An Old Topic That Keeps Poppering Up

A friend wrote me, mentioning that in a discussion group to which he belongs, some recent findings contra the dominant global warming theories led group members to declare those theories were now "falsified," and, per Popper, honest scientists ought to drop them post haste.

My reply:

It is a truism that Marx is better than the Marxists and that Freud is better than the Freudians. But it is a truism because it is so often true. Just so, Popper is better than (most of) the Popperians. Unlike your list mates, Popper knew that scientists always face a choice between rejecting the theory and the experiment. When confronted with the odd orbit of Uranus, scientists were not obliged to reject Newtonianism, but could "reject" the experiment instead. (Of course, in this case, they didn't exactly "reject" it, but sought another explanation for it -- what they "rejected" was the straightforward interpretation that their data falsified Newton's theory of gravity. But sometimes experimental results are simply thrown out -- like the multiple positive measurements made of "ether drift" in the 1920s!)

So Popper is not guilty of the elementary error being committed by your list mates. The problem with Popper is deeper. In the extreme version of his thought -- which is really the only version that sets him apart as a philosopher of science -- no experimental findings ever offer "support" for a theory, they simply fail to falsify it. Now, typically a scientist is going to make the call for rejecting Newtonianism or rejecting its falsification by the orbit of Uranus based on some consideration like, "We've got 150 years of good evidence supporting Newton -- my data must mean something else." But Popper left the scientist with no rational basis for choosing which to reject, since evidence can't support theories.

Popper was smart enough to recognize his impasse, and he tried to fudge with the idea of "corroboration," claiming that it is rational to choose the "best corroborated" theory. But either corroboration does support a theory -- in which case we're back to the model of induction created by Bacon and Boyle, and Popper has nothing novel to say -- or it doesn't, in which case, why should it influence the scientist's choice? This problem is well-known in the literature (see Salmon, W.C. (1988). "Rational Prediction," in The Limitations of Deductivism, pp. 47-60.), and its existence was, I suspect, decisive in forming the widespread view that Popper had made a bold try but had come up short. (E.g., the LSE philosophy department, founded by Popper, has no Popperians left in it -- even so, we read more of Popper and Hempel than of any other philosophers of science, so this was not a knee-jerk rejection, but careful consideration followed by reasoned rejection.)

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