 David Lewis produced a body of philosophical writing that, in four books and scores of articles, spanned every major philosophical area, with perhaps the greatest concentration in metaphysics, philosophy of language, philosophical logic, and philosophy of mind. Despite this astonishing variety, a newcomer to Lewis’s philosophy would be best advised to begin with his metaphysics (especially: 1986a, 1986e, 1999). There are several reasons. First, the majority of Lewis’s work either concerns, or substantially overlaps, topics in metaphysics. Second, the metaphysical positions Lewis stakes out are strikingly original and powerfully argued. Third, there is a coherence and systematicity to this work that makes it a particularly appropriate object for study, in that one sees trademark Lewisian philosophical maneuvers clearly on display. (Indeed, if one wished to learn how to do philosophy in a Lewisian style, the most efficient way to do so would be to study his work in metaphysics.) Finally, and perhaps most interestingly, Lewis’s metaphysics exerted a profound regulating influence on the rest of his philosophy: if some otherwise attractive position on some philosophical problem could not be made to square with his overall metaphysical outlook, then it would have to be abandoned.