How Lewis Can Meet the Integration Challenge

Abstract

We show that Lewis’s modal realism, and his serviceability-based argument for it, cohere with his epistemological contextualism. Modal realism explains why serviceability-based reasoning in metaphysics might be reliable, while Lewis’s contextualism explains why Lewis can properly ignore the possibility that serviceability isn’t reliable, at least when doing metaphysics. This is because Lewis’s contextualism includes a commitment to a kind of pragmatic encroachment, so that whether a subject knows can depend on how much is at stake with respect to whether the belief is true or false. Accordingly, we suggest that Lewis can count as knowing that serviceability is a reliable guide to truth in metaphysics, since the stakes are generally low there, and so can be justified in believing that modal realism is true based on its serviceability.