1 00:00:02,160 --> 00:00:06,745 As I said in the first lecture, arguments are used for many purposes. 2 00:00:06,745 --> 00:00:12,274 And, in the lecture just before this one, we saw that it can be used for persuasion 3 00:00:12,274 --> 00:00:15,241 and also for justification of various sorts. 4 00:00:15,241 --> 00:00:20,837 But persuasion and justification are not the only purposes for which arguments are 5 00:00:20,837 --> 00:00:23,737 given. Arguments are also given in order to 6 00:00:23,737 --> 00:00:27,041 explain things. So, we're going to spend this lecture 7 00:00:27,041 --> 00:00:31,289 talking about explanation. Indeed, what we're going to try to do is 8 00:00:31,289 --> 00:00:34,644 to explain explanation. We explain things all the time, 9 00:00:34,644 --> 00:00:39,125 and I'm going to give an example that'll probably really tick off my co-teacher 10 00:00:39,125 --> 00:00:41,220 wrong, because he's from Chapel Hill. But, 11 00:00:41,220 --> 00:00:46,993 my example, somebody might ask, why did the Duke basketball team win the national 12 00:00:46,993 --> 00:00:51,396 championship in 2010? The answer might be that they had great 13 00:00:51,396 --> 00:00:55,582 players, and a great coach, and, of course, they got lucky. 14 00:00:55,582 --> 00:00:59,984 you have to have some luck to win a national championship. 15 00:00:59,984 --> 00:01:05,253 But, in any case, an explanation of that event is a reason why it happened. 16 00:01:05,253 --> 00:01:10,882 so to explain something is to give a reason why it happened or to answer a 17 00:01:10,882 --> 00:01:15,669 question about why it happened. Notice that when you explain something, 18 00:01:15,669 --> 00:01:19,852 you assume that it's true. It wouldn't make any sense to ask, why 19 00:01:19,852 --> 00:01:22,924 did Duke win the national championship in 2011? 20 00:01:22,924 --> 00:01:26,726 because they didn't. You can only ask why this thing happened 21 00:01:26,726 --> 00:01:30,156 if it happened. So, we've already got one difference 22 00:01:30,156 --> 00:01:33,720 between explanation, and justification, and persuasion. 23 00:01:33,720 --> 00:01:38,159 When you try to persuade someone to believe something, that thing doesn't 24 00:01:38,159 --> 00:01:42,235 have to be true and they don't have to have believed it in advance. 25 00:01:42,235 --> 00:01:47,222 When you justify something, right? You can justify belief in something that they 26 00:01:47,222 --> 00:01:50,993 don't already believe. But when you explain something, both the 27 00:01:50,993 --> 00:01:55,311 arguer and the audience are assuming that, that thing happened, that the 28 00:01:55,311 --> 00:01:59,630 conclusion is true, and they're looking for the reasons why it happened. 29 00:01:59,630 --> 00:02:05,099 So, if the goal of explanation is not to persuade or to justify and the arguer and 30 00:02:05,099 --> 00:02:09,969 the, and the audience both already believe the conclusion, then what's the 31 00:02:09,969 --> 00:02:12,437 point? What's the goal of explanation? 32 00:02:12,437 --> 00:02:15,973 The goal of explanation is to increase understanding. 33 00:02:15,973 --> 00:02:21,376 Not to convince us that the conclusion is true, but to help us understand why its 34 00:02:21,376 --> 00:02:24,159 true. And we can do that in a number of 35 00:02:24,159 --> 00:02:26,320 different ways. Their actually, 36 00:02:26,320 --> 00:02:31,525 according to Aristotle, four different types of causes, he would call them, but 37 00:02:31,525 --> 00:02:36,663 we would probably call them explanations. The first, were, he called efficient 38 00:02:36,663 --> 00:02:39,908 causation, we'll just call it causal explanation. 39 00:02:39,908 --> 00:02:44,505 And that tells you why something happen. Why did the bridge collapse? 40 00:02:44,505 --> 00:02:49,305 Because there was an earthquake, that explains why the bridge collapsed. 41 00:02:49,305 --> 00:02:54,916 The second type of explanation, he called teleological or purposeful explanation 42 00:02:54,916 --> 00:02:58,770 because it's looking at the purpose or the telos or the goal. 43 00:02:58,770 --> 00:03:02,792 Why did Joe go to the grocery store? To buy milk. 44 00:03:02,792 --> 00:03:09,440 His goal of buying milk is what explains why he went to the grocery store. 45 00:03:09,440 --> 00:03:17,343 Third type of explanation is formal. Why does this peg not fit into this hole? 46 00:03:17,343 --> 00:03:22,211 And the answer is, because the peg is square and the hole is round. 47 00:03:22,211 --> 00:03:26,562 That's why it doesn't fit in the hole and that explains it. 48 00:03:26,562 --> 00:03:29,660 It helps you understand why it didn't fit. 49 00:03:29,660 --> 00:03:32,794 The fourth kind of explanation is material. 50 00:03:32,794 --> 00:03:36,876 Why is this golf club so light? Why's it weigh so little? 51 00:03:36,876 --> 00:03:40,812 The answer might be, because it's made out of graphite. 52 00:03:40,812 --> 00:03:45,842 That helps you understand why the weight is so low on this golf club. 53 00:03:45,842 --> 00:03:50,070 it would be a lot heavier if it were made out of steel. 54 00:03:50,070 --> 00:03:53,633 So, we can have four different types of explanation. 55 00:03:53,633 --> 00:03:58,525 We can have causal, we can have teleological, we can have formal, and we 56 00:03:58,525 --> 00:04:02,298 can have material. And all of those different types of 57 00:04:02,298 --> 00:04:07,400 explanation are aimed at helping us to understand why something happened. 58 00:04:07,400 --> 00:04:13,483 So did you hear that train whistle? We want to ask, why does the train emit 59 00:04:13,483 --> 00:04:17,514 such a loud noise? Well, one answer might be that what 60 00:04:17,514 --> 00:04:23,673 causes it to make that noise is that the conductor pull lever on the train which 61 00:04:23,673 --> 00:04:27,780 creates that noise. That would be a causal explanation. 62 00:04:27,780 --> 00:04:32,190 Another explanation might be the teleological explanation. 63 00:04:32,190 --> 00:04:37,736 The train was crossing an intersection with cars and wanted the cars to know 64 00:04:37,736 --> 00:04:41,814 that they're coming. Another explanation might be a formal 65 00:04:41,814 --> 00:04:45,329 explanation. Because the whistle on the top of the 66 00:04:45,329 --> 00:04:50,883 train has a certain shape that makes the air come out with a certain vibration. 67 00:04:50,883 --> 00:04:54,820 And a final explanation might be, a material explanation. 68 00:04:54,820 --> 00:05:00,304 Because air has a certain density and a certain material that makes it create 69 00:05:00,304 --> 00:05:03,960 that kind of sound. So, we can give all four types of 70 00:05:03,960 --> 00:05:09,053 explanations for the same event. Here's another example where we can apply 71 00:05:09,053 --> 00:05:12,304 all four types of explanation to a single event. 72 00:05:12,304 --> 00:05:16,434 Joe jumped out of an airplane, that's what caused him to fall. 73 00:05:16,434 --> 00:05:20,700 But then, why did he jump out of the airplane to get excitement? 74 00:05:20,700 --> 00:05:26,049 Why did he fall so fast, because of his shape, it was aerodynamic, and because of 75 00:05:26,049 --> 00:05:31,263 the material that he was made out of, heavy flesh, which was a lot denser than 76 00:05:31,263 --> 00:05:35,190 the surrounding air. So, all four of the factors go into an 77 00:05:35,190 --> 00:05:40,020 explanation of why Joe fell when he jumped out of the airplane. 78 00:05:40,020 --> 00:05:43,276 So next we need to talk about the forms of explanation. 79 00:05:43,276 --> 00:05:46,947 You can actually give explanations in, in several different forms. 80 00:05:46,947 --> 00:05:50,145 For example, if somebody says, why did you move to Duke? 81 00:05:50,145 --> 00:05:54,882 I might tell a story about things that happened before I moved to Duke that led 82 00:05:54,882 --> 00:05:59,204 me to want to move to Duke and I could talk about moving to Duke and, and all 83 00:05:59,204 --> 00:06:03,322 the nice people here and so on. You can give explanations in the form of 84 00:06:03,322 --> 00:06:06,495 narratives like that. But notice that, that's not going to 85 00:06:06,495 --> 00:06:10,280 imply that everybody in similar circumstances is going to behave in 86 00:06:10,280 --> 00:06:13,398 exactly the same way. So, you're not going to get general 87 00:06:13,398 --> 00:06:16,460 principles out of those types of narrative explanations. 88 00:06:16,460 --> 00:06:20,055 But other explanations are given in the form of arguments, 89 00:06:20,055 --> 00:06:23,713 and that's the kind that we're going to be interested in here. 90 00:06:23,713 --> 00:06:28,301 The form in which explanations occur in arguments is really pretty simple. 91 00:06:28,301 --> 00:06:33,384 One premise usually states some kind of general principle that can apply to a lot 92 00:06:33,384 --> 00:06:37,352 of different situations. And then, the second premise talks about 93 00:06:37,352 --> 00:06:42,250 the current situation and says that those types of features that the principle 94 00:06:42,250 --> 00:06:46,776 mentions are instantiated in this case. And then the conclusion says, that 95 00:06:46,776 --> 00:06:49,690 explains why it happened this way in this case. 96 00:06:49,690 --> 00:06:54,650 For example, if we want to know why objects fall, 97 00:06:54,650 --> 00:06:58,756 right? So, there's a book and it falls, if we 98 00:06:58,756 --> 00:07:02,790 want to explain that, we need to cite a general principle. 99 00:07:02,790 --> 00:07:07,996 But notice that not all objects fall, some objects actually rise, helium 100 00:07:07,996 --> 00:07:11,883 balloons rise. So, we need a principle that's going to 101 00:07:11,883 --> 00:07:15,770 explain why some objects fall, and other objects rise. 102 00:07:15,770 --> 00:07:20,976 Then, we'll understand why helium balloons rise, just to stick with that 103 00:07:20,976 --> 00:07:24,582 example. And the answer is that, when an object is 104 00:07:24,582 --> 00:07:30,482 suspended freely in a medium where the medium is more dense than the object, 105 00:07:30,482 --> 00:07:34,828 then it rises. And when an object is suspended freely in 106 00:07:34,828 --> 00:07:40,340 a medium where the object is more dense than the medium, thent if falls. 107 00:07:40,340 --> 00:07:45,385 So, you can explain why helium balloons rise by having as your first premise, 108 00:07:45,385 --> 00:07:50,165 whenever an object is sus, freely suspended in a medium, like a gas or a 109 00:07:50,165 --> 00:07:53,600 liquid, and the medium is more dense than the 110 00:07:53,600 --> 00:07:58,602 object, then object rises. Now, let's talk about the circumstances 111 00:07:58,602 --> 00:08:03,760 in this particular case. The helium balloon is less dense than the 112 00:08:03,760 --> 00:08:08,497 air that surrounds it, therefore the helium balloon rises. 113 00:08:08,497 --> 00:08:14,330 And that explains why the helium balloon rises, and you can see how you'd give 114 00:08:14,330 --> 00:08:17,770 another argument to explain why the book fell. 115 00:08:17,770 --> 00:08:22,856 Now, this form of argument gives some people the impression that any 116 00:08:22,856 --> 00:08:26,071 generalization can be used for explanation. 117 00:08:26,071 --> 00:08:30,035 But that's not quite right. One example is Bode's Law. 118 00:08:30,035 --> 00:08:36,532 Bode's Law says that 0.4 + 0.3 * 2 to the n can be used to predict all the 119 00:08:36,532 --> 00:08:43,215 distances between planets and the sun, where n is the number of the planet. 120 00:08:43,215 --> 00:08:48,632 So, if n is Venus, the n is zero. Earth is one, Mars is two, and so on. 121 00:08:48,632 --> 00:08:55,768 this law was actually used to predict both the largest asteroid in the asteroid 122 00:08:55,768 --> 00:09:00,797 belt, Ceres, and also Uranus. So, this law is a generalization that 123 00:09:00,797 --> 00:09:06,798 held for all the planets that they knew in Bode's day and also used to predict 124 00:09:06,798 --> 00:09:10,018 new observations of planets. Pretty cool. 125 00:09:10,018 --> 00:09:15,360 It actually turns out to fail when you get to other planets in, including 126 00:09:15,360 --> 00:09:16,970 Neptune and Pluto. But, 127 00:09:16,970 --> 00:09:20,768 still it worked pretty well for the data that they had. 128 00:09:20,768 --> 00:09:25,810 But nobody thought that this law explained why the planets were that far 129 00:09:25,810 --> 00:09:29,332 from the Sun. They happened to fall in that pattern. 130 00:09:29,332 --> 00:09:34,650 It could be used to predict, but it didn't explain why they were the distance 131 00:09:34,650 --> 00:09:39,482 they actually were from the Sun. So, Bode's Law gives you a nice example 132 00:09:39,482 --> 00:09:44,390 where you can have a generalization and a prediction without explanation. 133 00:09:44,390 --> 00:09:50,162 Now, here's an example where you can have explanation without prediction. 134 00:09:50,162 --> 00:09:56,336 Just think of a woman who has AIDS and gets pregnant and gives birth and her 135 00:09:56,336 --> 00:10:02,040 child has AIDS, too. Now, that would explain why the child was 136 00:10:02,040 --> 00:10:06,524 born with AIDS. But, it won't predict that the child will 137 00:10:06,524 --> 00:10:12,217 get AIDS because actually, less then 50% of the children who are born to mothers 138 00:10:12,217 --> 00:10:17,232 who have AIDS, have AIDS themselves. So, you can't get a prediction out of 139 00:10:17,232 --> 00:10:21,207 that disease state, but you can get an explanation when the 140 00:10:21,207 --> 00:10:25,789 child does, in fact, have AIDS. And notice also, that the fact that the 141 00:10:25,789 --> 00:10:30,707 mother has AIDS doesn't justify you in believing that the child has AIDS. 142 00:10:30,707 --> 00:10:35,895 What justifies you in believing that the child has AIDS is that you test the 143 00:10:35,895 --> 00:10:41,709 child's blood and find HIV in the blood. So, here we have an example where there's 144 00:10:41,709 --> 00:10:45,588 an explanation without justification or prediction. 145 00:10:45,588 --> 00:10:50,990 And so, explanation is very different from those other uses of argument. 146 00:10:50,990 --> 00:10:54,763 So then, more positively, what is the goal of explanation? 147 00:10:54,763 --> 00:11:00,221 Well, the goal of explanation is to fit this particular phenomenon into a general 148 00:11:00,221 --> 00:11:02,715 pattern. And, that's what all of these 149 00:11:02,715 --> 00:11:06,152 explanations do. Why do you want to fit them into a 150 00:11:06,152 --> 00:11:11,138 general pattern is simply to increase your understanding of why they came 151 00:11:11,138 --> 00:11:14,103 about. They came about because they fit into 152 00:11:14,103 --> 00:11:18,419 this particular type of pattern. And this kind of understanding them, 153 00:11:18,419 --> 00:11:21,357 fitting them into a well known pattern, is useful. 154 00:11:21,357 --> 00:11:25,975 Because most of the things that we want to explain are kind of weird, unusual, 155 00:11:25,975 --> 00:11:30,174 bewildering, surprising phenomenon. That's when you need an explanation. 156 00:11:30,174 --> 00:11:35,092 Because fitting into the pattern makes it a little less bewildering, a little less 157 00:11:35,092 --> 00:11:39,530 surprising because it shows that it's kind of like other things that have 158 00:11:39,530 --> 00:11:43,500 happened before. And that's what Bode's Law does not do. 159 00:11:43,500 --> 00:11:48,295 Because Bode's Law, although it holds for all the planets that had been observed in 160 00:11:48,295 --> 00:11:51,126 the day of Bode, it doesn't explain anything else. 161 00:11:51,126 --> 00:11:55,517 It doesn't fit it into a larger pattern with other planets around other solar 162 00:11:55,517 --> 00:11:58,175 systems. And now that we've discovered planets, 163 00:11:58,175 --> 00:12:02,624 we've found many planets around other stars that don't seem to follow Bode's 164 00:12:02,624 --> 00:12:05,848 Law at all. So, it doesn't fit our solar system into 165 00:12:05,848 --> 00:12:09,212 a general pattern. And that's why even though it's a 166 00:12:09,212 --> 00:12:14,129 generalization and was used to predict other planets, it does not provide an 167 00:12:14,129 --> 00:12:18,400 explanation of why the planets are certain distances from the Sun. 168 00:12:18,400 --> 00:12:24,184 So now, we've learned a little bit about what explanation is and what explanation 169 00:12:24,184 --> 00:12:27,184 is not. Explanation is an attempt to fit a 170 00:12:27,184 --> 00:12:32,996 particular phenomenon into a general pattern in order to increase our 171 00:12:32,996 --> 00:12:39,129 understanding of why it happened, and to remove bewilderment or surprise. 172 00:12:39,129 --> 00:12:44,922 Explanation is not persuasion, or justification, or generalization, or 173 00:12:44,922 --> 00:12:47,960 prediction. Those are other uses of argument. 174 00:12:47,960 --> 00:12:52,415 So, we've seen quite a variety of different uses of argument, but we've 175 00:12:52,415 --> 00:12:56,678 only scratched the surface. There can be lots more, and lots more to 176 00:12:56,678 --> 00:13:00,815 say about each of these. So, if you want to learn more about these 177 00:13:00,815 --> 00:13:05,334 purposes of argument, a good place to start would be chapter one of the 178 00:13:05,334 --> 00:13:08,007 accompanying text, understanding arguments. 179 00:13:08,007 --> 00:13:12,357 But we're going to leave this topic for now, and turn to a separate topic. 180 00:13:12,357 --> 00:13:16,900 In order to understand something you want to know, not just its purpose, but the 181 00:13:16,900 --> 00:13:20,983 material out of which it's made. So, the next few lectures will be about 182 00:13:20,983 --> 00:13:24,492 the material out of which arguments are made namely, language.