Lewisian Realism: Methodology, Epistemology, and Circularity

In this paper I argue that warrant for Lewis’ Modal Realism is unobtainable. I consider two familiar objections to Lewisian realism – the modal irrelevance objection and the epistemological objection – and argue that Lewis’ response to each is unsatisfactory because they presuppose claims that only the Lewisian realist will accept. Since, I argue, warrant for Lewisian realism can only be obtained if we have a response to each objection that does not presuppose the truth of Lewisian realism, this circularity is vicious. I end by contrasting Lewis’ methodology with Forrest’s in order to illustrate a rival method that does not fall victim to the objection I lay against Lewis.