Abstract

At least between the years 1960 and 1975 Quine defended the underdetermination thesis which asserts that there can be more than one incompatible physical theory supported by the totality of actual and possible evidence available to an investigator. Once the coherence of such a possibility is granted, one is confronted with a skeptical challenge: insofar as these theories are epistemically on a par, we cannot know which one is true. Scientific enterprise is threatened with falling short of delivering on its own promise of providing a methodology that yields knowledge. ;Quine attempts to defend his conception of science against the skeptical challenge that arises from underdetermination, while maintaining that his naturalistic, physicalistic system which denies the existence of a transcendent notion of truth can lay claim to a "robust" realism. ;Quine's best-known defense yields what he later came to call his "ecumenical" position, which amounts to arguing for the spuriousness of the putative fact of underdetermination. I argue that Quine's strategy does not work unless certain ambiguities in his concept of theory are resolved, and that once these are resolved, the strategy also leads to the undermining of the coherence of his indeterminacy of translation thesis. ;Another, more recent defense Quine has adopted leads to "sectarianism," which accepts the genuineness of underdetermined, incompatible theories, yet asserts that truth is predicable only of the assertions of one's current theory. Yet sectarianism also allows that one is free to switch between equally warranted theories. I argue that of the two ways in which the sectarian position can be interpreted, the first is powerless against the skeptical challenge and the second manages to avoid it only at the cost of adopting a perspective that does not satisfy even the minimal requirements of realism. ;The general, sobering conclusion that can be drawn from the specific problems facing Quine's philosophy is that an explanation of our epistemological position and its putative success is not automatically produced by the adoption of an "internalist," naturalist, or even scientistic perspective. A serious investigation of the skeptical challenge is vital for the modern philosopher of science, as it was for the traditional epistemologist