0:00:01.083,0:00:04.268 Every day we face issues like climate change 0:00:04.268,0:00:05.708 or the safety of vaccines 0:00:05.708,0:00:08.348 where we have to answer questions whose answers 0:00:08.348,0:00:11.659 rely heavily on scientific information. 0:00:11.659,0:00:15.033 Scientists tell us that the world is warming. 0:00:15.033,0:00:17.281 Scientists tell us that vaccines are safe. 0:00:17.281,0:00:19.465 But how do we know if they are right? 0:00:19.465,0:00:21.569 Why should be believe the science? 0:00:21.569,0:00:24.898 The fact is, many of us actually[br]don't believe the science. 0:00:24.898,0:00:27.314 Public opinion polls consistently show 0:00:27.314,0:00:29.634 that significant proportions of the American people 0:00:29.634,0:00:33.225 don't believe the climate is[br]warming due to human activities, 0:00:33.225,0:00:36.724 don't think that there is[br]evolution by natural selection, 0:00:36.724,0:00:40.805 and aren't persuaded by the safety of vaccines. 0:00:40.805,0:00:44.316 So why should we believe the science? 0:00:44.316,0:00:47.957 Well, scientists don't like talking about [br]science as a matter of belief. 0:00:47.957,0:00:50.444 In fact, they would contract science with faith, 0:00:50.444,0:00:53.068 and they would say belief is the domain of faith. 0:00:53.068,0:00:57.238 And faith is a separate thing[br]apart and distinct from science. 0:00:57.238,0:00:59.790 Indeed they would say religion is based on faith 0:00:59.790,0:01:04.254 or maybe the calculous of Pascal's wager. 0:01:04.254,0:01:07.110 Blaise Pascal was a 17th century mathematician 0:01:07.110,0:01:09.630 who tried to bring scientific reasoning to the question of 0:01:09.630,0:01:11.542 whether or not he should believe in God, 0:01:11.542,0:01:13.616 and his wager went like this: 0:01:13.616,0:01:15.935 well, if God doesn't exist 0:01:15.935,0:01:18.595 but I decide to believe in him 0:01:18.595,0:01:20.538 nothing much is really lost. 0:01:20.538,0:01:22.451 Maybe a few hours on Sunday. 0:01:22.451,9:59:59.000 [Laughter] 9:59:59.000,9:59:59.000 But if he does exist and I don't believe in him, 9:59:59.000,9:59:59.000 then I'm in deep trouble. 9:59:59.000,9:59:59.000 And so Pascal said, we'd better believe in God. 9:59:59.000,9:59:59.000 Or as one of my college professors said, 9:59:59.000,9:59:59.000 "he clutched for the handmill of faith". 9:59:59.000,9:59:59.000 He made that leap of faith 9:59:59.000,9:59:59.000 leaving science and rationalism behind. 9:59:59.000,9:59:59.000 Now the fact is though, for most of us 9:59:59.000,9:59:59.000 most scientific claims are a leap of faith. 9:59:59.000,9:59:59.000 We can't really judge scientific claims for ourselves in most cases. 9:59:59.000,9:59:59.000 And indeed this is actually true for most scientists as well 9:59:59.000,9:59:59.000 outside of their own specialties. 9:59:59.000,9:59:59.000 So if you think about it, a geologist can't tell you 9:59:59.000,9:59:59.000 wether a vaccine is safe. 9:59:59.000,9:59:59.000 Most chemists are not experts in evolutionary theory. 9:59:59.000,9:59:59.000 A physicist cannot tell you, despite the claims of some of them, 9:59:59.000,9:59:59.000 wether or not tobacco causes cancer. 9:59:59.000,9:59:59.000 So, if even scientists themselves have to make a leap of faith 9:59:59.000,9:59:59.000 outside their own fields, 9:59:59.000,9:59:59.000 then why do they accept the claims of other scientists? 9:59:59.000,9:59:59.000 Why do they believe each other's claims? 9:59:59.000,9:59:59.000 And should we believe those claims? 9:59:59.000,9:59:59.000 So what I'd like to argue is yes, we should. 9:59:59.000,9:59:59.000 But not for the reason that most of us think. 9:59:59.000,9:59:59.000 Most of us were taught in school that the reason we should 9:59:59.000,9:59:59.000 believe in science is because of the scientific method. 9:59:59.000,9:59:59.000 We were taught that scientists follow a method 9:59:59.000,9:59:59.000 and that this method guarantees the truth of their claims. 9:59:59.000,9:59:59.000 The method that most of us were taught in school, 9:59:59.000,9:59:59.000 we can call it the text book method, 9:59:59.000,9:59:59.000 is the hypo-deductive method. 9:59:59.000,9:59:59.000 According to the standard model, the textbook model, 9:59:59.000,9:59:59.000 scientists develop hypotheses, they deduce the 9:59:59.000,9:59:59.000 consequences for those hypotheses, 9:59:59.000,9:59:59.000 and then they go out into the world and they say: 9:59:59.000,9:59:59.000 Are those consequences true? 9:59:59.000,9:59:59.000 Can we observe them taking place in the natural world? 9:59:59.000,9:59:59.000 And if they are true, then the scientists say: 9:59:59.000,9:59:59.000 Great, we know the hypothesis is correct. 9:59:59.000,9:59:59.000 So there are many famous examples in the history 9:59:59.000,9:59:59.000 of science of scientists doing exactly this. 9:59:59.000,9:59:59.000 One of the most famous examples 9:59:59.000,9:59:59.000 comes from the work of Albert Einstein. 9:59:59.000,9:59:59.000 When Einstein developed the theory of general relativity 9:59:59.000,9:59:59.000 one of the consequences of his theory 9:59:59.000,9:59:59.000 was that space time wasn't just an empty void 9:59:59.000,9:59:59.000 but that it actually had a fabric. 9:59:59.000,9:59:59.000 And that that fabric was bent 9:59:59.000,9:59:59.000 in the presence of massive objects like the sun. 9:59:59.000,9:59:59.000 So if this theory were true then it meant that light 9:59:59.000,9:59:59.000 as it passed the sun 9:59:59.000,9:59:59.000 should actually be bent around it. 9:59:59.000,9:59:59.000 That was a pretty startling prediction 9:59:59.000,9:59:59.000 and it took a few years before scientists 9:59:59.000,9:59:59.000 were able to test it. 9:59:59.000,9:59:59.000 But they did test it in 1919 9:59:59.000,9:59:59.000 and low and behold it turned out to be true. 9:59:59.000,9:59:59.000 Starlight actually does bend as it travels around the sun. 9:59:59.000,9:59:59.000 This was a huge confirmation of the theory. 9:59:59.000,9:59:59.000 It was considered proof of the truth of this radical new idea 9:59:59.000,9:59:59.000 and it was written up in many newspapers around the globe. 9:59:59.000,9:59:59.000 Now sometimes this theory or this model 9:59:59.000,9:59:59.000 is referred to as the deductive-nomological model. 9:59:59.000,9:59:59.000 Meaning those academics like to make things complicated. [br][Laughter] 9:59:59.000,9:59:59.000 But also because in the ideal case it's about laws. 9:59:59.000,9:59:59.000 So nomological means having to do with laws. 9:59:59.000,9:59:59.000 And in the ideal case, the hypothesis isn't just an idea, 9:59:59.000,9:59:59.000 ideally it is a law of nature. 9:59:59.000,9:59:59.000 Why does it matter that it is a law of nature? 9:59:59.000,9:59:59.000 Because if it is a law, it can't be broken. 9:59:59.000,9:59:59.000 If it's a law then it will always be true 9:59:59.000,9:59:59.000 in all times and all places 9:59:59.000,9:59:59.000 no matter what the circumstances are. 9:59:59.000,9:59:59.000 And all of you know at least one example of a famous law. 9:59:59.000,9:59:59.000 Einstein's famous equation, E=MC2, 9:59:59.000,9:59:59.000 which tells us what the relationship is 9:59:59.000,9:59:59.000 between energy and mass. 9:59:59.000,9:59:59.000 And that relationship is true no matter what. 9:59:59.000,9:59:59.000 It turns out though that there are [br]several problems with this model. 9:59:59.000,9:59:59.000 The main problem is that it's wrong. 9:59:59.000,9:59:59.000 It's just not true. [Laughter] 9:59:59.000,9:59:59.000 And I'm going to talk about three reasons why it's wrong. 9:59:59.000,9:59:59.000 So the first reason is a logical reason, 9:59:59.000,9:59:59.000 it's the problem of the fallacy of affirming the consequent. 9:59:59.000,9:59:59.000 So that's another fancy academic way of saying 9:59:59.000,9:59:59.000 that false theories can make true predictions. 9:59:59.000,9:59:59.000 So just because the prediction comes true 9:59:59.000,9:59:59.000 doesn't actually logically prove that the theory is correct. 9:59:59.000,9:59:59.000 And I have a good example of that too, [br]again from the history of science. 9:59:59.000,9:59:59.000 This is a picture of the Ptolemaic universe 9:59:59.000,9:59:59.000 with the Earth at the center of the universe 9:59:59.000,9:59:59.000 and The Sun and the planets going around it. 9:59:59.000,9:59:59.000 The Ptolemaic model was believed 9:59:59.000,9:59:59.000 by many very smart people for many centuries. 9:59:59.000,9:59:59.000 Well why? 9:59:59.000,9:59:59.000 Well the answer is because it made [br]lots of predictions that came true. 9:59:59.000,9:59:59.000 The Ptolemaic system enabled astronomers 9:59:59.000,9:59:59.000 to make accurate predictions of the motions of the planet. 9:59:59.000,9:59:59.000 In fact more accurate predictions at first 9:59:59.000,9:59:59.000 than the Copernican theory which we now would say is true. 9:59:59.000,9:59:59.000 So that's one problem with the textbook model, 9:59:59.000,9:59:59.000 a second problem is a practical problem 9:59:59.000,9:59:59.000 and it's the problem of auxiliary hypotheses. 9:59:59.000,9:59:59.000 Auxiliary hypotheses are assumptions 9:59:59.000,9:59:59.000 that scientists are making, 9:59:59.000,9:59:59.000 that they may or may not even be aware that they're making. 9:59:59.000,9:59:59.000 So an important example of this comes from 9:59:59.000,9:59:59.000 comes from the Copernican model 9:59:59.000,9:59:59.000 which ultimately replaced the Ptolemaic system. 9:59:59.000,9:59:59.000 So when Nicolaus Copernicus said, 9:59:59.000,9:59:59.000 actually the Earth is not the center of the universe, 9:59:59.000,9:59:59.000 the sun is the center of the solar system, 9:59:59.000,9:59:59.000 the Earth moves around the sun. 9:59:59.000,9:59:59.000 Scientists said, well okay, Nicolaus, if that's true 9:59:59.000,9:59:59.000 we ought to be able to detect the motion 9:59:59.000,9:59:59.000 of the Earth around the sun. 9:59:59.000,9:59:59.000 And so this slide here illustrates a concept 9:59:59.000,9:59:59.000 known as stellar parallax. 9:59:59.000,9:59:59.000 And astronomers said, if the Earth is moving 9:59:59.000,9:59:59.000 and we look at a prominent star, let's say, Sirius. 9:59:59.000,9:59:59.000 Well I know I'm in Manhattan so you guys can't see the stars, 9:59:59.000,9:59:59.000 but imagine you're out in the country, [br]imagine you chose that rural life. 9:59:59.000,9:59:59.000 And we look at a star in December, we see that star 9:59:59.000,9:59:59.000 against the backdrop of distant stars. 9:59:59.000,9:59:59.000 If we now make the same observation six months later 9:59:59.000,9:59:59.000 when the Earth has moved to this position in June, 9:59:59.000,9:59:59.000 we look at that same star and we see it against a different backdrop. 9:59:59.000,9:59:59.000 That difference, that angular difference, is the stellar parallax. 9:59:59.000,9:59:59.000 So this is the prediction that the Copernican model makes, 9:59:59.000,9:59:59.000 astronomers looked for the stellar parallax 9:59:59.000,9:59:59.000 and they found nothing, nothing at all. 9:59:59.000,9:59:59.000 And many people argued that this proved [br]that the Copernican model was false. 9:59:59.000,9:59:59.000 So what happened? 9:59:59.000,9:59:59.000 Well in hindsight we can say that astronomers were making 9:59:59.000,9:59:59.000 two auxiliary hypotheses, both of which 9:59:59.000,9:59:59.000 we would now say were incorrect. 9:59:59.000,9:59:59.000 The first was an assumption about the size of the Earth's orbit. 9:59:59.000,9:59:59.000 Astronomers were assuming that the Earth's orbit was large 9:59:59.000,9:59:59.000 relative to the stars. 9:59:59.000,9:59:59.000 Today we would draw the picture more like this, 9:59:59.000,9:59:59.000 this comes from NASA, 9:59:59.000,9:59:59.000 and you see the Earth's orbit is actually quite small. 9:59:59.000,9:59:59.000 In fact, it's actually much smaller even than shown here. 9:59:59.000,9:59:59.000 The stellar parallax therefore, 9:59:59.000,9:59:59.000 is very small and actually very hard to detect. 9:59:59.000,9:59:59.000 And that leads to the second reason 9:59:59.000,9:59:59.000 why the prediction didn't work, 9:59:59.000,9:59:59.000 because scientists were also assuming 9:59:59.000,9:59:59.000 that the telescopes they had were sensitive enough 9:59:59.000,9:59:59.000 to detect the parallax. 9:59:59.000,9:59:59.000 And that turned out not to be true. 9:59:59.000,9:59:59.000 It wasn't until the 19th century that scientists were able to detect 9:59:59.000,9:59:59.000 the stellar parallax. 9:59:59.000,9:59:59.000 So, there's a third problem as well. 9:59:59.000,9:59:59.000 The third problem is simply a factual problem 9:59:59.000,9:59:59.000 that a lot of science doesn't fit the textbook model. 9:59:59.000,9:59:59.000 A lot of science isn't deductive at all, it's actually inductive. 9:59:59.000,9:59:59.000 And by that we mean that scientists don't necessarily 9:59:59.000,9:59:59.000 start with theories and hypotheses, often they just 9:59:59.000,9:59:59.000 start with observations of stuff going on in the world. 9:59:59.000,9:59:59.000 And the most famous example of that is one of the most 9:59:59.000,9:59:59.000 famous scientists who ever lived, Charles Darwin. 9:59:59.000,9:59:59.000 When Darwin went out as a young [br]man on the voyage of the Beagle, 9:59:59.000,9:59:59.000 he didn't have a hypothesis, he didn't have a theory. 9:59:59.000,9:59:59.000 He just knew that he wanted to have a career as a scientist 9:59:59.000,9:59:59.000 and he started to collect data. 9:59:59.000,9:59:59.000 Mainly he knew that he hated medicine 9:59:59.000,9:59:59.000 because the sight of blood made him sick so 9:59:59.000,9:59:59.000 he had to have an alternative career path. 9:59:59.000,9:59:59.000 So he started collecting data. 9:59:59.000,9:59:59.000 And he collected many things including his famous finches. 9:59:59.000,9:59:59.000 When he collected these finches he through them in a bag 9:59:59.000,9:59:59.000 and he had no idea what they meant. 9:59:59.000,9:59:59.000 Many years later back in London, 9:59:59.000,9:59:59.000 Darwin looked at his data again and began to develop 9:59:59.000,9:59:59.000 an explanation 9:59:59.000,9:59:59.000 and that explanation was the theory of natural selection. 9:59:59.000,9:59:59.000 Besides inductive science, 9:59:59.000,9:59:59.000 scientists also often participate in modeling. 9:59:59.000,9:59:59.000 One of the things scientists want to do in life 9:59:59.000,9:59:59.000 is to explain the causes of things. 9:59:59.000,9:59:59.000 And how do we do that? 9:59:59.000,9:59:59.000 Well, one way you can do it is to build a model 9:59:59.000,9:59:59.000 that tests an idea. 9:59:59.000,9:59:59.000 So this is a picture of Henry Cadell, 9:59:59.000,9:59:59.000 who was a Scottish geologist in the 19th century. 9:59:59.000,9:59:59.000 You can tell he's Scottish because he's wearing 9:59:59.000,9:59:59.000 a deerstalker cap and Wellington boots. 9:59:59.000,9:59:59.000 (Laughter) 9:59:59.000,9:59:59.000 And Cadell wanted to answer the question, 9:59:59.000,9:59:59.000 how are mountains formed? 9:59:59.000,9:59:59.000 And one of the things he had observed 9:59:59.000,9:59:59.000 is that if you look at mountains[br]like the Appalachians, 9:59:59.000,9:59:59.000 you often find that the rocks in them 9:59:59.000,9:59:59.000 are folded, 9:59:59.000,9:59:59.000 and they're folded in a particular way, 9:59:59.000,9:59:59.000 which suggested to him 9:59:59.000,9:59:59.000 that they were actually being[br]compressed from the side. 9:59:59.000,9:59:59.000 And this idea would later play a major role 9:59:59.000,9:59:59.000 in discussions of continental drift. 9:59:59.000,9:59:59.000 So he built this model, this crazy contraption 9:59:59.000,9:59:59.000 with levers and wood and here's his wheelbarrow, 9:59:59.000,9:59:59.000 buckets, a big sledgehammer. 9:59:59.000,9:59:59.000 I don't know why he's got the Wellington boots. 9:59:59.000,9:59:59.000 Maybe it's going to rain. 9:59:59.000,9:59:59.000 And he created this physical model in order 9:59:59.000,9:59:59.000 to demonstrate that you could in fact create 9:59:59.000,9:59:59.000 patterns in rocks, or at least in this case in mud, 9:59:59.000,9:59:59.000 that looked a lot like mountains 9:59:59.000,9:59:59.000 if you compressed them from the side. 9:59:59.000,9:59:59.000 So it was an argument about[br]the cause of mountains. 9:59:59.000,9:59:59.000 Nowadays, most scientists prefer to work inside, 9:59:59.000,9:59:59.000 so they don't build physical models so much 9:59:59.000,9:59:59.000 as to make computer simulations. 9:59:59.000,9:59:59.000 But a computer simulation is a kind of a model. 9:59:59.000,9:59:59.000 It's a model that's made with mathematics, 9:59:59.000,9:59:59.000 and like the physical models of the 19th century, 9:59:59.000,9:59:59.000 it's very important for thinking about causes. 9:59:59.000,9:59:59.000 So one of the big questions[br]to do with climate change, 9:59:59.000,9:59:59.000 we have tremendous amounts of evidence 9:59:59.000,9:59:59.000 that the earth is warming up. 9:59:59.000,9:59:59.000 This slide here, the black line shows 9:59:59.000,9:59:59.000 the measurements that scientists have taken 9:59:59.000,9:59:59.000 for the last 150 years 9:59:59.000,9:59:59.000 showing that the earth's temperature 9:59:59.000,9:59:59.000 has steadily increased, 9:59:59.000,9:59:59.000 and you can see in particular[br]that in the last 50 years 9:59:59.000,9:59:59.000 there's been this dramatic increase 9:59:59.000,9:59:59.000 of nearly one degree Centigrade, 9:59:59.000,9:59:59.000 or almost two degrees Fahrenheit. 9:59:59.000,9:59:59.000 So what, though, is driving that change? 9:59:59.000,9:59:59.000 How can we know what's causing 9:59:59.000,9:59:59.000 the observed warming? 9:59:59.000,9:59:59.000 Well, scientists can model it 9:59:59.000,9:59:59.000 using a computer simulation. 9:59:59.000,9:59:59.000 So this diagram illustrates a computer simulation 9:59:59.000,9:59:59.000 that has looked at all the different factors 9:59:59.000,9:59:59.000 that we know can influence the earth's climate, 9:59:59.000,9:59:59.000 so sulfate particles from air pollution, 9:59:59.000,9:59:59.000 volcanic dust from volcanic eruptions, 9:59:59.000,9:59:59.000 changes in solar radiation, 9:59:59.000,9:59:59.000 and, of course, greenhouse gases. 9:59:59.000,9:59:59.000 And they asked the question, 9:59:59.000,9:59:59.000 what set of variables put into a model 9:59:59.000,9:59:59.000 will reproduce what we actually see in real life? 9:59:59.000,9:59:59.000 So here is the real life in black. 9:59:59.000,9:59:59.000 Here's the model in this light grey, 9:59:59.000,9:59:59.000 and the answer is 9:59:59.000,9:59:59.000 a model that includes, it's the answer E on that SAT, 9:59:59.000,9:59:59.000 all of the above. 9:59:59.000,9:59:59.000 The only way you can reproduce 9:59:59.000,9:59:59.000 the observed temperature measurements 9:59:59.000,9:59:59.000 is with all of these things put together, 9:59:59.000,9:59:59.000 including greenhouse gases, 9:59:59.000,9:59:59.000 and in particular you can see that the increase 9:59:59.000,9:59:59.000 in greenhouse gases tracks 9:59:59.000,9:59:59.000 this very dramatic increase in temperature 9:59:59.000,9:59:59.000 over the last 50 years. 9:59:59.000,9:59:59.000 And so this is why climate scientists say 9:59:59.000,9:59:59.000 it's not just that we know that[br]climate change is happening, 9:59:59.000,9:59:59.000 we know that greenhouse gases are a major part 9:59:59.000,9:59:59.000 of the reason why. 9:59:59.000,9:59:59.000 So now because there all these different things 9:59:59.000,9:59:59.000 that scientists do, 9:59:59.000,9:59:59.000 the philosopher Paul Feyerabend famously said, 9:59:59.000,9:59:59.000 "The only principle in science 9:59:59.000,9:59:59.000 that doesn't inhibit progress is: anything goes." 9:59:59.000,9:59:59.000 Now this quotation has often[br]been taken out of context, 9:59:59.000,9:59:59.000 because Feyerabend was not actually saying 9:59:59.000,9:59:59.000 that in science anything goes. 9:59:59.000,9:59:59.000 What he was saying was, 9:59:59.000,9:59:59.000 actually the full quotation is, 9:59:59.000,9:59:59.000 "If you press me to say 9:59:59.000,9:59:59.000 what is the method of science, 9:59:59.000,9:59:59.000 I would have to say: anything goes." 9:59:59.000,9:59:59.000 What he was trying to say 9:59:59.000,9:59:59.000 is that scientists do a lot of different things. 9:59:59.000,9:59:59.000 Scientists are creative. 9:59:59.000,9:59:59.000 But then this pushes the question back: 9:59:59.000,9:59:59.000 if scientists don't use a single method, 9:59:59.000,9:59:59.000 then how do they decide 9:59:59.000,9:59:59.000 what's right and what's wrong? 9:59:59.000,9:59:59.000 And who judges? 9:59:59.000,9:59:59.000 And the answer is, scientists judge, 9:59:59.000,9:59:59.000 and they judge by judging evidence. 9:59:59.000,9:59:59.000 Scientists collect evidence in many different ways, 9:59:59.000,9:59:59.000 but however they collect it, 9:59:59.000,9:59:59.000 they have to subject it to scrutiny. 9:59:59.000,9:59:59.000 And this led to sociologist Robert Merton 9:59:59.000,9:59:59.000 to focus on this question of how scientists 9:59:59.000,9:59:59.000 scrutinize data and evidence, 9:59:59.000,9:59:59.000 and he said they do it in a way he called 9:59:59.000,9:59:59.000 "organized skepticism." 9:59:59.000,9:59:59.000 And by that he meant it's organized 9:59:59.000,9:59:59.000 because they do it collectively, 9:59:59.000,9:59:59.000 they do it as a group, 9:59:59.000,9:59:59.000 and skepticism, because they do it from a position 9:59:59.000,9:59:59.000 of distrust. 9:59:59.000,9:59:59.000 That is to say, the burden of proof 9:59:59.000,9:59:59.000 is on the person with a novel claim. 9:59:59.000,9:59:59.000 And in this sense, science[br]is intrinsically conservative. 9:59:59.000,9:59:59.000 It's quite hard to persuade the scientific community 9:59:59.000,9:59:59.000 to say, "Yes, we know something, this is true." 9:59:59.000,9:59:59.000 So despite the popularity of the concept 9:59:59.000,9:59:59.000 of paradigm shifts, 9:59:59.000,9:59:59.000 what we find is that actually, 9:59:59.000,9:59:59.000 really major changes in scientific thinking 9:59:59.000,9:59:59.000 are relatively rare in the history of science. 9:59:59.000,9:59:59.000 So finally that brings us to one more idea: 9:59:59.000,9:59:59.000 if scientists judge evidence collectively, 9:59:59.000,9:59:59.000 this has led historians to focus on the question 9:59:59.000,9:59:59.000 of consensus, 9:59:59.000,9:59:59.000 and to say that at the end of the day, 9:59:59.000,9:59:59.000 what science is, 9:59:59.000,9:59:59.000 what scientific knowledge is, 9:59:59.000,9:59:59.000 is the consensus of the scientific experts 9:59:59.000,9:59:59.000 who through this process of organized scrutiny, 9:59:59.000,9:59:59.000 collective scrutiny, 9:59:59.000,9:59:59.000 have judged the evidence 9:59:59.000,9:59:59.000 and come to a conclusion about it, 9:59:59.000,9:59:59.000 either yea or nay. 9:59:59.000,9:59:59.000 So we can think of scientific knowledge 9:59:59.000,9:59:59.000 as a consensus of experts. 9:59:59.000,9:59:59.000 We can also think of science as being 9:59:59.000,9:59:59.000 a kind of a jury, 9:59:59.000,9:59:59.000 except it's a very special kind of jury. 9:59:59.000,9:59:59.000 It's not a jury of your peers, 9:59:59.000,9:59:59.000 it's a jury of geeks. 9:59:59.000,9:59:59.000 It's a jury of men and women with Ph.D's, 9:59:59.000,9:59:59.000 and unlike a conventional jury, 9:59:59.000,9:59:59.000 which has only two choices, 9:59:59.000,9:59:59.000 guilty or not guilty, 9:59:59.000,9:59:59.000 the scientific jury actually has a number of choices. 9:59:59.000,9:59:59.000 Scientists can say yes, something's true. 9:59:59.000,9:59:59.000 Scientists can say no, it's false. 9:59:59.000,9:59:59.000 Or, they can say, well it might be true 9:59:59.000,9:59:59.000 but we need to work more[br]and collect more evidence. 9:59:59.000,9:59:59.000 Or, they can say it might be true, 9:59:59.000,9:59:59.000 but we don't know how to answer the question 9:59:59.000,9:59:59.000 and we're going to put it aside 9:59:59.000,9:59:59.000 and maybe come back to it later. 9:59:59.000,9:59:59.000 That's what scientists call "intractable." 9:59:59.000,9:59:59.000 But this leads us to one final problem: 9:59:59.000,9:59:59.000 if science is what scientists say it is, 9:59:59.000,9:59:59.000 then isn't that just an appeal to authority? 9:59:59.000,9:59:59.000 And weren't we all taught in school 9:59:59.000,9:59:59.000 that the appeal to authority is a logical fallacy? 9:59:59.000,9:59:59.000 Well, here's the paradox of modern science, 9:59:59.000,9:59:59.000 the paradox of the conclusions I think historians 9:59:59.000,9:59:59.000 and philosophers and sociologists have come to, 9:59:59.000,9:59:59.000 that actually science is the appeal to authority, 9:59:59.000,9:59:59.000 but it's not the authority of the individual, 9:59:59.000,9:59:59.000 no matter how smart that individual is, 9:59:59.000,9:59:59.000 like Plato or Socrates or Einstein. 9:59:59.000,9:59:59.000 It's the authority of the collective community. 9:59:59.000,9:59:59.000 You can think of it is a kind of wisdom of the crowd, 9:59:59.000,9:59:59.000 but a very special kind of crowd. 9:59:59.000,9:59:59.000 Science does appeal to authority, 9:59:59.000,9:59:59.000 but it's not based on any individual, 9:59:59.000,9:59:59.000 no matter how smart that individual may be. 9:59:59.000,9:59:59.000 It's based on the collective wisdom, 9:59:59.000,9:59:59.000 the collective knowledge, the collective work, 9:59:59.000,9:59:59.000 of all of the scientists who have worked 9:59:59.000,9:59:59.000 on a particular problem. 9:59:59.000,9:59:59.000 Scientists have a kind of culture of collective distrust, 9:59:59.000,9:59:59.000 this "show me" culture, 9:59:59.000,9:59:59.000 illustrated by this nice woman here 9:59:59.000,9:59:59.000 showing her colleagues her evidence. 9:59:59.000,9:59:59.000 Of course, these people don't[br]really look like scientists, 9:59:59.000,9:59:59.000 because they're much too happy. 9:59:59.000,9:59:59.000 (Laughter) 9:59:59.000,9:59:59.000 Okay, so that brings me to my final point. 9:59:59.000,9:59:59.000 Most of us get up in the morning. 9:59:59.000,9:59:59.000 Most of us trust our cars. 9:59:59.000,9:59:59.000 Well, see, now I think, I'm in Manhattan, 9:59:59.000,9:59:59.000 this is a bad analogy, 9:59:59.000,9:59:59.000 but most Americans who don't live in Manhattan 9:59:59.000,9:59:59.000 get up in the morning and get in their cars 9:59:59.000,9:59:59.000 and turn on that ignition, and their cars work, 9:59:59.000,9:59:59.000 and they work incredibly well. 9:59:59.000,9:59:59.000 The modern automobile hardly ever breaks down. 9:59:59.000,9:59:59.000 So why is that? Why do cars work so well? 9:59:59.000,9:59:59.000 It's not because of the genius of Henry Ford 9:59:59.000,9:59:59.000 or Carl Benz or even Elon Musk. 9:59:59.000,9:59:59.000 It's because the modern automobile 9:59:59.000,9:59:59.000 is the product of more than 100 years of work 9:59:59.000,9:59:59.000 by hundreds and thousands 9:59:59.000,9:59:59.000 and tens of thousands of people. 9:59:59.000,9:59:59.000 The modern automobile is the product 9:59:59.000,9:59:59.000 of the collected work and wisdom and experience 9:59:59.000,9:59:59.000 of every man and woman who has ever worked 9:59:59.000,9:59:59.000 on a car, 9:59:59.000,9:59:59.000 and the reliability of the technology is the result 9:59:59.000,9:59:59.000 of that accumulated effort. 9:59:59.000,9:59:59.000 We benefit not just from the benefit of Benz 9:59:59.000,9:59:59.000 and Ford and Musk 9:59:59.000,9:59:59.000 but from the collective intelligence and hard work 9:59:59.000,9:59:59.000 of all of the people who have worked 9:59:59.000,9:59:59.000 on the modern car. 9:59:59.000,9:59:59.000 And the same is true of science, 9:59:59.000,9:59:59.000 only science is even older. 9:59:59.000,9:59:59.000 Our basis for trust in science is actually the same 9:59:59.000,9:59:59.000 as our basis in trust in technology, 9:59:59.000,9:59:59.000 and the same as our basis for trust in anything, 9:59:59.000,9:59:59.000 namely, experience. 9:59:59.000,9:59:59.000 But it shouldn't be blind trust 9:59:59.000,9:59:59.000 anymore than we would have blind trust in anything. 9:59:59.000,9:59:59.000 Our trust in science, like science itself, 9:59:59.000,9:59:59.000 should be based on evidence, 9:59:59.000,9:59:59.000 and that means that scientists 9:59:59.000,9:59:59.000 have to become better communicators. 9:59:59.000,9:59:59.000 They have to explain to us not just what they know 9:59:59.000,9:59:59.000 but how they know it, 9:59:59.000,9:59:59.000 and it means that we have[br]to become better listeners. 9:59:59.000,9:59:59.000 Thank you very much. 9:59:59.000,9:59:59.000 (Applause)