EEB 122: Principles of Evolution, Ecology and Behavior

Lecture?23. The Logic of Science

https://oyc.yale.edu/ecology-and-evolutionary-biology/eeb-122/lecture-23

I?want to raise, in your minds, this issue of what constitutes science and what is not science, and what's good science and what's bad science, so that you'll yourself start to develop your own criteria.?

Now science is basically culture's answer to the big problem of epistemology, which is how can we know anything at all? How do we know that there is a material reality? And this issue, as you know, goes back to Plato and Aristotle, in the Western tradition, and in each of the other major cultural traditions these issues have been debated.?Basically if you look at what all the different parts of our culture do for our society, this is the role of science. It tries to give some kind of objective message about the nature of reality。

I'm going to assume that you know that David Hume demonstrated that inference doesn't lead infallibly to truth. And, in fact, what we've got going for us now is we've got a model of the universe in which the earth spins on its axis and planets go around the sun and stuff like that. That is a theory. It's a model of the universe, and it's been so extensively validated and connected to so many observations that it would be mad to deny its reality.?And what Hume essentially pointed out was that just the accumulation of instances is not leading you infallibly to the truth; that there could be alternative explanations.?

So that's a way of showing how a working hypothesis survives a contest of alternatives to become something that then gets operationally accepted as truth. It is conceivable that someone might now come up with an observation that would convince us that, at least in some cases, DNA wasn't the genetic code. But for all intents and purposes, this contest of alternative ideas, through experimental demonstrations, leads to something that science then accepts pretty much as truth. And what I'm telling you is that these theories about the structure of reality are basically arrived at by a contest of ideas that is being testing empirically over and over again, and you're accepting the last one that's left standing.?

Scientists?think there's a material reality and they think we can discover its nature. Not everybody on the planet agrees with that. We can eventually agree on what we've discovered. At the leading edge of science there's plenty of disagreement about the nature of reality; that's the whole point about the contest of alternative hypotheses. So what we call science is limited to knowledge about the part of material nature that is currently accessible by our current technology, our current techniques, our current investment, and on which we can agree; and that agreement can take some time.?

Now the part of knowledge that people can agree upon, through this debate of alternatives, is what we call science; and that means that somebody else can replicate your claim. They can't replicate your claim unless you've described it clearly. That means if you're reading a paper, for one of your papers, and somebody can't tell you clearly what they've done, they're not doing a good job. They have to be able to write clearly in order to complete this part of the logic.?

• T.C. Chamberlain says we fall in love with our own ideas, and therefore biased. When we look at a pattern of data, we will have a tendency to pick out the parts of it that support our preconceptions and to leave out the parts that don't support our preconceptions, and if you're interested in an objective view of reality, this is a bad thing to do.

• So how do we protect ourselves from this? Well the best way, he thought, was to explicitly come up with a set of multiple working hypotheses, that are actually different from each other, and then weigh the evidence for and against each of them. So this is a way of protecting ourselves against our love for our own ideas.

• Sometimes, several can all be correct, and that is the case whenever hypotheses are not mutually exclusive, where they could all actually be working at the same time. Sometimes that is true and sometimes that's not true. That tends not to be true when you're talking about particular molecular structures. There is normally just one molecular structure. If your techniques are not good, there are some alternatives, but when you get them really good, usually there's just one.

• But often there are several different selection pressures that will result in the same outcome. And you've seen that with sexual selection.?So a female could be choosing a male for good genes, or because he's got lots of resources, or because he'll have sexy sons, and in fact those could all be true at the same time.

One way to achieve objectivity is to try to demonstrate systematically that a hypothesis is wrong. And if you try to refute it, rather than to confirm it, and you can't refute it, it just is stubborn, it will not go away, then maybe it's right. So this is the idea behind Popper's falsifiability criterion.?

• Karl Popper, a very influential philosopher of science, member of the Vienna School,?engaged in very strong debate about how to make sense of the discovery of reality in the post-quantum mechanics world. And there had been a great deal of uncertainty in the basis of our knowledge?in the early twentieth century, with the discovery of quantum mechanics and of the theory of relativity.

• One of the responses is Popper's falsifiability criterion. So what Popper says is that we can never actually prove that an empirical statement is true, for there are always alternatives that are possible. So these alternatives we might not know about, but that would be a failure of our imagination, it would not be a failure of logic.

• However, we can demonstrate that things are false. So Popper claims this is what distinguishes science from math. You can prove a theorem in math; you cannot prove an observation in science. So proof means true at all times, in all places.?The thing that distinguishes science from math, in statements like that, is that math is 100% certain, and science is trying to get to the limit of that 100% certainty; so some of it's up there at 99.99, or even closer. But with math it's simply logically true, and with science it's a matter of empirical demonstration.?

So because of that, Popper suggested that the difference between science and non-science is falsifiability. If in principle you can demonstrate that something is false, if a certain observation that one could imagine could demonstrate it, then you're dealing with science, and if you cannot imagine ever making an observation that would demonstrate that something is false, then you're dealing with non-science.?

Why is it that some fields make progress faster than others??It's called strong inference.?So devise alternative hypotheses--that's Chamberlain. Devise crucial experiments to exclude hypotheses--that's Popper. Do the experiments so well that nobody can argue with you, and then recycle the procedure. So he said people who are making progress do that, and people who aren't making progress don't do that.?

So where does it work best? Well what's the single mechanism; what's the structure? That is where strong inference really works well. It doesn't really work so well where there are several different correct answers, where you've got multiple causation going on. That's often much more often the case in ecology and evolution than it is in molecular and cell biology, and it's certainly much more often the case in the social sciences than it is in the natural sciences. But it's a good philosophy. It's a good starting point. It's good to realize that that's a good standard to set, and to see how far you can push the process towards it.?

Now strong inference actually won't work at all in a field like astronomy, geology, paleontology or systematics. And that's because we can't do experiments. Nevertheless, we can do observations that are so precise that they become convincing. So there is a rigor in descriptive science that is not captured by this paradigm of strong inference. Continental drift and the Big Bang are accepted without experimental confirmation.?

And I think that what you'll find is that there is a theory about how it works, and the theory makes a long series of predictions, and many, many of these predictions have now been confirmed by observation; not by experiment but just by observation. And if you line up other alternative theories, for say the location of the continents on the planet, or say the residual cosmic radiation, or something like that for the Big Bang, you'll find that the alternatives don't do so well.?

Now there is another possibility for what goes on in science, and that is this romantic paradigm of Revolutionary science. If you would like to read a piece of glorious philosophical rhetoric, read Thomas Kuhn's 1962 book,?The Structure of Scientific Revolutions. He decided to make the Copernican Revolution?a scientific Revolution. And he described it as a paradigm shift, a shift in the whole way that we look at the world. And there have been some others. So Newton to Einstein, plate tectonics.?

And the idea here is that the paradigm shift is so profound that people are not able to communicate across the divide, so that once you have seen, for example, that the continents are in motion, you can actually no longer have an intelligent conversation with your geological colleague who doesn't realize that yet, because it's such a deep change in the way that you look at the world.?If that really is true, then the old generation has to die out before the insights of the new generation can be accepted.?

• Well I think that this is an interesting set of issues, because somebody like Charles Darwin really was a Revolutionary. There's been nobody who has more profoundly changed the way we think about the human condition and what a human being is than Darwin.?But Darwin didn't want to be a Revolutionary. He wanted to be a normal member of the British upper middle-class, who wasn't upsetting anybody. And he was conservative. He wanted to be acceptable to the establishment, and so he went through rather elaborate maneuvers, to try to make himself digestible.?

• Steve Gould was not really a Revolutionary but he wanted to appear to be one. If you go back and you look at what Steve's written about his encounter with Kuhn, in 1965, when he was a graduate student at Columbia, you can see that he was seduced by this idea that Revolutionary science is great science, and that's what he wanted to become.

• So he had important ideas; there's no question that Steve Gould had important ideas, but he wanted to sell them as a paradigm shift that would change profoundly the way that everybody looked at the world, and he actually overshot his mark and he created exaggerated expectations. So there was a bit of a backlash against him because he was making claims that couldn't really be supported. And that is, I think, kind of unfortunate because he had some important ideas; just oversold them.?

So is it worth worrying about being a Revolutionary scientist? Well I think we all have to be a bit modest about whether we can tell whether we're currently making a contribution that's going to make any difference at all. And the only thing that decides is history, and history chews this stuff over long after we are dead. So it's really only history that can identify a major scientific advance. It's very difficult, right in the middle of the generation that's experiencing it, even though it might have gotten a Nobel Prize, to be sure that it's really that fundamental, because it just takes perspective and time.?

So if you're on the scene and you're enmeshed in the process, your own estimate of the contribution is kind of unreliable; and, to go back to Chamberlain, we're all in love with our own ideas, and so we all have a tendency to think that what we're doing is the greatest thing ever. And that's simply just not necessarily true, and it's kind of hard to tell until history takes its course.?

So the best way to cause a change is to take the current state of affairs and push it as far as it will go. So taking the current state of science, what Kuhn might call boring, normal science, and pushing its limits and discovering where they break down is probably the most effective way, in the long-term, to really cause major scientific advance. ?

So if you make a premature attempt at Revolution and you overshoot the mark, then the attempt tends to collapse under its own weight. There's a whole cottage industry of criticisms of Kuhn. You can find conferences that have gone out and found maybe seventy or eighty different senses in which Kuhn used the word?paradigm?in that paper. So I would say that whether it's worth worrying about Revolutionary science at all, or whether it's worth trying to be a Revolutionary scientist, is an issue which is open to pretty serious discussion.?

Now what about post-modernism? Post-modernism is variously defined, and some of it I think is quite interesting and worth reading. When people say Post-Modern, they usually think of the French School of Literary Criticism and Philosophy; they think of Jacques Derrida, they think of Lacan, they think of Foucault. And there are insights that those guys have had, some of which I think should be part of the intellectual equipment of any well-educated person.?

And particularly among that crew I particularly admire Foucault because Foucault, for example, discusses things like is the definition of madness a function of the current power structure of society? I think that's an interesting question and I think that there's some historical evidence that it is, to a certain degree. So I think there are important issues there, and most of that I think has to do much more with literary criticism in the social sciences than it does with the natural sciences.?

But the people who got into this decided that they might want to turn this armament of literary ideas onto natural science. And they picked up on Kuhn, because if you could show that science consists of a series of Revolutionary paradigm shifts, that would mean that science is more socially constructed than empirically verified. So it's like one paradigm is one period of mass hysteria, and then the next paradigm is another period of mass hysteria; and there isn't anything going on here, other than that people are tending to agree with each other on the nature of reality, but then they're changing their minds. ?

Well most of science actually doesn't proceed according to Kuhn's model of Revolutionary science. It's going by the accretion of well-tested hypotheses. They're mostly much smaller than a paradigm. It's walking with small steps. So it's not built up the way that say Kuhn's Copernican Revolution would make it look like. And science does succeed in describing nature in ways that don't change as science advances.?

So the point is that when the natural science community gets down to the task, and it focuses long and hard on an important point, it can actually tell you pretty well what the nature of reality is; and it's not that we're dealing with successions of mass hysteria on something like that.?

Now that said, one of--there are moderate post-modernists who will say, "Yes, but the social and political context does bias the kinds of questions that are tested." And I think there's some truth to that. And I think there's some truth to the idea that if science was dominated by women, that they would be testing a different set of questions than if it were dominated by men. And I think that if it were dominated by Marxists, that they would be testing different sets of questions than if it were dominated by Capitalists.?

But I think that the objective weighing of alternatives is going to cause all of those different traditions to arrive at the same point eventually. Because Mother Nature doesn't care whether you're a man or a woman, or a Marxist or a Capitalist; Mother Nature just is, and she's going to give you answers.?

Now science consists of shared knowledge--that's what we can agree on--and that doesn't mean that science is a social construct. Science is accumulated by humans having social interactions, but that doesn't mean that it's arbitrary. So it's making progress, and it's expanding the part of reality we can agree on, and eventually reality has been checked by so many methods that we converge; any independent intellectual tradition would converge on reality as it actually is.?

And that doesn't matter whether you would start this process coming out of a Buddhist tradition or a Christian tradition or whatever; you would eventually end up with quantum chromodynamics in physics, and you would eventually end up with cell biology and evolution in biology.?

I think that there's a lot of fun that the philosophers of science have in arguing about what scientists actually do and what's the best way to do it. But I think the thing that the scientist needs to take away from it is just agreeing that we can all be critical about the hypotheses we pose, and that the tests that they have, have to withstand, and the ones that we can agree on they have withstood.?

If we can agree that we're going to be critical of each other, and we will do so in a civilized way, and we will insist that we will only accept constructive criticism, and we will agree that we will only try to give constructive criticism, because we want to have this play of alternatives, and we know that's the only way we can get to an accurate description of reality, then we can do good science. And I don't think that we have to get much fancier than that agreement, in philosophical terms.?

Now if we want to be philosophers of science, we can go and get as fancy as we want; that's another issue, that's another field. But what the working scientist at least needs to do is to realize that something like this is going on.?

So given that, should scientists, who largely agree on how to proceed, accept dicta that are handed down by philosophers who often don't agree on what they're taking about? Well I would say that scientists shouldn't accept simple recipes from philosophers, especially if they haven't done science themselves, but they should listen to reason from those who have the perspective of standing outside the endeavor. So one should not dismiss the philosophers out of hand. They're often very bright people who are making good points, but they may not have the practical experience to understand exactly what difference their points make.?

Now the final thing that I'd like to mention is a little bit about creativity. So where do ideas come from? And after all I've been talking about science as a play of alternatives, and we have alternative models, alternative hypotheses that we want to generate, and that if we can get them playing off of each other, then we can use that as a tool to try to perceive reality.?

Well the best study of where these ideas come from, that I'm aware of, is called?The Psychology of invention in the Mathematical Field,?by Jacques Hadamard.?The sequence basically is there has to be a period of hard work, and you have to push yourself right to the limit, trying to figure out the solution to some puzzle. Then you go to sleep, and maybe the next morning, or maybe two months later, something will occur to you. Your brain is processing overnight. It is making connections. It's trying out all sorts of things, and all of the clutter and bustle of every day is getting in the way.?

So these things don't happen to anybody. They only happen to those who have prepared themselves by working hard. So the overview of this is basically that creative new ideas, about how the world works, can come from anywhere. So this contest of alterative hypotheses in science, those new ideas can come from anywhere, but they most often emerge from the minds of people who have worked very hard to understand something. So that's the raw material.?

And, by the way, this raw material usually emerges in the minds of young people. It doesn't so frequently emerge in the minds of the old guys with white beards. It appears that in biology often they're between the ages of 30 and 40, just because it's a different kind of subject and it takes more background preparation. So those ideas are then subjected to rigorous tests, and the ones that remain standing become what we call science.?