Chapter 4: Popper

The logical positivists developed their theory of science as a part of a general theory of language, meaning, and knowledge. Popper was not much interested in these broader topics; his primary aim was to understand knowledge.

All of Popper’s philosophy starts from his proposed solution to the problem of demarcation. “Falsificationism” was the name Popper gave to his solution, and this is also referred to as the hyppthetico-deductive method. Falsificationism claims that a hypothesis is scientific if and only if it has the potential to be refuted by some possible observation. He also claimed that all testing in science has the form of attempting to refute theories by means of observation. Crucially, for Popper it is never possible to confirm or establish a theory by showing its agreement with observations. the only thing an observational test can do is to show that a theory is false. Popper believed it is not possible to confirm a theory, not even slightly, and no matter how many observations the theory helps us to predict successfully.

Popper had a fairly simple view of how testing in science proceeds. We take a theory that someone has proposed, and deduce an observational prediction from it. We then check to see if the prediction comes out as the theory says it will. If the prediction fails, then we have refuted, or falsified, the theory. If the prediction comes out as predicted, then all we should say is that we have not yet falsified the theory. The theory might be true, but we cannot say more than that. After repeated attempts to falsify, with no results, we can say that the theory has now survived repeated attempts to falsify it, but that’s all. We never stop trying to falsify it.

Science, according to Popper’s theory, changes via a two-step cycle that repeats endlessly.

Stage 1 is conjecture: a scientist will offer a hypothesis that might describe and explain some part of the world. A good conjecture is a bold one, one that takes a lot of risks by making novel predictions.

Stage 2 is attempted refutation: the hypothesis is subjected to critical testing, in an attempt to show that it is false.

Once the hypthesis is refuted we go back to stage 1 where a new conjecture is offered, which is followed by stage 2, and so on.

\ Popper made much of the difference between confirming and disconfirming statements as scientific law. If someone proposes a law of the form “All Fs are G”, all it takes is one observation of an F that is not a G to falsify the hypothesis. This is a matter of deductive logic.

Popper’s and the logical empiricists’ aim was to describe testing in situations where there is a huge or infinite number of cases covered by a hypothesized law or generalization. So Popper stressed that universal statements are hard or impossible to verify but easy, in principle, to falsify.

\ Popper’s picture of science’s search for truth is that all we can do us try out one theory after another. A theory that we have failed to falsify up to now might be true. But if so, we will never know this or even have reason to increase our confidence.

One thing that a scientist should not do, however, is react to the falsification of one conjecture by cooking up a new conjecture that is designed to just avoid the problems revealed by earlier testing, and that goes no further.

\ A case where individual A does the conjecture and individual B does the refutation will be suspicious to Popper. If individual A is a true scientist, they should take a critical attitude toward their own ideas. If individual A is completely fixated on their conjecture, and individual B is fixed on showing that A is wrong in order to advance a different conjecture, this is not good scientific behavior, according to Popper.

Good scientists should retain a tentative attitude toward all theories, including their own: “whenever we propose a solution to a problem, we ought to try as hard as we can to overthrow our solution, rather than to defend it”.

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Objections to Popper on Confirmation

Popper believed that theories can never be confirmed by observations, and he thought that inductive arguments are never justified.

A simple problem that Popper has a very difficult time with is that of the question of which design of a bridge is stable and will support the weight that it will carry, if needing to use physical theories. Engineers and scientists in this situation will undoubtedly tend to use physical theories that have survived empirical testing; they will use “tried and true” methods as far as possible. The empiricist approach to the philosophy of science holds that such a policy is rational.

Popper can say something about why we should prefer to use a theory that has not been falsified over a theory that has been falsified. Theories that have been falsified have been shown to be false. But suppose we have to choose between (1) a theory that has been tested many times and has passed every test and (2) a brand-new theory that has just been conjectured and has never been tested. Neither theory has been falsified. Why exactly would it be irrational, for Popper, to build the bridge using a new theory that has not yet been tested?

Popper said that a theory that has survived many attempts to falsify it is “corroborated”. And when we face choices like the bridge-building one, it is rational to choose corroborated theories over theories that are not corroborated.

If corroboration is so different from confirmation - so different that we cannot regard corroboration as any guide to a theory’s truth - then why should we choose a corroborated theory when we build the bridge?

Confirmation, as understood by the logical empiricists, is something like a letter of recommendation for a scientific theory. It says something about what it has done, and also makes claims for what it is likely to do in the future. Corroboration, for Popper, is more like saying what it has done, but does not contain explicit predictions about what it will do in the future. And Popper thought that no good reasons could be given for believing that past performance is a reliable guide to the future.

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Hypothetico-deductivism

Formulations of the hypothetico-deductive method differ, but some are basically a combination of Popper’s view of testing, and a less skeptical view of confirmation.