1 00:00:05,300 --> 00:00:09,710 Right, welcome to the second lecture on general philosophy. 2 00:00:09,710 --> 00:00:20,930 This completes the sort of general survey of historical change in concepts, which is mainly occupying these first two lectures. 3 00:00:20,930 --> 00:00:29,600 And I want to stress that I consider this history to be absolutely crucial to getting a proper understanding of 4 00:00:29,600 --> 00:00:37,100 the topics that we cover in general philosophy that will become more evident as we go through the pictures here. 5 00:00:37,100 --> 00:00:43,520 We've got Descartes, of course, on the left, then Thomas Hobbes, who enters the story today. 6 00:00:43,520 --> 00:00:48,620 Isaac Newton, Charles Darwin and Albert Einstein. 7 00:00:48,620 --> 00:00:55,310 Now you may well think that at least three of these are far better known as scientists than philosophers, 8 00:00:55,310 --> 00:01:03,970 but their ideas are of profound significance for philosophical thinking about these things. 9 00:01:03,970 --> 00:01:10,240 OK, first of all, a reminder, we came across Descartes last week. 10 00:01:10,240 --> 00:01:20,650 He had a brilliant idea, a synthesis that brought together the ideal of mechanism with an explanation of one 11 00:01:20,650 --> 00:01:25,690 of those these very puzzling phenomena the motion of the Moon around the Earth, 12 00:01:25,690 --> 00:01:36,370 the planets around the Sun. He denied the Aristotelian idea that bodies in nature, like stones or planets, 13 00:01:36,370 --> 00:01:45,730 are motivated by something like purposes striving to reach the centre of the universe or something like that matter for Descartes. 14 00:01:45,730 --> 00:01:48,820 As for Galileo is simply passive. 15 00:01:48,820 --> 00:01:58,000 His idea is that the essence of matter is extension extended ness in space, and that immediately means that space is a planet. 16 00:01:58,000 --> 00:02:05,440 There is no empty space because wherever you have extended space, you've got matter. 17 00:02:05,440 --> 00:02:11,470 It follows that the motion of matter can only go in vortices. 18 00:02:11,470 --> 00:02:18,760 And therefore, you've got an explanation of the motion of the planets around the Sun and so forth. 19 00:02:18,760 --> 00:02:23,290 As for mind, the essence of mind is quite distinct. 20 00:02:23,290 --> 00:02:31,750 The essence of mind is thinking mind is not extended. Matter is so it's a completely distinct kind of substance. 21 00:02:31,750 --> 00:02:40,270 And importantly for some, at least, as he presented at the beginning of the meditations, this makes room for immortality. 22 00:02:40,270 --> 00:02:47,260 He's very keen to promote his text as suitable for teaching in religious seminaries and so on. 23 00:02:47,260 --> 00:02:51,730 So making space for immortality is pretty crucial. 24 00:02:51,730 --> 00:03:04,380 But actually, in many ways, the most important aspect of Descartes work was taking mind strivings and things out of physical science. 25 00:03:04,380 --> 00:03:09,810 So we're going to be talking quite a bit today about physical ism. 26 00:03:09,810 --> 00:03:18,150 And I want to, first of all, introduce that in contrast with Cartesian dualism named after Descartes. 27 00:03:18,150 --> 00:03:23,370 So Cartesian dualism, you have physical bodies that consist of material substance. 28 00:03:23,370 --> 00:03:31,170 You've got mines quite distinct, consisting of immaterial substance thinking stuff. 29 00:03:31,170 --> 00:03:39,750 By contrast, materialism nowadays it tends to be called physical ism is the view that there's only one kind of substance, 30 00:03:39,750 --> 00:03:43,790 namely material, substance or physical substance. 31 00:03:43,790 --> 00:03:51,020 Notice, although I won't be saying much about this today, this is compatible with having a distinction between physical and mental properties. 32 00:03:51,020 --> 00:03:59,840 So you could say we consist entirely of material substance, but amongst our properties are mental properties as well as physical properties. 33 00:03:59,840 --> 00:04:06,730 So you can have a dualism of properties compatibly with being a materialist. 34 00:04:06,730 --> 00:04:14,680 So Thomas Hobbs comes in as a notorious figure, better known today for his political theory. 35 00:04:14,680 --> 00:04:23,140 He's still very, very prominent in reading lists on political theory, as many of you may know. 36 00:04:23,140 --> 00:04:30,670 So we have his portraits in Hartford College because he went to Modelling Hall, which morphed into Hertford College. 37 00:04:30,670 --> 00:04:34,390 So he's an Oxford man. He he was like Descartes, a pianist. 38 00:04:34,390 --> 00:04:39,190 He believed that the world was full of material substance. 39 00:04:39,190 --> 00:04:49,600 But he denied that mind is immaterial. So in corporeal substance, he claims, is just a contradiction in terms. 40 00:04:49,600 --> 00:04:58,540 And you can see here he's making fun of Descartes when men make a name of two names whose signification is a contradictory and inconsistent. 41 00:04:58,540 --> 00:05:08,590 The result is but insignificant sounds as this name and incorporeal body, all which is all one an incorporeal substance. 42 00:05:08,590 --> 00:05:20,580 He's taking Descartes theory, and he's providing it in Leviathan as a paradigm example of an abuse of words. 43 00:05:20,580 --> 00:05:31,620 Now, this was obviously very shocking. The obvious reason if you are a materialist, it makes it very hard to maintain either a belief in God. 44 00:05:31,620 --> 00:05:39,900 I mean, it follows that God is a material substance, which for most people is going to be tantamount to denying that there is a God. 45 00:05:39,900 --> 00:05:45,120 But also, it obviously seriously threatens immortality. 46 00:05:45,120 --> 00:05:51,750 So in the 17th century, this is thought seriously disruptive to morality. 47 00:05:51,750 --> 00:06:01,190 If you deny a future state, a heaven and [INAUDIBLE], then what motive is there for people being moral in this life? 48 00:06:01,190 --> 00:06:07,490 So lots of philosophers, as you can see him, these are only the most prominent ones lined up to refute Hobbes. 49 00:06:07,490 --> 00:06:18,930 The Leviathan came out in sixteen fifty one. We have a large number of responses to Leviathan attacking Hobbes materialism. 50 00:06:18,930 --> 00:06:26,220 Now, the main argument against Hobbs, and this still resonates, by the way, in 21st century debates, 51 00:06:26,220 --> 00:06:32,220 when people ask questions about whether computers could think or whether they could be conscious. 52 00:06:32,220 --> 00:06:36,840 A common argument that comes out is that there is something inconsistent with 53 00:06:36,840 --> 00:06:42,330 the idea of matter thinking and back in the 17th century and the 18th century. 54 00:06:42,330 --> 00:06:49,230 Indeed, this went along with the idea that we have seen from science that matter is inert. 55 00:06:49,230 --> 00:07:01,710 Aristotle was wrong. Galileo was right. Matter just keeps moving at the same speed in the same direction unless it's additive acted upon by a force. 56 00:07:01,710 --> 00:07:07,950 Of course, that's a major plank of Newton's theory that will come along later so that if matter is inert, 57 00:07:07,950 --> 00:07:16,650 then it can't have active powers like thinking. And in that case, it follows that the world cannot be purely material. 58 00:07:16,650 --> 00:07:28,680 We cannot be purely material indeed. But notice that this argument assumes that we can understand the powers of matter a priori. 59 00:07:28,680 --> 00:07:33,420 Now it's worth clarifying this term a priori, it's a very important one. 60 00:07:33,420 --> 00:07:39,810 It crops up a lot in philosophy. So I'm going to give you a dictionary definition of it here. 61 00:07:39,810 --> 00:07:46,890 A belief or claim is said to be justified a priori. If it's epistemic justification, 62 00:07:46,890 --> 00:07:58,320 the reasonable warrant for thinking it to be true does not depend at all on sensory or introspective or other sorts of experience. 63 00:07:58,320 --> 00:08:08,000 Whereas if it's justification does depend, at least in part on such experience, it is said to be justified a posteriori or empirically. 64 00:08:08,000 --> 00:08:17,570 This specific distinction has to do only with the justification of the belief and not at all with how the constituent concepts are required. 65 00:08:17,570 --> 00:08:27,080 OK, that last sentence is very important. So a standard example of an API where I truth is all bachelors are unmarried. 66 00:08:27,080 --> 00:08:34,160 OK, we define a bachelor as an unmarried man, so we can know a priori that all bachelors are unmarried. 67 00:08:34,160 --> 00:08:39,440 Now, clearly, we cannot get the concept of a bachelor except through experience. 68 00:08:39,440 --> 00:08:44,480 If you didn't have any experience, you wouldn't have the concept of a man. You certainly wouldn't have the concept of marriage. 69 00:08:44,480 --> 00:08:49,940 But the crucial point what makes it a priority is that having acquired those concepts, 70 00:08:49,940 --> 00:08:56,630 you don't then need to consult experience to find out whether it's true or false that all bachelors are unmarried. 71 00:08:56,630 --> 00:09:02,210 You can just see by examining the concept that that's the case. OK. 72 00:09:02,210 --> 00:09:10,940 So an API where I truth is something that you can know to be true without any justification from experience. 73 00:09:10,940 --> 00:09:22,430 And this argument against jobs that matter could not possibly think is relying on an April right claim because it's not saying look by experience, 74 00:09:22,430 --> 00:09:27,200 we can tell that matter doesn't think. And that's no good because jobs is going to say. 75 00:09:27,200 --> 00:09:34,850 On the contrary, we know by experience that matter can think because I'm a matter and I can think so. 76 00:09:34,850 --> 00:09:42,110 This argument is based on an a priori claim about the powers of matter, and we'll see that that's a problem. 77 00:09:42,110 --> 00:09:53,880 We'll come back to that a little bit later. So Robert Boyle, a very, very influential scientist in the 17th century, 78 00:09:53,880 --> 00:10:00,300 and he was actually a pioneer of chemistry, and he was very much a champion of the mechanical philosophy. 79 00:10:00,300 --> 00:10:05,040 But unlike Descartes and Hobbes, he was not a plainest. 80 00:10:05,040 --> 00:10:09,780 He did not think that the universe is completely filled up with matter. 81 00:10:09,780 --> 00:10:18,640 He thought there was stuff called universal matter formed into corpuscles what we would think of as atoms. 82 00:10:18,640 --> 00:10:25,500 But the word atom in those days was associated with Greek atom ism, which was notoriously atheist. 83 00:10:25,500 --> 00:10:36,170 So he preferred the word corpus Galarian ism. So you've got corpuscles little think of them as atoms made of stuff, universal matter. 84 00:10:36,170 --> 00:10:41,900 But they are inside a void. So the universe as a whole is empty, 85 00:10:41,900 --> 00:10:52,760 except where you have these material corpuscles and every thing that we see in the world is the result of interactions of these little corpuscles. 86 00:10:52,760 --> 00:11:01,040 And clearly that the kind of corpuscles that make up gold are going to be different from the corpuscles that make up LED. 87 00:11:01,040 --> 00:11:05,600 Maybe a different size, maybe a different shape, maybe put together in a different order. 88 00:11:05,600 --> 00:11:19,360 But essentially, you've got something like an atomic theory. But importantly, a distinction between empty space and matter. 89 00:11:19,360 --> 00:11:25,200 Another bit of the scientific story, which we'll see this all comes together very shortly. 90 00:11:25,200 --> 00:11:30,180 So a chuckle, Tycho Brahimi, a Danish astronomer, 91 00:11:30,180 --> 00:11:38,520 had built an observatory on an island and he was a nobleman, and he created astronomical instruments. 92 00:11:38,520 --> 00:11:43,860 Naked eye that were far, far more accurate than any that had previously been devised. 93 00:11:43,860 --> 00:11:55,590 And over many years, he plotted the paths of the planets and then Yohannes Kepler, who started out as brought his assistant, inherited all that data, 94 00:11:55,590 --> 00:12:02,370 but did some very clever mathematics and discovered that the data were actually most 95 00:12:02,370 --> 00:12:08,070 consistent with the hypothesis that the planets move around the Sun not in circles, 96 00:12:08,070 --> 00:12:17,760 but in ellipses. With the Sun at one focus of the ellipse, I've drawn a little image of something what it's like now. 97 00:12:17,760 --> 00:12:30,310 Kepler published tables, astronomical tables based on his calculations, predicting where the planets would be in the sky at any particular time. 98 00:12:30,310 --> 00:12:37,660 Now, prior to this, the tables that have been published based on Aristotle's theory and later on, 99 00:12:37,660 --> 00:12:45,580 Copernicus, which was sort of it's still fundamentally based on circles, were only of limited accuracy. 100 00:12:45,580 --> 00:12:52,910 And sometimes you might look look up in the sky. You see a planet in roughly the right place, but maybe it's five degrees out. 101 00:12:52,910 --> 00:12:58,070 Kepler's tables were more than a thousand times more accurate. 102 00:12:58,070 --> 00:13:03,890 They were phenomenally accurate. And you've got to remember that this was done without the aid of telescopes. 103 00:13:03,890 --> 00:13:11,490 Quite remarkable. Now over time. 104 00:13:11,490 --> 00:13:17,130 As people became aware that these tables were so fantastically accurate, 105 00:13:17,130 --> 00:13:23,190 it became accepted that actually the planets were moving in ellipses around the Sun, not circles. 106 00:13:23,190 --> 00:13:26,280 I mean, Galileo had already done for the Aristotelian theory. 107 00:13:26,280 --> 00:13:33,620 What Kepler did was show that the astronomical bodies do not move in circles, but ellipses. 108 00:13:33,620 --> 00:13:43,820 And this is where Isaac Newton comes in, because what Newton did was to show that if you have a force between bodies which is proportional 109 00:13:43,820 --> 00:13:49,180 to their mass and inversely proportional to the square of the distance between them. 110 00:13:49,180 --> 00:13:53,260 And if you have one very large body and one very much smaller body, 111 00:13:53,260 --> 00:14:01,550 the smaller body will move under the action of that force in an ellipse around the larger body with the larger body. 112 00:14:01,550 --> 00:14:09,090 That's a focus of the ellipse that's on the assumption that force equals mass times acceleration. 113 00:14:09,090 --> 00:14:09,600 Moreover, 114 00:14:09,600 --> 00:14:22,310 he showed that the same equations with the same constants worked for cannonballs on Earth and worked for the Moon and worked for the planets. 115 00:14:22,310 --> 00:14:27,020 Another thing he showed. This is all in his famous Principia Mathematica. 116 00:14:27,020 --> 00:14:32,540 He showed that a vortex cannot generate elliptical motion. 117 00:14:32,540 --> 00:14:44,730 So Descartes theory is in the vein. Now, all this might seem some distance from philosophy, but think back to that important argument against Hobbs. 118 00:14:44,730 --> 00:14:52,480 And as I say, that's an argument that still resonates today in discussions of mind and consciousness. 119 00:14:52,480 --> 00:14:56,470 Newton has postulated a force, he's got very strong evidence for it, too. 120 00:14:56,470 --> 00:14:59,350 It fits with the data brilliantly. 121 00:14:59,350 --> 00:15:07,600 He's postulated a force that acts as a distant at a distance between bodies with no intermediate mechanical connexion. 122 00:15:07,600 --> 00:15:15,520 But this seems completely unintelligible. OK, Descartes, in arguing against the Aristotelian CID, said this this idea of strivings, 123 00:15:15,520 --> 00:15:21,010 you know, a body striving to reach the centre of the Earth is ridiculous. The body would have to be conscious. 124 00:15:21,010 --> 00:15:26,800 It would have to know where the centre of the Earth is, what exactly the same applies to gravity. 125 00:15:26,800 --> 00:15:33,190 If you've got two bodies in space, how can this one be attracted to this one unless it somehow knows where it is? 126 00:15:33,190 --> 00:15:40,200 If you've got no mechanical interaction between them, how would you explain gravity? 127 00:15:40,200 --> 00:15:44,520 Now, the real problem here is it's not so much. 128 00:15:44,520 --> 00:15:48,930 OK, well, we just have to accept this unknown for this strange force gravity. 129 00:15:48,930 --> 00:15:52,590 You know, we have evidence that it exists, but we've no idea how. 130 00:15:52,590 --> 00:15:59,670 What's the problem with that? Well, the problem is that if matter can have an active force like gravity, 131 00:15:59,670 --> 00:16:09,300 why couldn't it have an active power like thinking once you allow that matter can have all sorts of properties that we can't understand. 132 00:16:09,300 --> 00:16:15,200 Materialism is far harder to attack. 133 00:16:15,200 --> 00:16:24,770 So Newton famously said hypotheses non thing go that can be interpreted in various ways, but he seems to be saying my equations work. 134 00:16:24,770 --> 00:16:34,560 I'm not going to worry about what the mechanism is, how it all works until I've got some data to base that on. 135 00:16:34,560 --> 00:16:41,250 But as I say, it has a real consequence for the argument about materialism. 136 00:16:41,250 --> 00:16:48,540 So one thing I want to really emphasise here is that scientific progress over the early modern period 137 00:16:48,540 --> 00:16:57,000 systematically pushed us progressively away from a natural and intuitive understanding of things. 138 00:16:57,000 --> 00:17:07,590 And this is carried on in later science. So Aristotle started from the very natural nice idea that we can understand the way things in nature work, 139 00:17:07,590 --> 00:17:13,980 both on the assumption that they've been designed intelligently and that they are crazy, intelligent themselves. 140 00:17:13,980 --> 00:17:26,010 They strive to achieve certain purposes. Galileo refuted that Descartes tried to get a theory which was compatible with simple mechanism, 141 00:17:26,010 --> 00:17:31,080 whereby things work in intelligible ways by one piece of matter, 142 00:17:31,080 --> 00:17:37,570 pushing on another in vortices and so we can understand where we feel that's intelligible. 143 00:17:37,570 --> 00:17:41,700 And then we get Keppler and Newton showing that that's that just seems to be wrong. 144 00:17:41,700 --> 00:17:45,730 OK, the mathematics just doesn't work with empirical observation, 145 00:17:45,730 --> 00:17:51,940 so we end up having to have this gravitational force, which seems completely unintelligible. 146 00:17:51,940 --> 00:17:58,060 I mean, we can understand it, understand it inverted commas to the extent of calculating what its upshot is. 147 00:17:58,060 --> 00:18:07,120 But we've no idea at all where it comes from or how matter generates it. 148 00:18:07,120 --> 00:18:14,110 And I'm not going to describe this in any detail, but we see the same in 20th century physics. 149 00:18:14,110 --> 00:18:22,540 All right, general relativity, we get the idea of space being linked intimately with time and somehow being curved, 150 00:18:22,540 --> 00:18:30,580 which most of us find extraordinarily difficult to get our heads around quantum mechanics. 151 00:18:30,580 --> 00:18:36,100 Fundamental particles will all be particles. They're very weird. 152 00:18:36,100 --> 00:18:40,300 Their behaviour is describable, but it's not really intelligible. 153 00:18:40,300 --> 00:18:51,910 So although physics retains the goal of accurate prediction and explanation of a sort, it seems somehow it's how to give up on making sense of things. 154 00:18:51,910 --> 00:19:02,290 So just spell it out. In science, we often talk about explaining something when we have formulae that generate the observation and we can say, 155 00:19:02,290 --> 00:19:06,850 Oh, that observation is consistent with our theory because look, we've done this calculation and it works out. 156 00:19:06,850 --> 00:19:11,710 We've explained it. That's not the same as rendering it intelligible. 157 00:19:11,710 --> 00:19:21,190 If the equations that we're using are ones that seem deeply unintuitive to us, then we may resist the idea that we really understand what's going on. 158 00:19:21,190 --> 00:19:25,900 And obviously, philosophers can ask serious questions about this notion of understanding. 159 00:19:25,900 --> 00:19:32,180 I'm not going to have time to go into that deeply now. I just want to illustrate for those of you who might not know about it. 160 00:19:32,180 --> 00:19:37,560 And here is a simulation of the two slit experiment. 161 00:19:37,560 --> 00:19:48,060 So Thomas Young devised this experiment, and what he found was that if you take a source of light, by the way, it's monochromatic light. 162 00:19:48,060 --> 00:19:58,200 I'll explain the colours in a moment. You've got a single source of light there, and the light is hitting a screen which has two slits in it. 163 00:19:58,200 --> 00:20:04,710 A man at the back of the apparatus, there's another another screen and. 164 00:20:04,710 --> 00:20:11,210 What you get if you shine light through like that, as you can see at the top. 165 00:20:11,210 --> 00:20:16,360 You end up with bands of light. 166 00:20:16,360 --> 00:20:25,130 OK, now that was taken to be very strong evidence for a wave theory of light. 167 00:20:25,130 --> 00:20:32,380 And now, by the way, the colours are indicating where we are through a wavelength, so we kind of going round the colour spectrum each wavelength. 168 00:20:32,380 --> 00:20:40,240 And so they enable me to highlight the interference and the brighter they are, the the bigger the amplitude. 169 00:20:40,240 --> 00:20:47,260 So what's going on here is if you imagine dropping two pebbles into a pond some distance apart. 170 00:20:47,260 --> 00:20:52,900 Each of the pebbles will cause a wave moving out from where you've dropped it. 171 00:20:52,900 --> 00:21:02,110 And if you've got waves from this pebble and waves from this pebble, then when they interact, they can either do so destructively. 172 00:21:02,110 --> 00:21:07,660 So this wave is high up and this one's in a trough and they kind of cancel out. 173 00:21:07,660 --> 00:21:14,480 Well, sometimes you can have a trough in this wave and a trough in this one and you end up with a deeper trough. 174 00:21:14,480 --> 00:21:26,330 So the kind of pattern you get from this interference is like that, and you can see it nicely explains where we get light on the screen at the back, 175 00:21:26,330 --> 00:21:35,780 that's where the the two light sources are constructively interfering rather than destructively interfering. 176 00:21:35,780 --> 00:21:47,180 OK, well, that's very nice. But then it was discovered early 20th century that a light kind of comes in particles. 177 00:21:47,180 --> 00:21:58,280 You can you cannot get less than a certain amount of any particular wavelength of light light particles called photons, the sort of packages of light. 178 00:21:58,280 --> 00:22:03,710 And whenever you try to detect light, you only ever detect it in terms of these photons. 179 00:22:03,710 --> 00:22:12,160 So if you take a a faint enough light, you will only ever detect it at one particular place. 180 00:22:12,160 --> 00:22:23,890 Now, once that's discovered, we can rethink our experiment and we send the light through the apparatus. 181 00:22:23,890 --> 00:22:33,100 One photon at a time. In other words, we make sure that the light is so weak that at any particular time, we only detect this at one point. 182 00:22:33,100 --> 00:22:43,240 If we put detectors there. And what's rather surprising is that we still get an interference pattern. 183 00:22:43,240 --> 00:22:47,800 Now, that's weird, right, because we're only sending the light out one photon at a time. 184 00:22:47,800 --> 00:22:55,110 It can only go through one slit at most. And yet somehow we're still getting an interference pattern. 185 00:22:55,110 --> 00:23:06,210 That seems spooky. All right, well, let's add detectors to the. 186 00:23:06,210 --> 00:23:07,140 Two slits. 187 00:23:07,140 --> 00:23:18,390 So now we're sending individual films through the apparatus, but we've added detectors so that we can tell which slit the photon is going through. 188 00:23:18,390 --> 00:23:30,360 And sure enough, it only ever goes through one. But now, as you can see, the interference pattern disappears. 189 00:23:30,360 --> 00:23:36,390 So it's very odd you try to think of photons of light as particles or you try to think of them as waves. 190 00:23:36,390 --> 00:23:41,550 And either way, I'm afraid our natural understanding fails to do it. 191 00:23:41,550 --> 00:23:52,200 If you have to think of them as some strange mixture of particles and waves, something very unfamiliar to our experience, 192 00:23:52,200 --> 00:23:58,350 we can do the mathematics, by the way, where we show probability distribution. 193 00:23:58,350 --> 00:24:02,970 You get a different. So we can work out. We can do the mathematics to explain what will happen. 194 00:24:02,970 --> 00:24:08,910 Of course, that maths is built into this computer programme, but trying to get an intuitive understanding of it, 195 00:24:08,910 --> 00:24:17,670 trying to think of it in terms of either waves in water or little billiard balls or whatever, just completely fails. 196 00:24:17,670 --> 00:24:24,810 So. That's a very important lesson, as science has developed. 197 00:24:24,810 --> 00:24:35,100 It's actually shown serious limitations to our intuitive understanding to explain how the world fundamentally is. 198 00:24:35,100 --> 00:24:43,050 OK. Let's now go back to physical ism. 199 00:24:43,050 --> 00:24:51,510 So the kind of physical ism that Thomas Hobbs adopted, materialism, 17th century materialism seemed very straightforward. 200 00:24:51,510 --> 00:24:57,390 Everything that exists consists of matter and matter is spatially extended uniform. 201 00:24:57,390 --> 00:25:03,240 Solid stuff. Whose causal interactions are purely mechanical. 202 00:25:03,240 --> 00:25:09,120 OK, so people like Descartes and Hobbes knew what they meant by matter. 203 00:25:09,120 --> 00:25:13,950 Then along came Newton, and matter becomes a bit more complicated. 204 00:25:13,950 --> 00:25:22,470 Now we've got forces acting on it. Forces like gravity, where we can't really render intelligible how that works. 205 00:25:22,470 --> 00:25:33,510 We can produce equations, but we can't give any commonsensical understanding of why one body attracts another across millions of miles. 206 00:25:33,510 --> 00:25:41,730 Of course, after Newton with modern physics, we find that matter isn't any solid, uniform material stuff. 207 00:25:41,730 --> 00:25:50,880 It's not like Boyle thought you haven't got corpuscles made of universal matter, differing only in their shape, size and texture. 208 00:25:50,880 --> 00:25:55,500 Actually, you've got a variety of fundamental particles. 209 00:25:55,500 --> 00:26:04,890 Some of them are mass slits. Some of them seem point like they have properties like charge and spin, even strangeness. 210 00:26:04,890 --> 00:26:15,240 And they operate within a space time continuum relativity, which seems from quantum mechanics to be in deterministic. 211 00:26:15,240 --> 00:26:24,240 So the Commons, when we think of matter now, when we discuss physical ism, you know, 10 physical stuff produce mind. 212 00:26:24,240 --> 00:26:32,150 We're asking a different kind of question from what Hobbes was asking because we've got such a different concept of matter. 213 00:26:32,150 --> 00:26:37,910 And this leads to something like hemp, something called Hemphill's dilemma. 214 00:26:37,910 --> 00:26:43,340 So take the claim everything in the universe is physical. 215 00:26:43,340 --> 00:26:50,190 There is no non-physical stuff in the universe. And what does that claim mean? 216 00:26:50,190 --> 00:26:57,330 Does it mean everything is physical in the sense that we currently understand physical? 217 00:26:57,330 --> 00:27:04,110 Well, that's probably false because our current physics is probably false, at least in part, 218 00:27:04,110 --> 00:27:09,870 not least because general relativity and quantum mechanics have not yet been rendered consistent. 219 00:27:09,870 --> 00:27:16,230 So it's very unlikely that everything is physical in a way that conforms to our current physical theory. 220 00:27:16,230 --> 00:27:26,520 On the other hand, if we mean everything is physical in the sense of conforming to what the ideal eventual perfect physical theory will be. 221 00:27:26,520 --> 00:27:33,780 Well, then it begins to look kind of true by definition that everything is physical because maybe in that true theory, 222 00:27:33,780 --> 00:27:38,620 you know, everything will be in there, including minds, by the way. 223 00:27:38,620 --> 00:27:50,710 And why not? So it's very, very difficult to put the thesis of materialism or physical ism in a way that doesn't beg questions. 224 00:27:50,710 --> 00:27:59,800 We think we understand what we're saying when we say that everything is physical, but actually it's not so clear that we do. 225 00:27:59,800 --> 00:28:08,830 OK, we'll return to this important question Mind-Body physical exam in a later lecture. 226 00:28:08,830 --> 00:28:18,980 I now want to talk. About our understanding of our own place in the world and here, Charles Darwin is the key figure. 227 00:28:18,980 --> 00:28:27,770 Now you may think find it odd having quite a lot on evolution in a lecture about general philosophy. 228 00:28:27,770 --> 00:28:39,020 But I want to suggest to you that actually all six of the topics concerning general philosophy can be illuminated by thinking in terms of evolution. 229 00:28:39,020 --> 00:28:49,730 Because with all of these topics, we are applying our intelligence to try to understand difficult problems. 230 00:28:49,730 --> 00:28:55,130 And if our intelligence is itself the result of an evolutionary process. 231 00:28:55,130 --> 00:29:03,380 Then that sheds light on how far we can expect it to be able to get to the bottom of these things. 232 00:29:03,380 --> 00:29:10,220 And there are some more thus far more specific Connexions that I'll complete. 233 00:29:10,220 --> 00:29:18,290 OK. So there are obvious similarities between humans and animals, people that obviously recognise these forever. 234 00:29:18,290 --> 00:29:24,300 But before Darwin, humans and animals were thought to be radically distinct. 235 00:29:24,300 --> 00:29:32,240 Man is made in the image of God. Animals are lower down in the ladder, according to Aristotle. 236 00:29:32,240 --> 00:29:37,760 Man is uniquely a rational animal that sets us apart from all the rest, 237 00:29:37,760 --> 00:29:45,710 and this kind of idea was systematised in the great chain of being, of which there is an image there. 238 00:29:45,710 --> 00:29:51,890 So this is Aristotle's ladder of nature systematised by a later philosopher near Neo Platon. 239 00:29:51,890 --> 00:30:03,680 It's called Platini's. And you can see that that there's the hierarchy in which he puts things all fitting neatly into the divine world order. 240 00:30:03,680 --> 00:30:10,730 Descartes again, thought that was a radical distinction between humans and animals. 241 00:30:10,730 --> 00:30:20,350 The beasts have no reason at all. They have no intelligence at all. Animals lack reason, perhaps even thought. 242 00:30:20,350 --> 00:30:28,540 But nevertheless, physically, they're similar to us in certain respects, the physical bodies act in many ways. 243 00:30:28,540 --> 00:30:35,200 Similarly, but they don't have the immaterial mind. 244 00:30:35,200 --> 00:30:40,390 Now along comes Darwin, and I want to give credit here also to Alfred Russel Wallace, 245 00:30:40,390 --> 00:30:46,360 who came up with the theory of natural selection up more or less at the same time as Darwin, actually a bit later. 246 00:30:46,360 --> 00:30:55,840 But he was quick to get it out, whereas Darwin had been pondering this for years and years and years, collecting loads of data but not publishing. 247 00:30:55,840 --> 00:31:01,330 Darwin was reluctant to publish because he could see that his work would be 248 00:31:01,330 --> 00:31:07,180 extremely controversial and dreamily troublesome for those who are religious, 249 00:31:07,180 --> 00:31:13,300 including in his own family. But along came Wallace, he wrote to Russell. 250 00:31:13,300 --> 00:31:20,290 Sorry. Along came Wallace, he wrote to Darwin, said, Here's my theory. 251 00:31:20,290 --> 00:31:28,820 Darwin realised it was the same as his. And they presented together the theory of natural selection. 252 00:31:28,820 --> 00:31:36,860 So kind of joint discovers both of them, interestingly, had been inspired by a clergyman, 253 00:31:36,860 --> 00:31:43,340 Thomas Malthus and Thomas Malthus wrote an essay on the principle of population, 254 00:31:43,340 --> 00:31:57,260 basically pointing out that animals the the the pace at which a population increases will generally be a geometric series. 255 00:31:57,260 --> 00:32:10,890 In other words, the more the larger population is, if it continues to breed at the same rate, then you will get an exponential increase in population. 256 00:32:10,890 --> 00:32:22,110 Now, that means that even if you somehow manage to increase the food supply by a constant amount year on year. 257 00:32:22,110 --> 00:32:27,720 Eventually, the population is going to outrun the food available. 258 00:32:27,720 --> 00:32:34,590 Now, I think it's quite hard to appreciate just what exponential growth does. 259 00:32:34,590 --> 00:32:38,850 So I've got here a little simulation. 260 00:32:38,850 --> 00:32:50,850 So imagine a population of rabbits and that population of rabbits is just a hundred of them and they are bang in the middle of the globe, 261 00:32:50,850 --> 00:33:01,350 you see there. OK, now we've got it so that these rabbits breed at what's actually a fairly modest rate for rabbits. 262 00:33:01,350 --> 00:33:06,300 If you've come across the habits of rabbits. 263 00:33:06,300 --> 00:33:17,400 They're growing at the population is growing at a rate of 10 percent per generation, just 10 percent with two months per generation 60 days. 264 00:33:17,400 --> 00:33:22,260 OK. And let's see what happens when we set this running. 265 00:33:22,260 --> 00:33:31,800 One thing about these rabbits, they have no predators. They don't get disease and they can spread around the world quite quickly. 266 00:33:31,800 --> 00:33:41,550 The only constraint on them is you cannot have more than one rabbit per square foot or if your metric about nine per square metre. 267 00:33:41,550 --> 00:33:51,070 Okay, so here's here we go. Right. 268 00:33:51,070 --> 00:34:00,410 That took fifty two point four years. Now that's exponential growth for you. 269 00:34:00,410 --> 00:34:13,210 Now, one way you can think about evolution is that unchecked, pretty much any biological species is going to do that. 270 00:34:13,210 --> 00:34:23,110 So you've got immense competition, only a tiny proportion of the possible offspring or the possible offspring of offspring or offspring of offspring, 271 00:34:23,110 --> 00:34:29,060 offspring of offspring and so on. Only a tiny proportion will survive. 272 00:34:29,060 --> 00:34:36,190 Now, if that so. What's going to determine which one survive, is it going to be me a chance? 273 00:34:36,190 --> 00:34:42,910 Well, there'll be a lot of chumps in it, of course. But when you've got that much selection taking place. 274 00:34:42,910 --> 00:34:49,990 Any factor which biases the chance is going overtime to have a very big effect. 275 00:34:49,990 --> 00:34:57,400 OK? There will be some which stand a slightly better chance of surviving because they're faster 276 00:34:57,400 --> 00:35:04,720 or stronger or more immune to certain poisons or able to digest more things or whatever. 277 00:35:04,720 --> 00:35:13,540 And when you've got that level of competition, those advantages are going to tell. 278 00:35:13,540 --> 00:35:17,620 So. This is what natural selection is. 279 00:35:17,620 --> 00:35:25,480 If animals or plants have these features, the characteristics are largely inherited with some random variation. 280 00:35:25,480 --> 00:35:31,210 So obviously, you can't invariably predict that taller parents will have taller kids. 281 00:35:31,210 --> 00:35:35,170 It doesn't always work that way. But by and large, the taller the parents are. 282 00:35:35,170 --> 00:35:43,720 That's all of the kids are going to be right. Some of these characteristics are relevant to survival and reproduction. 283 00:35:43,720 --> 00:35:51,520 That's obvious out there in nature, where gazelles are being chased by cheetahs and so forth, 284 00:35:51,520 --> 00:35:55,570 being a little bit faster as a gazelle gives you a much better chance of survival. 285 00:35:55,570 --> 00:35:59,920 If you can outrun the other one, you're less likely to be caught. 286 00:35:59,920 --> 00:36:08,030 And if you're a cheetah, being a little bit faster can enable you to catch a mule where otherwise you wouldn't. 287 00:36:08,030 --> 00:36:09,500 They live in a competitive environment. 288 00:36:09,500 --> 00:36:17,510 Well, the moral of the programme I've just shown you is that more or less everything in nature lives in a competitive environment. 289 00:36:17,510 --> 00:36:24,230 There is no way that you can have pure stability and no competition. 290 00:36:24,230 --> 00:36:29,530 Not in practise. And then natural selection is pretty much inevitable. 291 00:36:29,530 --> 00:36:42,850 It's pretty much inevitable that as the generations go on, proportionately more will will have what we now call the genes we the inherited the 292 00:36:42,850 --> 00:36:51,600 code that creates the inherited characteristics that are more conducive to survival. 293 00:36:51,600 --> 00:37:01,600 Now, some things can hugely speed this up. I've given the example of cheetahs and gazelles and where you get co-evolution. 294 00:37:01,600 --> 00:37:08,700 But this process can go really, really fast if you've got gazelles competing against cheetahs. 295 00:37:08,700 --> 00:37:20,490 Then if you're a gazelle and you are slower than usual, nature is going to have its effect on you very quickly in the form of a fast cheetah. 296 00:37:20,490 --> 00:37:26,240 Unlike wise, the fast cheetahs are going to get a pretty quick reward for being faster. 297 00:37:26,240 --> 00:37:33,440 So evolution will run really fast. And again, one can simulate this with computer programmes, 298 00:37:33,440 --> 00:37:46,750 and it's very apparent how introducing this element of competition between two competing species radically can speed things up. 299 00:37:46,750 --> 00:37:52,240 Sexual selection is also well worth introducing here. 300 00:37:52,240 --> 00:38:01,120 If you have sexually reproducing species, then typically you've got an asymmetry between females and males. 301 00:38:01,120 --> 00:38:09,760 Males are capable of having lots of offspring, females far fewer, and therefore females tend to be much more selective. 302 00:38:09,760 --> 00:38:14,350 And if females choose their mate according to particular characteristics, 303 00:38:14,350 --> 00:38:22,150 and the obvious example is pigeons choosing peacocks with impressive tails that can drive a runaway process. 304 00:38:22,150 --> 00:38:31,090 Basically, if you're a peacock or a pigeon, if you well. 305 00:38:31,090 --> 00:38:38,410 More or less, any person is going to be able to mate, but amongst the peacocks, some will do very well, 306 00:38:38,410 --> 00:38:44,770 and some, I'm afraid, will end up without a partner because the hens are being selective. 307 00:38:44,770 --> 00:38:50,440 So the competition is far more amongst the males than amongst the females. 308 00:38:50,440 --> 00:39:00,040 And as a result, you can get this, you know, the absurdity of a peacock tail, which must hinder the peacocking getting away from prey. 309 00:39:00,040 --> 00:39:10,510 But because it's so effective in attracting P hens that over balances and any negatives. 310 00:39:10,510 --> 00:39:18,160 OK, so evolution is a very sophisticated theory, there's the I've only mentioned a few of the parts of it. 311 00:39:18,160 --> 00:39:22,150 It's a very powerful. It explains a huge amount. 312 00:39:22,150 --> 00:39:31,330 I'm going to spend a fair bit of this lecture now just outlining some of the evidence for evolution and drawing a moral from this. 313 00:39:31,330 --> 00:39:36,320 I think it's well worth knowing this because there's a lot of misinformation about this. 314 00:39:36,320 --> 00:39:43,900 People like to say, Oh, evolution is only a theory. I talk about as though it's less than certain. 315 00:39:43,900 --> 00:39:52,750 Even when Darwin wrote of the origin of species, the the evidence he had was very, very strong. 316 00:39:52,750 --> 00:40:02,770 But the evidence we now have is absolutely overwhelming because we have found so much that fits in perfectly with the evolutionary story. 317 00:40:02,770 --> 00:40:13,290 We've got the fossil record, we've got vestiges that is evidence from the bodies of creatures that now exist. 318 00:40:13,290 --> 00:40:25,050 Which features that don't make any sense in terms of how they now live, but make perfect sense when seen as inherited from previous species. 319 00:40:25,050 --> 00:40:36,600 Got evidence from embryology and development the way in which foetuses develop, which to some extent recapitulate an evolutionary history. 320 00:40:36,600 --> 00:40:45,960 We've got evidence of biogeography where the animals and plants are distributed around the world, and most recently, we've got evidence of genetics. 321 00:40:45,960 --> 00:40:53,670 So basically, once once DNA was discovered and once people started analysing the genetic sequences, 322 00:40:53,670 --> 00:40:58,050 all lo and behold, it all fitted perfectly with an evolutionary story. 323 00:40:58,050 --> 00:41:02,550 So you can. There's lots of sources for this. I'm just going to mention a couple of them. 324 00:41:02,550 --> 00:41:05,160 One of them is obviously Wikipedia. 325 00:41:05,160 --> 00:41:14,250 The other one, I think this is an excellent book, and the authors kindly gave me some images for me to use in this lecture. 326 00:41:14,250 --> 00:41:20,610 So the images here, unfortunately, won't be able to get much from them on the handout. 327 00:41:20,610 --> 00:41:26,280 But the important thing is is the page numbers. If you if you want to follow this up, go and look at the book. 328 00:41:26,280 --> 00:41:34,350 You can see where these things are. So there are lots of transitional forms, when Darwin wrote. 329 00:41:34,350 --> 00:41:37,260 People were able to say of him. Hang on. 330 00:41:37,260 --> 00:41:46,320 If you're right, there should be lots of intermediate forms of animals intermediate between the ones that we now see. 331 00:41:46,320 --> 00:41:55,200 Well, those have since been discovered. Here's one example Tiktaalik discovered in 2004. 332 00:41:55,200 --> 00:42:01,210 It seems to be a genuine intermediate between a fish and an amphibian. 333 00:42:01,210 --> 00:42:10,870 And the year after Darwin wrote Archaeopteryx, famously intermediate between a small dinosaur and a modern bird. 334 00:42:10,870 --> 00:42:23,720 There are lots of others. Here's one example in the highest and sort of ancient pig like animal. 335 00:42:23,720 --> 00:42:30,720 And the modern whale and intermediates have been discovered all the way through. 336 00:42:30,720 --> 00:42:39,960 And this makes sense of why the whale has a vestigial pelvis and hind limb wouldn't make any sense if the whale was a fish. 337 00:42:39,960 --> 00:42:48,120 But explaining the whale as evolved from an animal somewhat like a pig does explain it. 338 00:42:48,120 --> 00:42:56,580 Humans and apes again in Darwin's time. There wasn't this richness of intermediate forms. 339 00:42:56,580 --> 00:43:06,570 Now there are. And you can see at the top left you got Homo sapiens, that's us at the bottom right, you've got the chimp. 340 00:43:06,570 --> 00:43:15,400 And there are a load of intermediates. I mean, the the story of human evolution is a complicated one, the seem to be lots of different species, 341 00:43:15,400 --> 00:43:19,510 and it's not absolutely clear, you know, which descended from what. And so on. 342 00:43:19,510 --> 00:43:30,490 What is clear is that there are lots of intermediates. Biogeography, well, there's lots of evidence for continental drift from Earth Sciences. 343 00:43:30,490 --> 00:43:47,870 I mean, for example, ocean rifts where you get spreading, where the magnetic bands on each side of the Rift are kind of match up and. 344 00:43:47,870 --> 00:43:55,850 The theory of continental drift became very well-accepted in the 60s and 70s before that had been extremely controversial. 345 00:43:55,850 --> 00:44:02,390 But if you put that evidence together with biogeography where fossils are to be found, 346 00:44:02,390 --> 00:44:14,240 where different kinds of trees are to be found, it makes lots of sense of what would otherwise be senseless. 347 00:44:14,240 --> 00:44:25,970 Instances of bad design. This is really vestiges, this is cases where we find that modern animals, including ourselves, 348 00:44:25,970 --> 00:44:33,560 have certain aspects which wouldn't make very good sense from the point of view of an intelligent designer. 349 00:44:33,560 --> 00:44:37,160 And one famous example is the blind spot in the eye. 350 00:44:37,160 --> 00:44:51,010 I mean, another is how humans give birth, which is notoriously painful and difficult and potentially carrying a risk of death in nature. 351 00:44:51,010 --> 00:45:01,630 But in another, a particularly vivid one is this nerve, the the left recurrent laryngeal nerve, which goes all the way down and back again. 352 00:45:01,630 --> 00:45:13,570 And that doesn't make any sense at all. From a design point of view, but it does make sense if you see as is being evolved ultimately from fishes. 353 00:45:13,570 --> 00:45:22,330 OK. I've not gone in detail through DNA evidence, but that I think is also tremendously important. 354 00:45:22,330 --> 00:45:31,780 So I just want to point out here an important consequence of all this. 355 00:45:31,780 --> 00:45:38,290 You will find people who want to deny evolution. Typically, they want to do so on religious grounds. 356 00:45:38,290 --> 00:45:45,210 But here is why I think if if you are religious, you should not be going that way. 357 00:45:45,210 --> 00:45:50,160 I don't actually think that evolution shows religion to be false. 358 00:45:50,160 --> 00:45:57,990 It doesn't show that there's no God. It may show that certain rather narrow fundamentalist views on religion are false ones that claim, 359 00:45:57,990 --> 00:46:02,340 for example, that Genesis gives an accurate story of the creation. 360 00:46:02,340 --> 00:46:08,820 But then, since there's more than one story in Genesis, that's fairly easy to conclude anyway. 361 00:46:08,820 --> 00:46:21,180 But here's the problem if you think there is a God who did not operate by evolution, but yet gave us all this evidence of evolution in the rocks, 362 00:46:21,180 --> 00:46:35,350 in the fossils, in the distribution of plants in our own DNA, then you have to believe in a creator who actually is deliberately deceiving us. 363 00:46:35,350 --> 00:46:42,560 Because why else would all that false evidence be there? And if you believe in a creator who can deceive us, 364 00:46:42,560 --> 00:46:50,010 then you've got no reason to believe that holy book on which you are basing your denial of evolution. 365 00:46:50,010 --> 00:47:00,430 You can't have it both ways. The evidence is there. If that was put there by a designer, then it was put there by a designer who was lying to us. 366 00:47:00,430 --> 00:47:10,720 In which case you could lie in other respects as well. Okay, so I want to explain why I think evolution is completely incontrovertible. 367 00:47:10,720 --> 00:47:18,400 All right. This is not a controversial view amongst people who know the evidence. 368 00:47:18,400 --> 00:47:21,460 What's the significance of it? 369 00:47:21,460 --> 00:47:37,050 Well, if we are continuous with animals and if our faculties have evolved in response to selective pressures over the multitudinous generations? 370 00:47:37,050 --> 00:47:42,740 Then that tells us something about our rational connexion with the world. 371 00:47:42,740 --> 00:47:52,910 And when we ask questions like, what can we know, how are we able to predict things about the world? 372 00:47:52,910 --> 00:48:01,580 What is the nature of personal identity? What is the nature of freedom or mind and body? 373 00:48:01,580 --> 00:48:11,640 If we bear in mind that the brains with which we are trying to get to the bottom of these things are evolved organs. 374 00:48:11,640 --> 00:48:16,200 Then we shouldn't be so surprised that sometimes our intuitive judgements about 375 00:48:16,200 --> 00:48:21,660 things may prove to be radically at odds with the real nature of things. 376 00:48:21,660 --> 00:48:28,520 Why be surprised that quantum particles act in ways that we find completely counterintuitive? 377 00:48:28,520 --> 00:48:38,600 That's exactly what you'd expect, because in the evolutionary scenario, an ability to understand quantum particles played no role at all. 378 00:48:38,600 --> 00:48:46,310 What was important was to be good with medium sized objects like rocks or spears. 379 00:48:46,310 --> 00:48:49,610 Being good with quantum particles would have been of no use to you at all. 380 00:48:49,610 --> 00:48:56,300 It would just be a waste of brain space. And this goes for a lot of these different topics. 381 00:48:56,300 --> 00:49:03,470 So I'm from the next lecture, we'll be focussing very specifically on these various topics, 382 00:49:03,470 --> 00:49:09,500 but I hope as we go through that you will bear in mind some of the lessons we've seen from these first two lectures, 383 00:49:09,500 --> 00:49:16,650 which I think very importantly on every single one of the six topics. Thank you.