1 00:00:10,550 --> 00:00:15,930 Okay, so we're going to finish today with personal identity. 2 00:00:15,930 --> 00:00:24,360 And as usual, we've got various luminaries there, John Locke, David Hume, Bernard Williams and Derek Parfit, 3 00:00:24,360 --> 00:00:33,270 three of them, with the exception of Hume, all closely associated with Oxford. 4 00:00:33,270 --> 00:00:38,280 OK, so we start by distinguishing two different questions. 5 00:00:38,280 --> 00:00:42,260 First, what is it to be a person? 6 00:00:42,260 --> 00:00:54,460 And that could invite a discussion of the mind body, the link between them, what it is that constitutes the mind and so forth. 7 00:00:54,460 --> 00:01:01,790 A different question. What is it for A and B to be the same person? 8 00:01:01,790 --> 00:01:10,280 That is the issue of personal identity. And it's obviously typically raised over time. 9 00:01:10,280 --> 00:01:18,100 What is it for a person at one time to be the same person as someone at a later time? 10 00:01:18,100 --> 00:01:25,050 What is it, for example, for me to be the same as I was as a baby? 11 00:01:25,050 --> 00:01:29,070 That we think of as the same person. Is that justified? 12 00:01:29,070 --> 00:01:37,440 And if so, why and how? And let me start also by drawing another distinction. 13 00:01:37,440 --> 00:01:42,680 Two different meanings of the words, same when you say two things are the same. 14 00:01:42,680 --> 00:01:51,030 You can mean that they're qualitatively similar. Or you can mean that they're numerically identical. 15 00:01:51,030 --> 00:02:00,170 And my advice would be, in all these discussions, avoid use of the word same just by itself because it is systematically ambiguous. 16 00:02:00,170 --> 00:02:06,760 So I would suggest that you use the word similar to mean qualitative identity when you want to say that. 17 00:02:06,760 --> 00:02:12,980 Think two things have similar qualities. They look they look more or less the same. 18 00:02:12,980 --> 00:02:18,960 They have various things in common. Talk of them is similar, not as the same. 19 00:02:18,960 --> 00:02:26,540 And if you want to say things that two things are numerically identical, say that they are one and the same. 20 00:02:26,540 --> 00:02:40,290 So the claim about personal identity is that I am one and the same person as that baby rather too many years ago. 21 00:02:40,290 --> 00:02:45,060 Now, the problem arises because of license's law again. 22 00:02:45,060 --> 00:02:49,530 We've seen this before. Back in, I think, the fourth lecture. 23 00:02:49,530 --> 00:02:59,680 But here we are again with Lightman's law. It seems to be a matter of logic that if A and B are one and the same thing. 24 00:02:59,680 --> 00:03:10,620 Then any property of a must also be A property of B. So let's call the property F, if it's true that F they. 25 00:03:10,620 --> 00:03:16,000 And A equals B. Then it follows logically that SFB. 26 00:03:16,000 --> 00:03:24,990 So take these examples, let a be me as a baby, let be. 27 00:03:24,990 --> 00:03:32,550 Be me today. And let the property SB weighs less than a stone. 28 00:03:32,550 --> 00:03:42,250 We have an apparent contradiction here, because I as a baby certainly weighed less than a stone today, I certainly weigh rather more. 29 00:03:42,250 --> 00:03:51,670 So it seems to follow that I as a baby cannot be numerically the same as me today, doesn't it? 30 00:03:51,670 --> 00:03:57,240 Well, actually, these sorts of problems are quite easily dealt with. You simply specify ethanol. 31 00:03:57,240 --> 00:04:07,450 Precisely. So instead of just saying weighs less than a stone, let's put a time index in, weighs less than a stone in 1958, 32 00:04:07,450 --> 00:04:14,530 which was the year I was born, as opposed to weighs less than a stone in 2009. 33 00:04:14,530 --> 00:04:23,320 The fact is that I, this very person, have the property of weighing less than a stone in 1958. 34 00:04:23,320 --> 00:04:28,420 And you can say, if you like, that I timelessly have that property of weighing less than a stone. 35 00:04:28,420 --> 00:04:41,420 Well, maybe a particular date in 1958. And that baby has the property of weighing more than a stone in 2009 because that very baby is me. 36 00:04:41,420 --> 00:04:50,670 At least if the claim of personal identity is true. So you can see that we can at least avoid overt contradiction. 37 00:04:50,670 --> 00:05:00,160 We do not have to say that there's some kind of serious problem in things having different properties at different times. 38 00:05:00,160 --> 00:05:10,540 Now, some philosophers have had difficulty seeing this. David Hume, the one most of fumes treatise, is actually logically very acute. 39 00:05:10,540 --> 00:05:20,410 But on this particular issue, he seems to have had a bit of a blind spot. He took the view that strict identity really required. 40 00:05:20,410 --> 00:05:29,860 Exact similarity was a major problem with saying that something that changes over time is nevertheless one and the same in his later work. 41 00:05:29,860 --> 00:05:35,860 He seems to have avoided the issue, and it may be that he came to see the error of his ways. 42 00:05:35,860 --> 00:05:43,480 But at any rate, there in the treaties he will find. I think this mistake made. 43 00:05:43,480 --> 00:05:45,520 OK, so that is a mistake. 44 00:05:45,520 --> 00:05:53,260 We don't have to say that if something changes over time, that therefore means that it's not one and the same thing over time. 45 00:05:53,260 --> 00:06:02,110 Indeed, if you think about it, we want to say the reverse. I mean, a person who did not change at all. 46 00:06:02,110 --> 00:06:07,510 Would not be a person. Right. A part of being a person is thinking. 47 00:06:07,510 --> 00:06:18,460 For example, breathing. Eating, metabolising, all the various things we do, all of those actually require change over time. 48 00:06:18,460 --> 00:06:26,590 It's quite impossible to breathe without changing over time. It's quite impossible to eat or talk or think without changing over time. 49 00:06:26,590 --> 00:06:37,850 So, so far from change being incompatible with personal identity, actually personal identity seems to require change over time. 50 00:06:37,850 --> 00:06:41,990 Nevertheless, there are limits. Some changes are fine, some aren't. 51 00:06:41,990 --> 00:06:47,300 So we're still left with the question, what is it that constitutes personal identity over time? 52 00:06:47,300 --> 00:06:54,800 What is it that makes me the same person as that baby and the various intermediate stages in between? 53 00:06:54,800 --> 00:07:00,230 Is it physical constitution? Or is it having the same immaterial substance? 54 00:07:00,230 --> 00:07:07,460 Is it that when I was born, God before I was born, indeed God implanted a soul made of immaterial substance. 55 00:07:07,460 --> 00:07:15,130 And somehow it's the continuity of that soul. That makes me the same person. 56 00:07:15,130 --> 00:07:25,000 Or is it a matter of the organic life of the animal that I am in the same way that we identify the identity of a tree as it grows over time, 57 00:07:25,000 --> 00:07:30,860 maybe we are just physical organisms. And that's how our identity is constituted. 58 00:07:30,860 --> 00:07:37,360 Or should it perhaps be psychological continuity is what makes me the same person as I was then. 59 00:07:37,360 --> 00:07:46,870 That there is a continuous line of psychological life. Now, notice that this question, the question I've highlighted there, 60 00:07:46,870 --> 00:07:56,500 what constitutes personal identity over time is not the same question as asking how we judge personal identity in practise. 61 00:07:56,500 --> 00:08:00,370 They're likely to be closely related, but they don't have to be the same. 62 00:08:00,370 --> 00:08:07,600 Suppose, for example, that you did think that personal identity was constituted by an immaterial soul. 63 00:08:07,600 --> 00:08:11,740 Well, since immaterial souls are inaccessible to us, 64 00:08:11,740 --> 00:08:19,480 you might nevertheless have to say that our way of judging personal identity in practise is through the physical organism. 65 00:08:19,480 --> 00:08:24,670 We believe that the same soul goes along with the same body from birth until death. 66 00:08:24,670 --> 00:08:30,130 Therefore, the way we actually judge personal identity in practise is using the physical body, 67 00:08:30,130 --> 00:08:35,260 even though really personal identity is constituted by the soul. 68 00:08:35,260 --> 00:08:42,440 And that way, you could quite happily say that the body is the pre-eminent criterion of personal identity during life whilst 69 00:08:42,440 --> 00:08:53,888 continuing to believe that you can make sense of personal identity in the hereafter through the survival of the soul.