WEBVTT 00:00:00.930 --> 00:00:04.058 Every day we face issues like climate change 00:00:04.058 --> 00:00:05.488 or the safety of vaccines 00:00:05.488 --> 00:00:08.528 where we have to answer questions whose answers 00:00:08.528 --> 00:00:11.989 rely heavily on scientific information. 00:00:11.989 --> 00:00:14.870 Scientists tell us that the world is warming. 00:00:14.870 --> 00:00:17.411 Scientists tell us that vaccines are safe. 00:00:17.411 --> 00:00:19.465 But how do we know if they are right? 00:00:19.465 --> 00:00:21.429 Why should be believe the science? 00:00:21.429 --> 00:00:24.898 The fact is, many of us actually don't believe the science. 00:00:24.898 --> 00:00:27.074 Public opinion polls consistently show 00:00:27.074 --> 00:00:30.084 that significant proportions of the American people 00:00:30.084 --> 00:00:33.625 don't believe the climate is warming due to human activities, 00:00:33.625 --> 00:00:36.564 don't think that there is evolution by natural selection, 00:00:36.564 --> 00:00:40.465 and aren't persuaded by the safety of vaccines. NOTE Paragraph 00:00:40.465 --> 00:00:44.096 So why should we believe the science? 00:00:44.096 --> 00:00:47.707 Well, scientists don't like talking about science as a matter of belief. 00:00:47.707 --> 00:00:50.294 In fact, they would contrast science with faith, 00:00:50.294 --> 00:00:53.260 and they would say belief is the domain of faith. 00:00:53.260 --> 00:00:57.038 And faith is a separate thing apart and distinct from science. 00:00:57.038 --> 00:01:00.190 Indeed they would say religion is based on faith 00:01:00.190 --> 00:01:03.884 or maybe the calculus of Pascal's wager. 00:01:03.884 --> 00:01:06.560 Blaise Pascal was a 17th-century mathematician 00:01:06.560 --> 00:01:09.370 who tried to bring scientific reasoning to the question of 00:01:09.370 --> 00:01:11.242 whether or not he should believe in God, 00:01:11.242 --> 00:01:13.846 and his wager went like this: 00:01:13.846 --> 00:01:16.395 Well, if God doesn't exist 00:01:16.395 --> 00:01:18.420 but I decide to believe in him 00:01:18.420 --> 00:01:20.398 nothing much is really lost. 00:01:20.398 --> 00:01:22.011 Maybe a few hours on Sunday. 00:01:22.011 --> 00:01:23.004 (Laughter) 00:01:23.004 --> 00:01:26.385 But if he does exist and I don't believe in him, 00:01:26.385 --> 00:01:28.402 then I'm in deep trouble. 00:01:28.402 --> 00:01:31.438 And so Pascal said, we'd better believe in God. 00:01:31.438 --> 00:01:33.610 Or as one of my college professors said, 00:01:33.610 --> 00:01:35.836 "He clutched for the handrail of faith." 00:01:35.836 --> 00:01:37.772 He made that leap of faith 00:01:37.772 --> 00:01:42.296 leaving science and rationalism behind. NOTE Paragraph 00:01:42.296 --> 00:01:44.992 Now the fact is though, for most of us, 00:01:44.992 --> 00:01:48.126 most scientific claims are a leap of faith. 00:01:48.126 --> 00:01:52.511 We can't really judge scientific claims for ourselves in most cases. 00:01:52.511 --> 00:01:55.351 And indeed this is actually true for most scientists as well 00:01:55.351 --> 00:01:57.681 outside of their own specialties. 00:01:57.681 --> 00:02:00.201 So if you think about it, a geologist can't tell you 00:02:00.201 --> 00:02:01.951 whether a vaccine is safe. 00:02:01.951 --> 00:02:04.951 Most chemists are not experts in evolutionary theory. 00:02:04.951 --> 00:02:07.210 A physicist cannot tell you, 00:02:07.210 --> 00:02:08.653 despite the claims of some of them, 00:02:08.653 --> 00:02:12.007 whether or not tobacco causes cancer. 00:02:12.007 --> 00:02:14.457 So, if even scientists themselves 00:02:14.457 --> 00:02:15.733 have to make a leap of faith 00:02:15.733 --> 00:02:17.655 outside their own fields, 00:02:17.655 --> 00:02:21.583 then why do they accept the claims of other scientists? 00:02:21.583 --> 00:02:23.881 Why do they believe each other's claims? 00:02:23.881 --> 00:02:27.171 And should we believe those claims? NOTE Paragraph 00:02:27.171 --> 00:02:29.947 So what I'd like to argue is yes, we should, 00:02:29.947 --> 00:02:32.830 but not for the reason that most of us think. 00:02:32.830 --> 00:02:35.160 Most of us were taught in school that the reason we should 00:02:35.160 --> 00:02:38.572 believe in science is because of the scientific method. 00:02:38.572 --> 00:02:41.488 We were taught that scientists follow a method 00:02:41.488 --> 00:02:43.844 and that this method guarantees 00:02:43.844 --> 00:02:45.840 the truth of their claims. 00:02:45.840 --> 00:02:49.260 The method that most of us were taught in school, 00:02:49.260 --> 00:02:50.836 we can call it the textbook method, 00:02:50.836 --> 00:02:53.620 is the hypothetical deductive method. 00:02:53.620 --> 00:02:56.714 According to the standard model, the textbook model, 00:02:56.714 --> 00:02:59.671 scientists develop hypotheses, they deduce 00:02:59.671 --> 00:03:02.131 the consequences of those hypotheses, 00:03:02.131 --> 00:03:03.841 and then they go out into the world and they say, 00:03:03.841 --> 00:03:06.215 "Okay, well are those consequences true?" 00:03:06.215 --> 00:03:09.548 Can we observe them taking place in the natural world? 00:03:09.548 --> 00:03:12.148 And if they are true, then the scientists say, 00:03:12.148 --> 00:03:15.004 "Great, we know the hypothesis is correct." NOTE Paragraph 00:03:15.004 --> 00:03:17.183 So there are many famous examples in the history 00:03:17.183 --> 00:03:20.062 of science of scientists doing exactly this. 00:03:20.062 --> 00:03:22.120 One of the most famous examples 00:03:22.120 --> 00:03:24.333 comes from the work of Albert Einstein. 00:03:24.333 --> 00:03:26.855 When Einstein developed the theory of general relativity, 00:03:26.855 --> 00:03:29.171 one of the consequences of his theory 00:03:29.171 --> 00:03:32.010 was that space-time wasn't just an empty void 00:03:32.010 --> 00:03:33.919 but that it actually had a fabric. 00:03:33.919 --> 00:03:35.520 And that that fabric was bent 00:03:35.520 --> 00:03:38.900 in the presence of massive objects like the sun. 00:03:38.900 --> 00:03:41.649 So if this theory were true then it meant that light 00:03:41.649 --> 00:03:43.177 as it passed the sun 00:03:43.177 --> 00:03:45.345 should actually be bent around it. 00:03:45.345 --> 00:03:47.745 That was a pretty startling prediction 00:03:47.745 --> 00:03:49.733 and it took a few years before scientists 00:03:49.733 --> 00:03:51.011 were able to test it 00:03:51.011 --> 00:03:53.521 but they did test it in 1919, 00:03:53.521 --> 00:03:55.971 and lo and behold it turned out to be true. 00:03:55.971 --> 00:03:59.129 Starlight actually does bend as it travels around the sun. 00:03:59.129 --> 00:04:01.623 This was a huge confirmation of the theory. 00:04:01.623 --> 00:04:03.428 It was considered proof of the truth 00:04:03.428 --> 00:04:04.740 of this radical new idea, 00:04:04.740 --> 00:04:06.592 and it was written up in many newspapers 00:04:06.592 --> 00:04:09.130 around the globe. NOTE Paragraph 00:04:09.130 --> 00:04:11.480 Now, sometimes this theory or this model 00:04:11.480 --> 00:04:14.914 is referred to as the deductive-nomological model, 00:04:14.914 --> 00:04:18.298 mainly because academics like to make things complicated. 00:04:18.298 --> 00:04:23.559 But also because in the ideal case, it's about laws. 00:04:23.559 --> 00:04:26.061 So nomological means having to do with laws. 00:04:26.061 --> 00:04:29.485 And in the ideal case, the hypothesis isn't just an idea: 00:04:29.485 --> 00:04:31.811 ideally, it is a law of nature. 00:04:31.811 --> 00:04:34.098 Why does it matter that it is a law of nature? 00:04:34.098 --> 00:04:36.826 Because if it is a law, it can't be broken. 00:04:36.826 --> 00:04:38.934 If it's a law then it will always be true 00:04:38.934 --> 00:04:40.178 in all times and all places 00:04:40.178 --> 00:04:42.384 no matter what the circumstances are. 00:04:42.384 --> 00:04:45.613 And all of you know of at least one example of a famous law: 00:04:45.613 --> 00:04:49.368 Einstein's famous equation, E=MC2, 00:04:49.368 --> 00:04:51.168 which tells us what the relationship is 00:04:51.168 --> 00:04:53.361 between energy and mass. 00:04:53.361 --> 00:04:57.361 And that relationship is true no matter what. NOTE Paragraph 00:04:57.361 --> 00:05:01.010 Now, it turns out, though, that there are several problems with this model. 00:05:01.010 --> 00:05:04.645 The main problem is that it's wrong. 00:05:04.645 --> 00:05:08.147 It's just not true. (Laughter) 00:05:08.147 --> 00:05:10.870 And I'm going to talk about three reasons why it's wrong. 00:05:10.870 --> 00:05:13.549 So the first reason is a logical reason. 00:05:13.549 --> 00:05:17.065 It's the problem of the fallacy of affirming the consequent. 00:05:17.065 --> 00:05:19.891 So that's another fancy, academic way of saying 00:05:19.891 --> 00:05:22.561 that false theories can make true predictions. 00:05:22.561 --> 00:05:24.555 So just because the prediction comes true 00:05:24.555 --> 00:05:27.777 doesn't actually logically prove that the theory is correct. 00:05:27.777 --> 00:05:31.708 And I have a good example of that too, again from the history of science. 00:05:31.708 --> 00:05:34.403 This is a picture of the Ptolemaic universe 00:05:34.403 --> 00:05:36.265 with the Earth at the center of the universe 00:05:36.265 --> 00:05:38.860 and the sun and the planets going around it. 00:05:38.860 --> 00:05:40.890 The Ptolemaic model was believed 00:05:40.890 --> 00:05:44.143 by many very smart people for many centuries. 00:05:44.143 --> 00:05:45.879 Well, why? 00:05:45.879 --> 00:05:49.316 Well the answer is because it made lots of predictions that came true. 00:05:49.316 --> 00:05:51.332 The Ptolemaic system enabled astronomers 00:05:51.332 --> 00:05:54.082 to make accurate predictions of the motions of the planet, 00:05:54.082 --> 00:05:56.601 in fact more accurate predictions at first 00:05:56.601 --> 00:06:00.925 than the Copernican theory which we now would say is true. 00:06:00.925 --> 00:06:03.907 So that's one problem with the textbook model. 00:06:03.907 --> 00:06:06.303 A second problem is a practical problem, 00:06:06.303 --> 00:06:09.538 and it's the problem of auxiliary hypotheses. 00:06:09.538 --> 00:06:12.367 Auxiliary hypotheses are assumptions 00:06:12.367 --> 00:06:14.146 that scientists are making 00:06:14.146 --> 00:06:17.189 that they may or may not even be aware that they're making. 00:06:17.189 --> 00:06:19.850 So an important example of this 00:06:19.850 --> 00:06:21.945 comes from the Copernican model, 00:06:21.945 --> 00:06:25.137 which ultimately replaced the Ptolemaic system. 00:06:25.137 --> 00:06:27.177 So when Nicolaus Copernicus said, 00:06:27.177 --> 00:06:29.827 actually the Earth is not the center of the universe, 00:06:29.827 --> 00:06:31.745 the sun is the center of the solar system, 00:06:31.745 --> 00:06:33.127 the Earth moves around the sun. 00:06:33.127 --> 00:06:36.855 Scientists said, well okay, Nicolaus, if that's true 00:06:36.855 --> 00:06:38.619 we ought to be able to detect the motion 00:06:38.619 --> 00:06:40.577 of the Earth around the sun. 00:06:40.577 --> 00:06:42.633 And so this slide here illustrates a concept 00:06:42.633 --> 00:06:44.441 known as stellar parallax. 00:06:44.441 --> 00:06:48.263 And astronomers said, if the Earth is moving 00:06:48.263 --> 00:06:51.463 and we look at a prominent star, let's say, Sirius -- 00:06:51.463 --> 00:06:53.877 well I know I'm in Manhattan so you guys can't see the stars, 00:06:53.877 --> 00:06:57.608 but imagine you're out in the country, imagine you chose that rural life — 00:06:57.608 --> 00:07:00.475 and we look at a star in December, we see that star 00:07:00.475 --> 00:07:03.240 against the backdrop of distant stars. 00:07:03.240 --> 00:07:06.194 If we now make the same observation six months later 00:07:06.194 --> 00:07:10.006 when the Earth has moved to this position in June, 00:07:10.006 --> 00:07:14.105 we look at that same star and we see it against a different backdrop. 00:07:14.105 --> 00:07:18.287 That difference, that angular difference, is the stellar parallax. 00:07:18.287 --> 00:07:21.150 So this is a prediction that the Copernican model makes. 00:07:21.150 --> 00:07:23.711 Astronomers looked for the stellar parallax 00:07:23.711 --> 00:07:28.693 and they found nothing, nothing at all. 00:07:28.693 --> 00:07:32.559 And many people argued that this proved that the Copernican model was false. NOTE Paragraph 00:07:32.559 --> 00:07:34.047 So what happened? 00:07:34.047 --> 00:07:36.730 Well, in hindsight we can say that astronomers were making 00:07:36.730 --> 00:07:39.277 two auxiliary hypotheses, both of which 00:07:39.277 --> 00:07:41.940 we would now say were incorrect. 00:07:41.940 --> 00:07:45.575 The first was an assumption about the size of the Earth's orbit. 00:07:45.575 --> 00:07:48.611 Astronomers were assuming that the Earth's orbit was large 00:07:48.611 --> 00:07:50.949 relative to the distance to the stars. 00:07:50.949 --> 00:07:53.413 Today we would draw the picture more like this, 00:07:53.413 --> 00:07:54.760 this comes from NASA, 00:07:54.760 --> 00:07:57.183 and you see the Earth's orbit is actually quite small. 00:07:57.183 --> 00:08:00.174 In fact, it's actually much smaller even than shown here. 00:08:00.174 --> 00:08:01.713 The stellar parallax therefore, 00:08:01.713 --> 00:08:05.297 is very small and actually very hard to detect. NOTE Paragraph 00:08:05.297 --> 00:08:07.271 And that leads to the second reason 00:08:07.271 --> 00:08:09.130 why the prediction didn't work, 00:08:09.130 --> 00:08:11.045 because scientists were also assuming 00:08:11.045 --> 00:08:14.055 that the telescopes they had were sensitive enough 00:08:14.055 --> 00:08:15.955 to detect the parallax. 00:08:15.955 --> 00:08:17.972 And that turned out not to be true. 00:08:17.972 --> 00:08:20.506 It wasn't until the 19th century 00:08:20.506 --> 00:08:22.190 that scientists were able to detect 00:08:22.190 --> 00:08:23.726 the stellar parallax. NOTE Paragraph 00:08:23.726 --> 00:08:26.372 So, there's a third problem as well. 00:08:26.372 --> 00:08:29.150 The third problem is simply a factual problem, 00:08:29.150 --> 00:08:31.966 that a lot of science doesn't fit the textbook model. 00:08:31.966 --> 00:08:34.239 A lot of science isn't deductive at all, 00:08:34.239 --> 00:08:36.007 it's actually inductive. 00:08:36.007 --> 00:08:38.523 And by that we mean that scientists don't necessarily 00:08:38.523 --> 00:08:40.754 start with theories and hypotheses, 00:08:40.754 --> 00:08:42.623 often they just start with observations 00:08:42.623 --> 00:08:45.032 of stuff going on in the world. 00:08:45.032 --> 00:08:47.602 And the most famous example of that is one of the most 00:08:47.602 --> 00:08:50.667 famous scientists who ever lived, Charles Darwin. 00:08:50.667 --> 00:08:53.829 When Darwin went out as a young man on the voyage of the Beagle, 00:08:53.829 --> 00:08:57.441 he didn't have a hypothesis, he didn't have a theory. 00:08:57.441 --> 00:09:00.507 He just knew that he wanted to have a career as a scientist 00:09:00.507 --> 00:09:02.519 and he started to collect data. 00:09:02.519 --> 00:09:05.249 Mainly he knew that he hated medicine 00:09:05.249 --> 00:09:07.067 because the sight of blood made him sick so 00:09:07.067 --> 00:09:09.335 he had to have an alternative career path. 00:09:09.335 --> 00:09:11.469 So he started collecting data. 00:09:11.469 --> 00:09:14.635 And he collected many things, including his famous finches. 00:09:14.635 --> 00:09:16.845 When he collected these finches, he threw them in a bag 00:09:16.845 --> 00:09:19.185 and he had no idea what they meant. 00:09:19.185 --> 00:09:21.472 Many years later back in London, 00:09:21.472 --> 00:09:23.705 Darwin looked at his data again and began 00:09:23.705 --> 00:09:26.153 to develop an explanation, 00:09:26.153 --> 00:09:29.451 and that explanation was the theory of natural selection. NOTE Paragraph 00:09:29.451 --> 00:09:31.510 Besides inductive science, 00:09:31.510 --> 00:09:34.446 scientists also often participate in modeling. 00:09:34.446 --> 00:09:36.782 One of the things scientists want to do in life 00:09:36.782 --> 00:09:39.050 is to explain the causes of things. 00:09:39.050 --> 00:09:40.568 And how do we do that? 00:09:40.568 --> 00:09:42.820 Well, one way you can do it is to build a model 00:09:42.820 --> 00:09:44.562 that tests an idea. NOTE Paragraph 00:09:44.562 --> 00:09:46.493 So this is a picture of Henry Cadell, 00:09:46.493 --> 00:09:49.359 who was a Scottish geologist in the 19th century. 00:09:49.359 --> 00:09:50.792 You can tell he's Scottish because he's wearing 00:09:50.792 --> 00:09:53.180 a deerstalker cap and Wellington boots. 00:09:53.180 --> 00:09:55.334 (Laughter) 00:09:55.334 --> 00:09:56.900 And Cadell wanted to answer the question, 00:09:56.900 --> 00:09:58.668 how are mountains formed? 00:09:58.668 --> 00:10:00.184 And one of the things he had observed 00:10:00.184 --> 00:10:02.758 is that if you look at mountains like the Appalachians, 00:10:02.758 --> 00:10:04.391 you often find that the rocks in them 00:10:04.391 --> 00:10:05.860 are folded, 00:10:05.860 --> 00:10:07.506 and they're folded in a particular way, 00:10:07.506 --> 00:10:08.950 which suggested to him 00:10:08.950 --> 00:10:11.899 that they were actually being compressed from the side. 00:10:11.899 --> 00:10:13.987 And this idea would later play a major role 00:10:13.987 --> 00:10:16.410 in discussions of continental drift. 00:10:16.410 --> 00:10:18.916 So he built this model, this crazy contraption 00:10:18.916 --> 00:10:21.068 with levers and wood, and here's his wheelbarrow, 00:10:21.068 --> 00:10:23.510 buckets, a big sledgehammer. 00:10:23.510 --> 00:10:25.408 I don't know why he's got the Wellington boots. 00:10:25.408 --> 00:10:26.985 Maybe it's going to rain. 00:10:26.985 --> 00:10:30.070 And he created this physical model in order 00:10:30.070 --> 00:10:34.035 to demonstrate that you could, in fact, create 00:10:34.035 --> 00:10:36.709 patterns in rocks, or at least, in this case, in mud, 00:10:36.709 --> 00:10:38.935 that looked a lot like mountains 00:10:38.935 --> 00:10:40.777 if you compressed them from the side. 00:10:40.777 --> 00:10:44.405 So it was an argument about the cause of mountains. NOTE Paragraph 00:10:44.405 --> 00:10:47.453 Nowadays, most scientists prefer to work inside, 00:10:47.453 --> 00:10:49.880 so they don't build physical models so much 00:10:49.880 --> 00:10:52.241 as to make computer simulations. 00:10:52.241 --> 00:10:55.080 But a computer simulation is a kind of a model. 00:10:55.080 --> 00:10:56.943 It's a model that's made with mathematics, 00:10:56.943 --> 00:11:00.176 and like the physical models of the 19th century, 00:11:00.176 --> 00:11:03.954 it's very important for thinking about causes. 00:11:03.954 --> 00:11:06.569 So one of the big questions to do with climate change, 00:11:06.569 --> 00:11:08.372 we have tremendous amounts of evidence 00:11:08.372 --> 00:11:10.252 that the Earth is warming up. 00:11:10.252 --> 00:11:12.716 This slide here, the black line shows 00:11:12.716 --> 00:11:14.836 the measurements that scientists have taken 00:11:14.836 --> 00:11:16.799 for the last 150 years 00:11:16.799 --> 00:11:18.209 showing that the Earth's temperature 00:11:18.209 --> 00:11:19.843 has steadily increased, 00:11:19.843 --> 00:11:22.689 and you can see in particular that in the last 50 years 00:11:22.689 --> 00:11:24.453 there's been this dramatic increase 00:11:24.453 --> 00:11:26.793 of nearly one degree centigrade, 00:11:26.793 --> 00:11:29.168 or almost two degrees Fahrenheit. NOTE Paragraph 00:11:29.168 --> 00:11:31.605 So what, though, is driving that change? 00:11:31.605 --> 00:11:33.940 How can we know what's causing 00:11:33.940 --> 00:11:35.456 the observed warming? 00:11:35.456 --> 00:11:37.170 Well, scientists can model it 00:11:37.170 --> 00:11:39.538 using a computer simulation. 00:11:39.538 --> 00:11:42.330 So this diagram illustrates a computer simulation 00:11:42.330 --> 00:11:44.451 that has looked at all the different factors 00:11:44.451 --> 00:11:47.056 that we know can influence the Earth's climate, 00:11:47.056 --> 00:11:49.808 so sulfate particles from air pollution, 00:11:49.808 --> 00:11:52.778 volcanic dust from volcanic eruptions, 00:11:52.778 --> 00:11:55.012 changes in solar radiation, 00:11:55.012 --> 00:11:57.390 and, of course, greenhouse gases. 00:11:57.390 --> 00:11:59.208 And they asked the question, 00:11:59.208 --> 00:12:02.904 what set of variables put into a model 00:12:02.904 --> 00:12:05.880 will reproduce what we actually see in real life? 00:12:05.880 --> 00:12:07.900 So here is the real life in black. 00:12:07.900 --> 00:12:10.180 Here's the model in this light gray, 00:12:10.180 --> 00:12:11.740 and the answer is 00:12:11.740 --> 00:12:16.127 a model that includes, it's the answer E on that SAT, 00:12:16.127 --> 00:12:18.268 all of the above. 00:12:18.268 --> 00:12:19.774 The only way you can reproduce 00:12:19.774 --> 00:12:21.602 the observed temperature measurements 00:12:21.602 --> 00:12:23.580 is with all of these things put together, 00:12:23.580 --> 00:12:25.719 including greenhouse gases, 00:12:25.719 --> 00:12:28.270 and in particular you can see that the increase 00:12:28.270 --> 00:12:30.154 in greenhouse gases tracks 00:12:30.154 --> 00:12:32.360 this very dramatic increase in temperature 00:12:32.360 --> 00:12:33.840 over the last 50 years. 00:12:33.840 --> 00:12:36.274 And so this is why climate scientists say 00:12:36.274 --> 00:12:39.382 it's not just that we know that climate change is happening, 00:12:39.382 --> 00:12:42.150 we know that greenhouse gases are a major part 00:12:42.150 --> 00:12:44.880 of the reason why. NOTE Paragraph 00:12:44.880 --> 00:12:47.268 So now because there all these different things 00:12:47.268 --> 00:12:48.757 that scientists do, 00:12:48.757 --> 00:12:52.243 the philosopher Paul Feyerabend famously said, 00:12:52.243 --> 00:12:53.869 "The only principle in science 00:12:53.869 --> 00:12:57.848 that doesn't inhibit progress is: anything goes." 00:12:57.848 --> 00:13:00.464 Now this quotation has often been taken out of context, 00:13:00.464 --> 00:13:02.582 because Feyerabend was not actually saying 00:13:02.582 --> 00:13:04.532 that in science anything goes. 00:13:04.532 --> 00:13:05.876 What he was saying was, 00:13:05.876 --> 00:13:07.900 actually the full quotation is, 00:13:07.900 --> 00:13:09.990 "If you press me to say 00:13:09.990 --> 00:13:11.636 what is the method of science, 00:13:11.636 --> 00:13:15.265 I would have to say: anything goes." 00:13:15.265 --> 00:13:16.343 What he was trying to say 00:13:16.343 --> 00:13:18.910 is that scientists do a lot of different things. 00:13:18.910 --> 00:13:21.218 Scientists are creative. NOTE Paragraph 00:13:21.218 --> 00:13:23.328 But then this pushes the question back: 00:13:23.328 --> 00:13:26.799 If scientists don't use a single method, 00:13:26.799 --> 00:13:28.698 then how do they decide 00:13:28.698 --> 00:13:30.156 what's right and what's wrong? 00:13:30.156 --> 00:13:32.050 And who judges? 00:13:32.050 --> 00:13:34.130 And the answer is, scientists judge, 00:13:34.130 --> 00:13:37.013 and they judge by judging evidence. 00:13:37.013 --> 00:13:40.422 Scientists collect evidence in many different ways, 00:13:40.422 --> 00:13:42.044 but however they collect it, 00:13:42.044 --> 00:13:44.621 they have to subject it to scrutiny. 00:13:44.621 --> 00:13:47.181 And this led the sociologist Robert Merton 00:13:47.181 --> 00:13:49.361 to focus on this question of how scientists 00:13:49.361 --> 00:13:51.040 scrutinize data and evidence, 00:13:51.040 --> 00:13:53.848 and he said they do it in a way he called 00:13:53.848 --> 00:13:55.767 "organized skepticism." 00:13:55.767 --> 00:13:57.651 And by that he meant it's organized 00:13:57.651 --> 00:13:59.129 because they do it collectively, 00:13:59.129 --> 00:14:00.758 they do it as a group, 00:14:00.758 --> 00:14:03.574 and skepticism, because they do it from a position 00:14:03.574 --> 00:14:05.028 of distrust. 00:14:05.028 --> 00:14:06.990 That is to say, the burden of proof 00:14:06.990 --> 00:14:09.471 is on the person with a novel claim. 00:14:09.471 --> 00:14:12.614 And in this sense, science is intrinsically conservative. 00:14:12.614 --> 00:14:15.186 It's quite hard to persuade the scientific community 00:14:15.186 --> 00:14:18.897 to say, "Yes, we know something, this is true." 00:14:18.897 --> 00:14:21.393 So despite the popularity of the concept 00:14:21.393 --> 00:14:22.990 of paradigm shifts, 00:14:22.990 --> 00:14:24.274 what we find is that actually, 00:14:24.274 --> 00:14:27.059 really major changes in scientific thinking 00:14:27.059 --> 00:14:30.779 are relatively rare in the history of science. NOTE Paragraph 00:14:30.779 --> 00:14:34.342 So finally that brings us to one more idea: 00:14:34.342 --> 00:14:38.050 If scientists judge evidence collectively, 00:14:38.050 --> 00:14:40.612 this has led historians to focus on the question 00:14:40.612 --> 00:14:42.031 of consensus, 00:14:42.031 --> 00:14:43.926 and to say that at the end of the day, 00:14:43.926 --> 00:14:45.860 what science is, 00:14:45.860 --> 00:14:47.530 what scientific knowledge is, 00:14:47.530 --> 00:14:50.909 is the consensus of the scientific experts 00:14:50.909 --> 00:14:53.063 who through this process of organized scrutiny, 00:14:53.063 --> 00:14:55.368 collective scrutiny, 00:14:55.368 --> 00:14:56.610 have judged the evidence 00:14:56.610 --> 00:14:59.407 and come to a conclusion about it, 00:14:59.407 --> 00:15:01.884 either yea or nay. NOTE Paragraph 00:15:01.884 --> 00:15:03.608 So we can think of scientific knowledge 00:15:03.608 --> 00:15:05.660 as a consensus of experts. 00:15:05.660 --> 00:15:07.432 We can also think of science as being 00:15:07.432 --> 00:15:09.010 a kind of a jury, 00:15:09.010 --> 00:15:11.524 except it's a very special kind of jury. 00:15:11.524 --> 00:15:13.628 It's not a jury of your peers, 00:15:13.628 --> 00:15:15.524 it's a jury of geeks. 00:15:15.524 --> 00:15:19.158 It's a jury of men and women with Ph.D.s, 00:15:19.158 --> 00:15:21.600 and unlike a conventional jury, 00:15:21.600 --> 00:15:23.290 which has only two choices, 00:15:23.290 --> 00:15:25.975 guilty or not guilty, 00:15:25.975 --> 00:15:29.376 the scientific jury actually has a number of choices. 00:15:29.376 --> 00:15:32.160 Scientists can say yes, something's true. 00:15:32.160 --> 00:15:34.740 Scientists can say no, it's false. 00:15:34.740 --> 00:15:37.280 Or, they can say, well it might be true 00:15:37.280 --> 00:15:40.324 but we need to work more and collect more evidence. 00:15:40.324 --> 00:15:41.940 Or, they can say it might be true, 00:15:41.940 --> 00:15:43.640 but we don't know how to answer the question 00:15:43.640 --> 00:15:44.950 and we're going to put it aside 00:15:44.950 --> 00:15:47.873 and maybe we'll come back to it later. 00:15:47.873 --> 00:15:51.875 That's what scientists call "intractable." NOTE Paragraph 00:15:51.875 --> 00:15:54.481 But this leads us to one final problem: 00:15:54.481 --> 00:15:57.419 If science is what scientists say it is, 00:15:57.419 --> 00:15:59.960 then isn't that just an appeal to authority? 00:15:59.960 --> 00:16:01.022 And weren't we all taught in school 00:16:01.022 --> 00:16:04.249 that the appeal to authority is a logical fallacy? 00:16:04.249 --> 00:16:07.281 Well, here's the paradox of modern science, 00:16:07.281 --> 00:16:09.553 the paradox of the conclusion I think historians 00:16:09.553 --> 00:16:12.154 and philosophers and sociologists have come to, 00:16:12.154 --> 00:16:15.655 that actually science is the appeal to authority, 00:16:15.655 --> 00:16:19.431 but it's not the authority of the individual, 00:16:19.431 --> 00:16:21.830 no matter how smart that individual is, 00:16:21.830 --> 00:16:25.695 like Plato or Socrates or Einstein. 00:16:25.695 --> 00:16:28.809 It's the authority of the collective community. 00:16:28.809 --> 00:16:31.795 You can think of it is a kind of wisdom of the crowd, 00:16:31.795 --> 00:16:35.921 but a very special kind of crowd. 00:16:35.921 --> 00:16:37.811 Science does appeal to authority, 00:16:37.811 --> 00:16:39.861 but it's not based on any individual, 00:16:39.861 --> 00:16:42.447 no matter how smart that individual may be. 00:16:42.447 --> 00:16:44.198 It's based on the collective wisdom, 00:16:44.198 --> 00:16:46.840 the collective knowledge, the collective work, 00:16:46.840 --> 00:16:48.738 of all of the scientists who have worked 00:16:48.738 --> 00:16:51.455 on a particular problem. 00:16:51.455 --> 00:16:54.251 Scientists have a kind of culture of collective distrust, 00:16:54.251 --> 00:16:56.451 this "show me" culture, 00:16:56.451 --> 00:16:58.401 illustrated by this nice woman here 00:16:58.401 --> 00:17:01.483 showing her colleagues her evidence. 00:17:01.483 --> 00:17:03.340 Of course, these people don't really look like scientists, 00:17:03.340 --> 00:17:05.326 because they're much too happy. 00:17:05.326 --> 00:17:09.338 (Laughter) NOTE Paragraph 00:17:09.338 --> 00:17:13.660 Okay, so that brings me to my final point. 00:17:13.660 --> 00:17:16.308 Most of us get up in the morning. 00:17:16.308 --> 00:17:17.718 Most of us trust our cars. 00:17:17.718 --> 00:17:19.260 Well, see, now I'm thinking, I'm in Manhattan, 00:17:19.260 --> 00:17:20.558 this is a bad analogy, 00:17:20.558 --> 00:17:23.382 but most Americans who don't live in Manhattan 00:17:23.382 --> 00:17:25.120 get up in the morning and get in their cars 00:17:25.120 --> 00:17:27.649 and turn on that ignition, and their cars work, 00:17:27.649 --> 00:17:29.650 and they work incredibly well. 00:17:29.650 --> 00:17:32.365 The modern automobile hardly ever breaks down. NOTE Paragraph 00:17:32.365 --> 00:17:35.148 So why is that? Why do cars work so well? 00:17:35.148 --> 00:17:37.652 It's not because of the genius of Henry Ford 00:17:37.652 --> 00:17:40.743 or Karl Benz or even Elon Musk. 00:17:40.743 --> 00:17:42.885 It's because the modern automobile 00:17:42.885 --> 00:17:47.919 is the product of more than 100 years of work 00:17:47.919 --> 00:17:49.509 by hundreds and thousands 00:17:49.509 --> 00:17:50.845 and tens of thousands of people. 00:17:50.845 --> 00:17:52.956 The modern automobile is the product 00:17:52.956 --> 00:17:55.745 of the collected work and wisdom and experience 00:17:55.745 --> 00:17:58.092 of every man and woman who has ever worked 00:17:58.092 --> 00:17:59.700 on a car, 00:17:59.700 --> 00:18:02.615 and the reliability of the technology is the result 00:18:02.615 --> 00:18:05.298 of that accumulated effort. 00:18:05.298 --> 00:18:08.155 We benefit not just from the genius of Benz 00:18:08.155 --> 00:18:09.221 and Ford and Musk 00:18:09.221 --> 00:18:11.989 but from the collective intelligence and hard work 00:18:11.989 --> 00:18:14.240 of all of the people who have worked 00:18:14.240 --> 00:18:15.910 on the modern car. 00:18:15.910 --> 00:18:17.960 And the same is true of science, 00:18:17.960 --> 00:18:20.804 only science is even older. 00:18:20.804 --> 00:18:23.378 Our basis for trust in science is actually the same 00:18:23.378 --> 00:18:26.052 as our basis in trust in technology, 00:18:26.052 --> 00:18:30.039 and the same as our basis for trust in anything, 00:18:30.039 --> 00:18:32.317 namely, experience. NOTE Paragraph 00:18:32.317 --> 00:18:34.161 But it shouldn't be blind trust 00:18:34.161 --> 00:18:36.921 any more than we would have blind trust in anything. 00:18:36.921 --> 00:18:39.762 Our trust in science, like science itself, 00:18:39.762 --> 00:18:41.675 should be based on evidence, 00:18:41.675 --> 00:18:43.177 and that means that scientists 00:18:43.177 --> 00:18:45.225 have to become better communicators. 00:18:45.225 --> 00:18:48.112 They have to explain to us not just what they know 00:18:48.112 --> 00:18:49.840 but how they know it, 00:18:49.840 --> 00:18:53.730 and it means that we have to become better listeners. NOTE Paragraph 00:18:53.730 --> 00:18:55.149 Thank you very much. NOTE Paragraph 00:18:55.149 --> 00:18:57.452 (Applause)