is what the brain does."

  • The mind reflects the workings of the brain just like

  • computation reflects the working of a computer.

  • Now, why would you hold such an outrageous view?

  • Why would you reject dualism in favor of this alternative?

  • Well, a few reasons. One reason is dualism has

  • always had its problems. For one thing,

  • it's a profoundly unscientific doctrine.

  • We want to know as curious people how children learn

  • language, what we find attractive or unattractive,

  • and what's the basis for mental illness.

  • And dualism simply says, "it's all nonphysical,

  • it's part of the ether," and hence fails to explain it.

  • More specifically, dualists like Descartes

  • struggle to explain how a physical body connects to an

  • immaterial soul. What's the conduit?

  • How could this connection be made?

  • After all, Descartes knew full well that there is such a

  • connection. Your body obeys your commands.

  • If you bang your toe or stub your toe you feel pain.

  • If you drink alcohol it affects your reasoning,

  • but he could only wave his hands as to how this physical

  • thing in the world could connect to an immaterial mind.

  • Descartes, when he was alive, was reasonable enough

  • concluding that physical objects cannot do certain things.

  • He was reasonable enough in concluding, for instance,

  • as he did, that there's no way a merely physical object could

  • ever play a game of chess because--and that such a

  • capacity is beyond the capacity of the physical world and hence

  • you have to apply--you have to extend the explanation to an

  • immaterial soul but now we know--we have what scientists

  • call an existence proof. We know physical objects can do

  • complicated and interesting things.

  • We know, for instance, machines can play chess.

  • We know machines can manipulate symbols.

  • We know machines have limited capacities to engage in

  • mathematical and logical reasoning,

  • to recognize things, to do various forms of