1 00:00:05,270 --> 00:00:12,710 Welcome to the first of eight lectures on general philosophy, and in these first two lectures, 2 00:00:12,710 --> 00:00:20,600 I'm going to be giving a historical background to a lot of the discussion that comes later. 3 00:00:20,600 --> 00:00:24,890 In this first lecture, some of the figures will be considering, well, 4 00:00:24,890 --> 00:00:36,310 Monty Python's God at the far left, then Plato and Aristotle Galileo and Rene Descartes. 5 00:00:36,310 --> 00:00:41,530 Let's start by asking what general philosophy is. 6 00:00:41,530 --> 00:00:46,930 Well, it's contrasted with ethics or moral philosophy. 7 00:00:46,930 --> 00:00:54,580 It is focussing on theoretical questions and particularly some central questions of epistemology. 8 00:00:54,580 --> 00:01:00,190 That's the question of what can we know and metaphysics? 9 00:01:00,190 --> 00:01:09,130 What is the fundamental nature of things? Part of the point of this course is to illustrate how philosophy is done. 10 00:01:09,130 --> 00:01:15,430 It will show you types of argument methods of enquiry that you can use more generally. 11 00:01:15,430 --> 00:01:20,900 And the course, as you'll have seen from the reading list, has a historical focus. 12 00:01:20,900 --> 00:01:27,760 The six topics are all introduced through the writings of great philosophers of the 17th and 18th centuries, 13 00:01:27,760 --> 00:01:34,530 namely Rennie Descartes, John Locke and David Hume. 14 00:01:34,530 --> 00:01:39,560 Now it's worth spending a little time on the role of these lectures. 15 00:01:39,560 --> 00:01:48,950 Much of your learning in Oxford will be structured around small tutorials, typically in pairs, so it'll be two of you and a tutor. 16 00:01:48,950 --> 00:01:53,900 And this provides a wonderful opportunity for developing your philosophical skills. 17 00:01:53,900 --> 00:02:04,310 Normally, you'll be asked to write an essay for a tutorial like that, and the tutorial will be focussed on critical discussion of your ideas. 18 00:02:04,310 --> 00:02:11,180 That's something that you can only acquire in that way, and it's a very valuable learning experience. 19 00:02:11,180 --> 00:02:17,420 But tutorials are not expected to cover everything that you learn. 20 00:02:17,420 --> 00:02:25,910 Lectures are provided to give the context, wider coverage to go through topics that you won't have time to do in all your 21 00:02:25,910 --> 00:02:32,490 tutorials showing how different topics linked together within a broader framework. 22 00:02:32,490 --> 00:02:39,120 So the kinds of skills that you acquire in your tutorials, where you're being challenged on your own ideas, 23 00:02:39,120 --> 00:02:43,830 where you're learning to think carefully and critically about those ideas, 24 00:02:43,830 --> 00:02:55,770 those skills, you can apply much more widely if you've acquired the general knowledge of the topic area through lectures. 25 00:02:55,770 --> 00:03:00,600 Now, the topics that we consider in general, philosophy are especially fundamental. 26 00:03:00,600 --> 00:03:06,240 They draw on and they contribute to worldviews that go back to antiquity. 27 00:03:06,240 --> 00:03:13,940 And importantly, they remain of tremendous interest in our lives today. 28 00:03:13,940 --> 00:03:21,350 So I'm going to say a little bit about the role of history within this course. 29 00:03:21,350 --> 00:03:32,930 One pragmatic point, I'll note is that the examiners for general philosophy would like to see understanding of the primary texts, 30 00:03:32,930 --> 00:03:41,240 they consider it a virtue that you should be able to show significant acquaintance with historical material. 31 00:03:41,240 --> 00:03:49,190 It's an interesting question why should that be? And I'll come to that in a moment. 32 00:03:49,190 --> 00:04:00,230 Specifically, we've got six topics Descartes is listed on the reading list, the three of them, Hume is listed for four of them. 33 00:04:00,230 --> 00:04:04,550 John Locke is listed for personal identity and the particular works. 34 00:04:04,550 --> 00:04:12,560 Here are Descartes meditations. An addition is shown at the top there on the right. 35 00:04:12,560 --> 00:04:23,330 David Hume's enquiry concerning human understanding. And the chapter on personal identity from Locke's essay. 36 00:04:23,330 --> 00:04:27,800 The six topics, all of them have a pretty wide linkage. 37 00:04:27,800 --> 00:04:32,270 Historically, knowledge and scepticism will be coming across. 38 00:04:32,270 --> 00:04:36,980 Descartes sceptical arguments and his evil genius. 39 00:04:36,980 --> 00:04:44,810 The veil of perception is associated with John Locke and with actually a fair amount of early modern philosophy, 40 00:04:44,810 --> 00:04:49,700 the idea that our perceptions don't give us immediate access to what's really there. 41 00:04:49,700 --> 00:04:57,950 So how do we know what's there? And we'll be seeing Hume playing a large role with regard to scepticism. 42 00:04:57,950 --> 00:05:04,700 He's an advocate of what he calls mitigated scepticism, as we'll see in about the fourth lecture, 43 00:05:04,700 --> 00:05:11,430 Hume's argument concerning induction will play a large role in the third lecture. 44 00:05:11,430 --> 00:05:19,170 God and the evil we will come to towards the end of the lectures. Uh, Descartes famously argued for God's existence. 45 00:05:19,170 --> 00:05:27,000 Hume equally famously argues against it, appealing particularly to the problem of evil. 46 00:05:27,000 --> 00:05:36,930 Free will is a topic that continues to be discussed, often in much the same terms as it was in the early modern period. 47 00:05:36,930 --> 00:05:40,440 Thomas Hobbs and David Hume advocated compatible ism, 48 00:05:40,440 --> 00:05:52,020 which is still a very popular view of free will and took a naturalistic view of man is part of nature, which again has resonated down the centuries. 49 00:05:52,020 --> 00:05:56,160 Descartes is particularly associated with claims about mind and body, 50 00:05:56,160 --> 00:06:00,660 and we'll be talking a bit in the next lecture and later on in the lecture series about 51 00:06:00,660 --> 00:06:07,590 the relation between mind and body and lock features in respect of personal identity. 52 00:06:07,590 --> 00:06:16,570 He started out a discussion which is again continued down to the present day. 53 00:06:16,570 --> 00:06:23,830 Before going on, I want to mention some previous lectures that I did, these were recorded in two thousand and nine to 10. 54 00:06:23,830 --> 00:06:30,400 You can see they're freely available and they're slightly different from the current lectures in various ways. 55 00:06:30,400 --> 00:06:36,700 There's obviously a fair bit of overlap, but they include some topics that are not now in the syllabus, 56 00:06:36,700 --> 00:06:43,690 perception and primary and secondary qualities. They don't include material on golden evil, which wasn't then in the syllabus, 57 00:06:43,690 --> 00:06:48,040 and they give a little bit more detail to some of the historical background. 58 00:06:48,040 --> 00:06:51,220 So the current lectures aimed to complement those. 59 00:06:51,220 --> 00:06:57,370 These lectures contain more thematic material, drawing more connexions between subjects and more links. 60 00:06:57,370 --> 00:07:05,160 Also with other Oxford disciplines that you may be studying alongside philosophy. 61 00:07:05,160 --> 00:07:12,570 OK. Let's go back now to that question of why we should bother with philosophers history. 62 00:07:12,570 --> 00:07:19,470 Why does history play such a large role in our introduction to general philosophy? 63 00:07:19,470 --> 00:07:24,060 If you want more detailed discussions in the centenary of Hume's birth, 64 00:07:24,060 --> 00:07:31,950 he was born in 1711 and in 2011 there were lots and lots of activities going on to celebrate his 300 years. 65 00:07:31,950 --> 00:07:39,780 And I ended up giving quite a few talks that year, as you can imagine. And amongst those, I was discussing precisely this issue. 66 00:07:39,780 --> 00:07:44,860 Why are philosophers so interested in the history of philosophy? 67 00:07:44,860 --> 00:07:48,990 And there's a couple of papers there on the web. You're very welcome to go and look at them. 68 00:07:48,990 --> 00:07:52,980 You'll see there on the David Hume dot org website. 69 00:07:52,980 --> 00:07:59,250 And incidentally, all of David Hume's philosophical works can be obtained free from David Hume dot org, 70 00:07:59,250 --> 00:08:11,480 as well as lots of pictures of papers that I've written. So here briefly, are some responses, well, first of all, the agenda got set by these people. 71 00:08:11,480 --> 00:08:21,950 Many of the problems that we're looking at are problems that arose for the first time in a discernibly modern guys in the 17th and 18th centuries. 72 00:08:21,950 --> 00:08:24,170 That's not a coincidence, right? 73 00:08:24,170 --> 00:08:34,820 The reason they arose then was because that was when the scientific revolution was happening and the modern world view came about over that time. 74 00:08:34,820 --> 00:08:39,920 So there's a very, very big difference between the worldview that you get in the 1500s, 75 00:08:39,920 --> 00:08:47,360 say, and the 17 and 18 hundreds and a lot of problems that beset us now arose then. 76 00:08:47,360 --> 00:08:58,380 And not surprisingly, those problems got raised for the first time and in a very vivid form by some of the best writers and thinkers of that period. 77 00:08:58,380 --> 00:09:00,600 Now, as a result, 78 00:09:00,600 --> 00:09:08,520 the labels that we attach to various prominent positions within those debates naturally carry the names of the philosophers involved. 79 00:09:08,520 --> 00:09:16,230 For example, Cartesian dualism is the form of dualism advocated by Descartes. 80 00:09:16,230 --> 00:09:19,140 It's named after him human compatible ism. 81 00:09:19,140 --> 00:09:26,790 So if you're discussing freewill, an important position is compatible ism, and there are various varieties of that. 82 00:09:26,790 --> 00:09:32,370 One of them is associated with Thomas Hobbs, a slightly different version with David Hume. 83 00:09:32,370 --> 00:09:43,070 Many modern philosophers may have exactly similar views in various ways, but we don't name them after them because Hobson Hume got their first. 84 00:09:43,070 --> 00:09:44,750 Perhaps even more importantly, 85 00:09:44,750 --> 00:09:55,790 these were very great minds that the people whose works you will be reading from the 17th and 18th centuries were absolute undisputed geniuses. 86 00:09:55,790 --> 00:10:00,230 Moreover, they were addressing these problems for the general public. 87 00:10:00,230 --> 00:10:12,700 They weren't writing for academic philosophers. And as a result, their work is accessible, much more so than many modern discussions that you'd have. 88 00:10:12,700 --> 00:10:19,630 Another point about historical perspective, philosophical ideas have very broad, very deep interconnections. 89 00:10:19,630 --> 00:10:23,830 I've said already that even people who are specialising in one particular area 90 00:10:23,830 --> 00:10:30,430 of philosophy invariably find that their study links to lots of other areas. 91 00:10:30,430 --> 00:10:40,330 Now, one problem with studying philosophy as it were in disciplinary silos like when you come to do your final honours papers, 92 00:10:40,330 --> 00:10:44,380 for example, is that you don't get time to see all of these links. 93 00:10:44,380 --> 00:10:51,010 Inevitably, if you're focussing in on one particular area, say moral philosophy, 94 00:10:51,010 --> 00:11:00,130 you're not going to be discussing at the same time links that there may be with, say, philosophy of religion or epistemology or metaphysics. 95 00:11:00,130 --> 00:11:09,400 But there are very large links there, and often those links are easiest to see in the writings of older philosophers because 96 00:11:09,400 --> 00:11:14,920 people like Descartes and Hume were trying to develop comprehensive philosophical views, 97 00:11:14,920 --> 00:11:23,020 taking account of lots and lots of different areas. They weren't, as it were academic philosophers trying to publish in some specialised journal. 98 00:11:23,020 --> 00:11:33,120 So by looking at the way that their ideas interlock in history, you get an appreciation of these wider connexions. 99 00:11:33,120 --> 00:11:41,880 Now, another point a very important point is that a lot of the same themes recur throughout history. 100 00:11:41,880 --> 00:11:44,460 Sometimes these aren't so obvious. 101 00:11:44,460 --> 00:11:52,050 But I've come across cases recently where discussion say in the philosophy of mind, you know, issues about artificial intelligence, 102 00:11:52,050 --> 00:11:57,200 can machines think some of the issues that are raised there, 103 00:11:57,200 --> 00:12:03,970 some of the arguments that are given there are ever so similar to arguments that were given in the 17th century. 104 00:12:03,970 --> 00:12:08,290 And important responses were given in the 17th and 18th centuries, 105 00:12:08,290 --> 00:12:17,290 and often now people will discuss these things in complete ignorance of the prior discussion. 106 00:12:17,290 --> 00:12:24,070 Finally, we have to be aware of our own historical blinkers. 107 00:12:24,070 --> 00:12:29,170 We all come to our studies with particular preconceptions. 108 00:12:29,170 --> 00:12:36,010 And this is true of academics as well as students and ordinary people in the streets as it were. 109 00:12:36,010 --> 00:12:44,050 It's really healthy to be looking at philosophical views from very alien times. 110 00:12:44,050 --> 00:12:51,790 So, for example, you may well be an atheist and you may read Descartes and think it's strange that he relies so much on God. 111 00:12:51,790 --> 00:12:57,880 But actually, you can learn a lot from seeing how he does and how God functions in his system. 112 00:12:57,880 --> 00:13:01,210 You shouldn't be saying, Oh, well, he's got different beliefs for me. Therefore, 113 00:13:01,210 --> 00:13:15,540 I'm going to take no account of it because often looking at a worldview that's profoundly different from our own can highlight things about our view. 114 00:13:15,540 --> 00:13:25,290 Now, in general philosophy, we're going to be focussing, particularly on ways of understanding the world and our place in it. 115 00:13:25,290 --> 00:13:27,780 So this is if you like theoretical philosophy. 116 00:13:27,780 --> 00:13:35,520 So this course could equally have been called introduction to theoretical philosophy, and that's contrasted with practical philosophy. 117 00:13:35,520 --> 00:13:44,430 So practical philosophy in particular, would be ethics and political theory questions about how we should behave. 118 00:13:44,430 --> 00:13:51,480 Now, obviously, I'm going to be focussing on there for the history of epistemology and metaphysics. 119 00:13:51,480 --> 00:13:56,610 There is an equally important story to be told on the practical side. 120 00:13:56,610 --> 00:13:59,550 And I'm not going to be saying very much of that, 121 00:13:59,550 --> 00:14:12,150 but you will see from today's lecture and next week's lecture that philosophical thinking has had an absolutely profound effect on the world. 122 00:14:12,150 --> 00:14:16,890 I think it's entirely plausible that philosophy, more than any other discipline, 123 00:14:16,890 --> 00:14:23,040 brought about the modern world in contradistinction with the mediaeval and ancient world. 124 00:14:23,040 --> 00:14:32,250 And although, as I say, not going to be talking about the practical aspect of that, that is also obviously extremely important. 125 00:14:32,250 --> 00:14:42,840 The fact that now we don't believe in the divine right of kings now we believe that government legitimate government comes from a democratic mandate, 126 00:14:42,840 --> 00:14:55,260 et cetera. So from time to time in these lectures, 127 00:14:55,260 --> 00:15:01,440 I'm going to be saying things that link with particular other disciplines that are studied together with philosophy in Oxford, 128 00:15:01,440 --> 00:15:06,600 as you know, we have no single honours philosophy degree amongst the combine degrees. 129 00:15:06,600 --> 00:15:12,840 We have its philosophy and theology and these are intimately connected. 130 00:15:12,840 --> 00:15:23,410 If we go back into history. Most philosophical thought across most of history has been intimately connected with religion. 131 00:15:23,410 --> 00:15:32,310 Religion seems to be pretty much universal in at least ancient human societies. 132 00:15:32,310 --> 00:15:39,180 Religion and philosophy have many positive, but also some negative links. 133 00:15:39,180 --> 00:15:44,460 One issue here is that religions typically emphasise orthodoxy. 134 00:15:44,460 --> 00:15:48,300 You've got to believe the right thing if you're going to be in the club, 135 00:15:48,300 --> 00:15:54,180 if you're going to achieve salvation, if you're going to be in favour with religious leaders and so on. 136 00:15:54,180 --> 00:16:02,310 And that means that in periods when religion or a particular view of religion has been dominant, 137 00:16:02,310 --> 00:16:07,380 that's often been rather bad for philosophical variety. 138 00:16:07,380 --> 00:16:12,450 And this happened hugely in the when the Roman Empire became Christian. 139 00:16:12,450 --> 00:16:18,300 Thanks to Constantine, a lot of ancient philosophical schools were basically stamped out. 140 00:16:18,300 --> 00:16:22,230 So Plato's Academy, for example, have been going for eight hundred years. 141 00:16:22,230 --> 00:16:35,050 And it just stopped. There we will be seeing that in the period that we are looking at the early modern period. 142 00:16:35,050 --> 00:16:46,090 Some of these ancient influences actually came back. And so I'm going to now take a detour through looking at some of the the Christian background, 143 00:16:46,090 --> 00:16:57,820 and then we'll see how problems emerged in the early modern period, which essentially brought about the birth of modern philosophy. 144 00:16:57,820 --> 00:17:05,290 OK, well, most of you are probably familiar with the the Genesis story in the beginning, 145 00:17:05,290 --> 00:17:09,640 God created the heavens and the Earth, and he did it in this order. 146 00:17:09,640 --> 00:17:17,620 You might find it a little bit strange that the Earth got created before the Sun and the birds got created before land animals. 147 00:17:17,620 --> 00:17:19,180 But there you are. 148 00:17:19,180 --> 00:17:32,680 What I'd want to draw attention to is that when a man was created, he was let us make humankind in our image according to our likeness, says God. 149 00:17:32,680 --> 00:17:38,200 Let them have dominion over all the animals. So God created humankind in his image. 150 00:17:38,200 --> 00:17:43,690 In the image of God, he created them male and female. He created them. 151 00:17:43,690 --> 00:17:48,700 OK. Genesis Chapter two you actually get a different order of creation. 152 00:17:48,700 --> 00:17:57,310 And here it is very clear that humans are being given dominion over the Earth. 153 00:17:57,310 --> 00:18:05,630 Eve is being created out of Adam's rib as a helper for him. 154 00:18:05,630 --> 00:18:10,310 You can see very much. We are in the image of God. 155 00:18:10,310 --> 00:18:18,870 The world is being made for us. What sort of philosophical view does that suggest? 156 00:18:18,870 --> 00:18:27,990 Well, it suggests that the world is going to be something with which we are intimately connected, 157 00:18:27,990 --> 00:18:35,550 of which we can learn using our god-given faculties in a pretty direct way. 158 00:18:35,550 --> 00:18:42,480 It also suggests that the world is going to be infused with Tilly ology with purpose. 159 00:18:42,480 --> 00:18:53,530 The world has been created by a God who's put us there in his image for a reason to do his works. 160 00:18:53,530 --> 00:19:02,160 And you can see an ancient philosophy links with these views. 161 00:19:02,160 --> 00:19:11,820 And in particular, the philosophies of Plato and Aristotle in various ways fitted quite nicely with this general view of the world. 162 00:19:11,820 --> 00:19:19,950 And it's not surprising, therefore, that these were the philosophers who are most popular with early Christians Plato, 163 00:19:19,950 --> 00:19:25,500 Neo, Plato and some have huge impact on the development of Christianity in the mediaeval period. 164 00:19:25,500 --> 00:19:32,380 Aristotle became taken on board, particularly through the influence of Thomas Aquinas. 165 00:19:32,380 --> 00:19:36,700 Now, what I want to suggest is this is a very natural way of thinking about the world, 166 00:19:36,700 --> 00:19:46,060 and there are psychological experiments that back up that we very naturally think about things clear logically in terms of purposes. 167 00:19:46,060 --> 00:19:53,540 So suppose you take a young child and you say, why do you think mountains exist? 168 00:19:53,540 --> 00:20:02,700 Is it to give animals a place to climb, or is it because volcanoes cooled into lumps? 169 00:20:02,700 --> 00:20:11,570 And young children overwhelmingly prefer the teleological answer, they'll say mountains are there to give animals a place to climb. 170 00:20:11,570 --> 00:20:16,670 Why is the Sun in the sky to keep us warm water trees fall to provide shade? 171 00:20:16,670 --> 00:20:23,700 What is rainfall to give us water for drinking? Always the teleological answer. 172 00:20:23,700 --> 00:20:32,130 Now, interesting recent experiments with patients with Alzheimer's have shown that they do the same. 173 00:20:32,130 --> 00:20:39,380 So it seems that naturally we are inclined to judge things in terms of purposes. 174 00:20:39,380 --> 00:20:47,980 We learn through our education, particularly through science education, that that's not actually the best explanation of lots of things in the world. 175 00:20:47,980 --> 00:20:55,340 But then if unfortunately we suffer from Alzheimer's disease and we lose our memories, we lose what science? 176 00:20:55,340 --> 00:21:02,800 Scientific education has given us. We go back to thinking teleological. 177 00:21:02,800 --> 00:21:15,400 So as I say, it's not surprising that the most influential early philosophies tended to be very teleological inform. 178 00:21:15,400 --> 00:21:23,080 And just a couple of examples which match with this general idea, Plato, his famous theory of forms, 179 00:21:23,080 --> 00:21:32,470 this links with the idea that the world has been created for us that if we use our reason, we can be in tune for it. 180 00:21:32,470 --> 00:21:36,610 Tune with it. We can discern how things really are. 181 00:21:36,610 --> 00:21:43,630 If we want to understand the essential nature of things, we don't do it primarily by empirical observation. 182 00:21:43,630 --> 00:21:54,310 We do it by reason. Aristotle, too, he's got a theory of perception where when we see things the form of what we see, 183 00:21:54,310 --> 00:21:59,170 the perceptible form of it somehow imprints itself on our organs. 184 00:21:59,170 --> 00:22:07,480 So we see directly what's there because our sense organs become similar to what we are perceiving. 185 00:22:07,480 --> 00:22:15,610 And you'll see that this is a huge contrast with what we get in the early modern period. 186 00:22:15,610 --> 00:22:27,310 Another point and this brings us towards accounts of physics is to do with how physical things behave. 187 00:22:27,310 --> 00:22:35,450 So suppose I take a stone, imagine that's a stone, and I let go of it. 188 00:22:35,450 --> 00:22:41,020 It falls. Why does it fall? 189 00:22:41,020 --> 00:22:55,570 Well, prior to 16:00, the standard account was this there are four elements in the universe below the Moon Earth, 190 00:22:55,570 --> 00:23:02,290 water, air and fire, and they all have their natural place in the universe. 191 00:23:02,290 --> 00:23:09,220 Earth at the centre, water around that air around that fire around that. 192 00:23:09,220 --> 00:23:18,550 And so if you take something that's primarily made of Earth like a stone that will naturally strive to reach its place in the universe, 193 00:23:18,550 --> 00:23:27,900 the centre of the Earth. And that's why when you let it go, it falls, it is striving to reach its natural place. 194 00:23:27,900 --> 00:23:36,710 So the point I'm making here is that not only is the world designed by a purposive creator for us. 195 00:23:36,710 --> 00:23:43,220 But also physical things in the World Act, according to something like purposes, strivings. 196 00:23:43,220 --> 00:23:50,240 They are trying to achieve a particular final ends. 197 00:23:50,240 --> 00:23:59,300 So Aristotelian science, we've got these four terrestrial elements, as I've said, they naturally move to reach their place. 198 00:23:59,300 --> 00:24:09,520 Heavier things that contain more Earth are going to fall faster towards their natural place in proportion to their weight. 199 00:24:09,520 --> 00:24:14,680 Nature abhors a vacuum, we'll come to that a little bit later. 200 00:24:14,680 --> 00:24:20,020 There are some things, of course, that don't fall towards the Earth, the heavenly bodies. 201 00:24:20,020 --> 00:24:28,270 If you look up at the Moon and the stars and the sun and planets, they don't fall to Earth. 202 00:24:28,270 --> 00:24:36,190 They must therefore be made of something different. And Aristotle called this Aether this fifth element. 203 00:24:36,190 --> 00:24:40,330 And the reason why they move in circles. Why did they have any body to move in circles? 204 00:24:40,330 --> 00:24:46,950 Because that's the closest they can get to the perfection of an eternal, eternal creator? 205 00:24:46,950 --> 00:24:52,940 So again, we've got a purposive account of why things act as they do. 206 00:24:52,940 --> 00:24:58,870 So here is is one image of Aristotle's universe. 207 00:24:58,870 --> 00:25:06,610 You can see you've got water on Earth, air and fire, then the sphere of the Moon and everything beyond the sphere of the Moon is made 208 00:25:06,610 --> 00:25:13,860 of Aether and you've got the planets moving on sort of crystalline spheres. 209 00:25:13,860 --> 00:25:22,880 And the fix stalls around the outside. Now, this sort of general view of the world lasted a long time, 210 00:25:22,880 --> 00:25:31,410 and I think one vivid way of making this clear is to look at the map on Monday from Hereford Cathedral. 211 00:25:31,410 --> 00:25:41,310 So this map was dated around 13:00. And it's based on the writings of a pupil of Saint Augustine of Hippo. 212 00:25:41,310 --> 00:25:58,100 And those writings go come from about 400. So we've got a work being produced in 13:00 based on an authority 900 years earlier. 213 00:25:58,100 --> 00:26:07,310 And you can see that the map puts Jerusalem at the centre. I've marked Roman Hereford. and Noah's Ark and Eden and Babylon. 214 00:26:07,310 --> 00:26:16,510 That's the world as it looks in 13:00, and it hasn't changed much for 900 years. 215 00:26:16,510 --> 00:26:28,810 Now, an awful lot changed in the period between the mediaeval world and the period we're going to be looking at mainly the 17th and 18th centuries. 216 00:26:28,810 --> 00:26:41,750 All sorts of things started creating cracks in this edifice, an edifice which was lost largely based on the Bible and Aristotle. 217 00:26:41,750 --> 00:26:47,180 Population grew, there was lots of trade. There was discovery of the new world. 218 00:26:47,180 --> 00:26:53,180 So the trips to America, obviously Columbus in fourteen, ninety two, but lots of others. 219 00:26:53,180 --> 00:26:59,420 There was lots of economic disruption in the new world. Lots of silver was discovered. 220 00:26:59,420 --> 00:27:03,740 Lots of gold actually was brought back from various parts of Africa. 221 00:27:03,740 --> 00:27:10,340 And this caused a lot of economic disruption. The realisation that ancient maps were wrong, I mean, 222 00:27:10,340 --> 00:27:17,210 imagine if you've been brought up to think that gives a correct account of the geography of the world, 223 00:27:17,210 --> 00:27:23,660 and then somebody sails off and discovers a completely new land. 224 00:27:23,660 --> 00:27:27,830 And suppose they discover that people there have quite different religions, 225 00:27:27,830 --> 00:27:32,750 inevitably that is going to give you pause about your own if you've been brought 226 00:27:32,750 --> 00:27:38,630 up thinking that a certain set of beliefs is pretty much incontestably correct. 227 00:27:38,630 --> 00:27:44,840 And then you find that there's another group of people somewhere else who've been brought up with quite different beliefs. 228 00:27:44,840 --> 00:27:54,990 It's very natural to ask yourself, how confident can I be that the beliefs that I was given as a child are in fact correct? 229 00:27:54,990 --> 00:28:05,880 There are a lot of technological changes. I mean, gunpowder came to the West and had a huge impact with regard to the centralisation of power. 230 00:28:05,880 --> 00:28:13,600 It also had a major impact in bringing about, for example, the fall of Constantinople. 231 00:28:13,600 --> 00:28:20,500 So a lot of political impacts, work came about because of technological developments. 232 00:28:20,500 --> 00:28:33,130 And finally, here, some heretical classical texts that I mentioned were suppressed under the Christian ization of the Roman Empire were rediscovered, 233 00:28:33,130 --> 00:28:42,240 and those had a profound effect in philosophy. Then along came the Reformation. 234 00:28:42,240 --> 00:28:49,490 So in 15 17, Luther famously rebelled against the Church of Rome. 235 00:28:49,490 --> 00:28:54,170 From the point of view of the University of Oxford, actually, this was slightly unfortunate. 236 00:28:54,170 --> 00:28:59,300 One of the things that Luther really didn't like was the sale of indulgences, 237 00:28:59,300 --> 00:29:05,540 the fact that the Roman Catholic Church had a doctrine of purgatory that is, 238 00:29:05,540 --> 00:29:10,030 if you die and you've been sinful, but God doesn't want to condemn them, 239 00:29:10,030 --> 00:29:15,080 you to eternal hellfire, then you go to a rather nasty place called purgatory. 240 00:29:15,080 --> 00:29:19,460 And how long you spend in purgatory depends on how good or bad you've been. 241 00:29:19,460 --> 00:29:32,270 But crucially crucially, you can buy yourself less time in purgatory by donating to the church or, of course, to universities. 242 00:29:32,270 --> 00:29:39,500 So this was a very useful doctrine from the point of view of the development funds of the University of Oxford. 243 00:29:39,500 --> 00:29:43,550 But Luther thought this was a bad thing. 244 00:29:43,550 --> 00:29:50,870 A lot of Europe, especially northern Europe, became Protestant because Luther's wasn't the only variety of Protestantism. 245 00:29:50,870 --> 00:29:56,270 John Calvin, for example, was extremely influential and a lot of others. 246 00:29:56,270 --> 00:30:03,050 But in general, a lot of northern Europe became Protestant. 247 00:30:03,050 --> 00:30:09,110 And this provoked a Counter-Reformation from Roman Catholics, for example, the Inquisition. 248 00:30:09,110 --> 00:30:18,500 Basically, there were a lot of very heated doctrinal disputes, and this gave rise to armed conflict. 249 00:30:18,500 --> 00:30:26,840 So there were a lot of wars around Europe arising from religious differences, and these were differences between different groups of Christians. 250 00:30:26,840 --> 00:30:31,490 And we see this nowadays. I mean, particularly in the Muslim world where you say, 251 00:30:31,490 --> 00:30:39,320 see Sunnis and Shias apparently killing each other with abandon simply because they have a different variety of Islam. 252 00:30:39,320 --> 00:30:46,820 Well, in the 17th century, there was lots of that amongst Christians. 253 00:30:46,820 --> 00:30:54,650 The thirty years war, which raged mainly across Germany, was particularly horrible. 254 00:30:54,650 --> 00:31:07,720 That went on from 16 18 to 16 48. However, we in England saw the Civil War, and these all fundamentally arose from differences in religious doctrine. 255 00:31:07,720 --> 00:31:18,250 In 16 48, the peace of Westphalia came about not through any real decision of the war and certainly not any agreement on doctrine, 256 00:31:18,250 --> 00:31:23,590 but basically it was described as a piece of exhaustion. 257 00:31:23,590 --> 00:31:31,090 The war had so decimated so much of the land that it was decided that the best thing to do was 258 00:31:31,090 --> 00:31:36,760 for the the various parts of Germany to be divided into appropriate print stems or whatever. 259 00:31:36,760 --> 00:31:42,790 And if your prince was a Catholic, then you had to be a Catholic. If your prince was a Protestant, you had to be a Protestant. 260 00:31:42,790 --> 00:31:52,810 That brought an end to the war. Not very satisfactory from a philosophical point of view, but very satisfactory from a practical point of view. 261 00:31:52,810 --> 00:32:02,110 OK. So in those last few slides, I've explained why over this period, 262 00:32:02,110 --> 00:32:13,540 from about fifteen hundred for the next 100 150 years, there was a huge amount of tumult across Europe. 263 00:32:13,540 --> 00:32:21,790 A lot of questioning of established orthodoxies. And you can imagine that if you've got get lots of debate between different religious groups, 264 00:32:21,790 --> 00:32:30,640 even if there are all sorts of things that they agree on, that's naturally going to raise all sorts of epistemological worries. 265 00:32:30,640 --> 00:32:39,190 That is worries about what we can know. I mean, suppose, for example, that I'm a Catholic and I believe in the Eucharist. 266 00:32:39,190 --> 00:32:47,290 I believe that in the Eucharist service, the bread and wine become literally the body and blood of Christ. 267 00:32:47,290 --> 00:32:53,590 And I am faced with Protestants who argue against that and I am debating with them. 268 00:32:53,590 --> 00:32:58,780 Not only might that make me doubt whether I've been told the truth about the Eucharist or 269 00:32:58,780 --> 00:33:03,970 whether I can be confident in what the really religious leaders have told me about that. 270 00:33:03,970 --> 00:33:13,270 It might naturally shake my confidence about other things too. I mean, if different people have different beliefs, but apparently on a similar basis, 271 00:33:13,270 --> 00:33:18,340 namely that they've been told it by their parents and by the religious authorities. 272 00:33:18,340 --> 00:33:28,590 But those beliefs all conflict, and it's clear that that isn't a universally reliable source of authority. 273 00:33:28,590 --> 00:33:36,780 But a particular cause for the scientific revolution was quite different, and that was nothing to do with politics. 274 00:33:36,780 --> 00:33:47,370 It was to do with astronomy. Now, astronomical motions have been of interest to mankind for thousands of years, partly, 275 00:33:47,370 --> 00:33:55,260 of course, the calendar ways of identifying times of year by when the stars come round. 276 00:33:55,260 --> 00:33:58,720 But also astrology. 277 00:33:58,720 --> 00:34:07,900 Now, from this point of view, the planets are particularly interesting, the stars just rotate around the world in a in a very regular form. 278 00:34:07,900 --> 00:34:17,040 But amongst these stars, there are these bright objects we call planets that move relative to the other stars. 279 00:34:17,040 --> 00:34:23,700 And they don't just move in straightforward circles around the Earth. 280 00:34:23,700 --> 00:34:35,340 Sometimes they exhibit retrograde motion. So although Mars say, may appear to be moving in a steady direction night after night. 281 00:34:35,340 --> 00:34:42,220 There come times when Mars seems to move backwards in the sky. Not in the direction that you would expect. 282 00:34:42,220 --> 00:34:46,150 Now, nowadays we we can explain that quite easily, 283 00:34:46,150 --> 00:34:53,500 it's because the Earth is as it were overtaking Mars on the inside, on its orbit because Mars is outside the Earth. 284 00:34:53,500 --> 00:34:59,110 And therefore, as that overtaking is taking place, Mars move seems to move backwards relative to the Earth, 285 00:34:59,110 --> 00:35:04,260 and the Earth seems to move backwards relative to Mars. So if you were standing on Mars, 286 00:35:04,260 --> 00:35:12,420 you'd see the Earth changing direction to another interesting point is that Venus never appears in the sky more than about 45 degrees. 287 00:35:12,420 --> 00:35:15,930 I think the maximum is 47 seven away from the Sun. 288 00:35:15,930 --> 00:35:24,060 So the Venus is known as the morning or the evening star because we only ever see it in the morning or the evening, never dead of night. 289 00:35:24,060 --> 00:35:38,110 It's never opposite the sun in the sky. Now, Aristotle had taught that the planets move in circles, so how does that make sense? 290 00:35:38,110 --> 00:35:47,290 How can we get an account which explains these retrograde motions and these facts about the motion of Venus? 291 00:35:47,290 --> 00:35:52,150 Well, essentially they brought in epic cycles. Now here's an example with Venus. 292 00:35:52,150 --> 00:35:58,230 Imagine that Venus is travelling around the Earth on the solid circle. 293 00:35:58,230 --> 00:36:05,250 But it it's moving around a point on that solid circle on its own smaller circle. 294 00:36:05,250 --> 00:36:12,090 So the point of rotation of Venus is circle is itself rotating around the Earth. 295 00:36:12,090 --> 00:36:19,490 So we we have an epic cycle that is a circle within a circle. 296 00:36:19,490 --> 00:36:25,910 And you'll notice that with this model, Venus will never be too far away from the sun in the sky. 297 00:36:25,910 --> 00:36:37,550 So by fixing the appropriate geometry, you can get something close to the truth that we observe through our telescopes or indeed with our eyes. 298 00:36:37,550 --> 00:36:40,100 In the case of Mars and the outer planets, by the way, 299 00:36:40,100 --> 00:36:51,380 what you have is a large circle around the Earth and then another circle circling around that so that Mars is going round the Earth, 300 00:36:51,380 --> 00:37:04,910 but sometimes moving backwards. Interestingly, the AP cycles for the outer planets tend to have a duration of 365 days. 301 00:37:04,910 --> 00:37:14,800 Interesting coincidence. Now, Galileo in 16 09 built a telescope. 302 00:37:14,800 --> 00:37:18,460 The telescope had been invented the previous year in Holland. 303 00:37:18,460 --> 00:37:26,350 He developed a more accurate telescope, and he had the bright idea of turning it up to the sky. 304 00:37:26,350 --> 00:37:38,650 And what he saw completely decimated the previous astronomical orthodoxy, I've listed various things that Galileo saw. 305 00:37:38,650 --> 00:37:45,580 He saw that the Moon did not seem to be the perfect body that had previously been thought. 306 00:37:45,580 --> 00:37:50,050 This aethereal perfection. No, it seemed to have mountains and valleys. 307 00:37:50,050 --> 00:37:54,070 It looked like it was a rocky body like the Earth. 308 00:37:54,070 --> 00:38:02,410 He saw moons orbiting around Jupiter, loads and loads of stars, apparently giving the impression that they weren't. 309 00:38:02,410 --> 00:38:07,370 We didn't just have a fixed range of stars around some celestial globe. 310 00:38:07,370 --> 00:38:13,340 There were more and more as far as you could see. And he saw phases of Venus. 311 00:38:13,340 --> 00:38:22,400 Now I just want to explain that. Suppose we have a model like this, suppose that Venus is indeed orbiting around an AP cycle itself, 312 00:38:22,400 --> 00:38:32,660 going around a circuit between the Earth and the Sun. What is the largest amount of Venus that we will ever see? 313 00:38:32,660 --> 00:38:38,240 Well, we will see the part of Venus only that is illuminated by the Sun. 314 00:38:38,240 --> 00:38:44,940 And I've put Venus there on the on the diagram about as far as it can be in terms of our seeing it, 315 00:38:44,940 --> 00:38:50,900 you'll see if we look from the Earth towards Venus, what we will see is a crescent. 316 00:38:50,900 --> 00:38:57,290 So I've shown the kind of present you might expect to see there because the only bit we're seeing 317 00:38:57,290 --> 00:39:04,340 is the part that's illuminated by the Sun and which simultaneously is in our line of sight. 318 00:39:04,340 --> 00:39:10,550 Importantly, if this model is true, we will never see anything like a full Venus. 319 00:39:10,550 --> 00:39:15,840 We will only ever see a crescent. Now what Galileo saw? 320 00:39:15,840 --> 00:39:21,710 You can't tell with the naked eye. Venus is so bright you just see this point of light. 321 00:39:21,710 --> 00:39:28,060 But what Galileo saw is that although Venus is often a crescent. 322 00:39:28,060 --> 00:39:34,510 It isn't always. Sometimes we do see pretty much a full Venus, never completely full, of course, 323 00:39:34,510 --> 00:39:39,670 because for that it would have to be the other side of the Sun and we would not be able to see it because the sun's too bright. 324 00:39:39,670 --> 00:39:47,350 But we do see Venus, with most of it illuminated by the Sun, which implies that Venus is on the other side of the Sun. 325 00:39:47,350 --> 00:39:55,950 So basically, the Aristotelian model simply can't work. Now, that's actually quite a profound discovery, 326 00:39:55,950 --> 00:40:02,250 it not only implies that the Earth is not the centre of the universe because we are orbiting around the Sun, 327 00:40:02,250 --> 00:40:10,320 but it also implies that Aristotle's physics must be incorrect because Aristotle has said that the 328 00:40:10,320 --> 00:40:15,930 reason stones fall is that they're trying to reach their natural place in the centre of the universe. 329 00:40:15,930 --> 00:40:21,000 If the Earth is no longer the centre of the universe, then that account is out of the window. 330 00:40:21,000 --> 00:40:23,950 We've got to have a new physics. 331 00:40:23,950 --> 00:40:32,290 And once you start looking in detail at the Aristotelian picture, what Galileo realised was that there were lots of other things that Galileo did. 332 00:40:32,290 --> 00:40:37,240 Aristotle could not explain, like the flight of a cannonball. 333 00:40:37,240 --> 00:40:46,420 So ancient accounts had cannonballs firing up under the the force of the cannon more or less straight. 334 00:40:46,420 --> 00:40:49,990 And then when the force of the cannon gave out, they would fall vertically. 335 00:40:49,990 --> 00:41:02,680 So cannonballs supposedly flew like that, whereas Galileo realised that actually cannonballs fly more or less in a parabola. 336 00:41:02,680 --> 00:41:12,850 A sledge sliding on flat ice, imagine that you're on a flat pond iced over and you push a sledge on the Aristotelian account, 337 00:41:12,850 --> 00:41:20,680 it's rather odd that the sledge keeps going after you let go of it because the natural motion of the sledge is downwards, not along. 338 00:41:20,680 --> 00:41:24,430 And once the force of the push has gone, how does it keep going? 339 00:41:24,430 --> 00:41:32,920 Well, some theorists reckoned it was to do with vortices in the air keeping it going, but essentially the physics doesn't work. 340 00:41:32,920 --> 00:41:40,840 And as we saw, Aristotle claimed that heavier bodies fall faster in proportion to their weight. 341 00:41:40,840 --> 00:41:46,240 Galileo showed that that was incorrect, and supposedly he did so by dropping a cannonball, 342 00:41:46,240 --> 00:41:52,330 a large cannonball in a very small ball from the top of the leaning tower of Pisa, and they fell at pretty much the same speed. 343 00:41:52,330 --> 00:41:54,650 I mean, that's probably apocryphal. 344 00:41:54,650 --> 00:42:04,450 It's he probably didn't actually conduct that experiment, but a very similar experiment was conducted on the moon by Apollo astronaut David Scott. 345 00:42:04,450 --> 00:42:11,380 And sure enough, a feather and a hammer fell at the same speed. 346 00:42:11,380 --> 00:42:19,060 So let's contrast the Aristotelian science with Galileo's replacement in Aristotelian science. 347 00:42:19,060 --> 00:42:27,160 Things work according to their purposes. In Galileo's new science, heavenly matter, an earthly matter are the same kind of thing. 348 00:42:27,160 --> 00:42:36,040 The moon is made of the same kind of thing as the Earth, and things don't behave as they do because they have intrinsic purposes. 349 00:42:36,040 --> 00:42:41,530 But rather, they work as they do because causes act on them. 350 00:42:41,530 --> 00:42:44,560 Matter, according to Galileo, is inert. 351 00:42:44,560 --> 00:42:55,600 It's not active, and how it behaves depends on the causes that act on it, rather than its attempt to reach some final situation. 352 00:42:55,600 --> 00:43:07,180 So here's a nice illustration of Aristotelian explanation and how in the 17th century it was being rejected. 353 00:43:07,180 --> 00:43:10,960 So imagine you've got a siphon pipe like you have at school. 354 00:43:10,960 --> 00:43:18,340 There's water in the top beaker and that's rising up the siphon pipe and falling down into the bottom beaker. 355 00:43:18,340 --> 00:43:25,660 How does that work? Well, the Aristotelian explanation was that we get water falling down on the right hand 356 00:43:25,660 --> 00:43:30,970 side of the pipe because it's trying to reach its natural place closer to the Earth. 357 00:43:30,970 --> 00:43:35,530 That would leave a vacuum, a gap at the top of the tube. 358 00:43:35,530 --> 00:43:46,300 But nature abhors a vacuum. Nature does not like there to be vacuums, and therefore water rises up the left hand side to avoid there being a vacuum. 359 00:43:46,300 --> 00:43:58,850 So you can see it's a purpose of explanation. And Moliere in the Mallard, Imagineer ridicules this kind of explanation. 360 00:43:58,850 --> 00:44:03,590 So a doctor is asked, Why does opium make one sleep? 361 00:44:03,590 --> 00:44:11,200 And the answer is because it contains a dormant virtue whose nature is to make the senses soporific. 362 00:44:11,200 --> 00:44:17,520 Hopeless. Why does opium make you sleep? Because it contains something that sleep inducing? 363 00:44:17,520 --> 00:44:21,630 Right. It's not any kind of explanation in the same way. 364 00:44:21,630 --> 00:44:25,200 Nature abhors a vacuum. What does that mean? It just means vacuums don't occur. 365 00:44:25,200 --> 00:44:33,270 It's not telling you. It's not giving any explanatory account of why. 366 00:44:33,270 --> 00:44:38,790 So in place of this kind of teleological physics where we say nature is trying 367 00:44:38,790 --> 00:44:43,590 to achieve a particular kind of thing and we just have to take that as a given. 368 00:44:43,590 --> 00:44:53,880 Thinkers from Galileo onto Newton instead saw the paradigm of scientific explanation in terms of causal explanation, 369 00:44:53,880 --> 00:45:03,420 where you explain what's pushing the thing on its way rather than looking in terms of the end point to which it's going. 370 00:45:03,420 --> 00:45:09,270 And the paradigm of such causation is mechanical contact. 371 00:45:09,270 --> 00:45:18,930 And motions become calculable mathematically, and this seems significantly better in various ways. 372 00:45:18,930 --> 00:45:23,190 We actually get what looked like genuine explanations as to how things behave. 373 00:45:23,190 --> 00:45:32,880 We get laws of motion, which are quantitative, where we can calculate where we can see that things really do behave in the way that's expected. 374 00:45:32,880 --> 00:45:36,570 It's not just an arbitrary supposition that such and such will happen. 375 00:45:36,570 --> 00:45:40,080 We can see why it happens. 376 00:45:40,080 --> 00:45:47,340 It seems intelligible if you think in terms of mechanical contact when, say, one billiard ball bashes into another billiard ball. 377 00:45:47,340 --> 00:45:54,090 We think we can understand why that makes the other one move. It's not that the second ball is trying to achieve any purpose. 378 00:45:54,090 --> 00:46:03,480 It's rather that the first one is pushing it along. That seems genuinely intelligible, and as I say, it's precisely predictive and testable. 379 00:46:03,480 --> 00:46:12,420 So lots of scientific advantages. But notice that we do have a problem here. 380 00:46:12,420 --> 00:46:20,370 Galileo was claiming that matter doesn't strive left to itself, it's just inert material, 381 00:46:20,370 --> 00:46:26,520 things like billiard balls will just carry on moving in a uniform direction. 382 00:46:26,520 --> 00:46:30,430 It's a uniform speed unless they're acted upon by a force. 383 00:46:30,430 --> 00:46:38,820 That's why when you push the sledge on the lake, it will just continue going until it's acted on by a force, for example, air resistance friction. 384 00:46:38,820 --> 00:46:50,010 It will eventually stop. And the heavenly bodies are, according to Galileo, made from exactly the same kind of stuff as Earth. 385 00:46:50,010 --> 00:46:54,630 But then we have a real problem. Why is it then the Moon orbits the Earth? 386 00:46:54,630 --> 00:46:58,320 Why do the planet's orbit the Sun? 387 00:46:58,320 --> 00:47:06,750 You may get a nice explanation of things like billiard balls, but the heavens still seem to remain a significant problem. 388 00:47:06,750 --> 00:47:14,760 And this is way where Descartes comes in, and he will occupy a fair bit of time in what we do in these lectures. 389 00:47:14,760 --> 00:47:23,520 He's obviously he's known as the father of modern philosophy, but just now I'm going to focus on the physics. 390 00:47:23,520 --> 00:47:29,760 So Descartes uses some of the sceptical arguments, the rediscovered sceptical arguments from those manuscripts, 391 00:47:29,760 --> 00:47:38,910 I mentioned those heretical manuscripts raising all sorts of sceptical worries that had been suppressed for centuries in the West, 392 00:47:38,910 --> 00:47:45,810 but then were rediscovered, and he used these arguments to attack the Aristotelian orthodoxy. 393 00:47:45,810 --> 00:47:52,500 He basically said, I'm only going to accept a theory that can stand up against sceptical arguments, 394 00:47:52,500 --> 00:48:01,320 and hence I'm not going to agree to accept a theory whose only support is tradition and authority. 395 00:48:01,320 --> 00:48:09,270 He goes along with Galileo, the mechanical philosophy, but he gives a grounding for it in a theory of matters essence. 396 00:48:09,270 --> 00:48:18,540 I'll explain in a moment. He also famously makes the mind so Descartes is the original Cartesian duellist. 397 00:48:18,540 --> 00:48:27,480 He thinks that matter and mind are quite distinct, and they have different laws apply to those. 398 00:48:27,480 --> 00:48:32,520 Now we often think today of Descartes as being a philosopher. 399 00:48:32,520 --> 00:48:35,970 You might describe as a spookiest he believes in spooky things. 400 00:48:35,970 --> 00:48:45,690 These non-material minds, actually. At the time, the biggest impact of Descartes was that he was taking mind out of physical science. 401 00:48:45,690 --> 00:48:50,940 He was saying that the physical things do not have anything like a mind in them. 402 00:48:50,940 --> 00:48:55,650 They are not moved by purposes and so forth. 403 00:48:55,650 --> 00:48:58,890 So in terms of the physical science, 404 00:48:58,890 --> 00:49:09,340 the more important point about dividing matter from mind is to separate them and remove mind from the domain of physical science. 405 00:49:09,340 --> 00:49:17,830 He was the main major natural philosopher. This isn't so well known, we tend to think of Descartes as a a conventional philosopher now, 406 00:49:17,830 --> 00:49:27,670 but his focus was just as much on the physical world as on the arguments for which he's so well known now in the meditations. 407 00:49:27,670 --> 00:49:34,990 One thing you may have come across the coordinates you learn at school the X and Y coordinates, they're called Cartesian coordinates. 408 00:49:34,990 --> 00:49:39,250 That's because Descartes, who was a great mathematician, invented them. 409 00:49:39,250 --> 00:49:45,400 You can see that he made various other discoveries to just very quickly here. 410 00:49:45,400 --> 00:49:54,970 I'm not going to go through this in detail, but when you look, when you're reading the meditations as I hope you will, it's on your reading list. 411 00:49:54,970 --> 00:50:05,200 Here are some sort of highlights as you go through. He's looking for a basis for philosophy that is not appealing to authority, as I've said. 412 00:50:05,200 --> 00:50:12,280 He wants arguments sufficiently strong to refute the sceptics. He famously comes up with the statement. 413 00:50:12,280 --> 00:50:20,200 I think therefore I am the one thing I can be absolutely certain of is my own existence. 414 00:50:20,200 --> 00:50:29,110 Very importantly, too, he goes on to say by pondering physical objects, and he gives the example of a piece of wax. 415 00:50:29,110 --> 00:50:39,490 I can see that by through my mind, I am able to understand its nature and the nature of matter, he says, is simple geometrical extension. 416 00:50:39,490 --> 00:50:50,070 What makes something matter is that extended in space, unlike our minds, which are on extended. 417 00:50:50,070 --> 00:50:58,950 And then he goes on to prove the existence of God. To say that since he's created by God, he can ultimately trust his faculties. 418 00:50:58,950 --> 00:51:08,690 But I want to come. I want to focus more on this issue of matter as geometrical extension. 419 00:51:08,690 --> 00:51:17,780 He thinks that because matter is just extended stuff, it follows, as Galileo had claimed that bodies are just passive. 420 00:51:17,780 --> 00:51:22,340 They simply act on are acted on by all the things. 421 00:51:22,340 --> 00:51:31,730 They have no intrinsic purposes. They are simply passive or inert. 422 00:51:31,730 --> 00:51:40,550 But fascinatingly and importantly, this gives an explanation of that puzzle that we were left with. 423 00:51:40,550 --> 00:51:48,470 How is it that the Moon orbits the Earth and that the planet's orbit the Sun? 424 00:51:48,470 --> 00:51:56,790 Well, if the essence of matter is extension, if matter is just extended, stuff extended in space. 425 00:51:56,790 --> 00:52:02,700 It follows that wherever you have extension in space, you have matter. 426 00:52:02,700 --> 00:52:12,450 It immediately follows that the universe is a planet. There is no empty space because it's the essence of matter is simple spatial extension. 427 00:52:12,450 --> 00:52:17,520 And as I've said, wherever you have spatial spatial extension, you have matter. 428 00:52:17,520 --> 00:52:23,070 Now what follows? Imagine that you have a very large soup tureen. 429 00:52:23,070 --> 00:52:34,640 It's absolutely full of soup and you're stirring it. Then as you push on your spoon, it pushes the soup here. 430 00:52:34,640 --> 00:52:41,330 Does it leave an empty space? No, because the suit behind comes in to fill the space. 431 00:52:41,330 --> 00:52:47,810 And that has to happen. If your tureen is absolutely full of soup and you are stirring it, then pushing it. 432 00:52:47,810 --> 00:52:55,190 Any place has to force the the whole lot round so that it fills in the space. 433 00:52:55,190 --> 00:53:03,740 So all motion in within this soup tureen will take the form of vortices whirlpools. 434 00:53:03,740 --> 00:53:07,220 So if space is completely full of matter, 435 00:53:07,220 --> 00:53:14,720 which it must be because the essence of matter is just extended extended ness and therefore where you have extension, you have matter. 436 00:53:14,720 --> 00:53:21,500 It immediately follows that all motion in the universe, all physical motion must take the form of vortices. 437 00:53:21,500 --> 00:53:29,180 And if that is so, then it's no longer difficult to explain why you have the Moon moving around the Earth in a vortex, 438 00:53:29,180 --> 00:53:41,060 the planets moving around the sun in vortices and lots and lots of other little vortices which make up our own bodies and the wider world. 439 00:53:41,060 --> 00:53:46,645 And there I will stop. Thank you very much.