| February 13, 2007 |
Professor Shelly Kagan: We've been working our way through Plato's arguments for the immortality of the soul. And last time I spent a fair bit of time working through objections to, not quite the last argument we're going to look at, but the penultimate argument, in which Plato tries to argue for the simplicity of the soul. The set of connected ideas, you'll recall, were these: that Plato wants to suggest that in order to be destroyed you've got to have parts; to destroy something is to basically take its parts apart. If he could only convince us that the soul was simple, it would follow that it was indestructible and, hence, immortal. He asks, what's our evidence for some things being indestructible? What kinds of things are simple? Well, these are--he then goes on to claim--invisible things, things that don't change. After all, changing is a matter of the rearrangement of the parts. And so, if something can change, it can't be simple. Maybe it could be destroyed. But if we could become convinced that the soul was not composite, if it was something that couldn't change, then it would simple. Perhaps then it would indestructible. And then he goes on to suggest that the invisibility of the soul is evidence for it's being changeless, and hence simple, and hence indestructible. So that's the argument we worked through last time. And I spent a fair bit of time suggesting that if you pin down precisely what Plato means by invisible, the argument doesn't actually go through.
Before leaving that argument, there are a couple of extra remarks I want to make about it. First, we probably shouldn't have been so quick to want to buy into the suggestion that the soul is changeless. After all, if you think about it, it seems that at least on the face of it the soul does indeed change. On one day you believe, for example, that it's hot; on another day you believe that it's cold. On one day you believe that so and so is a nice person; on the next day you believe that so and so is a mean person. You desire to learn the piano, the next day you give up on that desire. Your beliefs, your goals, your intentions, your desires--these things are all constantly changing. And so, at least on the face of it, it looks as though we might well want to say the soul--if we do believe there are souls--the soul is changing as well, in terms of what thoughts and beliefs it's housing.
So we should have been skeptical in the first place of any argument that said, based on the invisibility of the soul, we can conclude that it's changeless. It doesn't seem to be in fact changeless. Furthermore, we should be, or at least we might well be, skeptical of the claim that the soul is simple. Indeed, Plato himself, in other dialogues, argues against the simplicity of the soul. Now, that doesn't mean he's right in the other dialogues, but at least suggests that we shouldn't be so ready to assume that sort of position is correct. In The Republic, famously, Plato goes on to argue that the soul has at least three different parts. There's a rational part that's in charge of reasoning; there's a spirited part that's sort of like the will; there's a part that has to do with appetite, desires for food, drink, sex, what have you. Plato elsewhere argues the soul is not simple at all. So perhaps it shouldn't shock us that the argument he's sketching here for the simplicity of the soul based on the changeless, invisible nature of the soul--perhaps it shouldn't shock us that that argument doesn't succeed after all.
Finally, although I gave Plato, previously, the assumption that if only we could establish the simplicity of the soul, it would follow that soul was indestructible--after all, you couldn't break a soul by tearing its pieces apart if it didn't have pieces, if it didn't have parts--nonetheless, I just want to register the thought that it's not actually obvious that simples can't be destroyed. Well, they clearly can't be destroyed by the particular method of destruction that involves taking them apart. If they don't have parts, you can't take them apart. But for all that, it still seems conceptually possible for a simple to be destroyed in the following sense: it goes out of existence. After all, where did the simples come from in the first place? Well, at least from a logical point of view, it seems as though there's no difficulty in imagining that at one point a given simple didn't exist and then at the next point it popped into existence. Well, how did that happen? Maybe God said--God says at the beginning of Genesis, "Let there be light." So maybe He says, "Let there be simples." At a given moment they weren't there; the next moment they were. Well, after a while maybe God says, "Let the simples no longer exist." Given moment there they were; the next moment, they no longer exist.
Seems as though that idea makes sense, and so even if we agreed that the soul was simple, even if we granted everything in Plato's argument up to this point and said, "the soul really is simple," it still wouldn't follow that it's immortal. We'd still have to worry about the possibility that the simple soul might simply pop out of existence at a given point, perhaps the very point when the body gets destroyed. So I'm inclined to think that this most recent argument of Plato's--the argument from simplicity--no, that's not successful either.
Before leaving that argument, there's one other piece of business I want to discuss. This is a footnote that I put aside, a point that I put aside previously. You'll recall that we were worried about--The objection got raised the right way to think about the soul is like the harmony of a harp. And this was originally offered as a counterexample to the thought that invisible things couldn't be destroyed. But harmony could be destroyed. It was invisible, so invisible things could be destroyed. But I noticed, I mentioned that, look, whether or not this is a problem for the argument, it's an interesting suggestion in its own right. Because the suggestion that the mind is to the body, the soul is to the body, like harmony is to an instrument with strings, seems to me to be an early attempt to describe something like the physicalist conception of the mind. Just as harmony is something that gets produced by a well-tuned instrument, the soul or the mind is something that gets produced by a well-tuned body. Now Plato's got some objections to the suggestion that we should think of the mind as the harmony of the body. And so I want to take just a moment and talk about those objections because, of course, if they were compelling objections that might well give us reason to doubt the physicalist view. Whether or not Plato's arguments for the immortality of the soul work, he might still have some good arguments against the physicalist conception.
But in thinking about these objections, it's important to bear in mind that it's only meant--the harmony analogy is only meant--as just that, as an analogy. Right? The claim isn't, or at least it shouldn't be, understood as saying literally, "the mind is harmony." It's rather, the mind is like harmony; it's the sort of thing to the body like harmony is to a harp, something that can be produced by a well-functioning, well-tuned physical object. A well-tuned instrument can produce melody and harmony. A well-tuned, properly functioning body can produce mental activity. That's the suggestion. And so even if it turns out that there are some ways in which the mind isn't exactly like harmony, it doesn't show us that the physicalist view is wrong.
Well, so let's quickly look at what Plato's arguments were. First--this is, I think, an interesting argument--Plato says, harmony clearly cannot exist before the existence of the harp itself. Right? The melodiousness of the harp can't exist prior to the physical construction of the harp. And if mind were the sort of thing that was produced by the proper functioning of the physical body, then pretty obviously the mind could not exist prior to the creation of the physical body. However, Plato has already argued earlier in the dialogue that the soul does exist prior to the existence of the body. That's the argument from recollection. If the soul exists prior to the body, it can't be like harmony; physicalism has clearly got to be false.
But I said that I didn't find the argument--I tried to explain why I didn't find the argument from recollection persuasive. I certainly do want to agree that if we became convinced that the soul did exist prior to the existence of the body, we would certainly want to agree that the soul is not like harmony. But I don't think the argument from recollection succeeds.
Plato's second objection is to point out that harmony can vary. We talk about the melodiousness of the harp. Well, it could be harmonious in a variety of different ways and, indeed, to different degrees. Something--an instrument--could be more or less harmonious. What it's playing can be in greater or lesser harmony. But it doesn't seem as though souls come in degrees. You've got a soul or you don't have a soul. That's the argument, that's the objection. You've got a mind or you don't have a mind. But perhaps we should--That's the objection, and of course if that was right then again we might have to conclude, well, whatever the mind is, it's not quite like harmony is to the body.
But I'm not so sure we should agree that the mind can't come in degrees. It can at least--The mental aspects can come in degrees. We can have varying degrees of intelligence, varying degrees of creativity, varying degrees of reasonableness, varying degrees of ability to communicate. So just as, we might say, just as the functioning of the harp can come in varying degrees--more or less harmony--the functioning of the body in terms of its mind can come in varying degrees. So that second objection doesn't seem to me very compelling.
Third objection, Plato points out--Socrates points out--that the soul can be good or it could be evil, wicked. When the soul is good, when you've got somebody who has got their stuff together, we might speak of them as having a harmonious soul. If the soul were to the body like harmony is to the instrument and the soul can be harmonious, it would seem as though we'd have to be able to talk about harmony being harmonious. So just as we can talk about the harmony of the soul, we'd have to be able to--if the soul is like the harmony of the body--we'd have to be able to talk about the harmony of the harmony. But we don't talk about harmony of the harmony.
I'm not quite sure what to make of this objection. This might be a point where it would be well to remind ourselves of the fact that the suggestion was never that the soul just literally is harmony. It's just similar to harmony, says the physicalist, in the way that harmony gets produced by the body--by the instrument. In that same way, mind or mental activity gets produced by the body. We don't have to say that everything that's true of the mind is true of harmony and everything that's true of harmony is true of the body--or the mind.
Still, I think there's a bit more we can say in response to this objection, and that's this: Just as it's true that we can talk about minds or souls being good or wicked, we can talk about different kinds of harmony. There are--Certain harmonies are sweeter than others; some of them are more jarring and atonal or discordant. Although we might not normally talk about how harmonious the harmony is, it seems as though harmonies can come in different sorts and different kinds. And then, it turns out we really would have an analogy to the mind, which can come in different sorts and different kinds. So I think this third objection isn't really compelling either.
Finally, Plato raises one more objection. He says, "Look, the soul is capable of directing the body, bossing it around, and indeed capable of opposing the body." You know, your body might want that piece of chocolate cake, but your soul says, "No, no. You're on a diet. Don't eat it." Right? Your soul can oppose the body. But if the soul was just harmony of the body, how could it do that? After all, the harmoniousness of the harp can't affect what the harp does. All the causal interaction is one way, as we might put it. In the case of the harp and the musicality and the melodiousness and the harmony, the physical state of the harp causes the melodiousness to be the way it is. But the harmoniousness of the harp, doesn't ever change or alter or direct the way the physical object the harp is.
In contrast, not only can the body affect the soul, the soul can affect the body. So that suggests it can't really be like harmony and the harp after all. I think that's a pretty interesting objection. Since we do think, at least in the kind of position that we've been taking for this class, that the soul can affect the body, we might ask, how could it be that it's--that the physicalist view is right? If talk about the mind is just a way of talking about what the body can do, how can the abilities of the body affect the body itself?
I think the answer to this objection is probably going to be something like, what's really going on when we talk about the soul affecting the body is that--when we say certain functions of the body are affecting the body--that certain mental functions are affecting the body--how does this happen causally? Well, something like the physical parts of the body that underwrite, that lie beneath the proper functioning, the proper mental functioning of body, those are able to alter the other parts of the body.
So look, right now I'm telling by body, "Wiggle my fingers." My soul is giving instructions to my body. How does that happen? That's my mind giving instructions to my body. How does that happen on the physicalist view? Well, my mind giving instructions to my body, "wiggle my fingers," is just one part of my body, my brain, giving instructions to another part of my body, the muscles in my fingers. So, although we talk about the mind altering the body, strictly what's going on there, says the physicalist, is just one part of the body affecting another part of the body. Can we have something like that with a harp? Well, maybe not. Right? Maybe the harp's too simple a machine to have one part of it affect another part of it in that way. Even if that were true, that wouldn't give us reason to reject the physicalist conception. It would just give us reason to think the harp's not very much like the mind and the body. It's just the beginnings of a picture, of a physicalist picture.
Still, even if we think about the harp and musicality, I think we can see something analogous. Suppose I pluck a string on my harp, producing a certain note. As we know, the vibrations of one string can set into play the other strings vibrating as well. And so, suddenly, what's happening in one part of the harp affects what's going on in other parts of the harp. The musicality of my playing a certain chord on the harp may create certain kinds of overtones in the harp, setting the harp vibrating in various other ways. Well, that would be analogous--perhaps not a precise analogy, but at least a rough analogy to what goes on when my mind affects my body--to--if one part of my body affects other parts of my body.
So, on the one hand, I want to give Plato a fair bit of credit for taking the physicalist view seriously enough to try to criticize it. And since when he was writing there weren't the kind of complicated thinking machines that we've got nowadays, it's no criticism of Plato that he used simple machines like musical instruments to try to think about what a physicalist picture would look like. I want to give him credit, but I also want to suggest that the objections that he raises to the physicalist view just don't succeed. All right.
Now, there's one other argument that I want to consider in our dialogue. And after the appeal to the simplicity of the soul, there's a very long complicated discussion about what constitutes an adequate explanation, and Socrates gives some of his history there and talks about what he's looking for in trying to find adequate explanations of things. And these passages are very, very difficult and happily for our purposes we don't really need to go there.
Before the dialogue ends though, there's one further argument, which I'll dub, "the argument from essential properties." Now again, it's important to bear in mind as we try to make sense of this passage that Plato is writing at a time when we don't have, we didn't have, all the conceptual apparatus that we have nowadays. We stand on his shoulders; we've inherited some of the distinctions that he was the first to try to put into play. And so although, again, he's about to--I'm about to sketch or reconstruct an argument and claim that that the argument doesn't actually work, this isn't really meant by way of being dismissive of Plato. I want to give him a tremendous amount of credit. He's trying to see his way through a morass of issues that are still confusing to us today, though I think we can see somewhat further than he was able to see.
At any rate, the distinction we need to understand the final argument, is the distinction between an essential property and a contingent property. An essential property is a property that a given object must have; it always has as long as it exists at all. A contingent property is a property that an object may have, may happen to have its entire existence, but could've existed without. So my car is blue. That's a contingent property of my car. I could take it to the paint shop and get it painted red, in which case it would be red. It would no longer be blue, but the car would still exist. My car is blue, but it could be red; it could exist as a red car. And even if I never, over the entire course of existence of my car, never get it painted, so that from the moment it came into creation to the moment it gets smashed it's always blue--still, we understand perfectly well the idea that it could've been red. There's nothing incompatible with the idea that this car exists and is red. So that's an example of a contingent property.
And I might have a pencil, and the pencil is whole. And I never break it, but I could've broken it. That's a contingent property, whether the pencil is whole or broken. I take a piece of metal; it's a contingent property whether it's straight or bent. I bend it; now it's bent. I might straighten it back out; now it's straight. Many, many properties are contingent properties. You're happy, you're sad, you're awake, you're asleep.
But some properties, in contrast, are essential properties. For the particular thing that we're thinking about, it's not possible to have that thing and not have the property in question. Plato gives the example of fire and being hot. Fire is hot. That's a property that it's got, but it's not a contingent property; it's an essential property. It's not as though some fire is hot and some fire is cold or, "Oh yes, it just happens that over the entire life of the fire the fire is hot, but we could have made it cold." There's no such thing; there could be no such thing as cold fire. As long as you've got a bit of fire, it's hot. Take away the heat, you take away the fire, you destroy the fire. You can't have cold fire. That's an example of an essential property.
That is to say, Plato sees, as indeed I take it we all see at least roughly, that there's some sort of distinction there, and he's trying to see his way clear on these matters. That remains a controversial question today--until today. Are there really essential properties in the way we take there to be? If so, which properties are essential? Which ones are contingent? Water is composed of H2O--that's its atomic structure. Is that an essential property of water? Could you have something that was water without being composed of H2O--hydrogen and oxygen in that way? Well, some people say yes, some people say no--but most of us we want to say, "Oh, there's an example of an essential property. To be water, you must have that atomic structure." All right. That's the thought.
Now, armed with this distinction, Plato says, "Here's an essential property for the soul. Wherever there's a soul, it's alive." Now, by "alive," I take it Plato means it's thinking, or it's capable of thought. Wherever you've got a soul, you've got something capable of thought. I suppose one could try to resist this claim of Plato's, but I find it reasonably plausible. I start thinking about minds, and I ask myself, "Could there be a mind that was incapable of thought?" Maybe not. Maybe that's just built into minds by definition. Just like you couldn't have something that was fire without it being hot, you couldn't have something that was a mind without it being capable of thought. It's important to say the word capable here. Right? It's not as though all minds always are thinking. I presume there are stretches during the night when my mind is not thinking, not dreaming. Still, it's capable of thought even thought it's not thinking at the time. But you say, "No. Here's a mind that's not even capable of thought." I want to say, "Then, it's just not a mind."
So all right, maybe being capable of thought is an essential property of the mind. Plato thinks about the mind in terms of souls, so maybe being capable of thought is an essential property of the soul. And I think that's what Plato means when he suggests the mind is essential--the soul is essentially alive. It's a necessary property, as we might put it, of the soul, that it's alive, that it's capable of thought. So I want to say, "Not an implausible claim." Let's give it to Socrates.
But once we give it to Socrates, Plato thinks now he's pretty much done. After all, think about what it means to say that something's got an essential property. Fire's got the essential property of being hot. It means there are only two possibilities. Either you've got some fire and it will be hot, or the fire has been destroyed, it's been put out. Those are the only two possibilities. You either have--If heat is an essential property of fire, either you've got some fire and it's hot, or the fire no longer exists, it's been put out. There's no third possibility of a non-hot fire, of a cold fire. So, if you've got the claim that life's an essential property of the soul, only two possibilities: either you've got the soul and it's alive--to wit, it's capable of thought--or the soul's been destroyed.
But Plato thinks we can rule out that other possibility. How? Well, it's by thinking about this particular essential property. There's nothing in the idea that fire has the essential property of being hot to make us think it couldn't be destroyed, but there is something, Plato thinks, in the idea of being essentially alive to rule out the possibility of its being destroyed.
In fact, as you say the very words you begin to feel the force, the pull of Plato's position. If the soul is essentially alive, if it's necessarily alive, it's got to be alive. It can't be destroyed. That's, I think, at least the kind of argument that Plato means to put forward. He does it in terms of the phrase, "deathless." He says, I want to actually get this up here on the board [See Figure 9.1]. One--life is an essential property of the soul. But if you think about what that means, it follows that the soul is deathless. After all, if the soul is--If it's essentially alive, that means it can't be dead. So it's deathless. But after all, anything that's deathless can't die. So the soul cannot die, which is just to say it's indestructible. So, soul can't be destroyed. Something like this seems to be Plato's argument. One, life's an essential property of the soul, but we can just summarize that by saying the soul is deathless. But if the soul is deathless, it can't die. If it can't die, it can't be destroyed, it's indestructible. So the soul can't be destroyed. Remember, once we said the soul was alive, there were only two possibilities. If the soul was essentially alive, either we have the soul, it's alive, capable of thought, or it's destroyed. But if the soul can't be destroyed, that leaves only the possibility the soul is alive, capable of thought. That's just what Plato thinks; the soul will always exist, capable of thought.
Well, it won't shock you to hear that I don't think this argument actually works. And I think where it goes wrong is there's a certain kind of ambiguity in the idea of being deathless. What does it mean to say that something is deathless? I think there are two possible interpretations of that phrase [See Figure 9.2]. If something is deathless, then it can't be that--well, what? One possibility is, it can't be that the soul exists and is dead. That's one possible interpretation. To say that something is deathless means you'll never have a soul that exists and the same time that it exists it's dead. But there's a second possible interpretation of deathless. It can't be that the soul was destroyed. It's very easy to confuse these two interpretations of deathless, A and B. And basically, this is what I think is going on with Plato. He's running back and forth between these two interpretations. If life is an essential property of the soul, then that means we will never have, as it were, a soul in our hand that exists and is dead. Just in the same way that you'll never have a piece of fire in your hand, as it were, that exists and is cold. It can't happen. Wherever you've got a soul, it is alive. So it's deathless in sense number, in sense A.
Since wherever you've got a soul it must be alive, it couldn't be the case that the soul exists and is dead. So it's deathless in sense A. But for all that, it could still be, logically speaking, that the soul could be destroyed, just like a fire can be put out. We could imagine something that couldn't be destroyed. Then of course it would be deathless in sense B, a much stronger sense of deathless. What Plato needs, what Plato wants, is to convince us that the soul is deathless in sense B: It's true of the soul that it can't be that it was destroyed. But all he's entitled to is sense A: You'll never have a soul that exists and is dead, because being alive is an essential property of the soul. But the mere fact that where there's a soul it's alive, doesn't mean the soul couldn't be destroyed. Just like from the fact that where there's fire it's hot doesn't mean the fire can't be destroyed.
It's, I think, pretty easy to get confused in thinking about these issues. It's difficult to see your way clearly to these two different notions of deathless. It's difficult to get to the point where you can clearly use the language of essential properties without getting screwed up. Still, I think that's what happened here. We grant Plato the thought that the soul has an essential property of being alive; from this, it follows that where there's a soul it is alive, and hence, it's deathless in sense A. But once we start thinking about the category, the notion of being deathless, we're tempted to re-understand that as being deathless in sense B, can't be destroyed. And that, I think, doesn't follow.
All right. Where does that leave us? Plato's gone through a series of arguments for the immortality, the indestructibility of the soul, and I've argued that none of them work. Some of them are worth taking seriously. That's why we've spent the last week or so going over them. But none of them, as far as I can see, are successful. And I hardly need remind you that this comes on the heels of a previous week or two in which we talked about various other arguments for the very existence of an immaterial soul. And I've argued that none of those arguments work either. As far as I can see then, the arguments that might be offered for the existence of an immaterial soul, let alone an immortal soul, the arguments don't succeed. It's not that the idea of a soul is in any way silly; it's not that it's not worth thinking about. It's that when we ask ourselves, "Do we have any good reason to believe in an immaterial soul?" and actually try to spell out what those reasons might be, as we look more carefully we see the arguments are not very compelling.
So I'm prepared to conclude there is no soul. There's no good reason to believe in souls. And I so I conclude--at least there's no good enough reason to believe in souls--and so I conclude there are none.
And this is the position that here on out I'm going to be assuming for the rest of the class. I'm going to have us continue to think about death, but now think about death from the physicalist perspective. Given the assumption that the body is all there is, that talk about the mind is just a way of talking about the abilities of the body to do certain special mental activities. There are no extra things beyond the body, no immaterial souls.
Now, it wouldn't be unreasonable at this point to accuse me of begging the question. After all, think about what I've done. I've put all of the burden of proof on the fan of souls. I've asked the dualist, "Give me some reason to believe your position." And I've said the arguments on behalf of dualism aren't very convincing. Don't I now need, in fairness, to do the same thing for the physicalist? Don't I need to turn to the physicalist and say, "Give me some reason to believe that physicalism is true? Give me some reason to believe souls don't exist." After all, I turned to the dualist and said, "Give me some reason to believe in souls." Those arguments didn't work. Don't I now need to turn to the physicalist and say, "Give me some reason not to believe in souls? Prove that souls don't exist." Isn't that fair?
So let's pause and ask ourselves, how do you go about proving that something doesn't exist? Or, to put it in a slightly better way, when do you need to prove that something doesn't exist? When we have examples of things whose existence we don't believe in, how do we decide when we're justified in disbelieving them? Take something like dragons. Let me assume that everybody in this class, in this room, does not believe in the existence of dragons. How do I prove that there aren't any dragons? I mean, there could be dragons. Couldn't there? But there aren't any. We don't believe in dragons. So don't you need to disprove the existence of dragons before you continue on your way of not believing in them? I imagine nobody in this room believes in the existence of Zeus, the Greek god. How do you disprove the existence of Zeus? Don't we have an obligation to prove that Zeus doesn't exist? But how could you do that?
Well, unsurprisingly, I don't actually think you do have an obligation to disprove those things. That doesn't mean you don't have any obligations. You just have to be very careful about what the intellectual obligations come to. So back to dragons. What do we need to do for dragons? Well, the most important thing you need to do, to justify your skepticism about dragons, is to refute all of the arguments that might be offered on behalf of dragons.
My son's got a book about dragons with some very nice photographs. So, one of the things I need to do in order to justify my skepticism about dragons is explain away the photographs, or the drawings, or what have you. I need to explain why it is that we have pictures, even though there really aren't any dragons. Well, some of these are just drawings, and people were drawing things out of their imagination. The things that look like photographs, nowadays with computer generated graphics, you can make things that look like photographs, and given Photoshop you can make things that look like pictures of just about anything that doesn't even exist.
How do I prove there aren't any unicorns? Well, I look at the various reported sightings of unicorns and I try to explain them away, "Well, you know, it's the first time people, Europeans, saw the rhinoceros. It sort of reminded them of a horse with a big horn. And maybe that's where the reports of rhinoceros came--or the various reports of the unicorn came from. The various unicorn horns that have been offered in various collections, upon examination by biologists turn out to be narwhal horns, horns from whales, and so forth and so on." You look at each bit of evidence that gets offered on behalf of the unicorn and you debunk it. You explain why it's not compelling. And when you're done, you're entitled to say, "You know, as far as I can tell, there aren't any unicorns. As far as I can tell, there aren't any dragons." It's not as though you've got some obligation to look in every single cave anywhere on the surface of the Earth and say, "Oh, no dragons in there, no dragons in there, no dragons in there, no dragons in there, no dragons in there." You are pretty much justified in being skeptical about the existence of dragons once you've undermined the arguments for dragons.
Now, there might be something more that you could do. In at least some cases, you can go on to argue the very idea of the kind of thing we're talking about is impossible. It's not just--Take dragons again; it's not just that there's no good reason to believe in dragons. The very idea of a dragon may be scientifically incoherent, at least given the science as we understand it. I mean, dragons are supposed to breath fire. So that must mean they've got fire in their belly. But how does the fire continue to exist in their belly, absent--lack of oxygen? Why isn't the fire in their belly busy burning and destroying the membranes of their stomach or whatever? All right, you could, I suppose, try to prove that dragons were scientifically impossible. And if you could, then you'd have an extra reason to not believe in them. But it's not as though you have to prove that something's impossible to be justified in not believing in it. I don't think unicorns are impossible. I just don't think there are any. Surely, there could be horses with a single long horn growing out of their forehead. There just aren't any.
So armed with these ideas, come back to the discussion of souls. Do I, as a physicalist who does not believe in the existence of souls, immaterial entities above and beyond the body, do I need to disprove the existence of souls? "Well, there's no soul here, no souls there." No. What I need to do is to take a look at each argument that gets offered for the existence of a soul and rebut it--explain why those arguments are not compelling. I don't need to prove that souls are impossible. I just need to undermine the case for souls. If there's no good reason to believe in souls, that actually constitutes a reason to believe there are no souls.
Now, if you want to, you could go on and try to prove that souls are impossible in the same way that maybe dragons are impossible. But I'm not sure that I myself find such impossibility claims especially persuasive. I don't believe in the existence of souls, but that doesn't mean that I find the idea of an immaterial entity like the soul impossible. Now, some people might say, "Well, you know, it violates science as we know it. It violates physics to have there be something immaterial." But science is constantly coming around to believe in entities or properties that it didn't believe in previously. Maybe it just hasn't gotten around to believing in souls yet. Or if current science rules out the possibility of souls, maybe we should say, "So much the worse for current science."
So I'm not somebody who wants to say we can disprove the existence of souls. I don't think we can disprove them. I don't think the idea of a soul is in any way incoherent. There are philosophers who've thought that. I'm not one of them. But I don't think I need to disprove the existence of a soul to be justified in not believing in it. Unicorns aren't impossible, but for all that, I'm justified in thinking there aren't any. Why? Because all the evidence for unicorns just doesn't add up to very convincing case. Souls are not impossible, but for all that, I think I'm justified in believing there aren't any. Why? Because when you look for the--look at the arguments that have been offered to try to convince us of the existence of souls, those arguments just aren't very compelling, or so it seems to me. So, from this point on out, I'll be assuming the physicalist view is correct, and will be thinking about the issues of death as they'd be understood from the physicalist point of view.
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