Skepticism, Information, and Closure: Dretske’s Theory of Knowledge

According to Fred Dretske’s externalist theory of knowledge a subject knows that p if and only if she believes that p and this belief is caused or causally sustained by the information that p. Another famous feature of Dretske’s epistemology is his denial that knowledge is closed under known logical entailment. I argue that, given Dretske’s construal of information, he is in fact committed to the view that both information and knowledge are closed under known entailment. This has far-reaching consequences. For if it is true that, as Dretske also believes, accepting closure leads to skepticism, he must either embrace skepticism or abandon his information theory of knowledge. The latter alternative would seem to be preferable. But taking this route would deprive one of the most powerfully developed externalist epistemologies of its foundation.