Discussion: In Defense of the Quine-Duhem Thesis: A Reply to Greenwood

Abstract

While discussing the work of Kuhn and Hanson, John Greenwood (1990) misidentifies the nature of the relationship between the incommensurability of theories and the theory-ladenness of observation. After pointing out this error, I move on to consider Greenwood's main argument that the Quine-Duhem thesis suffers from a form of epistemological self-defeat if it is interpreted to mean that any recalcitrant observation can always be accommodated to any theory. Greenwood finds this interpretation implausible because some adjustments to auxiliary hypotheses undermine too much of the prior observational evidence for the test theory. I argue that Greenwood mistakes the logico-metaphysical Quine-Duhem thesis for an epistemological one. All the argument he takes to undercut it actually illustrates how well the thesis works on a practical level. This is illustrated with an example from contemporary immunology.