Scepticism, Rationalism and Externalism

Brian Weatherson

Brown University

How do we know that our evidence is not massively misleading? One powerful sceptical argument, I think the best sceptical argument, rests on the following two premises. First, we can't know a priori that our evidence is not massively misleading. Second, we can't know a posteriori that our evidence is not massively misleading. So we can't know our evidence is not massively misleading. In this paper I give a careful version of this argument applied to the relationship between our evidence and the future, and argue that we need to make some sacrifices if we are to avoid being ensnared by it. In particular, I argue someone who accepts a moderately weak form of internalism about justification, and who rejects the rationalist claim that we can have a priori knowledge of deeply contingent truths, has no response to this sceptical argument. So we should either abandon that form of internalism, or accept the rationalist claim. (A full version of this paper is online at: http://www.brown.edu/Departments/Philosophy/homepages/weatherson/sre8.pdf .)