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OK. Welcome to our fifth general philosophy lecture, and today we're going to be returning to the topic of the mind.

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And starting on the topic of personal identity, there's quite a lot to say on personal identity and some of the historical stuff.

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You will see that I've put in an appendix to the handout.

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I won't actually be talking through the slides on the appendix, but you can get that stuff online from my previous sets of lectures.

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OK, here we've got, uh, Descartes and John Locke, who really started off the early modern debate on personal identity.

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Frank Jackson, we'll see an important argument of his.

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Bernard Williams a very provocative thought experiment that he came up with Bernie Williams was for many years,

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white professor of moral philosophy at Corpus and Derek Parfitt, who spent his career at All Souls here in Oxford.

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So we've already seen a little bit about Cartesian dualism.

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He's a duellist interaction is HTC's mind and body is quite separate substances, but they're able to influence each other.

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So if I decide to raise my arm, that's my mind influencing my body.

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If on the other hand, I stuck my toe in feel pain, that's my body influencing my mind.

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Two views that will be coming up with in later discussion Eppie phenomenal ism.

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That's the claim that mental events are phenomenal. They're caused by brain events, but they are causally inert themselves.

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So our consciousness, our feelings are by-products of what's going on in our brains by products,

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which themselves have no causal impact and physical ism.

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We've come across it used to be called materialism in the early modern period, the claim that only physical things exist.

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So therefore the mind has to be a phenomenon arising from material things.

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We saw that there's some difficulty in defining exactly what physical ism entails.

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Temple's problem will be coming back to that. But let's just have those three positions in our mind in what follows.

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OK, so this is repeating to some extent stuff that we saw in the second lecture Cartesian Dualism.

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The body's material. The mind is immaterial. Body and mind have quite separate properties, in particular the body's fundamental property.

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Its essence is extension extended ness in space, whereas the mind's fundamental property is thinking.

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Now notice this substance dualism. It's not just saying that there are mental and physical properties, it's saying there's mental and physical stuff.

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So as we saw when we were discussing this before, it's entirely possible for a materialist someone who thinks the the only stuff is material.

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Nevertheless, to think that material stuff can have mental properties, that that wouldn't make them a Cartesian duellist.

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Now, in the discourse on the method, Descartes seems to argue like this one can debate whether this really is Descartes argument or whether maybe

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he's condensing somewhat misleadingly a more elaborate argument like the one he presents in the meditations.

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But at any rate, this argument seems to be there, and it gives a useful example to ponder.

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I can doubt that my body exists. I can't doubt that I exist like my mind.

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Therefore, I am not identical with my body, and this is not a good argument.

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It's fallacious. We can see it's fallacious by taking a different example.

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The Morning Star in the Evening Star so has phosphorus, are ancient names for the Evening Star and Morningstar, respectively.

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The Evening Star is the brightest object apart from the Moon that appears in the evening.

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The Morning Star is the brightest object that appears in the morning, obviously after The Sun has gone down and before the Sun comes up, respectively.

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We now know, but the ancients didn't know that these are in fact the same object the planet Venus.

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Now somebody could perfectly well doubt that these phosphorus.

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OK, you might not believe the astronomers, or you might simply not have been informed, but you can't doubt that phosphorus is phosphorus.

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Any object is identical with itself.

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So it follows, according to Dark Arts Logic, or it seems to that has is not phosphorous, and we know that's false.

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So there must be something wrong with the argument. Well, the argument is implicitly appealing to something that's commonly called Liden,

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it's his law and likeness is law basically says that if A and B of the same thing.

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One in the same than any property that they has.

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Must also be a property of B.

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That just seems common sense and what they got to argument seems to be doing is treating being doubted by me to exist as a property.

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So I can't doubt that I exist. I can doubt that my own body exists.

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Therefore, I and my body have different properties because one of them has that property of being doubted and the other doesn't,

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and therefore they can't be the same thing. But there's a fallacy here because being doubted by me to exist is not a genuine property.

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It's a relation. It's a relation between me and something which is presented in a particular way.

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So the epistemological relations between me and Hesburgh and me and phosphorous may be different.

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You know, I may have seen the Evening Star many times, but never seen the morning star, in which case my beliefs about the two will be different.

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That doesn't mean that they're not the same object.

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So the way in which we come to know something or be aware of it or become certain of it need not reflect its ultimate nature.

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And there's another potential fallacy lurking in dark arts works.

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As he's well known and we we've seen before, Descartes finds this principle.

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I think therefore I am I can be absolutely certain of my own existence because I am thinking.

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And from that, it follows that I am a thinking thing.

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In the sense, I am something that thinks that Descartes slides from I am a thinking thing in that sense, too.

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I am something whose essence is to think, and that's a different claim.

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Now, John Locke notoriously speculated in his essay it caused a lot of upset.

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He speculated that God, if he wished, could make matter think.

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So imagine you've got a stone, an unthinking stone,

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a man God in his omnipotence decides to give the stone the power of thought, according to Locke, that would be possible.

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Now, clearly, in that case,

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you'd have a thinking thing whose essence is not thinking there's nothing essential to the stone about being a thinking thing.

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It just happens to have been given the property of thinking. Descartes seems to think that our thought is absolutely essential to us.

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That doesn't follow simply from the fact that we are a thinking thing.

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So that again, it's an example of sliding from epistemology, from how we know about something to drawing a conclusion about its ultimate nature.

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Now in the meditation's culminating in meditation six, the last meditation, Descartes gives a more sophisticated argument.

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And here he appeals to a supposed clear and distinct perception of the nature of things.

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So I clearly and distinctly understand myself as essentially a thinking, non extended thing.

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Now again, you can we can question the premise, OK, but this is how Descartes is arguing.

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I have a clear and distinct understanding of body as extended and not essentially thinking anything

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that I clearly and distinctly understand could be created by God in the way that I understand it.

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So if you imagine you've got a very clear and distinct understanding of what a particular scenario would involve, there's no contradictions in it.

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In that case, an omnipotent God could if he wish to create things like that.

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It follows, then that God could create me separately from my body, and therefore I am in fact genuinely distinct from it.

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So I've mentioned some of the premises here can be disputed, I don't want to go into those, but let's look at that final step.

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God could have created my mind separately from my body.

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Therefore, it is possible for my mind to exist without my body existing.

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Therefore, my mind and my body are in fact, distinct things.

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Now you might worry about this. You might think this.

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This looks illicit because it's a move from what could possibly be the case to what is actually the case.

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But the logic there does seem quite strong. Let's go back to his brass and phosphorus, Jespersen phosphorus are not, in fact, distinct things.

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They are, in fact one and the same thing. It follows from that that actually it is not possible for one of them to exist without the other existing.

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So if somehow we knew that he was in fact possible for us to exist without phosphorus existing, that would imply that they were distinct things.

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And so Descartes argument seems to be using that kind of logic,

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if it's genuinely possible for my mind to exist without my body because God could have created them that way,

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then my mind and my body must in fact be different things. So here we have an argument from metaphysics to metaphysics.

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But how can Descartes establish the truth of his final premise?

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Let's say he seems to be arguing God could have created my mind separately from my body.

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For all I know, therefore, it's genuinely possible for my mind to exist without my body existing.

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So if that's the way he's arguing, if in fact his claim that God could create my mind without my body is based simply on for all I know,

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then I'm afraid we're back again to an argument from epistemology to metaphysics.

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Let's take Piro, the ancient sceptic. I assume Pirro, for all Pirro knows Hester's could exist without phosphorus.

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Right? You could have the evening star existing without the morning star.

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As far as he knows, it doesn't actually follow that it's genuinely possible for his spirits to exist without phosphorus existing.

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So again, this move from epistemological possibility to metaphysical possibility is very dodgy.

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So let's just pin those two down, epistemological possibility is possibility for all I know.

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So suppose somebody says it is possible that one two three four five six seven eight nine one two three is a prime number.

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What they mean is, for all I know, it's a prime number. It's possible.

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I mean, imagine you're given a list of numbers and you asked to check which of those are prime and you work through them and you say,

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Well, I've checked the first five, but the the last five might all be prime for all I know.

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It doesn't actually follow that those those numbers could genuinely, as a metaphysical possibility, be prime.

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And in fact, the number I've just cited one two three four five six seven eight nine one two three is in fact divisible by three.

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You can check that by adding up the digits and see that they divide the sum divide by three.

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So it's not actually metaphysically possible that that be a prime number.

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So we've got two kinds of possibility, there's epistemological possibility.

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Think for all I know and there's metaphysical possibility what is genuinely possible in the nature

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of things that is commonly elucidated in contemporary philosophy in terms of possible worlds.

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So when we say it is possible or possibly true, we mean there is some possible world in which is true.

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So think of a possible world as being an imagined way that things could be,

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except it's got to be a coherent way things could be if it's going to be a possible world.

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It better not contain any contradictions. And something is necessarily true if it's true in every possible world.

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So that number is divisible by three in all possible worlds.

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Right. It's a necessary truth. It could not, possibly in the metaphysical sense, be false.

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Now, how can we establish possibilities in necessities? I've said that we can we can try and think about possible scenarios, ways things could be.

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We try to conceive a situation. And if we succeed in doing that, we judge it possible.

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That's a standard way of doing things.

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And you'll see here we have Jack Berkeley and Hume all appealing to the conceive ability principle, the humour appeals to it something like 30 times.

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So he uses it a lot. Whatever we conceive is possible, at least in the metaphysical sense.

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Locke also seems to allude to the principle. So it's it's pretty popular in the early modern period.

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But you can see that there is a problem with the conceive ability principle and a nice way of focussing on this is gold box conjecture.

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Back when I was a first year student, we had three nice examples, and one of them was the full colour theorem and one of them was famous last theorem.

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And one of them is gold box conjecture. And both of the other two have since been proved.

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So please, if any of you were mathematicians, as some of you know that we will be tried to avoid proving Globus conjecture, please.

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At least while my career in philosophy continues because I don't know quite what example I'll go for if I lose this one.

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OK, so go both. Back in 1742, he conjectured every even numbered every even integer greater than two can be written as the sum of two prime numbers.

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OK. And I've given some examples that now people have tested this, as you can imagine by computer,

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they've gone through huge numbers, and so far no counterexample has turned up.

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If I had to bet, I would say, I reckon Girlboss conjecture is probably true,

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but such bets are dodgy with mathematical things, it's not quite clear how far our normal inductive practises work there.

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It might turn out to be false. We just don't know.

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OK. Can I conceive that gold box conjecture is true?

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Well, apparently, yes, I just said if I had to bet, I'd bet on it being true.

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Doesn't that require my conceiving, it being true? But I can also conceive of it being false contact.

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I can imagine what it would be know to read in the paper tomorrow.

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Some mathematicians somewhere has come up with some counter example to gold box conjecture.

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It's nothing inconceivable about that. But according to the conceive ability principle,

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like it's impossible for me both to conceive that go conjecture is true and conceive that it's false because if I can conceive of it,

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being true in the conceive ability principle is correct, then actually go bust conjecture is possibly true.

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And if I can conceive of being false on the conceivable security principle is correct, then go bust conjecture is possibly false.

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But an arithmetical claim can't be both possibly true and possibly false an arithmetical claim, if true, is necessarily true.

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There's no way that a number of its prime can be possibly not prime or a number

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that is the sum of two other numbers could possibly fail to be the sum of that.

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So it looks like if we want to retain the conceive ability principle, we're going to have to say that we're talking about conceive ability in a fairly

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strong sense to conceive of something in such a way as to guarantee its possibility.

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You actually have to grasp what it would be for it to be true in a fairly full blooded way,

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a way that will not apply to something an infinite claim like gold dust conjecture.

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OK, so I raised that problem. This is still a matter, incidentally, of live philosophical debates.

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A decade or so ago, there was a collection of papers published on the conceivable bility principle, with contemporary philosophers debating it.

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The problem here is that if we don't have something like the conceive ability principle, then how can we establish that there are other possibilities?

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But on the other hand, it looks like just going by what we think we can conceive may not be an entirely reliable criterion.

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Now back to Descartes, I'd said Descartes arguments are not particularly persuasive because they rely on claims about his grasp of

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himself as an essentially non extended thing and his body as an essentially extended non-thinking thing.

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But. The notion of conceive ability has been turned against Descartes in order to actually cast doubt on his theory,

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not just on his premises, but to claim that there is something internally incoherent about Cartesian dualism.

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And this focuses on the interaction, it's claimed the fact that you've got mind,

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this thinking on extended stuff, you've got body, this extended non-thinking stuff.

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And yet there is supposed to be causal interaction between them.

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And it's often been put against Descartes that this kind of interaction is completely mysterious, unintelligible, even incoherent on his theory.

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And I just want to point out for Descartes that that might be a serious problem.

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This is debated by scholars. I'm not convinced that it's a serious problem even for Descartes, as many claim.

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But if it is a problem for Descartes, the reason is because Descartes often talks as though causation ought to be intelligible.

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But notice Hume doesn't make any such claim, think back to humans, Adam thought experiment.

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Hume thinks there is nothing specially intelligible about one billiard ball making another billiard ball move.

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It's just habit. It's seeing it again and again. That makes us find it so natural that makes us think we understand it when really we don't.

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In such it, if we go on that theory, therefore I'm humans.

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View of causation. Causation just is a matter of one thing regularly being followed by another.

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Why shouldn't that apply to mental and physical things?

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There is, however, an explanatory gap here. It's very difficult to imagine I'm put yourself in the position of God, right?

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You are about to create a thinking thing that interacts with physical things.

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Try to imagine what sorts of causal laws you could come up with.

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It's not so easy. To come to contemporary discussions of these things.

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Appeal is quite often made to something called the causal closure principle.

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This is the principle that physical event. So the probability is of physical events are determined entirely by physical causes.

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And this is also referred to as the completeness of physics.

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So the idea is if you want to give an account of physical events, all you need to appeal to is other physical events and physical laws.

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Notice that it doesn't imply determinism, you could go for the causal closure of physics and still allow probabilities,

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for example, in quantum phenomena or whatever. But if causal closure is true, every single movement of my mouth and hands and so forth,

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which are obviously physical happenings, have a complete physical explanation.

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And you can see that if you take this principle, which is very popular amongst contemporary philosophers of science,

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it seems to rule out the possibility or it might seem to rule out the possibility that mental events can have any causal impact.

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OK, so this again, seems to be a problem for interaction between mind and body.

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And you might as a result, think, well, OK, we better just say mine is completely physical.

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But on behalf of duellist and others, I just want to point out causal closure is often assumed as education common sense.

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People who are working in science tend to assume that ultimately everything will have a physical explanation.

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But I do want to point out that we don't have actually any compelling evidence for that.

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The laws that we have in science are typically all other things being equal laws.

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You know, force equals mass times acceleration, so a body will continue to move in a straight line at a constant speed unless acted upon by a force.

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Yeah, but maybe there are mental forces. Maybe there are. How would you rule that out?

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It's not like the experiments that physicists do can control for the possibility of mental events having physical effects in the brain.

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And I can't see how any experiment yet devised would rule that out.

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There might be social stuff that's interacting with our neurones.

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I'm not claiming this is plausible or it's something I believe. But you know, let's get real with regard to how much can be shown by our experiments.

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It's not obviously absurd. And in previous generations, plenty of very good thinkers thought the contrary.

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Let's now bring an evolutionary perspective into this. And as I've said before, when in the second lecture,

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compared to many of the sorts of speculations that we've been dealing with, evolutionary science is very solidly founded.

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We've got extremely good evidence for ourselves being evolved from lower forms of life.

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Now, if human minds evolved without special divine intervention.

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I mean, obviously, you could say, well, at some point in the evolutionary progression,

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God injected a soul into the human mind that doesn't look very plausible,

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but it's very hard to see without that how any completely distinct mental substance could get involved in a physically evolving system.

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So dualism actually does seem to me very implausible, but not so much for physical reasons, but rather for evolutionary reasons.

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Moreover, if you think about very familiar mental physical correlations, if we eat healthy food.

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Suppose, for example, we eat honey, you might think honey.

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That's not very healthy. It's full of calories. Yes.

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But when we were evolving, you know, hundreds of thousands of years ago, the search for calories was crucial.

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Right? You weren't likely to overeat, but you were quite likely to starve. So eating something that's full of calories brings us a lot of pleasure.

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Because in the evolutionary scenario, it's good for us.

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And things that damages causes pain. This is entirely familiar.

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But why would that be true if mental happenings had no physical upshot?

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If my consciousness of pain or pleasure is just an epic phenomenon, if it actually has no causal impact on how I behave,

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then it cannot have any evolutionary impact on who survives and who doesn't.

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Who reproduces and who doesn't. So the fact that there is this very familiar correlation between pleasurable

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sensations and things that in the evolutionary scenario were good for us and painful,

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painful sensations and things that were bad for us, that demands to be explained.

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And the obvious explanation is an evolutionary one that's only going to work if there is some interaction between what happens in our minds,

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our feelings and so forth. And physical things, how our bodies behave.

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So I'm suggesting that even though we find it extremely hard to understand

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what's going on in the interaction between our consciousness and our bodies,

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I'm confident that these considerations are strong here, unlike the the general metaphysical claims about physical ism.

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Now I've been talking about consciousness, that word can be used in a number of ways.

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The particular one that's most prominent in these discussions in philosophy of mind is what's commonly called phenomenal, conscious consciousness.

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The the what it's like,

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what it is like from the inside to experience things and a common hypothesis that philosophers like contemplating about these things.

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The so-called zombies. Not these kinds of zombies. All right.

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A philosophical zombie is essentially a physical duplicate of me,

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say a molecule for molecule identical but with no consciousness following all the same

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physical laws with neurones that work in exactly the same way as mine but no consciousness,

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the lights seem to be on nobody at home now, appealing to the conceive ability principle.

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You might think, well, zombies are perfectly conceivable.

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Why shouldn't we conceive an exact physical duplicate of me who acts according to exactly the same physical laws and so forth,

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and yet is not conscious? Now, if we accept that as a genuine possibility, then we can argue like it, like this.

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Zombies are a genuine possibility.

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So human brain states like mine could exist exactly as they do without being accompanied by phenomenal conscious states.

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Therefore, phenomenological, sorry, therefore phenomenal conscious states are not human brain states, and therefore physical ism is false.

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So appeal to the possibility of zombies can be used and is used to argue for substantial conclusions about the nature of consciousness.

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Personally, I think the problem here is going to be to establish that the premise clearly

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somebody who is a physical asset is simply going to deny that zombies are in fact,

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a genuine possibility. I want briefly to mention another influential argument.

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It's on your reading list, I'm not going to say very much about it, but I shall just introduce it.

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This is the so-called knowledge argument of Frank Jackson.

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Imagine a scientist, Mary, who she's a colour scientist, and she learns all the physical facts about colour and colour perception.

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But she herself doesn't actually see in colour for some reason, she only sees black, white shades of grey.

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Maybe there's something wrong with her optic nerves or whatever it might be. OK, so she's extremely knowledgeable about colour science.

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But then her eyes are corrected. She now is able to see colour for the first time.

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And the claim is that she now learnt something about colour that she didn't previously know.

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She now learns, Oh, that's what red is.

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She didn't know before she used the term, she was aware that red was the colour of blood and so on, but she didn't know what colour it actually was.

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Therefore, phenomenal colour properties, the kind of thing that she learns about when she sees colour for the first time cannot be physical.

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She knew all the physical facts. These weren't amongst them.

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And therefore at least we seem false to property dualism, if not Cartesian substance dualism.

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OK, so I just want to make one point about this argument, which is it seems to me that it just begs the question.

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It's just assuming from the start that Mary can know all the physical facts without knowing how colour looks.

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OK? Now, I'm not saying that's necessarily wrong.

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And the thought experiment may be a vivid way of encouraging you to accept that.

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But there's an argument. I think it falls down for that reason. It doesn't give an independent ground for.

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So supposing that to be true. And we do see a real problem here.

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I mean, if you think about physical facts. We don't see those as easily accommodating perspectives.

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What it's like seeing things from my point of view, how would that fit into physics?

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And it does seem that there's a real difficulty here,

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but it's not clear to me that the knowledge argument really helps us to understand that there have been.

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It's the kind of argument that provokes loads and loads of different responses.

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Philosophers love these thought experiments, you know, simple,

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vivid thought experiments with strong conclusion that tracks them at one might say like flies and you get lots and lots of different explanations.

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And I mentioned a couple of websites there, but that will give you an idea of the extensive debate.

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I'm not going to say more about that here. So I want to go back to lecture two and just give this a little bit of historical perspective.

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We saw Hobbs great materialist publishing Leviathan in sixteen fifty one and it's a big scandal.

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He's claiming that the only stuff that exists is material,

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and then we have loads of philosophers queuing up to refute him on the ground that there are some things matter simply couldn't do.

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Notably matter, couldn't think matter, couldn't be conscious. So we can be quite sure that we are not material.

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And then we saw how once gravity was found to be a force that acted across distances without contact,

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without mechanical contact, that caused problems for this view,

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because gravity seems to be completely unintelligible, we can't understand why bits of matter would attract each other over empty space.

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And if matter can have the property of gravity, why couldn't have the property of thought?

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So that sort of argument could be used to support materialism or physical ism.

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But recall also Temple's dilemma.

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Suppose we contemplate the idea that matter might have, in addition to gravitational properties, matter could have psychic properties.

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Hard to see how that fit into physics, as I've said, but let's suppose it did.

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Would somebody who embraces that still want to call themselves a physical IST if matter becomes weird and spooky,

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physical ism loses some of its hard headed appeal. But some people some philosophers recently have been attracted down this kind of line,

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and it can be combined with the evolutionary considered considerations I mentioned before.

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So suppose we accept that we are evolved beings.

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We've evolved as physical beings within a physical scenario, but we have consciousness.

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Maybe then we should postulate that matter does have some kind of elemental consciousness all the way down,

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so we get to what's called Sikhism the pen Sikhism is the theory that conscious psychic properties of there in matter right from the beginning.

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Again, this doesn't square well with traditional conceptions of physical ism,

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but clearly it would enable you to maintain that everything exists made of the same stuff.

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It's just stuff that has both physical and psychic properties.

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Maybe you might prefer just to say, actually, this is getting pretty weird.

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Maybe we should just accept that these things are going to be too difficult for us to understand.

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If the human brain is simple enough for us to understand, then maybe it's too simple for us to understand it.

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But that sounds paradoxical, but basically we're only going to be able to understand a brain that has a certain level of simplicity.

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But maybe one would need more than that level of simplicity to have a brain sophisticated enough to understand how all this works.

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You probably won't be surprised knowing my temptations towards humour and scepticism to appeal to the great man saying that in things like this,

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we got into fairyland long air. We have reached the last steps of our theory and there we have no reason to trust our common

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methods of argument or to think that our usual analogies and probabilities have any authority.

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Our line is too short to fathom such immense ambitions.

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So here he is, talking about something different, but it's a sort of general message.

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The thought is this too can be bolstered by an evolutionary scenario.

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Why should we expect that our evolved brains are going to be up to solving this sort of problem?

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And it might be that in order to solve the Mind-Body problem, we're going to need another 50, 100, 200 years of sustained scientific investigation.

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An analogy I quite like is putting yourself in the position of a physicist in the 17th or 18th century trying to understand the nature of matter.

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Could you possibly have come up with quantum mechanics? No way.

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It took a lot of research, a lot of experiment, a lot of calculation,

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a lot of critical discussion to come up with a theory that actually had the conceptual power to do what quantum mechanics does.

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And maybe we are going to need new conceptual innovations, which we now cannot even envisage before we can get to grips with some of these things.

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So on that note, let's move on to a related problem personal identity.

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As I said, I'm not going to attempt to cover this completely in what remains of this lecture, but we can make a start.

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OK, so distinguished two questions. What is it to be a person?

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And there you might think about the mind and all the rest, but we're focussing here on a different question.

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It's what is it for A and B to be the same person?

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And usually we're thinking of the same over time.

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Very important point to make here, do watch for this when you're writing philosophical essays and so on.

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Notice that words like same and identical have two distinct meanings.

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You can either mean that things are the same. Qualitatively, they're similar, or you can mean that they are literally the same thing.

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One and the same. And I strongly advise you most of the time to use the word similar for one of these.

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And one in the same for the other to avoid that ambiguity.

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OK, so we come back to life, Mrs Law, and I just want to dispel a possible problem that that might seem to imply for identity over time.

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OK, so we've said if I can be the same thing, they have to have all the same properties.

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OK, let AEB me as a baby six years ago as it happens and then be me today.

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And let f be the property weighs less than a stone. OK, so a weighs less than a stone.

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B clearly doesn't weigh less than a stone, so A and B are not the same.

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And you might think this proves that I in 1958 and I now are different things, but actually that can be dealt with very easily.

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We just say no. The relevant property is weighs less than a stone in 1958 and weighs less than a stone in 2018.

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Take your pick. It's actually a property of me that I weigh less than a stone in 1958.

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It's actually a property of that baby that it weighs more than a stone in 2018.

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So as long as we index properties, according to time, there isn't a problem from Leyden since his law with allowing for across temporal identity.

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Notice, even Hugh nods in the treaties. I'm afraid he makes the mistake more than once.

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Of assuming that identity over time, numerical identity over time actually requires qualitative identity similarity over time.

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We've got the question what constitutes personal identity over time?

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Let's allow that it's possible that I am that baby are literally the same individual.

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But what is it about us that makes us the same individual?

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Is it spatial temporal continuity?

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You know, imagine an omniscient being looking down and be able to trace the path that Peter Milliken has followed from that hospital,

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you know, 60 years ago to now, maybe.

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Is it physical constitution or is there an immaterial substance?

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Is it that I've got the same soul as that baby? Uh.

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Is it psychological continuity or might it be organic life?

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Notice, by the way, that's not the same as asking how we judge it in practise, this isn't the sort of third person question.

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How would you ascertain whether I am in fact the same individual as the one born in that hospital 60 years ago?

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That's a different question. What we're asking is what makes me actually one the same individual.

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Now, again, going with the evolutionary perspective, it's very tempting to go with the human organism.

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I'm a human animal and therefore personal identity should track animal identity.

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But this does have some apparently undesirable implications.

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Incidentally, I've mentioned that there are slides which are not going to be going through in the appendix to the handout.

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And John Locke, one of the merits of his discussion, is clearly to distinguish.

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Identity of an organism, of a biological organism from identity of a person.

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Here, the problem is, all right, one of the problems. It's very plausible that we, this human organism, was once a foetus.

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And let's go back, you know, right to the beginning, the first week or so long before there was any brain there.

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It would seem to follow that I was once not a person.

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I mean, if I am a human organism and this human organism was once just a bundle of cells that doesn't look like a person.

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So it seems to follow that I wasn't. Of course, some of this is controversial, but many people would take personhood to involve things like thinking.

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And it seems to imply that personhood in that sense,

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at least becomes an accidental property of a property of mine, a property that I once didn't have.

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And of course, a property that I want in the future.

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I might lose right if I cease to be able to think. But the human organism is still going, you know, my heart is still going.

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But any higher functions of my brain have stopped. Have I ceased to be?

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Well, if I'm identical with the human organism, no. If I'm identical with the thinking person may be.

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I mentioned John Locke already. He actually wanted to identify personal identity with continuity of consciousness.

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So the person is the conscious thinking individual. He had particular reasons for wanting to do this.

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I think it fitted in very well with the Christian perspective and also with his agnostic perspective

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that he's agnostic about the fundamental natures of things since we cannot know about soul stuff.

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We cannot know whether there is one immaterial soul existing and in conjunction with this body throughout my life,

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maybe the soul soul stuff metabolises. Maybe it turns over through one's life just like one's body does.

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But if personal identity is constituted by continuity of consciousness, I don't need to worry about that.

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It's the identity of the thinking person.

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Now, one way of supporting this is thought experiments, Locke gave the example of a prince who one day wakes up in the body of a cobbler.

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So he opens his eyes, he's expecting to be in a palace, actually.

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He's in a cobbler's hut. Do we think that person is actually the prince or the cobbler?

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And according to Locke, it's the prince. It's the consciousness of the prince there.

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Therefore, it's the prince in the body of the cobbler. A modern variant on this thought experiment is from Bernard Williams.

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So this this I mean, this doesn't require postulation of soul stuff and so forth here,

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we've actually got parts of the body being switched, but in in in some respects it's similar to Locke's thought experiment.

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So let's suppose your brain is to be switched with mine. And then various things may be going to befall us, you know,

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maybe one of them is going to be treated nicely and one of them is going to be treated badly.

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So your brain will come into my body, my body, my brain will go into your body.

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Which individual do you think you would be more concerned about from a first personal, selfish point of view?

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And it's plausible, isn't it, that our selfish concern would track the brain?

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Why? Because that's where psychological continuity resides.

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I would be more concerned about the body that has my brain in it rather than the rest of me.

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Even though the rest of me is obviously bigger than my brain. I mean, one way of making this vivid is this.

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You know, I'm getting older, the body creaks a bit and so forth.

385
00:46:45,590 --> 00:46:56,040
I imagine one day I'm walking down the high street and I see some, some strapping youth.

386
00:46:56,040 --> 00:47:04,530
Who, however, doesn't look particularly well blessed in the brain department, and I say, look, you know, I'm I'm an Oxford professor.

387
00:47:04,530 --> 00:47:08,760
You know, and I've got a pretty decent brain.

388
00:47:08,760 --> 00:47:24,290
Wouldn't you rather have my brain? And if he if he agrees and we go through the operation, imagine which of us is going to be pleased when we wake up.

389
00:47:24,290 --> 00:47:28,580
But I do want we can think about these thought experiments, and they are quite entertaining.

390
00:47:28,580 --> 00:47:32,870
But notice actually a priori, we can't know what would happen.

391
00:47:32,870 --> 00:47:41,270
I mean, it seems pretty plausible that if you could trance my brain into a strapping youth's body,

392
00:47:41,270 --> 00:47:51,800
I would indeed retain memory of, well, this, for example, and be suitably pleased by the change in body.

393
00:47:51,800 --> 00:47:56,540
On the other hand, I mean, suppose my brain was to be transplanted into a female body.

394
00:47:56,540 --> 00:48:01,600
I might actually think somewhat differently. I would have different hormones and so forth.

395
00:48:01,600 --> 00:48:08,570
What we can't know a priori what effect it would have transplanting a brain from one body to another.

396
00:48:08,570 --> 00:48:16,910
And when you come across thought experiments, which talk about downloading memories and things like that and uploading them to someone else,

397
00:48:16,910 --> 00:48:26,060
I would advise you to be very sceptical because unless we've got some clue about what the physical mechanism is and how this is supposed to work,

398
00:48:26,060 --> 00:48:35,140
these are just imaginary thought experiments, and it's not at all clear that they would actually be genuine possibilities.

399
00:48:35,140 --> 00:48:41,980
Anyway, back to Locke's theory, we got the idea that what really concerns us is psychological continuity.

400
00:48:41,980 --> 00:48:49,870
And that does seem plausible, but an obvious problem here is that our memory and our consciousness are not continuous.

401
00:48:49,870 --> 00:48:58,680
Most obviously, we sleep. We can forget things. We can even lapse into a coma and then recover.

402
00:48:58,680 --> 00:49:03,180
Now, it probably in the case of Williams thought experiment,

403
00:49:03,180 --> 00:49:10,350
and we seem to be OK with regard to this because we've got the brain that the brain is

404
00:49:10,350 --> 00:49:17,070
continuous and the continuity of the brain assures us that when we go to sleep and wake up,

405
00:49:17,070 --> 00:49:22,380
we are the same individual, a bit like if you turn off a computer and then turn it back on again.

406
00:49:22,380 --> 00:49:28,950
We have continuity because we've got a continuing physical presence.

407
00:49:28,950 --> 00:49:38,730
So if we focus on brain continuity, that may be a more plausible line than talking about continuity of the physical organism.

408
00:49:38,730 --> 00:49:43,140
So a person only comes into existence when the brain comes into existence,

409
00:49:43,140 --> 00:49:52,410
and from then on, personal identity is constituted by the continuity of the the brain.

410
00:49:52,410 --> 00:50:00,000
But things aren't quite so simple and again, empirical discovery Trump's thought experiment.

411
00:50:00,000 --> 00:50:09,720
It turns out that if the corpus callosum, which connects the cerebral hemispheres is cut, there's an operation called Comix Europe Ultimi,

412
00:50:09,720 --> 00:50:19,320
which is sometimes used in cases of severe epilepsy, and you end up with a single human brain, giving rise to two behaviours.

413
00:50:19,320 --> 00:50:21,450
So there's one case reported, for example,

414
00:50:21,450 --> 00:50:31,230
where a man's right hand was attempting to do something violent and the left hand was stopping the right hand doing it.

415
00:50:31,230 --> 00:50:39,980
So you've got evidence of two separate consciousness is within the same brain because the communication between them is cut.

416
00:50:39,980 --> 00:50:48,790
OK, now suppose we have a situation where a single brain is cut into.

417
00:50:48,790 --> 00:50:59,660
And then each half is transplanted into a new body. In that case, it seems you'd have two new persons, and both of them would have brain continuity.

418
00:50:59,660 --> 00:51:08,210
I mean, insofar as they've got a brain, it's continuous with the brain of the previous person and they've got memory continuity as well.

419
00:51:08,210 --> 00:51:11,750
So we seem to have a sort of branching.

420
00:51:11,750 --> 00:51:19,250
Another way in which we could be led towards this sort of thing, and here we are going into science fiction thought experiments,

421
00:51:19,250 --> 00:51:24,890
imagine Star Trek Transportation were to become possible transporter beams.

422
00:51:24,890 --> 00:51:31,250
My body is copied atom by atom to a new place.

423
00:51:31,250 --> 00:51:40,540
Well, how should I view this? Would you be tempted if the scientists came along and said, Hey, we developed this transporter beam?

424
00:51:40,540 --> 00:51:45,550
Would you like to give it a go? No fear, no.

425
00:51:45,550 --> 00:51:49,930
Because I think this is killing me, right? I think this is destroying me.

426
00:51:49,930 --> 00:52:00,450
It may be making a replica, you know, at some distance. But actually, I wouldn't touch it with a barge pole, at least not to start with.

427
00:52:00,450 --> 00:52:09,090
But imagine it became common. Imagine, you know, all my students and during the vacations were going off around the world.

428
00:52:09,090 --> 00:52:15,750
Where did you go to Australia? Oh, really? How did you get there? Well, I transported, you know, I only took five minutes.

429
00:52:15,750 --> 00:52:21,300
Much better than, you know, a twenty four hour journey by flying and all the airlines go out of business, right?

430
00:52:21,300 --> 00:52:25,590
Or the long range airlines because everybody is transporting all over the place.

431
00:52:25,590 --> 00:52:33,750
And every time a student comes back from one of these vacations, they seem as far as I can tell, you know, to be the same person, everything's fine.

432
00:52:33,750 --> 00:52:38,120
Well, at that point. At that point, maybe I would do it.

433
00:52:38,120 --> 00:52:42,530
I mean, it's a bit like, you know, people who are scared of flying and then you go along to an airport and you just see

434
00:52:42,530 --> 00:52:47,240
thousands and thousands of aircraft taking off one after another and you realise,

435
00:52:47,240 --> 00:52:55,410
OK, yeah, it is safe. And one might well think the same about Star Trek transportation.

436
00:52:55,410 --> 00:52:59,780
But a problem of duplication arises here, because if.

437
00:52:59,780 --> 00:53:08,210
If I can be transported from one place to another by copying all the atoms, why can't I be copied to two places at once?

438
00:53:08,210 --> 00:53:15,050
Or imagine the situation where you know, I go over to some conference, say in America or something?

439
00:53:15,050 --> 00:53:25,330
I go to the transporter to come back. I'm still there.

440
00:53:25,330 --> 00:53:35,500
Oh, dear. Something's gone wrong. Okay, so I get on the phone to my wife and say, Hello darling, the transport, it didn't work.

441
00:53:35,500 --> 00:53:40,950
I'm still here. Oh, but you just arrived.

442
00:53:40,950 --> 00:53:46,150
Woops. So now there are two of me.

443
00:53:46,150 --> 00:53:49,810
You can imagine this would give rise to quite a lot of problems.

444
00:53:49,810 --> 00:54:00,480
Um, I think what I'd probably do is ask my wife to go and do the same, and then at least there'd be two wives.

445
00:54:00,480 --> 00:54:05,460
Unfortunately, I wouldn't be able to do the same with the House, so I'm not quite sure how we work out,

446
00:54:05,460 --> 00:54:16,020
but I've always wanted an identical twins, so I'm now, as I say, notice we can't know whether this is actually possible.

447
00:54:16,020 --> 00:54:19,680
I think we shouldn't assume when we're thinking through these experiments.

448
00:54:19,680 --> 00:54:21,180
I mean, of course, it's a crazy experiment.

449
00:54:21,180 --> 00:54:28,650
There's no way that you could get enough information to record the position of every atom in the body and transport it.

450
00:54:28,650 --> 00:54:33,270
There's just no way that that could happen practically.

451
00:54:33,270 --> 00:54:36,900
But I want to make another point. We cannot know in advance that this would work.

452
00:54:36,900 --> 00:54:44,190
We cannot know in advance that copying every atom, even if it were physically possible, would generate an identical person.

453
00:54:44,190 --> 00:54:50,400
Maybe there really is subtle stuff, and maybe the soul wouldn't be copied because we're only copying the physical atoms.

454
00:54:50,400 --> 00:54:53,340
So actually, if it did work, if the transporter did work,

455
00:54:53,340 --> 00:55:01,500
we would have discovered something about ourselves, something that might not have been the case.

456
00:55:01,500 --> 00:55:04,470
So just to finish off on leading to next time,

457
00:55:04,470 --> 00:55:17,100
I'm Derek Parfitt suggested it's a mistake to think just in terms of personal identity if this sort of thing happened, if duplication happened.

458
00:55:17,100 --> 00:55:19,410
I'll go back to Williams thought experiment,

459
00:55:19,410 --> 00:55:27,750
which individual would I be concerned about the one who remained on the Transporter platform in America or the one who was transported home?

460
00:55:27,750 --> 00:55:34,290
And the answer is probably both. I would see both of them as being continuance of me.

461
00:55:34,290 --> 00:55:40,260
I would have to give up the strict notion of identity because they are clearly not identical to each other.

462
00:55:40,260 --> 00:55:49,860
And so there's no way they can both be identical to me because if they is identical with B and B with C, then A has to be identical with C.

463
00:55:49,860 --> 00:56:00,340
So maybe we have to give up the notion of personal identity. And we would have to think in terms of personal survival.

464
00:56:00,340 --> 00:56:08,710
And this raises a fundamental question, if what really matters about personal identity is continuity of concern,

465
00:56:08,710 --> 00:56:16,750
which individual would I think of as the object of my future selfish concern?

466
00:56:16,750 --> 00:56:21,970
Then it's pertinent to investigate what it's rational to care about,

467
00:56:21,970 --> 00:56:28,390
and it is intuitively plausible that there are special reasons for caring about my future self.

468
00:56:28,390 --> 00:56:30,370
Reasons that wouldn't apply to anything else.

469
00:56:30,370 --> 00:56:39,640
So maybe we can get into this problem of identity and survival by contemplating the issue of rational concern.

470
00:56:39,640 --> 00:56:45,850
And indeed, one popular theory known psychological egoism claims that in fact,

471
00:56:45,850 --> 00:56:53,170
ultimately the only thing we care about for the future is ourselves and things that impact on us,

472
00:56:53,170 --> 00:57:03,400
in which case we see a very intimate connexion between our concern about the future and our continuing selves.

473
00:57:03,400 --> 00:57:07,520
And they're all finished for today. Thank you.