Science and philosophy: falsification

I'm simply going to state Karl Popper's claim and explain what it means. In further posts, I'll talk about the justification for his claim, and why we should care about the claim and its justification. If I feel like it, I'll talk about some weaknesses in Popper's case, and how they can be strengthened. However, that will require additional research that I would have to do in my copious free time. We'll see.

Popper's central claim is that a statement is scientific only if it is falsifiable. Note that this condition is necessary but not sufficient: a statement can, for example, be falsifiable and actually false, in which case it is not scientific. (Some might argue that Popper never says this, but it seems so trivial that if he really doesn't say so explicitly, it is uncharitable to believe he doesn't take it for granted.)

A statement is falsifiable if and only if there is an empirical observation that could in principle actually be observed that would render the statement false. If we do in fact observe a falsifying observation, then the statement is definitely false. However, if we bend over backwards to attempt to observe something that would falsify the statement, and we are unable to do so, we gain confidence in the truth of the statement; we can use probability theory (Bayesian or frequentist) to quantify our confidence. We can be certain that some statements are false, because we make a falsifying observation, but we can never be certain that any statement is actually true.

For example, take the statement, "Objects always fall when we drop them." This statement is falsifiable: if I drop something, and I observe it not falling, then the statement is definitely false. However, no matter how many times I drop something and observe it actually falling, I cannot be certain that things always fall when I drop them, everywhere on Earth for all time. The best I can do is say having observed things falling when I drop them many times, I have confidence in the statement, but if I were to ever actually observe a counterexample, then I would have to revise my theory.

In contrast, consider the statement, "God created the universe." The syllogism

1. If God had not created it, the universe would not exist
2. The universe exists
3. Therefore, God created the universe

is certainly valid, and (2) is confirmed by observation. But the syllogism is not falsifiable: if no universe exists, we could not observe that fact. (We are part of the universe; if the universe did not exist, neither would we.) Therefore, the syllogism is not scientific: we could not in principle observe its falsity.

In principle, Popper's claim is very straightforward; in practice it's a lot more complicated. Most importantly, we cannot evaluate statements independently: all statements depend on a theoretical context, the larger structure of a scientific theory, the construction of our measurement devices, and the nature of language itself. Hence, we cannot isolate single statements for falsification; instead we can only falsify larger theoretical constructs. The best we can say if we observe something that falsifies a statement within a theoretical context, then something in the context (including the statement) is false, but we can't be sure precisely what part of the context (or the entire context) is incorrect.

For example, I'm watching the Feynman lectures. Feynman talks about observations of the moons of Jupiter that falsified Newton's theory of gravity. Instead of modifying the theory of gravity itself, scientists changed the theoretical context by adding the premise that the speed of light is finite, with a definite value.

But this ambiguity does not damage Popper's central point. Popper does not give us any guidance on how to fix problems, he merely claims that if it is impossible in principle to have this particular problem, i.e. impossible to observe something contrary to the theoretical context, then whatever it is you're doing, you're not doing science.

Science and philosophy: Introduction

What is "science"? What makes one endeavor scientific and another endeavor non-scientific?

It's tempting to say that science is what scientists do. It's a tempting answer, because different kinds of scientists do a lot of different things. The way biologists do biology is very different from the way physicists do physics; if they are very different, why is it legitimate to label both as "science" but label mathematics or philosophy as "not-science" just because mathematics and philosophy are very different from physics and biology. It's also tempting because we can say that science is just another social category; to talk about science abstractly risks the fallacy of reification. In much the same sense being "American" is just what people in the United States happen to do; to talk abstractly about some essential "Americanism" that would be true regardless of what any Americans actually did would be nonsensical reification.

A lot of people, myself included, think that, unlike Americanism, there really is something essential about science, something essential that would be true even if everyone who called themselves "scientists" didn't do it. Moreover, it's important to think and talk about the essential nature of science because science, done "correctly," has immense social value; done incorrectly, science is useless or harmful. Furthermore, what actual professional scientists actually do is a vastly more rigorous version of a general mode of thought, a mode that everyone should employ, at least about some of their ideas and behaviors.

Of course, there are no other modes of thought, modes that are not science, that also have value; I do not advocate "scientism" in the sense that science is the only valuable mode of thought.

If there really is something essential about science, then philosophers are better-situated than scientists to talk about it. Paradoxically, if there is something essential about science, then it is possible that scientists do things scientifically out of habit or tradition, without reflection or specific intention. They could be doing things scientifically, but doing those things not because they know those things are scientific, but just out of habit. It might also be true that because science, as actually practiced, is socially situated, scientists do specific things that might be irrelevant or contrary to what is essentially scientific because of their social situation. It could take an outsider to discern which of those things really comprise the essence of science, and which are just arbitrary habits or extraneous social behavior. For example, I've worked with a lot of scientists. Many of them have no idea what statistical tests do or how statisticians actually interpret them; they just click a button in Stata or Excel, and if the p value is less than 0.05, they publish. The statistics are essentially scientific; the choice of 0.05 (or any other specific number) as the threshold of significance is not essential to science.

Again, I don't wish to deprecate the social aspects of science: scientists are part of society, and they have to fit their practices to the larger social context. Still, if there is such a thing as what is essentially science, it is still important to discern what is scientific and what is social.

Philosophers are also well-situated to talk about the essential nature of science because when doing actual philosophy (rather than "philosopholgy," the study of the somewhat arbitrarily constructed canon of philosophy) are the least susceptible to authority and privilege. A philosophical work stands or falls on its argument, not on the reputation or privilege of its author. Robert Nozick's Anarchy, State, and Utopia, for example, is "authoritative" on a version of Libertarianism not because he holds any particular power to define it, but because he makes good arguments (well, as good as can be expected) and has persuaded a lot of people that his version of Libertarianism makes sense.

In this series, I will be talking about the philosophy of science as a philosopher. I claim no special privilege to define the essential nature of science, or even to establish that there is such a thing as an essential nature of science: my work, like all philosophy, stands or falls on the persuasiveness of my arguments.