Cosma Shalizi (1998): Deborah Mayo, Error and the Growth of Experimental Knowledge: "Mayo's key notion is that of a severe test... the severity of a passing result is the probability that, if the hypothesis is false, our test would have given results which match the hypothesis less well than the ones we actually got do.... If a severe test does not turn up the error it looks for, it's good grounds for thinking that the error is absent...

...By putting our hypotheses through a battery of severe tests, screening them for the members of our "error repertoire," our "canonical models of error," we can come to have considerable confidence that they are not mistaken in those respects. Instead of a method for infallibly or even reliably finding truths, we have a host of methods for reliably finding errors: which turns out to be good enough. Experimental inquiry, for Mayo, consist of breaking down the question at hand into a series of small bits, each of which is relatively easily subjected to severe tests for error.... If we guess that a certain effect (the bending of spoons, let us say) is due to a certain cause (e.g., the psychic powers of Mr. Uri Geller), it is not enough that spoons bend reliably in his presence: we must also rule out other mechanisms which would produce the same effect (Mr. Geller's bending the spoons with his hands while we're not looking, his substituting pre-bent spoons for unbent ones ditto, etc., through material for several lawsuits for libel). But this solves the Quine-Duhem problem.

In fact, it gets better. Recall that methodological underdetermination (which goes by the apt name of MUD in Error) is the worry that no amount or quality of evidence will suffice to pick out one theory as the best, because there are always indefinitely many others which are in equal accord with that evidence, or, to use older language, equally well save the phenomena. But saving the phenomena is not the same as being subjected to a severe test: and, says Mayo, the point is severe testing.

While I'm mostly persuaded by this argument, I'm less sanguine than Mayo is about our ability to always find experimental tests which will let us discriminate between two hypotheses. I'm fully persuaded that this kind of testing really does underwrite our knowledge of phenomena, of (in Nancy Cartwright's phrase) "nature's capacities and their measurement," and Mayo herself insists on the importance of experimental knowledge in just this sense (e.g., the remarks on "asking the wrong question," pp. 188--9). I'm less persuaded that we can usually or even often make justified inferences from this "formal" sort of experimental knowledge, knowledge of the distribution of experimental outcomes, to "substantive" statements about objects, processes and the like (e.g., from the experimental success of quantum mechanics to wave-functions).

As an unreconstructed (undeconstructed?) scientific realist, I make such inferences, and would like them to be justified, but find myself left hanging...


#shouldread #books #cognition

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