Empirical equivalence and underdetermination

Jarrett Leplin in A Novel Defense of Scientific Realism (1997) argues that if the thesis of empirical equivalence is cogent, then the thesis of underdetermination cannot even get off the ground. Part of Leplin's argument rests on the claim that auxiliary hypotheses can be independently confirmed, thus enabling us to determine the epistemic worth of a theory. This, in turn, helps in determining about what we should be realists. Leplin's claims are demonstrated to be problematic. Leplin wants, inconsistently, to use only those auxiliary hypotheses which dovetail with confirmed theories. Finally, a detail of Leplin's argument is found wanting.