PHIL 176: Death

Lecture 3

 - Arguments for the Existence of the Soul, Part I


The lecture focuses on arguments that might be offered as proof for the existence of the soul. The first series of arguments discussed is those known as “inferences to the best explanation.” That is, we posit the existence of things we cannot see so as to explain something else that is generally agreed to take place.

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PHIL 176 - Lecture 3 - Arguments for the Existence of the Soul, Part I

Chapter 1. Introduction: The P-Functioning Body [00:00:00]

Professor Shelly Kagan: Today we’re going to take up the discussion where we left it last time. We were talking about two main positions with regard to the question, “What is a person?”

On the one hand, we have the dualist view; that’s the view that we spent a fair bit of time sketching last meeting. The dualist view, according to which a person is a body and a soul. Or perhaps, strictly speaking, what we should say is the only part that’s essential to the person is the soul, though it’s got a rather intimate connection to a particular body. That’s the dualist view. In contrast to that, we’ve got the physicalist view, according to which there are just bodies. A person is just a body, as we might put it. Now, the crucial point here, the point I was turning to as we ended last time, is that although a person on the physicalist view is just a body, a person isn’t just any old body. A person is a body that has a certain set of abilities, can do a certain array of activities. People are bodies that can think, that can communicate, that are rational, that can plan, that can feel things, that can be creative, and so forth and so on.

Now, we might argue about what’s the exact best list of those abilities. For our purposes, I think that won’t be crucial, and so I’ll sometimes talk about this set of abilities without actually having a canonical list. Just think of them as the set of abilities that people have, the things that we can do that other physical objects — chalk, radios, cars — those things can’t do. Call those the abilities that make something a person. To just introduce a piece of jargon, we could call those the P abilities, P for person. Or we could talk about the various kinds of ways — this is the physicalist way of thinking about it — according to the physicalist, a person is just a body that has the ability to fulfill the various P functions. And we can talk, then, about a person as a P-functioning body. Or we could say that a person is a body that is P-functioning.

It’s important to see that the idea is, although it’s a body, it’s not just any old body. Indeed, it’s not just any old human body. After all, if you rip out your gun, shoot me in the heart, I bleed to death, we still have a human body in front of us. But we don’t have a P-functioning body. We don’t have a body that’s able to think, a body that’s able to plan, to communicate, to be creative, to have goals. So the crucial thing about having a person is having a P-functioning body.

Chapter 2. The Mind According to Physicalists and Dualists [00:03:02]

Now, what’s a mind on this view? On the physicalist view, it’s still perfectly legitimate to talk about minds. The point, though, is that from the physicalist perspective, the best thing to say is, talk about a mind is a way of talking about these various mental abilities of the body. We nominalize it. We talk about it using a noun, the mind. But talk of the mind is just a way of talking about these abilities that the body has when it’s functioning properly.

This is similar, let’s say, to talking about a smile. We believe that there are smiles. Physicalists don’t deny that there are minds. Just like we don’t deny, we all believe, that there are smiles. But what is a smile? Well, a smile is just a way of talking about the ability of the body to do something. This characteristic thing we do with our lips exposing our teeth and so forth. It’s a smile, a rather dorky smile, but there’s a smile. Now, if you were listing the parts of the body, you would list the teeth, you would list the lips, you would list the gums, you would list the tongue, but you wouldn’t list the smile. So, should we conclude, as dualists, that smiles are these extra nonphysical things that have a special intimate relationship with bodies? Well, you could imagine a view like that, but it would be rather a silly view.

Talk about a smile is just a way of talking about the body’s ability to smile. There’s no extra part. Even though we have a noun, the smile, that if you’re not careful might lull you into thinking there must be a thing, the smile. And then you’d have all these metaphysical conundrums. Where is the smile located? It seems to be in the vicinity of the mouth. But the smile isn’t the lips. The smile isn’t the teeth. So it must be something nonphysical. No, that would just be a silly way to think about smiles. Talk of smiles is just a way of talking about the ability of the body to smile, to form a smile. That’s an ability that we have, our bodies have.

Similarly, then, according to the physicalist, talk of the mind, despite the fact that we have a noun there, is just a way of talking about the abilities of the body to do various things. The mind is just a way of talking about the fact that our body can think, can communicate, can plan, can deliberate, can be creative, can write poetry, can fall in love. Talk of all of those things is what we mean by the mind, but there’s no extra thing, the mind, above and beyond the body. That’s the physicalist view.

So it’s important, in particular, to understand that from the physicalist’s point of view, the mind is not the brain. You might think, “Look, according to physicalists minds are just brains.” And that wouldn’t be a horrendously misleading thing to say, because according to the best science that we’ve got, the brain is the part of the body that is the seat or house or the underlying mechanical structure that gives us these various abilities. These P functions are functions that we have by virtue of our brain. So that might tempt you into saying the mind on the physicalist view is just a brain.

But we probably shouldn’t say that. After all, if you shoot me, there’s my corpse lying on the stage. Well, there’s my brain. My brain is still there in my head. But we no longer have a person. The person has died. The person, it seems, no longer exists. Whether strictly that’s the best thing to say or not is a question we’ll have to come to in a couple of weeks. But it seems pretty clear that the mind has been destroyed, even though the brain is still there. So I think, at least when there’s the need to be careful — maybe we don’t normally have a need to be careful — but when there’s the need to be careful, we should say, talk of the mind is a way of talking about the P-functioning of the body. Our best science suggests that a well-functioning body can perform these things, can think and plan and fall in love by virtue of the fact that the brain is functioning properly. That’s the physicalist view.

On the dualist view, what was death? Death is presumably the separation of the mind and the body, perhaps the permanent separation, with the destruction of the body. What’s death on the physicalist view? Well, there is no extra entity, the soul. The mind is just the proper P-functioning of the body. So, the mind gets destroyed when the ability of the body to function in that way has been destroyed. Death is, roughly, the end of this set of functioning. Again, this probably should be cleaned up and in a couple of weeks we’ll spend a day or half period trying, to clean it up and make it somewhat more precise. But there’s nothing mysterious about death from the physicalist point of view, at least about the basic idea of what’s going on in death.

I’ve got a stereo. Suppose I hold up my boombox for you and it’s playing music. It’s one of the things it can do. And I drop in on the ground, smashing it. Well, it no longer can function properly. It’s broken. There’s no mystery why it can’t function once it’s broken. Death is basically just the breaking down of the body, on the physicalist point of view, so that it no longer functions properly.

One other point worth emphasizing and sketching the physicalist view is this. So, as I said, physicalists don’t deny that there are minds. Even though we say “we’re just bodies,” that doesn’t mean that we’re just any old body. It’s not as though the physicalist view is, “we’re bodies that have some illusion of thinking.” No, we’re bodies that really do think. So there really are minds. We could, on the physicalist point of view, call those souls. Just like there’s no danger in talking of the mind from the physicalist perspective, there wouldn’t be any serious danger in talking about a soul. And so, in certain contexts, I’m perfectly comfortable — in my physicalist moods, I am perfectly comfortable — talking about this person’s soul. He’s got a good soul, a bad soul, how the soul soars when I read Shakespeare, or what have you.

There’s nothing upsetting or improper about the language of the soul, even on the physicalist point of view. But in this class, just to try to keep us from getting confused, as I indicated before and I want to remind you, I’m going to save the word “soul”; I’m going to at least try to save the word “soul” for when I’m talking about the dualist view. So we might put it this way. The neutral term is going to be “mind.” We all agree that people have minds, sort of the house or the seat of our personalities. The question is, “What is a mind?” The dualist position is that the mind is a soul and the soul is an immaterial object. So when I use the word “soul,” I will try to reserve it for the metaphysical view, according to which souls are something immaterial. In contrast to that, we’ve got the physicalist view. Physicalists also believe in minds. But minds are just a way of talking about the abilities of the body. So physicalists do not believe in any immaterial object above and beyond the body that’s part of a person. Just to keep things clear, I will say that physicalists, materialists, do not believe in souls. Because, for the purposes of this class, I’m going to reserve the word “soul” for the immaterialist conception of the mind. In other contexts — no harm in talking about souls.

Chapter 3. Inferences to the Best Explanation to Prove the Soul’s Existence [00:12:17]

So these are the two basic positions: the dualist view on the one hand, the physicalist view on the other. The question we need to turn to — I take it that just as the dualist view is a familiar one, so it’s true that the physicalist view is a familiar one. Whether or not you believe it, you are familiar with the fact that some people believe it, or at least you wonder whether it’s true. Does science require that we believe in the physicalist view or not?

The question we want to turn to, then, is, “Which of these two views should we believe: the dualist position or the physicalist position?” And the crucial question, presumably, is, “Should we believe in the existence of a soul?” Both sides believe in bodies. As I say, the dualist position, as we’re understanding it, is not a view that says there are only minds, there are no bodies. Dualists believe that there are bodies. They believe that there are souls as well as bodies. Physicalists believe there are bodies but no souls. So there’s an agreement that there are bodies. Here is one. Each one of you is sort of dragging one around with you. There’s agreement that there’s bodies. The question is, “Are there anything beyond bodies?” Is there anything beyond the body? Is there a soul? Are there souls? That’s the question that’s going to concern us for a couple of weeks.

If we ask ourselves, “What reasons do we have to believe in a soul?” we might start by asking, what reasons do we have to believe in anything? How do we prove the existence of things? For lots of familiar everyday objects, the answer is fairly straightforward. We prove their existence by using our five senses. We just see them. How do I know that there are chairs? Well, there are some chairs in front of me. Open my eyes, I see them. How do I know that there is a lectern? Well, I see it. I can touch it. I feel it. How do I know that there are trees? I see them. How do I know that there are birds? I see them. I hear them. How do I know that there are apples? I see them. I taste them. So forth and so on.

That approach pretty clearly isn’t going to work for souls, because a soul — and again, we’ve got in mind this metaphysical view, according to which its something immaterial — isn’t something we see. It’s not something we taste or touch or smell or hear. We don’t directly observe souls with our five senses.

You might wonder, well, don’t I sort of directly observe it in myself that I have a soul? Although I guess there have been people who’ve made that sort of claim, it seems false to me. I can only ask each of you to sort of introspect for a second. Turn your mind’s eye inward and ask. Do you see a soul inside you? I don’t think so. I see things outside me. I feel certain sensations in my body, but it doesn’t seem as though I observe a soul. Even if I believe in a soul, I don’t see it.

How do we prove the existence of things we can’t see or hear or taste and so forth? The usual method, maybe not the only method, but the usual method is something like this. Sometimes, we posit the existence of something that we can’t see so as to explain something else that we all agree takes place. Why do I believe in the existence of atoms? I don’t see individual atoms. Why do I believe in the existence of atoms so small that I can’t see them? Because atomic theory explains things. When I posit the existence of atoms with certain structures and certain sort of ways of interacting and combining and building up, when I posit atoms, suddenly I can explain all sorts of things about the physical world. So, I infer the existence of atoms based on the fact that doing that allows me to explain things that need explaining. This is a kind of argument that we use all the time. How do I posit — why do I believe in x-rays, even though I don’t see them? Because doing that allows me to explain certain things. Why do I believe in certain planets too far away to be observed directly through a telescope? Because positing them allows you explain things about the rotation of the star or the gravitational fluctuations, what have you. We make inferences to the existence of things we can’t see, when doing that helps us to explain something we can’t otherwise explain. This pattern of argument, which is ubiquitous, is called “inference to the best explanation.”

I want to emphasize this bit about “best explanation.” What we’re justified in believing are those things that we need, not simply when they would offer us some kind of explanation, but when they offer us the best explanation that we can think of. So look, why am I justified in believing in germs, various kinds of viruses that I can’t see, or bacteria or what have you, that I can’t see? Because doing that allows me to explain why people get sick. But there’s other things that would allow me to explain that as well. How about demons? I could believe in demons and say, “Why does a person get sick and die? Well, it is demonic possession.” Why aren’t I justified in believing in the existence of demons? It’s a possible explanation. But what we seem to be justified in believing is not just any old explanation, but the “best explanation.” So we’ve got two rival explanations. We’ve got, roughly, germ theory and we’ve got demon theory. We have to ask ourselves, “Which of these does a better job of explaining the facts about disease?” Who gets what kinds of diseases? How diseases spread, how they can be treated or cured, when they kill somebody.

The fact of the matter is, demon theory doesn’t do a very good job of explaining disease, while germ theory does do a good job. It’s the better explanation. So we’re justified in believing in germs, but not demons. It’s a matter of inference, not just to any old explanation, but inference to the best explanation.

Chapter 4. Can Only the Soul Justify Feature F? [00:19:55]

All right, so, what we need to ask ourselves, then, is, “What about the soul?” We can’t observe souls. But here’s a possible way of arguing for them. Are there things that need to be explained that we could explain if we posited the existence of a soul, an immaterial object, above and beyond the body? Are there things that the existence of a soul could explain and explain better than the explanation that we would have if we had to limit ourselves to bodies? You might put it this way as sort of the easiest version of this kind of argument, for our purposes. Are there things about us that the physicalist cannot explain? Are there mysteries or puzzles about people that the physicalist just draws a blank, but if we become dualists, we can explain these features?

Suppose there was a feature like that, feature F. Then we’d say, “Look, although we can’t see the soul, we have reason to believe in the soul, because positing the existence of a soul helps us to explain the existence of feature F, which we all agree we’ve got.” Suppose it was true that you couldn’t explain love from the physicalist perspective. But we all know that people do fall in love, but souls would allow us to explain that. Boom, we’d have an argument for the existence of a soul. It would be an example of “inference to the best explanation.” Now, the crucial question, of course, is, “What’s the relevant feature F?” Is there some feature that the physicalist can’t explain and so we need to appeal to something extra-physical to explain it? Or the physicalist can only do a rotten job of explaining, like demon theory did? And then, if we were to appeal to something nonphysical, we would do a better job of explaining. If we could find the right F, and make out the argument, the physicalist can’t explain it or does a bad job of explaining it and the dualist does a better job of explaining it, we’d have reason to believe in the soul. Like all arguments in philosophy, it would be a tentative argument. We’d sort of have some reason to believe in the soul until we sort of see what next argument comes down the road. But at least it would give us some reason to believe in the soul.

What I want to do is ask, “What might feature F be?” Is there any such feature F? It’s probably also worth underlining the fact that what I’ve really been doing is running through a series of arguments. “Inference to the best explanation” is not a single argument for the soul. It’s rather the name for a kind of argument. Depending on what F you fill in the blank with, what pet feature or fact you’re trying to explain by appeal to the soul, you get a different argument. So let’s ask ourselves, “Are there things that we need to appeal to the soul in order to explain these things about us?” Here’s a first try.

Actually, let me start by saying I’m going to distinguish two broad families of characteristics we might appeal to. We might say, one set of approaches focus on ordinary, familiar, everyday facts about us. The fact that we love, the fact that we think, the fact that we experience emotions, what have you — these are ordinary features of us. I’m going to start with those and then I’ll turn, eventually, to another set of possible things that might need explaining, which we might think of as extraordinary, supernatural things. Maybe there are certain supernatural things about communication from the dead or near-death experiences that need to be explained in terms of the soul. We’ll get to those, but we’ll start with ordinary, everyday, hum-drum facts about us. Even though they’re ordinary and familiar, it still could turn out that we need to appeal to souls in order to explain them.

So, to start, how about this? Start with a familiar fact, which I’ve already drawn your attention to a couple of times, that you can have a body that’s dead. You could have a corpse, and that’s clearly not a person. It’s not a living being. It’s not a person. It doesn’t do anything. It just lies there; whereas your body, my body is animated. I move my hands around, my mouth is going up and down, it walks from one part of the stage to the other part of the stage. Maybe we need to appeal to the soul in order to explain what animates the body. The thought would be, when the soul and the body have been separated — such the dualist explains — the soul has lost its ability to give commands to the body. So the body is no longer animated. So we’ve got a possible explanation of the difference between an animated and an unanimated or an inanimate body to it. Is the soul in contact of the right sort with the body? There’s a possible explanation. You might say, “Look, the physicalist can’t tell us that, because all the physical parts are still there when you’ve got the corpse, at least if it’s a fresh corpse before the decay has set in. So, we need to appeal to the existence of a soul in order to explain the animation of bodies like the ones that you and I have.”

Well, I said I was going to run through a series of arguments but that doesn’t mean that — the lights have just turned off; I don’t know why — that doesn’t mean that I think the arguments will all work. I announced on the first day of class that I don’t, myself, believe in the existence of a soul. As such, it shouldn’t be any surprise to you that what I’m going to do as we run through each of these arguments is to say, “I’m not convinced by it and here’s why.” Now since I think that the arguments I’m about to sketch — and I’ve just started sketching the first of is — fails I hope you’ll think it over and you’ll eventually come to agree with me, yeah, these arguments don’t really work after all. But what’s more important to me is that you at least think about each of these arguments. Is this a convincing argument for the existence of a soul? If you think so, what response do you want to offer to the objections that I’m giving? If this argument doesn’t work, is there another argument for the existence of a soul that you think is a better one?

First argument, you need the soul in order to explain the animation of the body. From the physicalist point of view, of course, the answer is going to be “too quick.” To have an animated body, you need to have a functioning body. It’s true that when you’ve got a corpse, you’ve got all the parts there, but clearly they’re not functioning properly. But all that shows us is, the parts have broken. Remember my stereo? I dropped my stereo. It falls on the stage. It doesn’t work anymore. It stops giving off music. My boombox stops giving off music. That’s not because previously — we had a CD inside of it, we had some batteries. We dropped the whole thing. It’s not as though previously there was something nonmaterial there. We’ve got all the same parts there, but the parts are now broken. They’re not connected to each other in the right way. The energy is not flowing from the batteries through the wires to the CD component. There’s nothing mysterious from the physicalist perspective about the idea that a physical object can break. Although we need to offer a story about what makes the parts work when they’re connected with each other and interacting in the right way, there’s no need to appeal to anything beyond the physical.

Suppose we try to refine the argument. Suppose we say, “You need to appeal to the soul in order to explain not just that the body moves around, flails, but the body acts purposefully.” We need something to be pulling the strings, to be directing the body. That’s what the soul does, so says the dualist. In response, the physicalist is going to say, “Yes it’s true that bodies don’t just move around in random patterns.” Human bodies don’t do that. So we need something to direct it, but why couldn’t that just be, one particular part of the body plays the part of the command module? Suppose I’ve got a heat-seeking missile which tracks down the plane. As the plane tries to dodge it, the missile corrects its course. It’s not just moving randomly, it’s moving purposefully. There had better be something that explains, that’s controlling, the motions of the missile. But for all that, it could just be a particular piece of the missile that does it.

More gloriously, we could imagine building some kind of a robot that does a variety of tasks. It’s not moving randomly, but the tasks are all controlled by the CPU within the robot. The physicalist says we don’t need to appeal to anything as extravagant as a soul in order to explain the fact that bodies don’t just move randomly, but they move in purposeful ways that are controlled.

For each objection, there’s a response. You could imagine the dualist coming back and saying, “Look, in the case of the heat-seeking missile or the robot for that matter, although it’s doing things, it’s just obeying orders. And the orders were given to it from something outside itself.” Something programmed the robot or the missile. So don’t we need there to be something outside the body that programs the body? That could be the soul.

That’s a harder question. Must there be something outside the body that controls the body? One possibility, of course, is, why not say that people are just robots as well and we get our commands from outside? On a familiar religious view, God built Adam out of dirt, out of dust. Adam is just a certain kind of robot then. God breathes into Adam. That’s sort of turning it on. Maybe people are just robots commanded from outside by God. But that doesn’t mean that there’s anything more to us than there is to the robot. That’s one possible response. A different response, of course, is why couldn’t we have robots that just build more robots? Then, if you ask, “Where did the commands come from?” the answer is, “When they were built, they were built in such a way as to have certain instructions that they begin to follow out.” Just like people have a genetic code, perhaps, that gives us various instructions that we begin to follow out, or certain innate psychology or what have you.

The argument quickly becomes very, very messy. The fan of the soul begins to want to protest, “Look, we’re not just robots. We’re not just robots with some sort of program in our brain that we’re following. We’ve got free will. Robots can’t have free will. So there’s got to be something more to us than robots. We can’t just be physical things.” This is an interesting argument, and I think it’s a new argument. We started with the idea you needed to appeal to souls in order to roughly explain why human bodies move, why we’re animated or why we move in nonrandom ways. I think it’s fairly clear that you don’t need to appeal to souls in order to do that. Appeal to a physical body suffices, I think, to have an explanation as to the difference between an animated and an inanimate body, how bodies will move in nonrandom ways. If the brain is our CPU, then we’ll behave in deliberate, purposeful ways just like a robot will behave in deliberate, purposeful ways. So this initial argument, I think, is not compelling.

Still, we might wonder, what about this new argument? What about the fact that — We said there’s a family of arguments, all of which have the general structure, inference to the best explanation, you need souls in order to explain feature F. Plug in a different feature F and you get a new argument. The one we started with — you need the soul to explain the animation of the body — that argument, I think, doesn’t work. Now we’ve got a new one. You need the soul in order to explain free will. Let me come back to that argument later. It’s a good argument. It’s an argument well worth taking seriously, but let’s come back to it later.

Chapter 5. Abilities, Desires, Emotions – Candidates for Feature F [00:35:07]

First, let’s run through some other things that might be appealed to as candidates for feature F. Suppose somebody says, “Look, it’s true that we don’t need to appeal to souls in order to explain why bodies move around in a nonrandom fashion. But people have a very special ability” — and so the argument goes — “that mere bodies couldn’t have, physicalists can’t explain. That’s the ability to think. It’s the ability to reason. People have beliefs and desires. And based on their beliefs about how to fulfill their desires, they make plans. They have strategies. They reason about what to do. This tightly connected set of facts about us — beliefs, desires, reasoning, strategizing, planning — you need to appeal to a soul” — so the argument goes — ;”to explain that. No mere machine could believe. No mere machine has desires. No mere machine could reason.”

It’s easy to see why you might think that sort of thing when you stick to simple machines. It’s pretty clear that there are lots of machines that it doesn’t seem natural to ascribe beliefs or desires or goals or reasoning to. My lawnmower, for example, doesn’t want to cut the grass. Even though it does cut the grass, it doesn’t have the desire. It doesn’t think to itself, “How shall I get that blade of grass that’s been eluding me?” So it’s easy to see why we might be tempted to say no mere machine could think or reason or have beliefs or desires.

That argument’s much less compelling nowadays than I think it would have been 20 or 40 years ago. In an era of computers with quite sophisticated computer programs, it seems, at the very least, natural to talk about beliefs, desires, and reasoning and strategizing.

So suppose, for example, we’ve got a chess-playing computer. On my computer at home I’ve got a program that allows my computer to play chess. I, myself, stink at chess. This program can beat me blind. I move my bishop, the computer moves its queen. What do we say about the computer? Why did the computer move its queen, or virtual queen? Why did the computer move its queen? The natural thing to say is, it’s worried about the fact that the king is exposed and it’s trying to block me by capturing my bishop. That is what we say about computer-playing programs. Think about what we’re doing. We’re ascribing desires to the program. We’re saying it’s got an ultimate desire to win the game. A certain subsidiary desire is to protect its king, to capture my king. A certain other subsidiary desire is, no doubt, to protect its various other pieces along the way. It’s got beliefs about how to do that by blocking certain paths or by making other pieces on my side vulnerable. It’s got beliefs about how to achieve its goals. Then, it puts those combinations of beliefs and desires into action by moving in a way that’s a rational response to my move. It looks as though the natural thing to say about the chess-playing computer is, it does have beliefs. It does have desires. It does have intentions. It does have goals. It does reason. It does all of this. It’s rational to this limited extent. It’s only able to play chess. But to that extent, it’s doing all these things and yet we’re not tempted to say, are we, that the computer has a nonphysical part? We can explain how the computer does all of this in strictly physical terms. Of course, once you start thinking of it this way, it’s natural to talk this way across a variety of things that the computer may be trying to do.

It’s perfectly open to you, as dualists, to respond by saying, “Although we personify the computer, we treat it as though it was a person, as though it had beliefs and desires and so forth, it doesn’t really have the relevant beliefs and desires, because it doesn’t have any beliefs and desires, because no physical object could have beliefs and desires.” In response to that, I just want to say, “Isn’t that just prejudice?”

Of course, it is true that if we simply insist no physical object could really have beliefs or desires, then it will follow that when we are tempted to ascribe beliefs and desires to my chess-playing computer, we’re falling into an illusion. That will follow once we assume that no physical object has beliefs or desires. But what reason is there for saying it has no beliefs or desires? What grounds are there for withholding ascriptions of beliefs and desires to the computer? That’s far from obvious.

Here’s a possibility. Desires, at the very least, seem to be, at least in typical cases, very closely tied to a series of emotions. You get excited when you’re playing chess at the prospect of capturing my queen and crushing me. You get worried when your pieces are threatened. Of course, more generally, you get excited, your heart goes pitter-pat, when your girlfriend or boyfriend says they love you. Your stomach sinks, you have that sinking feeling in the pit of your stomach, when you get a bad grade on a test.

Maybe what’s really going on is the thought that there’s an aspect of desire that has a purely behavioral side, that’s moving pieces around in a way that would make sense if you had this goal. And maybe machines can do that. But there’s an aspect of desires, the emotional side, that machines can’t have, but we clearly do have. Maybe we want to build that emotional side into talk of desires.

So maybe if we want to say machines don’t have a mental life and couldn’t have a mental life, what we really mean is no machine could feel anything emotionally. So let’s distinguish. Let’s say there’s a way of talking about beliefs and desires which is just going to be captured in terms of responding in a way that makes sense given the environment. Maybe computers and robots could do that. But there’s clearly a side of our mental life, the emotional side, where we might really worry, could a robot feel love? Could it be afraid of anything?

Again, our question was, “Do we need to appeal to souls to explain something about us?” The physicalist says “no”; the dualist says “yes.”

If what we mean is the mental, but that the aspect, the behavioral aspect of the mental, where even a chess-playing computer probably has it, then that’s not a very compelling argument. The physicalist will say, “Look, that aspect of the mental is pretty clear. We can explain it in physical terms.” But let’s just switch the argument. What about emotions? Can a robot feel emotions? Could a purely physical being fall in love? Could it be afraid of things? Could it hope for something? The latest version of our argument then is, “People can feel emotions. But if you think about it, it’s pretty clear no robot could feel emotions. No merely physical thing could feel emotions. So there must be more to us than a merely physical thing.” That’s the argument we’ll start with next time.

[end of transcript]

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