WEBVTT 99:59:59.999 --> 99:59:59.999 Every day we face issues like climate change 99:59:59.999 --> 99:59:59.999 or the safety of vaccines 99:59:59.999 --> 99:59:59.999 where we have to answer questions whose answers 99:59:59.999 --> 99:59:59.999 rely heavily on scientific information. 99:59:59.999 --> 99:59:59.999 Scientists tell us that the world is warming. 99:59:59.999 --> 99:59:59.999 Scientists tell us that vaccines are safe. 99:59:59.999 --> 99:59:59.999 But how do we know if they are right? 99:59:59.999 --> 99:59:59.999 Why should be believe the science? 99:59:59.999 --> 99:59:59.999 The fact is, many of us actually don't believe the science. 99:59:59.999 --> 99:59:59.999 Public opinion polls consistently show 99:59:59.999 --> 99:59:59.999 that significant proportions of the American people 99:59:59.999 --> 99:59:59.999 don't believe the climate is warming due to human activities, 99:59:59.999 --> 99:59:59.999 don't think that there is evolution by natural selection, 99:59:59.999 --> 99:59:59.999 and aren't persuaded by the safety of vaccines. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 So why should we believe the science? 99:59:59.999 --> 99:59:59.999 Well, scientists don't like talking about science as a matter of belief. 99:59:59.999 --> 99:59:59.999 In fact, they would contract science with faith 99:59:59.999 --> 99:59:59.999 and they would say belief is the domain, faith. 99:59:59.999 --> 99:59:59.999 And faith is a separate thing apart and distinct from science. 99:59:59.999 --> 99:59:59.999 Indeed they would say religion is based on faith 99:59:59.999 --> 99:59:59.999 or maybe the calculous of Pascal's wager. 99:59:59.999 --> 99:59:59.999 Blaise Pascal was a 17th century mathematician 99:59:59.999 --> 99:59:59.999 who tried to bring scientific reasoning to the question of 99:59:59.999 --> 99:59:59.999 wether or not he should believe in God 99:59:59.999 --> 99:59:59.999 and his wager went like this: 99:59:59.999 --> 99:59:59.999 Well, if God doesn't exist but I decide to believe in him 99:59:59.999 --> 99:59:59.999 nothing much is really lost. 99:59:59.999 --> 99:59:59.999 Maybe a few hours on Sunday. 99:59:59.999 --> 99:59:59.999 [Laughter] 99:59:59.999 --> 99:59:59.999 But if he does exist and I don't believe in him, 99:59:59.999 --> 99:59:59.999 then I'm in deep trouble. 99:59:59.999 --> 99:59:59.999 And so Pascal said, we'd better believe in God. 99:59:59.999 --> 99:59:59.999 Or as one of my college professors said, 99:59:59.999 --> 99:59:59.999 "he clutched for the handmill of faith". 99:59:59.999 --> 99:59:59.999 He made that leap of faith 99:59:59.999 --> 99:59:59.999 leaving science and rationalism behind. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 Now the fact is though, for most of us 99:59:59.999 --> 99:59:59.999 most scientific claims are a leap of faith. 99:59:59.999 --> 99:59:59.999 We can't really judge scientific claims for ourselves in most cases. 99:59:59.999 --> 99:59:59.999 And indeed this is actually true for most scientists as well 99:59:59.999 --> 99:59:59.999 outside of their own specialties. 99:59:59.999 --> 99:59:59.999 So if you think about it, a geologist can't tell you 99:59:59.999 --> 99:59:59.999 wether a vaccine is safe. 99:59:59.999 --> 99:59:59.999 Most chemists are not experts in evolutionary theory. 99:59:59.999 --> 99:59:59.999 A physicist cannot tell you, despite the claims of some of them, 99:59:59.999 --> 99:59:59.999 wether or not tobacco causes cancer. 99:59:59.999 --> 99:59:59.999 So, if even scientists themselves have to make a leap of faith 99:59:59.999 --> 99:59:59.999 outside their own fields, 99:59:59.999 --> 99:59:59.999 then why do they accept the claims of other scientists? 99:59:59.999 --> 99:59:59.999 Why do they believe each other's claims? 99:59:59.999 --> 99:59:59.999 And should we believe those claims? NOTE Paragraph 99:59:59.999 --> 99:59:59.999 So what I'd like to argue is yes, we should. 99:59:59.999 --> 99:59:59.999 But not for the reason that most of us think. 99:59:59.999 --> 99:59:59.999 Most of us were taught in school that the reason we should 99:59:59.999 --> 99:59:59.999 believe in science is because of the scientific method. 99:59:59.999 --> 99:59:59.999 We were taught that scientists follow a method 99:59:59.999 --> 99:59:59.999 and that this method guarantees the truth of their claims. 99:59:59.999 --> 99:59:59.999 The method that most of us were taught in school, 99:59:59.999 --> 99:59:59.999 we can call it the text book method, 99:59:59.999 --> 99:59:59.999 is the hypo-deductive method. 99:59:59.999 --> 99:59:59.999 According to the standard model, the textbook model, 99:59:59.999 --> 99:59:59.999 scientists develop hypotheses, they deduce the 99:59:59.999 --> 99:59:59.999 consequences for those hypotheses, 99:59:59.999 --> 99:59:59.999 and then they go out into the world and they say: 99:59:59.999 --> 99:59:59.999 Are those consequences true? 99:59:59.999 --> 99:59:59.999 Can we observe them taking place in the natural world? 99:59:59.999 --> 99:59:59.999 And if they are true, then the scientists say: 99:59:59.999 --> 99:59:59.999 Great, we know the hypothesis is correct. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 So there are many famous examples in the history 99:59:59.999 --> 99:59:59.999 of science of scientists doing exactly this. 99:59:59.999 --> 99:59:59.999 One of the most famous examples 99:59:59.999 --> 99:59:59.999 comes from the work of Albert Einstein. 99:59:59.999 --> 99:59:59.999 When Einstein developed the theory of general relativity 99:59:59.999 --> 99:59:59.999 one of the consequences of his theory 99:59:59.999 --> 99:59:59.999 was that space time wasn't just an empty void 99:59:59.999 --> 99:59:59.999 but that it actually had a fabric. 99:59:59.999 --> 99:59:59.999 And that that fabric was bent 99:59:59.999 --> 99:59:59.999 in the presence of massive objects like the sun. 99:59:59.999 --> 99:59:59.999 So if this theory were true then it meant that light 99:59:59.999 --> 99:59:59.999 as it passed the sun 99:59:59.999 --> 99:59:59.999 should actually be bent around it. 99:59:59.999 --> 99:59:59.999 That was a pretty startling prediction 99:59:59.999 --> 99:59:59.999 and it took a few years before scientists 99:59:59.999 --> 99:59:59.999 were able to test it. 99:59:59.999 --> 99:59:59.999 But they did test it in 1919 99:59:59.999 --> 99:59:59.999 and low and behold it turned out to be true. 99:59:59.999 --> 99:59:59.999 Starlight actually does bend as it travels around the sun. 99:59:59.999 --> 99:59:59.999 This was a huge confirmation of the theory. 99:59:59.999 --> 99:59:59.999 It was considered proof of the truth of this radical new idea 99:59:59.999 --> 99:59:59.999 and it was written up in many newspapers around the globe. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 Now sometimes this theory or this model 99:59:59.999 --> 99:59:59.999 is referred to as the deductive-nomological model. 99:59:59.999 --> 99:59:59.999 Meaning those academics like to make things complicated. [Laughter] 99:59:59.999 --> 99:59:59.999 But also because in the ideal case it's about laws. 99:59:59.999 --> 99:59:59.999 So nomological means having to do with laws. 99:59:59.999 --> 99:59:59.999 And in the ideal case, the hypothesis isn't just an idea, 99:59:59.999 --> 99:59:59.999 ideally it is a law of nature. 99:59:59.999 --> 99:59:59.999 Why does it matter that it is a law of nature? 99:59:59.999 --> 99:59:59.999 Because if it is a law, it can't be broken. 99:59:59.999 --> 99:59:59.999 If it's a law then it will always be true 99:59:59.999 --> 99:59:59.999 in all times and all places 99:59:59.999 --> 99:59:59.999 no matter what the circumstances are. 99:59:59.999 --> 99:59:59.999 And all of you know at least one example of a famous law. 99:59:59.999 --> 99:59:59.999 Einstein's famous equation, E=MC2, 99:59:59.999 --> 99:59:59.999 which tells us what the relationship is 99:59:59.999 --> 99:59:59.999 between energy and mass. 99:59:59.999 --> 99:59:59.999 And that relationship is true no matter what. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 It turns out though that there are several problems with this model. 99:59:59.999 --> 99:59:59.999 The main problem is that it's wrong. 99:59:59.999 --> 99:59:59.999 It's just not true. [Laughter] 99:59:59.999 --> 99:59:59.999 And I'm going to talk about three reasons why it's wrong. 99:59:59.999 --> 99:59:59.999 So the first reason is a logical reason, 99:59:59.999 --> 99:59:59.999 it's the problem of the fallacy of affirming the consequent. 99:59:59.999 --> 99:59:59.999 So that's another fancy academic way of saying 99:59:59.999 --> 99:59:59.999 that false theories can make true predictions. 99:59:59.999 --> 99:59:59.999 So just because the prediction comes true 99:59:59.999 --> 99:59:59.999 doesn't actually logically prove that the theory is correct. 99:59:59.999 --> 99:59:59.999 And I have a good example of that too, again from the history of science. 99:59:59.999 --> 99:59:59.999 This is a picture of the Ptolemaic universe 99:59:59.999 --> 99:59:59.999 with the Earth at the center of the universe 99:59:59.999 --> 99:59:59.999 and The Sun and the planets going around it. 99:59:59.999 --> 99:59:59.999 The Ptolemaic model was believed 99:59:59.999 --> 99:59:59.999 by many very smart people for many centuries. 99:59:59.999 --> 99:59:59.999 Well why? 99:59:59.999 --> 99:59:59.999 Well the answer is because it made lots of predictions that came true. 99:59:59.999 --> 99:59:59.999 The Ptolemaic system enabled astronomers 99:59:59.999 --> 99:59:59.999 to make accurate predictions of the motions of the planet. 99:59:59.999 --> 99:59:59.999 In fact more accurate predictions at first 99:59:59.999 --> 99:59:59.999 than the Copernican theory which we now would say is true. 99:59:59.999 --> 99:59:59.999 So that's one problem with the textbook model, 99:59:59.999 --> 99:59:59.999 a second problem is a practical problem 99:59:59.999 --> 99:59:59.999 and it's the problem of auxiliary hypotheses. 99:59:59.999 --> 99:59:59.999 Auxiliary hypotheses are assumptions 99:59:59.999 --> 99:59:59.999 that scientists are making, 99:59:59.999 --> 99:59:59.999 that they may or may not even be aware that they're making. 99:59:59.999 --> 99:59:59.999 So an important example of this comes from 99:59:59.999 --> 99:59:59.999 comes from the Copernican model 99:59:59.999 --> 99:59:59.999 which ultimately replaced the Ptolemaic system. 99:59:59.999 --> 99:59:59.999 So when Nicolaus Copernicus said, 99:59:59.999 --> 99:59:59.999 actually the Earth is not the center of the universe, 99:59:59.999 --> 99:59:59.999 the sun is the center of the solar system, 99:59:59.999 --> 99:59:59.999 the Earth moves around the sun. 99:59:59.999 --> 99:59:59.999 Scientists said, well okay, Nicolaus, if that's true 99:59:59.999 --> 99:59:59.999 we ought to be able to detect the motion 99:59:59.999 --> 99:59:59.999 of the Earth around the sun. 99:59:59.999 --> 99:59:59.999 And so this slide here illustrates a concept 99:59:59.999 --> 99:59:59.999 known as stellar parallax. 99:59:59.999 --> 99:59:59.999 And astronomers said, if the Earth is moving 99:59:59.999 --> 99:59:59.999 and we look at a prominent star, let's say, Sirius. 99:59:59.999 --> 99:59:59.999 Well I know I'm in Manhattan so you guys can't see the stars, 99:59:59.999 --> 99:59:59.999 but imagine you're out in the country, imagine you chose that rural life. 99:59:59.999 --> 99:59:59.999 And we look at a star in December, we see that star 99:59:59.999 --> 99:59:59.999 against the backdrop of distant stars. 99:59:59.999 --> 99:59:59.999 If we now make the same observation six months later 99:59:59.999 --> 99:59:59.999 when the Earth has moved to this position in June, 99:59:59.999 --> 99:59:59.999 we look at that same star and we see it against a different backdrop. 99:59:59.999 --> 99:59:59.999 That difference, that angular difference, is the stellar parallax. 99:59:59.999 --> 99:59:59.999 So this is the prediction that the Copernican model makes, 99:59:59.999 --> 99:59:59.999 astronomers looked for the stellar parallax 99:59:59.999 --> 99:59:59.999 and they found nothing, nothing at all. 99:59:59.999 --> 99:59:59.999 And many people argued that this proved that the Copernican model was false. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 So what happened? 99:59:59.999 --> 99:59:59.999 Well in hindsight we can say that astronomers were making 99:59:59.999 --> 99:59:59.999 two auxiliary hypotheses, both of which 99:59:59.999 --> 99:59:59.999 we would now say were incorrect. 99:59:59.999 --> 99:59:59.999 The first was an assumption about the size of the Earth's orbit. 99:59:59.999 --> 99:59:59.999 Astronomers were assuming that the Earth's orbit was large 99:59:59.999 --> 99:59:59.999 relative to the stars. 99:59:59.999 --> 99:59:59.999 Today we would draw the picture more like this, 99:59:59.999 --> 99:59:59.999 this comes from NASA, 99:59:59.999 --> 99:59:59.999 and you see the Earth's orbit is actually quite small. 99:59:59.999 --> 99:59:59.999 In fact, it's actually much smaller even than shown here. 99:59:59.999 --> 99:59:59.999 The stellar parallax therefore, 99:59:59.999 --> 99:59:59.999 is very small and actually very hard to detect. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 And that leads to the second reason 99:59:59.999 --> 99:59:59.999 why the prediction didn't work, 99:59:59.999 --> 99:59:59.999 because scientists were also assuming 99:59:59.999 --> 99:59:59.999 that the telescopes they had were sensitive enough 99:59:59.999 --> 99:59:59.999 to detect the parallax. 99:59:59.999 --> 99:59:59.999 And that turned out not to be true. 99:59:59.999 --> 99:59:59.999 It wasn't until the 19th century that scientists were able to detect 99:59:59.999 --> 99:59:59.999 the stellar parallax. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 So, there's a third problem as well. 99:59:59.999 --> 99:59:59.999 The third problem is simply a factual problem 99:59:59.999 --> 99:59:59.999 that a lot of science doesn't fit the textbook model. 99:59:59.999 --> 99:59:59.999 A lot of science isn't deductive at all, it's actually inductive. 99:59:59.999 --> 99:59:59.999 And by that we mean that scientists don't necessarily 99:59:59.999 --> 99:59:59.999 start with theories and hypotheses, often they just 99:59:59.999 --> 99:59:59.999 start with observations of stuff going on in the world. 99:59:59.999 --> 99:59:59.999 And the most famous example of that is one of the most 99:59:59.999 --> 99:59:59.999 famous scientists who ever lived, Charles Darwin. 99:59:59.999 --> 99:59:59.999 When Darwin went out as a young man on the voyage of the Beagle, 99:59:59.999 --> 99:59:59.999 he didn't have a hypothesis, he didn't have a theory. 99:59:59.999 --> 99:59:59.999 He just knew that he wanted to have a career as a scientist 99:59:59.999 --> 99:59:59.999 and he started to collect data. 99:59:59.999 --> 99:59:59.999 Mainly he knew that he hated medicine 99:59:59.999 --> 99:59:59.999 because the sight of blood made him sick so 99:59:59.999 --> 99:59:59.999 he had to have an alternative career path. 99:59:59.999 --> 99:59:59.999 So he started collecting data. 99:59:59.999 --> 99:59:59.999 And he collected many things including his famous finches. 99:59:59.999 --> 99:59:59.999 When he collected these finches he through them in a bag 99:59:59.999 --> 99:59:59.999 and he had no idea what they meant. 99:59:59.999 --> 99:59:59.999 Many years later back in London, 99:59:59.999 --> 99:59:59.999 Darwin looked at his data again and began to develop 99:59:59.999 --> 99:59:59.999 an explanation 99:59:59.999 --> 99:59:59.999 and that explanation was the theory of natural selection. NOTE Paragraph 99:59:59.999 --> 99:59:59.999 Besides inductive science, 99:59:59.999 --> 99:59:59.999 scientists also often participate in modeling.