1 00:00:10,280 --> 00:00:16,250 So let's move on now to another Cartesian topic, dualism. 2 00:00:16,250 --> 00:00:21,230 This is certainly the view for which Descartes is now best known. 3 00:00:21,230 --> 00:00:30,860 If you find the word Cartesian in a philosophical text, the most likely accompaniment is the word dualism. 4 00:00:30,860 --> 00:00:35,450 Cartesian dualism is fairly straightforwardly stated. 5 00:00:35,450 --> 00:00:43,550 He takes the body to be material made of matter whose essence is extension. 6 00:00:43,550 --> 00:00:52,760 And he takes the mind to be made of a completely different substance, immaterial substance, nonmaterial whose essence is thinking. 7 00:00:52,760 --> 00:00:57,140 So we've got two distinct substances. Now, that's very important. 8 00:00:57,140 --> 00:00:58,920 Notice to be a Cartesian dualist. 9 00:00:58,920 --> 00:01:06,200 It's not enough that you just think mind and body are different or even that mind and body have different properties. 10 00:01:06,200 --> 00:01:17,110 You've got to think that there are different substances. And that is a very substantial claim. 11 00:01:17,110 --> 00:01:24,930 Now, in the discourse on method, Descartes argues something like this, I can doubt that my body exists. 12 00:01:24,930 --> 00:01:31,410 I cannot doubt that I exist. Therefore, I am not identical with my body. 13 00:01:31,410 --> 00:01:36,360 Quite a tempting argument, at least to start with. 14 00:01:36,360 --> 00:01:40,620 Put yourself in the position of the sceptic. What can I be sure of? 15 00:01:40,620 --> 00:01:45,420 Well, the only thing I can be sure of is my own thoughts and my own perceptions. 16 00:01:45,420 --> 00:01:55,080 So I'm absolutely certain that I exist. But when I contemplate my body, if it's all an illusion, I cannot be sure that my body exists. 17 00:01:55,080 --> 00:01:59,550 Surely then my mind and my body must be distinct things. 18 00:01:59,550 --> 00:02:06,960 For example, I can imagine myself transported maybe to an afterlife or something like that in which I don't have a body. 19 00:02:06,960 --> 00:02:11,310 But I still think I can imagine myself in that situation. 20 00:02:11,310 --> 00:02:22,380 So surely I and my body must be distinct things. It seems quite plausible, but actually, as it stands, this argument is fallacious. 21 00:02:22,380 --> 00:02:30,300 So here's an example. Hesperus and Phosphorus are ancient names for Venus. 22 00:02:30,300 --> 00:02:34,440 Phosphorus is the morning star. Hesperus the evening star. 23 00:02:34,440 --> 00:02:38,100 The ancients didn't know that they were the same heavenly body. They are. 24 00:02:38,100 --> 00:02:42,780 In fact, Venus, of course, is quite close to the sun hits between us and the sun. 25 00:02:42,780 --> 00:02:49,800 So it only ever appears in the morning or the evening. Never in the middle of the night. 26 00:02:49,800 --> 00:03:02,010 Okay, so imagine somebody who does not know that Hesperus and phosphorous are the same and they might present this argument. 27 00:03:02,010 --> 00:03:08,580 I can doubt that Hesperus is phosphorous. Indeed, maybe I do doubt that Hesperus is phosphorous. 28 00:03:08,580 --> 00:03:15,430 But I can't doubt that phosphorus is phosphorus. Therefore, Hesperus isn't phosphorus. 29 00:03:15,430 --> 00:03:21,190 Because Hesperus and Phosphorus have different properties, okay? One of them I can doubt to be phosphorus. 30 00:03:21,190 --> 00:03:29,650 The other one I can't out to be phosphorus. And there's no way that the same thing can have different properties. 31 00:03:29,650 --> 00:03:33,120 So that's appealing to a room called Liden. 32 00:03:33,120 --> 00:03:37,480 It's his law. In fact, life mixes. Law is used in different ways by different people. 33 00:03:37,480 --> 00:03:42,760 But this is one particular form of it, if I can be of the same thing. 34 00:03:42,760 --> 00:03:57,910 Then any property of a must also be A property of B. So if you have F.A.A., that means F is a property of A and A and B at the same F, B follows. 35 00:03:57,910 --> 00:04:07,660 So if F is the property of being doubted by me to exist, A is me and B is my body. 36 00:04:07,660 --> 00:04:18,490 We get Descartes argument from the discourse and by suitable substitution you can get the argument that I just put about Hesperus and phosphorus. 37 00:04:18,490 --> 00:04:21,730 But you can see that this is fallacious. 38 00:04:21,730 --> 00:04:31,390 If you put the problem, if you count as a property, something like being doubted by me to be to be prime minister, you can get. 39 00:04:31,390 --> 00:04:36,280 I don't doubt that the prime minister is the prime minister. I doubt that Gordon Brown is the prime minister. 40 00:04:36,280 --> 00:04:44,670 Therefore, Gordon Brown isn't the prime minister. Very easy to produce lots of examples of fallacies. 41 00:04:44,670 --> 00:04:54,160 And the simplest way to avoid it is simply to highlight that being doubted by me to be something is not a genuine property of the object. 42 00:04:54,160 --> 00:05:01,180 When I doubt whether Hesperus is phosphorous. My doubt is not a fact about that planet. 43 00:05:01,180 --> 00:05:07,960 It's a fact about me. And it's about the fact that I am not aware that the appearance of this planet in the 44 00:05:07,960 --> 00:05:15,790 morning is an appearance of the same planet that appeared in the evening some weeks ago. 45 00:05:15,790 --> 00:05:26,260 It's not a fact about the planet so much as about me. So that argument of Descartes is well known to be fallacious. 46 00:05:26,260 --> 00:05:35,740 But he produces a more interesting argument in the sixth meditation, which is certainly much better, but has questionable premises. 47 00:05:35,740 --> 00:05:51,580 And it goes like this. When I contemplate myself, I can very clearly understand myself as being a thinking, non extended thing. 48 00:05:51,580 --> 00:05:56,440 I can see, at any rate, that I'm definitely a thinking thing because here I am thinking. 49 00:05:56,440 --> 00:06:02,480 So I'm obviously a thinking thing and I can have a clear understanding of what fault 50 00:06:02,480 --> 00:06:11,480 is sufficient to enable me to see that I am potentially not an extended thing. 51 00:06:11,480 --> 00:06:16,680 I also likewise have a clear understanding of body as extended and not thinking. 52 00:06:16,680 --> 00:06:23,310 So when I contemplate a physical object, I'm aware that it is necessarily extended. 53 00:06:23,310 --> 00:06:29,100 And I'm also aware that it is not essential to its being that it be a thinking thing. 54 00:06:29,100 --> 00:06:33,930 Indeed, it seems hard to see how a physical extended body can be. 55 00:06:33,930 --> 00:06:40,040 A thinking thing certainly doesn't seem to be essential to it be so. 56 00:06:40,040 --> 00:06:50,660 Well, if I can clearly understand what it would be for me to be a thinking thing and not extended and for extended things not to be thinking, well, 57 00:06:50,660 --> 00:07:03,050 in that case, it's possible for God to create a world in which these things that I'm clearly understanding as possibilities are actual truths. 58 00:07:03,050 --> 00:07:11,510 And it follows that if God could create me as a thinking thing distinct from my body as an extended thing, 59 00:07:11,510 --> 00:07:27,450 then they must indeed be genuinely distinct things. If they were not distinct, God would not even God would not be able to create them as separate. 60 00:07:27,450 --> 00:07:35,070 Now, I've mentioned that you've got a very crude argument in the discourse in the meditation's, you've got a much more sophisticated argument. 61 00:07:35,070 --> 00:07:44,580 But even in the meditation's, Descartes does try to make this move from doubt to knowledge of his essence. 62 00:07:44,580 --> 00:07:52,560 So here's a quotation. What should I now say that I am when I might be deceived by an evil demon or dreaming? 63 00:07:52,560 --> 00:07:57,030 At present, I'm not admitting anything except what is necessarily true. 64 00:07:57,030 --> 00:08:06,270 I am then, in a strict sense, only a thing that thinks that is I'm a mind or intelligence or intellect or reason. 65 00:08:06,270 --> 00:08:14,340 What kind of thing is that? A thinking thing? So notice what he's doing. 66 00:08:14,340 --> 00:08:23,400 He's using his scepticism. Remember, he started out saying, I'm not going to accept anything except what he's completely certain. 67 00:08:23,400 --> 00:08:31,380 He then points out that he is certain of his own thinking and his own existence and moves on to say, therefore, I can be sure of that. 68 00:08:31,380 --> 00:08:38,740 But that's the only thing I can be sure of. I am a thinking thing. 69 00:08:38,740 --> 00:08:48,210 But this is a dubious move to distinguish two different meanings of a thinking thing. 70 00:08:48,210 --> 00:08:57,480 What do we mean when we say that a thinking thing? Well, we could just mean something that thinks or we could mean something. 71 00:08:57,480 --> 00:09:04,170 Whose essence is to think? Something which is in its own essence, a thinking thing that cannot be anything else. 72 00:09:04,170 --> 00:09:16,710 That cannot not think. And those are two very different claims and the kind of move that Descartes is making here from epistemology to metaphysics. 73 00:09:16,710 --> 00:09:29,550 That is, he is arguing from how we come to know something to what it is that is in general a very suspicious move. 74 00:09:29,550 --> 00:09:33,330 Knowing that, I am thinking it does follow that I am a thinking thing. 75 00:09:33,330 --> 00:09:41,100 In one sense, if I am actually thinking, then I must be something whose which is capable of thinking, 76 00:09:41,100 --> 00:09:47,070 at least if you don't put too much stress on the word thing. 77 00:09:47,070 --> 00:09:52,470 But it doesn't at all follow that I'm something whose essence is to think. 78 00:09:52,470 --> 00:10:01,550 So suppose, for example, I mentioned a couple of lectures ago about John Locke coming out with the speculation that God could make matter. 79 00:10:01,550 --> 00:10:09,260 Think so. He imagined God took a stone and made it think the stone thinks to itself. 80 00:10:09,260 --> 00:10:15,360 Ah, I know I'm a thinking thing. Even the stone only knows that it's a thinking thing. 81 00:10:15,360 --> 00:10:20,250 It doesn't know it's an extended thing because it has the same problems as we do. 82 00:10:20,250 --> 00:10:23,250 It's only aware of its own perceptions. 83 00:10:23,250 --> 00:10:30,210 It could then conclude that it was something whose essence is to think and it would immediately be proved wrong. 84 00:10:30,210 --> 00:10:40,180 When God withdrew from it, the power of thinking on the stone would still exist. 85 00:10:40,180 --> 00:10:47,350 What about the final move of Descartes argument, this seems rather more defensible, though, on the face of it, it might seem dubious. 86 00:10:47,350 --> 00:10:55,660 God could have created my mind and body as separate entities. Therefore, it is possible for my mind and body to exist separately. 87 00:10:55,660 --> 00:11:01,400 Therefore, my mind and body are, in fact, distinct things. 88 00:11:01,400 --> 00:11:08,830 Now, at first sight, this might seem to be committing exactly the same fallacy that I've just been talking about. 89 00:11:08,830 --> 00:11:16,270 It might look as though something metaphysical a fact about what could be the actual 90 00:11:16,270 --> 00:11:25,690 distinctness of two things is being inferred from what is just a hypothetical possibility. 91 00:11:25,690 --> 00:11:29,440 Well, it's very important that the possibility be understood in the right way. 92 00:11:29,440 --> 00:11:39,340 So let me give you an example. Suppose I look up in the sky one day and I see Hesperus, we could do later. 93 00:11:39,340 --> 00:11:50,120 I look up and I see phosphorous. Maybe I don't know that anybody's even suggested that these are the same heavenly body. 94 00:11:50,120 --> 00:12:06,760 Or maybe the thought occurs to me and I say to myself, well, it is possible for Hesperus to be snuffed out while phosphorous survives. 95 00:12:06,760 --> 00:12:13,570 Maybe I'm thinking of some cosmic catastrophe. That's heavenly body. 96 00:12:13,570 --> 00:12:21,010 Hesperus could meet with some accident while phosphorous survives. 97 00:12:21,010 --> 00:12:26,200 So there's a real possibility of one of them existing without the other. 98 00:12:26,200 --> 00:12:33,660 Therefore, they cannot be the same object. 99 00:12:33,660 --> 00:12:40,350 No, actually, there's nothing wrong with that last move, but it depends on how you interpret possibility, 100 00:12:40,350 --> 00:12:47,670 because actually when I speculate, it is possible for one of them to be snuffed out while the other survives. 101 00:12:47,670 --> 00:12:55,740 Actually, you can respond to that by saying, no, it isn't possible. Unbeknown to you, it isn't possible because they are, in fact, the same object. 102 00:12:55,740 --> 00:13:05,250 And if they are in fact, the same object, then it isn't possible for something to happen to Hesperus without it also happening to phosphorous. 103 00:13:05,250 --> 00:13:12,750 But on the other hand, you might be inclined to say, well, surely the person in that situation contemplating these two object. 104 00:13:12,750 --> 00:13:24,750 It is a real possibility. Yes, but only epistemologically when you say it is a real possibility that what one means is for all I know, 105 00:13:24,750 --> 00:13:31,830 for all I know, one of the objects could meet with a calamity while the other one survives. 106 00:13:31,830 --> 00:13:36,810 Yes, that's true. But that's a truth about my knowledge. 107 00:13:36,810 --> 00:13:43,590 It's not actually true that one of those objects could really meet with a calamity while the other does not, 108 00:13:43,590 --> 00:13:47,040 because they are, in fact the same object. 109 00:13:47,040 --> 00:13:56,250 So, again, you have to be very careful when you talk about the properties of mind and body and so forth, or indeed heavenly bodies. 110 00:13:56,250 --> 00:14:06,260 Are you actually talking about your knowledge of them or are you talking about their own properties, essences, cetera? 111 00:14:06,260 --> 00:14:08,970 Hesperus and phosphorous are in fact the same object. 112 00:14:08,970 --> 00:14:14,910 At least that's what we believe, because you might think, well, scientists could discover, you know, 113 00:14:14,910 --> 00:14:22,710 next week that there's been some some great hoax and they're not actually the same object after all. 114 00:14:22,710 --> 00:14:27,230 Yes, sure. For all we know, in a sense, that could happen. 115 00:14:27,230 --> 00:14:38,720 But if they are the same object, in fact, then whatever happens to one of them must happen to the other.