Lewis's Worldmate Relation and the Apparent Failure of Humean Supervenience

Abstract

This paper considers two aspects of Lewis's metaphysics to which spatiotemporal relations appear central, with the aim of showing them to be less so. First, Lewis reluctantly characterises what it is for two things to be part of the same possible world in terms of an analogically spatiotemporal category of relations, rather than a wider natural external category. But Lewis's reason for restricting himself to the narrower category is unpersuasive. Second, Humean supervenience is formulated with spatiotemporal relations at its core. But that seems negotiable. A reason for caring about this is that quantum mechanics is supposed to threaten Lewis's metaphysics by introducing natural external relations that are not (even analogically) spatiotemporal, hence the interest in how central spatiotemporal relations really are.