Wednesday, July 11, 2012

A Lesson from Glymour's Theory and Evidence

In his Theory and Evidence, Clark Glymour presents his "bootstrap" theory of confirmation, which is essentially a conceptual analysis of the notion of confirmation (i.e. positive evidential relevance) that attempts to extend the hypothetico-deductive account to allow a theory to be confirmed by evidence that is derived from the very theory in question, in just the cases in which that kind of circularity is unproblematic.  Glymour's theory is extremely ingenious but faces at least one decisive objection (given here).  Attempts to patch the theory to address that objection did not get very far, and the theory was  more or less abandoned.

I suspect that the most important passage in Theory and Evidence is not one in which Glymour presents or defends his theory, but the final paragraph of the book in which he reflects on what he has accomplished.  His insight and his candor are remarkable:
There is nothing in this book that corresponds to an attempt to show that the methods I have described are justified or uniquely rational.  There are arguments for the methods, arguments that purport to show that the strategy achieves our intuitive demands on confirmation relations better than do competing strategies, but these arguments do not show that the bootstrap strategy will lead us to the truth in the short run or the long run, or will lead us to the truth if anything can, or is required by some more primitive canon of rationality.  There are such arguments for other confirmation theories, although none of them are wholly good arguments; perhaps it would be better to have a bad argument than of one of these kinds for the for the bootstrap strategy than to have none at all.  But the strategy does not depend on frequencies, and there is as yet no framework of degrees of belief within which to place it, and so none of the usual lines of argument seems relevant at all.  One has only the sense that unless the world is perversely complex, the strategy will help us to locate false hypotheses and separate them from true ones.  A sense is not an argument.  I am partly consoled by the thought that one cannot do everything; sometimes, alas, one cannot do very much at all.
To me the message of this passage and of the fate of Theory and Evidence and many similar projects is that conceptual analysis is an ineffective way to arrive at normative conclusions, even if the concept being analyzed (e.g. confirmation/evidence) has normative import.  Showing that a normative claim follows from more basic normative claims is perhaps a more promising approach, but to my mind the best approach of all is to show that abiding by a normative claim will help us achieve some end we care about.  If it doesn't do that, then why should we regard it as normative?

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