耶魯大學(xué)開(kāi)放課程——哲學(xué)：死亡Death 6

    Death: Lecture 6 Transcript

    February 1, 2007        

    Professor Shelly Kagan: At the end of last class, we started sketching an argument that comes from Descartes, the Cartesian argument, that says merely by the process of thinking, on the basis of thought alone, it tends to show that the mind--We all agree that there are minds. What the argument attempts to show is that this mind must be something separate from my body. And what's amazing about the argument is that it works on the basis of a pure thought experiment. The thought experiment, you recall, was one in which I imagine, I tell myself a story in which what I'm doing is I'm imagining my mind existing without my body. It doesn't seem especially difficult to do that. But then, we add this extra philosophical premise. If I can imagine one thing without the other, then it must be that those are two things. So my mind must not be my body. My mind must not be the same thing as my body or a way of talking about my body, because of course if my mind just was--talking about my mind just was--a way of talking about my body, then to try to imagine my mind without my body would be trying to imagine my body without my body. And that, obviously, can't happen.

    Look. Suppose we try to imagine a world in which Shelly exists but Kagan doesn't. You can't, right? Because of course, they're just a single thing, Shelly Kagan. And so if you've imagined Shelly existing then of course you're imagining that single thing, Shelly Kagan, existing. And if you imagine Kagan not existing, then you're imagining that single thing, Shelly Kagan, not existing. So you can't even imagine a world in which Shelly exists but Kagan doesn't.

    Now, it's important not to be confused about this. We can easily imagine a world in which I don't have the last name Kagan or perhaps to switch it around, Shelly's not my name. Suppose my parents had named me Bruce. Nothing would be easier. Imagine a world in which Kagan exists, but Shelly doesn't exist, because nobody in the world is named Shelly.;

    The question is not, "Can you imagine me with a different name?" Bruce instead of Shelly, easy enough. It's rather, "Can you imagine a world in which the very thing that you really are picking out when you refer to me by the name Shelly--namely this thing--can you imagine a world in which that thing exists, but the thing that you're picking up when you use the word Kagan does not exist?" And that you can't do, because in the real world of course Shelly and Kagan pick out just two different names of this very same thing. This thing right here. So imagining a world in which Shelly exists but Kagan doesn't or Kagan exists but Shelly doesn't, that's trying to imagine a world in which I exist but I don't. And that's, of course, incoherent.

    So if you can--On the other hand, contrast. Can I imagine a world in which my left hand exists, but my right hand doesn't? Easy. Why is it so easy? Because of course there's two different things. Of course, that doesn't mean that in the real world one of them does exist and the other one doesn't. But it does show that in the real world they are two different things. That's why I could imagine a world with one but not the other. Try to imagine a world in which somebody's smile exists but their body doesn't. You can't do it. You can't have the smile without the body. And of course, no mystery about that. That's because the smile isn't really some separate thing from the body. Talking about smiles, as we've noted before, is just a way of talking about either what the body can do or what a certain area of the body can do.

    You can try to imagine it. In Alice in Wonderland, the Cheshire Cat disappears and all we have left, the last thing that disappears, is the smile. But of course, when you imagine the Cheshire Cat only having the smile there, you're still imagining the cat's lips, teeth, maybe tongue, whatever it is. If you try to imagine a smile with no body at all, it can't be done. Why? Because the smile isn't something separate from the body.

    "Try to imagine my mind," says Descartes, "without my body." Easy. From which it follows that my mind and my body must not be one thing. They must, in fact, be two things. That's why it's possible to imagine the one without the other.

    So this Cartesian argument seems to show us that the mind is something separate from, distinct from, not reducible to, not just a way of talking about, my body. So it's got to be something extra above and beyond my body. It's a soul. That's what Descartes argued. And as I say, to this day, philosophers disagree about whether this argument works or not. I don't think it does work and in a second I'll give you a counter example. And then, having given the counter example… That is to say, what I'm going to give is an example of an argument just like it, or at least an argument that seems to be just like it where we can pretty easily see that that argument doesn't work. And so something must go wrong with Descartes' argument as well.

    Well, here's the counter example. Some of you, I'm sure most of you, maybe all of you, are familiar with the Evening Star. The Evening Star is the, roughly speaking, first heavenly body that's visible in the sky as it gets dark, at least at certain times of the year. And I'm sure you're also familiar then with the Morning Star. The Morning Star is that heavenly body which is the last heavenly body that's still visible as dawn comes in and it begins to get light. So as a first pass, the Evening Star is the first star that's visible and the Morning Star is the last star that's visible at the right times of the year. The world that we live in has both the Evening Star and the Morning Star. But try to imagine a world in which the Evening Star exists, but the Morning Star does not. Seems fairly straightforward, right? I get up in the morning as dawn's approaching. I look around and the Morning Star is not there. There is no star where the Morning Star had been or where people have claimed it would be or something. But the Evening Star still exists. When I go out as sun sets and dusk falls, there is the Evening Star.

    So, as I say, it's a trivial matter to imagine a world in which the Evening Star exists and the Morning Star does not. And so we've got a--we could imagine then a--Descartes-like argument saying, "If I can imagine the Evening Star without the Morning Star, that shows the Evening Star and the Morning Star must be two different heavenly bodies." But in fact, that's not so. The Evening Star and the Morning Star are the very same heavenly body. In fact, it's not a star at all. It's a planet. It's Venus, if I recall correctly. So look, there's only one thing. The Evening Star is Venus. The Morning Star is Venus. So there couldn't be a world in which the Evening Star exists, but the Morning Star doesn't, because that would be a world in which Venus exists and Venus doesn't exist. Obviously, that's not possible.

    Of course what you can imagine is a world in which Venus isn't visible in the morning. Still, that's not a world in which the Morning Star doesn't exist, given that what we mean by the Morning Star is that heavenly object, whatever it is, that in this world we pick out at that time in the morning looking up at the sky. So when I refer to the Morning Star, I'm talking about Venus, whether or not I realize it's Venus. When I talk about the Evening Star, I'm referring to Venus, whether or not I realize that Venus is the Evening Star. So as long as Venus is around, well, there's the Evening Star, there's the Morning Star, there's Venus. You can't have a world in which the Morning Star doesn't exist but the Evening Star does. Although you could have a world in which Venus doesn't show up in the morning. Still, from the fact that I can imagine the world in which I look around for the Morning Star--there it isn't. I look around for the Evening Star--there it is. You might have thought that showed--didn't Descartes prove to us that that shows--the Evening Star and the Morning Star are two different things? Well no, obviously it didn't. So let's think about what that means.

    So we've got this argument that Descartes puts forward. I can imagine my mind without my body. And Descartes says that shows that, in fact, my mind is something separate from my body. Well, I can imagine the Evening Star without the Morning Star, so Son of Descartes, "Descarteson," has to say, "Oh, so that shows that the Morning Star and the Evening Star are two different things." But "Descarteson" would be wrong when he says that. The Morning Star and the Evening Star aren't two different things. They're just one thing, namely Venus. In fact, the sentence, "They are one thing," is slightly misleading, right? It's just one thing, Venus. If that argument, if the argument--If trying to run the Cartesian argument for astronomy fails, yet it seems to be an exactly analogous argument, we ought to conclude that the argument for the distinctness of the mind and the body must fail as well.

    Now, that seems to me to be right. I think the Cartesian argument does fail. And I think the example of the Evening Star and the Morning Star--which is not at all original to me--that this example shows, this counter example shows, that Descartes' original argument doesn't work either. At least, that's how it seems to me, though as I say, there are philosophers that say, "No, no. That's not right. Maybe somehow we misunderstood how the argument goes and it doesn't exactly--although these two arguments seem parallel, they're not, in fact, parallel. There's some subtle differences that if we're not looking carefully, we'll overlook." But, as I say, the debate goes on. One of the reasons for thinking it's not clear whether the argument fails or not is because it's hard to pin down, where exactly did it go wrong?

    Look, take the argument of the planets, the Morning Star and the Evening Star example. I take it that we all agree that when we attempt to run the Cartesian argument in terms of the Morning Star and the Evening Star, it fails. But it's harder to say what went wrong? How did it go wrong? Why did it go wrong?

    What are the possibilities? Well, we said, look, first claim, first premise. I can imagine a world in which the Evening Star exists, but the Morning Star doesn't. Well, I suppose one possible response would be, "You know, you couldn't really do that. You thought you were imagining a world in which the Evening Star exists and the Morning Star doesn't, but you weren't really imagining a world in which the Evening Star exists and the Morning Star doesn't. You misdescribed what it is you've imagined." That's not a silly thing to say about the astronomy case. Maybe that's the right diagnosis.:

    Could we similarly say, "I didn't really imagine a world in which my mind exists but my body doesn't"? That little story I told last time, I thought I was describing a world in which my mind exists and my body doesn't, but it wasn't really imagining a world like that. That doesn't seem so persuasive over there. It did seem as though I was imagining it.

    What else could go wrong with the astronomy example? Well, maybe I did imagine a world in which the Morning Star exists and the Evening Star doesn't exist, but maybe imagining doesn't mean it's possible. Normally, we think, if we imagine something, it means it's possible. Here I don't mean, of course, empirically possible. I could imagine a world with unicorns. It doesn't mean I think unicorns are physically possible. All we mean here is logically possible. I can imagine a world with unicorns. It seems to follow that unicorns are logically possible. Imagination seems to be a guide to possibility; but maybe not always. Maybe sometimes we can imagine something that's really impossible. Try to imagine--can you do that or can you not do that?--try to imagine a round square. Can you imagine it? Can you not imagine it? In certain moods, I sort of feel I can just begin to imagine it. Of course, it doesn't really mean it's possible. It seems like it's impossible. So maybe imagination is a flawed guide to possibility. So maybe that's what we should say about the mind-body case. "Yeah, I can imagine a world in which my mind exists but my body doesn't. But that doesn't show that it's really possible, logically possible to have a world in which my mind exists and my body doesn't." Maybe that's where the argument goes wrong. On the other hand, isn't imagination our best guide to logical possibility? Isn't the reason I think unicorns are logically coherent is because I can imagine them so easily?

    Another possibility. Maybe we should say, the mere fact that it's possible for A and B to be separate--for A to exist without B for example, that's clearly where they're separate--the mere fact that it's possible for them to be separate doesn't mean that in the actual world they are separate. Maybe the argument goes wrong by assuming that identity--when A is equal to B, it's always equal to B, no matter what. Maybe identity, as philosophers like to put it, maybe identity is contingent. Maybe A could be the same thing as B in this logically possible world, but we could imagine a completely different logically coherent world in which A was not the same thing as B. If that's right, then maybe the conclusion should be "well, you know, yeah, the Cartesian thought experiment shows that there could be a world in which there are minds that are not identical to bodies. But that doesn't mean that in this world the mind is not identical to my body. Maybe in this world, minds and bodies are identical, even though in other logically possible worlds the identity comes apart. Identity is not necessary, but contingent, as the philosophers put it."'

    It's not clear that that's right either. The notion of contingent identity is very puzzling. After all, if A really is B, how could they come apart? There's only one thing there. There's nothing to come apart. There's just A equals B, that single thing. What's to come apart?( m& B. p$ h, V# j3 }% @

    So where exactly does the argument break down? Is it that I'm not really imagining? I'm just thinking I'm imagining? Is it that imagination's not really a good guide to possibility? I just--Often it is, but not always. Is it that identity is contingent? The interesting thing about Descartes' argument is that it's easy to see something has gone wrong in the case of the Morning Star and the Evening Star, but it's difficult to pin down what exactly went wrong. Different philosophers agree that something's gone wrong in the Morning Star and the Evening Star case, but disagree about the best diagnosis of where the mistake went in. Armed with your pet diagnosis of where the argument goes wrong there, you've got to ask, "Does it also go wrong in the mind and body case?"

    Well, we could spend more time, but I'm not going to. I think Descartes' argument fails. I think the Morning Star, Evening Star case shows us that arguments like this, at the very least, can't be taken at face value. Just because it looks as though we can imagine it and just because it seems as though from the fact that we can imagine one without the other, it just won't necessarily follow that we really do have two things that are separate and not identical in the real world. I'd be happy to discuss with you, outside class, at greater length my favorite theories as to where the argument goes wrong and why I think it goes wrong in Descartes' case as well. But I suggest that the argument goes wrong. It's not right. And so, Descartes' attempt to establish the distinctness of the mind, the immateriality of the mind, on the basis of this Cartesian thought experiment, I think that's unsuccessful.

    Well, we've spent--Let's step back and think of where we've been. We've spent the last week and a half or so, maybe a bit more, two weeks, talking about arguments for the existence of the soul. And unsurprisingly--since I announced this was going to be the result before the class had barely gotten started--I don't think any of these arguments work. I believe the attempts to establish the existence of a soul, an immaterial object, the house of consciousness separate and distinct from the body, I think those arguments fail. But I recognize that this is something that reasonable people can disagree about. And so this is, as will be many times the case over the course of this semester, something that I invite you to continue to reflect on for yourself. If you believe in a soul, what's the argument for it?

    Well, what we're about to turn to is Plato's discussion of these issues in the dialogue the Phaedo, which, as I told you last week, purports to lay out the final day's discussion with Socrates before he is killed by--he kills himself--by drinking the hemlock in accordance with the punishment that's been given to him. Now, in the course of this discussion, Socrates and his disciples argue about not so much the existence of the soul, but the question really is the immortality of the soul. After all, even if you believe in a soul, as I have remarked previously, that doesn't give us yet any reason to believe the soul continues to exist after the death of your body. The kind of dualist position that we are considering in this class is an interactionist position, where the soul commands the body. That's what makes my fingers move right now. And the body can affect the soul. If I poke my body, I feel it in my mind. So the mind, the soul, and the body are obviously very tightly connected. And so it could be--even if the soul is something separate from the body--that when the body dies, the soul dies as well. That's the question that's driving the discussion in the Phaedo.

    Do we have any good reason to believe the soul survives the death of the body? And more particularly still, do we have good reason to believe it's immortal? Socrates believes in the immortality of the soul. And so, he attempts to defend this position, justify it to his disciples who are worried that it may not be true. It's important to realize--as you read the dialogue, it becomes fairly apparent--that there isn't so much any defense of the belief in the soul. There's some of it, but it's not the primary goal. For the most part, the existence of the soul is just taken for granted in the dialogue. Plato, as a dualist, portrays Socrates as being a dualist and that's just taken for granted. The question that the philosophical discussion turns on is not, "Is there a soul?" but rather, "Does it survive the death of the body? Is it immortal?"

    Now, as I said, this is Socrates' last day on earth and you'd expect him to be pretty bummed. You'd expect him to be sad. And one of the just striking things is that Socrates is in a very happy, indeed jovial, mood, joking with his friends. Why is that? Well, of course, it's because he thinks, first of all, there's a soul and it will survive and it's immortal. But more importantly still--those are all crucial but there's an extra ingredient as well--he thinks he's got good reason to believe, when he dies he's going to go, basically, to what we'd call heaven. He thinks there's a realm populated by good gods and maybe other philosophical kindred souls. And if you got your stuff together here on life, you'll get to go to that when you die. And so he's excited. He's pleased.

    Why does he think he's going to go? Well, in thinking about Socrates' belief in the existence of a soul, it's important to understand, it's important to notice, that his take on which stuff gets assigned to the body, what are the bodily things versus what are the soul-like things, is rather different from the way, I think, most of us nowadays would draw the line. When I talked about arguments for the existence of a soul, I said, "Look, here's one possible argument. I see colors. No physical object could, no purely physical object could see colors. I can taste tastes and have the smell of coffee and so forth." But Socrates thinks all those bodily sensations--that's all stuff that the body takes care of. So unlike those modern dualists who think we need to appeal to something immaterial in order to explain bodily sensations, Socrates thinks no, no, the body takes care of all the bodily sensations, all the desirings and the wantings and the emotions and the feelings and the cravings. That's all body stuff.

    What the soul does--Socrates thinks--the soul thinks. The soul, in its essence, is rational. It takes care of the thinking side of things. What does the soul think about? Well, the soul thinks about all sorts of things, doubtless. But one of the things that it can do, one of the things that sort of provides the underpinnings, as we'll see, for Plato's arguments for the immortality of the soul is the soul can think about--;well, here I'll have to introduce a word of philosophical jargon. Sometimes the idea, sometimes the term is called "ideas." Sometimes the term is called "forms." But the thought is that the soul can think about certain pure concepts or ideas like justice itself, or beauty itself, or goodness itself, or health itself. So to explain all this we need now a sort of crash course in Plato's metaphysics. Obviously, this will be rather superficial. Those of you who would like to know more about it, I recommend reading more Platonic dialogues or taking a class in ancient philosophy. But here's the basic idea.

    There's all sorts of beautiful objects in the world. Objects can vary in terms of how beautiful they are. But Plato's got the idea that there's nothing in this world that's perfectly beautiful. And yet for all that, we can think about beauty itself. Well, we might put it this way. We might say, ordinary, humdrum, everyday, physical objects are somewhat beautiful. They're partially beautiful. As, sometimes, Platonists put it, they "participate" in beauty. They partake of beauty to varying degrees. But none of them should be confused with beauty itself. Or, take justice. There are various arrangements, social arrangements, that can be just or unjust to varying degrees. But we don't think anywhere in the world there's any society that's perfectly just. Yet for all that, the mind can think about perfect justice. And notice how ordinary empirical social arrangements fall short of perfect justice. So whatever perfect justice is, it's not one more thing in the empirical world. It's something we can think about. It's something that things in the empirical world can participate in or partake of to varying degrees. But we shouldn't confuse the physical things which can be just, the people who can be virtuous to one degree or another, with perfect virtue or perfect justice. That's something that only the mind can think about, that we don't actually have in the world, the empirical world itself.

    Or take being round. The mind can think about perfect circularity. But no physical object is perfectly circular. There are only things that are circular to a greater or lesser degree. So, by thinking about it, by thinking about these kinds of issues, we can see that the mind has some kind of handle on these perfect, well, we need a word. And as I say, Plato gives us a word, "ideas." Sometimes it's translated as "ideas" or "forms." These things that we can think about that are the template, or at least the standard, or maybe at the very least it's that which the ordinary humdrum things can participate in to varying degrees: perfect justice, justice itself, beauty itself, goodness itself, circularity itself, health itself. All of these things are, as philosophers nowadays call them, Platonic forms. Ordinary material objects of this world can partake of the various Platonic forms, but they should not be confused with the Platonic forms. But we still--even though we don't bump into the Platonic forms in this world--we can think about them. Our mind has a kind of grasp of them.:

    Of course, the problem is, we're distracted by the comings and goings, the hurly burly of the ordinary everyday world. And so we don't have a very good grasp of the Platonic forms. We're able to think about them, but we're distracted. What the philosopher tries to do--this is Socrates' thought, or Plato's thought that he puts in Socrates' mouth--what the philosopher tries to do is free himself from the distractions that the body poses--the desire for food, the craving for sex, being concerned about pain. All this stuff, hungering after pleasure, all this stuff gets in the way of thinking about the Platonic forms. What the philosopher tries to do, then, so as to better focus on these ideal things, is to disregard the body, put it aside, separate his mind as much as possible from it. That's what Socrates says he's been trying to do. And so because of that, he's got a better handle on these ideal forms. And then, he believes, when death comes and the final separation occurs of the mind and the body, his mind gets to go up, his soul gets to go up to this heavenly realm. Philosophers nowadays call it "Plato's heaven." He gets to go up to Plato's heaven where he can have more direct contact with these things, with the forms.

    Now, I don't have the time here to say enough to try and make it clear why this Platonic metaphysical view is a view that not only is worth taking seriously, but to this day, many, many philosophers think that, at least in it's basic strokes, must be right. But let me at least give you one example that may give you a feel for it. Think of math. Think of some simple mathematical claim like 2 + 2 = 4. When we say that 2 + 2 = 4 or 2 + 3 = 5, we're saying something about numbers that our mind is able to grasp. But what are numbers anyway? They're certainly not physical objects. It's not as though someday you're going to open up an issue of National Geographic where the cover story's going to be "At long last, explorers have discovered the number two." It's not as though the number two is something that you see or hear or taste or could bump into. Whatever the number two is, it's something that our mind can grasp but isn't actually in the physical world.

    That's the Platonic take on mathematics. There are numbers. The mind can think about them. Things can partake of them. If I were to hold up two pieces of paper, there's a sense in which they are participating in "twohood." But of course, this is not the number two here. If I were to rip these pieces of paper, I wouldn't be destroying the number two. So the number two, the numbers, three, whatever it is, whatever they are, are these Platonic abstract entities that don't exist in space and time. Yet, for all that, the mind can think about them. That's the idea. And it's not a silly idea. It seems like a very compelling account of what's going on in mathematics. What mathematicians are doing is using their mind to think about these Platonic ideas of mathematics. Except Plato's thought was, everything is like that. It's not just math, but justice itself is like that. There are just or unjust things in the world. The mind can think about them, but justice itself--this perfect, this idea of being perfectly just--that's something the mind can think about, but it's not here in the world. It's another abstract Platonic form.

    So that's the picture. Plato's idea is that if we start doing enough metaphysics, we can see there must be this realm of Platonic ideas, Platonic forms. And we can see that we are able to grasp them through the mind. This can't be a job the body does, because the body's only got its bodily capacities, right? It's able to do the five-senses thing. It's the soul that thinks about the Platonic forms. And as Plato's then going to go on to try to argue, given this picture of what the mind can do, he thinks he can persuade us that the mind, the soul, not only survives the death of your body, but will last forever. It's perfect. It's immaterial and can't be destroyed. It's immortal. So he offers a series of arguments for that conclusion, for that position, and starting next time, we'll work our way through those arguments.