Conceivability, Explanation, and Defeat

Christopher Hill and Joseph Levine have argued that the conceivabilities involved in anti-materialist arguments are defeated as evidence of possibility. Their strategy assumes the following principle: the conceivability of a state of affairs S constitutes evidence for the possibility of S only if the possibility of S is the best explanation of the conceivability of S. So if there is a better explanation of the conceivability of S than its possibility, then the conceivability of S is thereby defeated as evidence of possibility. Hill and Levine proceed to offer alternative explanations of these conceivabilities, concluding that these conceivabilities are thereby defeated as evidence. However, this strategy fails because their explanations generalize to all conceivability judgments concerning phenomenal states. Consequently, one could defend absolutely any theory of phenomenal states against conceivability arguments in just this way. This result conflicts with too many of our common sense beliefs about the evidential value of conceivability with respect to phenomenal states. The general moral is that the application of such principles of explanatory defeat is neither simple nor straightforward