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Before [Plato's dialogue Phaedo] ends...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.
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