1 00:00:10,850 --> 00:00:16,660 OK, let's move away from somebody whom nobody wanted to admit being influenced by. 2 00:00:16,660 --> 00:00:26,750 To someone who had a very great and overt influence in 17th century science, Robert Boyle, 3 00:00:26,750 --> 00:00:36,020 probably one of the two greatest scientists of the century, along with Isaac Newton, certainly in Britain. 4 00:00:36,020 --> 00:00:43,700 Boyle was interested in chemistry. He worked in Oxford and in trying to make sense of chemical behaviour. 5 00:00:43,700 --> 00:00:49,820 He speculated that material substances are composed of lots of corpuscles like atoms. 6 00:00:49,820 --> 00:00:59,030 He didn't use the word atom. Why not? Well, the word atom was associated with Athie ism, with Epicurean ism and Lucretia ism. 7 00:00:59,030 --> 00:01:05,590 Going back to the ancient world. So he preferred the word corpuscular arianism. 8 00:01:05,590 --> 00:01:18,340 His theory was that substances are composed of little lumps of stuff, the shapes of the lumps might change the way they're organised to the texture. 9 00:01:18,340 --> 00:01:21,270 Mike, vary in different substances. 10 00:01:21,270 --> 00:01:31,770 But essentially, the different chemical properties of different substances are to be explained in terms of their micro structure. 11 00:01:31,770 --> 00:01:37,360 Now, very importantly, Boyle's. Theory is different from Descartes. 12 00:01:37,360 --> 00:01:40,660 Remember, Descartes thought that the essence of matter is extinction. 13 00:01:40,660 --> 00:01:46,320 Wherever you have extinction, wherever you have geometrical size, you have matter. 14 00:01:46,320 --> 00:01:55,060 Boyle didn't say that Boyle drew a distinction between penetrable and impenetrable extension. 15 00:01:55,060 --> 00:02:02,020 So matter has the property of impenetrability, one bit of matter cannot go into another. 16 00:02:02,020 --> 00:02:06,610 It will inevitably push it if the two are brought into contact. 17 00:02:06,610 --> 00:02:11,680 But in addition, Boyle made room for empty space. 18 00:02:11,680 --> 00:02:21,640 So Boyle was happy to accept that the world was not a plenum. That's in addition to these material corpuscles that make up the substances we see. 19 00:02:21,640 --> 00:02:26,550 There are spaces between them. Avoid. 20 00:02:26,550 --> 00:02:33,660 That makes his theory quite a lot more powerful than Descartes and Descartes theory is actually rather dubiously coherent. 21 00:02:33,660 --> 00:02:40,800 If you think about it, because if if all if wherever you have extension, you have matter. 22 00:02:40,800 --> 00:02:47,550 Then it's hard to see the difference, how you can have a difference between different types of stuff. 23 00:02:47,550 --> 00:02:53,820 If they if they are all extended and the essence of matter is just extension, 24 00:02:53,820 --> 00:02:58,860 then it looks like wherever you have a cubic metre of stuff, you've got a cubic metre of stuff. 25 00:02:58,860 --> 00:03:00,750 That's all there is to it. 26 00:03:00,750 --> 00:03:09,750 Whereas if you're allowed empty spaces, well, then you can see how you can have very easily different arrangements of corpuscles within substances. 27 00:03:09,750 --> 00:03:16,850 A kind of atomic theory. But his theory otherwise is in a similar spirit to Descartes. 28 00:03:16,850 --> 00:03:20,210 He draws a distinction between primary and secondary qualities. 29 00:03:20,210 --> 00:03:24,950 That name, incidentally, primary secondary, is most famously associated with John Locke. 30 00:03:24,950 --> 00:03:28,490 John Locke was very much influenced by Boyle. 31 00:03:28,490 --> 00:03:35,000 So you draw a distinction between the fundamental properties of matter, the extension, the size, the shape, 32 00:03:35,000 --> 00:03:44,820 the motion and the secondary qualities that we observe, the colour, the smell, the taste and so forth. 33 00:03:44,820 --> 00:03:47,980 And the explanation of the latter is in terms of the former. 34 00:03:47,980 --> 00:03:54,430 The reason why something has the colour that it does is to be explained in terms of the micro structure, 35 00:03:54,430 --> 00:04:04,870 the way the corpuscles are arranged, maybe the shape of the corpuscles, the way light bounces off them and so forth. 36 00:04:04,870 --> 00:04:16,770 OK. Let's go back briefly to the heavens. 37 00:04:16,770 --> 00:04:24,070 Johannes Kepler was an assistant of a nobleman called TYKO Brockie. 38 00:04:24,070 --> 00:04:32,830 Tyco built an observatory which enabled him to observe and note down the motion of the planets 39 00:04:32,830 --> 00:04:41,810 over many years to an accuracy far greater than anyone had previously been able to do. 40 00:04:41,810 --> 00:04:52,520 In analysing these results, Kepler after Brocky had died and he'd inherited all this data. 41 00:04:52,520 --> 00:04:58,510 Kepler worked out that the best explanation of all this was that the planets, 42 00:04:58,510 --> 00:05:04,850 instead of moving in circles or circles, round circles, were actually moving in ellipses. 43 00:05:04,850 --> 00:05:09,410 So I've drawn a rough diagram at the top right there. 44 00:05:09,410 --> 00:05:15,410 You can see that you've got an oval shape and ellipse and the sun is not at the centre of the ellipse. 45 00:05:15,410 --> 00:05:22,080 The sun is to one side. It's a focus of the ellipse. 46 00:05:22,080 --> 00:05:34,220 So Kepler worked this out on the basis of observation. If you assume that the planets are moving around the sun in that way. 47 00:05:34,220 --> 00:05:41,420 Then he found out that the observed motion of the planets fits much better. 48 00:05:41,420 --> 00:05:53,160 He published in tables based on these calculations, and they turned out to be over a thousand times better than any previous method. 49 00:05:53,160 --> 00:05:56,470 I think about eighteen hundred times better or something like that. 50 00:05:56,470 --> 00:06:03,090 The accuracy was phenomenal compared with anything that had been achieved before. 51 00:06:03,090 --> 00:06:09,570 So inevitably, over time, it did take time for people to realise how accurate these tables were. 52 00:06:09,570 --> 00:06:14,670 The hypothesis got to be accepted. OK. 53 00:06:14,670 --> 00:06:29,210 This makes room for Isaac Newton. Well, Isaac Newton can be seen as following both Descartes and therefore Galileo and Boyle. 54 00:06:29,210 --> 00:06:36,590 He looked at these results about the motion of the planets and tried to come up with a theory that would explain them. 55 00:06:36,590 --> 00:06:41,150 He was a brilliant mathematician and he was one of the inventors of the calculus, 56 00:06:41,150 --> 00:06:50,630 together with lightnings and through very clever geometrical calculation and arguments involving calculus. 57 00:06:50,630 --> 00:07:00,680 He came to the conclusion that if you postulate a force of gravity acting between objects in inverse proportion to the square of the distance, 58 00:07:00,680 --> 00:07:10,970 that means if two bodies are two units apart, the gravitational force is a quarter of what it would be if they were one unit apart. 59 00:07:10,970 --> 00:07:18,490 If they fight three units apart, the gravitational force between them is one ninth. 60 00:07:18,490 --> 00:07:25,660 Now, suppose you have a force like that, so the closer things are, the more gravity is that there is between them. 61 00:07:25,660 --> 00:07:30,580 And suppose you postulate that the force of gravity is proportional to the mass of each body. 62 00:07:30,580 --> 00:07:34,390 So the bigger an object, the more gravity there is on it. 63 00:07:34,390 --> 00:07:44,110 And suppose you postulate that the acceleration of a body, that is the amount it deviates from the straight line motion that it would otherwise take. 64 00:07:44,110 --> 00:07:51,760 Suppose you postulate that it deviates from that in a way that is proportional to the force and inversely proportional to the mass. 65 00:07:51,760 --> 00:07:59,760 So the bigger the force, the more it accelerates. The bigger the body for a given force, the less it accelerates. 66 00:07:59,760 --> 00:08:08,300 What do you get? And the answer is you get elliptical motion. 67 00:08:08,300 --> 00:08:20,940 Now, that is a fantastic result. You have this problem that people have been trying to explain for centuries, millennia, the motion of the planets. 68 00:08:20,940 --> 00:08:26,760 You have kept coming along and giving predictions that are far more accurate than any previous attempt. 69 00:08:26,760 --> 00:08:41,120 And hot on his heels. You have an explanation of elliptical motion, which is amazingly simple in terms of just one false on one law. 70 00:08:41,120 --> 00:08:52,160 Not only that. Exactly the same theory with exactly the same equations could be used to explain the motion of cannonballs on Earth. 71 00:08:52,160 --> 00:09:03,540 If you drop a stone or throw a stone, the motion can be explained by exactly the same equations that Newton used to explain the motion of the planets. 72 00:09:03,540 --> 00:09:12,750 So, again, just like Galileo, when Galileo's big results was that the substance of the moon looked very much like 73 00:09:12,750 --> 00:09:18,300 the substance of the earth with mountains and valleys and craters and so forth. 74 00:09:18,300 --> 00:09:25,030 Now we find that exactly the same laws can be used to explain the motion of both. 75 00:09:25,030 --> 00:09:32,110 Newton also proved, incidentally, that a vortex could not generate elliptical motion. 76 00:09:32,110 --> 00:09:38,620 It's almost impossible to have a vortex that generates elliptical rather than circular motion. 77 00:09:38,620 --> 00:09:45,780 So Descartes theory, which had never been that popular in Britain anyway, was discredited. 78 00:09:45,780 --> 00:09:52,620 Over these years, incidentally, Descartes theories lingered much, much longer in France than they did on this side of the channel. 79 00:09:52,620 --> 00:09:58,560 There was quite a lot of nationalism about these things. OK. 80 00:09:58,560 --> 00:10:05,800 Now, let's reflect on this. We've got this wonderful scientific achievement. It's perhaps the most important scientific work ever published. 81 00:10:05,800 --> 00:10:17,020 You can bring here. Think of that in the context that we were looking at before. 82 00:10:17,020 --> 00:10:24,490 We have the background of the Aristotelian theory of motion, which is scribed desires to physical objects, 83 00:10:24,490 --> 00:10:31,680 which saw them as analogous to human beings or animals desiring striving to reach particular objectives. 84 00:10:31,680 --> 00:10:39,120 And that seemed objectionable. Occult, weird, spooky. 85 00:10:39,120 --> 00:10:45,900 We want to get rid of that. We want to go explain things in a very down to earth mechanistic way, one thing bashing into another. 86 00:10:45,900 --> 00:10:55,670 That seems much more comprehensible, much more subject to human understanding and analysis. 87 00:10:55,670 --> 00:11:01,570 Okay. Descartes theory of the orbiting planets fitted in with that. 88 00:11:01,570 --> 00:11:07,990 But Newton's doesn't. Newton is postulating this weird force between bodies. 89 00:11:07,990 --> 00:11:12,310 How can the Earth be attracted to the sun unless it knows where the sun is? 90 00:11:12,310 --> 00:11:16,390 How can the moon be attracted to the earth unless it knows where the earth is? 91 00:11:16,390 --> 00:11:26,720 It seems very peculiar. So a lot of people objected to Newton's postulation of this gravitational force. 92 00:11:26,720 --> 00:11:32,780 They didn't like it because it didn't conform with the ideal of mechanistic understanding. 93 00:11:32,780 --> 00:11:38,090 Others, particularly followers of Newton, said, no, no. It's a proof of God's existence. 94 00:11:38,090 --> 00:11:42,620 We know, don't we? That matter cannot think right. 95 00:11:42,620 --> 00:11:49,580 It's the kind of power that matter can't have course matter by itself, can't be attracted to another body either. 96 00:11:49,580 --> 00:11:57,830 No, it must be God's action. So it's a proof of God's existence that things move in the way they do. 97 00:11:57,830 --> 00:12:01,670 Now, Newton himself took an instrumentalist attitude. 98 00:12:01,670 --> 00:12:06,290 Very famous phrase, hypotheses, non thingo. 99 00:12:06,290 --> 00:12:13,980 I feign no hypothesis. So Newton was asked, what do you make of gravity, gravity? 100 00:12:13,980 --> 00:12:22,920 Well, he said slightly different things at slightly different times. But the most famous response of that of his was to say. 101 00:12:22,920 --> 00:12:31,400 I'm not going to try to make up any explanation of how gravity works, why it does what it does. 102 00:12:31,400 --> 00:12:40,490 All I'm going to say is that the observations are consistent with it, working as I describe. 103 00:12:40,490 --> 00:12:44,120 So I've got these equations which explain how gravity works. 104 00:12:44,120 --> 00:12:50,000 It's proportional to the masses of the two objects, inversely proportional to the square of distance between them. 105 00:12:50,000 --> 00:12:54,860 If you postulate a force like that, it explains the phenomena. I'm not gonna go further. 106 00:12:54,860 --> 00:13:00,440 I'm not going to try to explain why. Maybe it's God's action. 107 00:13:00,440 --> 00:13:05,070 Maybe there's some sort of aethereal fluid that somehow brings it about. 108 00:13:05,070 --> 00:13:13,060 But if the behaviour of things is explained by this theory, that's good enough. 109 00:13:13,060 --> 00:13:17,530 Now, this is a well, I've called it methodological instrumentalism, 110 00:13:17,530 --> 00:13:25,920 instrumentalism is essentially the theory that when the view that when you have a scientific theory. 111 00:13:25,920 --> 00:13:36,420 What matters is the results that it delivers. So let's suppose you have a scientific theory in terms of atoms. 112 00:13:36,420 --> 00:13:40,890 As long as it delivers the right results, you don't care about whether there really are any atoms. 113 00:13:40,890 --> 00:13:45,360 Maybe there aren't any any atoms. Doesn't matter if the theory delivers the right result. 114 00:13:45,360 --> 00:14:02,368 That's good enough. That's instrumentalism. You see, a scientific theory is an instrument for delivering results.