David Lewis was the last notable systematic philosopher of the twentieth century. He is known for many important and lucidly expressed contributions to diverse areas of philosophy, including philosophy of language, theory of mind, and metaphysics. He is remembered, in particular, for his audacious advocacy of the reality of all possible worlds.

David Kellogg Lewis was born in Oberlin, Ohio, on 28 September 1941 to John Donald and Ewart Kellogg Lewis, both of whom were college professors. He majored in chemistry at Swarthmore College, but after spending a term at the University of Oxford and attending lectures by Gilbert Ryle, he switched to philosophy. Following his graduation in 1962, he studied under W. V. Quine at Harvard University. In the fall of 1963 he attended a seminar given by the visiting Australian philosopher J. J. C. Smart, one of the earliest and most influential advocates of the mind-body (or psychophysical) identity theory...