Lewis on Set Theory

henceforth PC) undertakes a fundamental re-examination of the relationship between merelogy, the general theory of parts, and set theory, the general theory of collections. He assumes a certain minimum background familiarity with both subjects, and limitations of space make the same assumption inevitable in the present account. Varzi (2011) is recommended as a clear, concise survey of mereology in general. Karen Bennett's chapter in the present volume discusses Lewis's version of mereology in particular. Among the asumptions surveyed by Varzi, Lewis's are about the strongest, including unrestricted composition, the claim that any things whatsoever have a fusion, but leaving open whether everything is a fusion of atoms, or things with no parts other than themselves. For set theory in the form in which it will be considered here, Boolos (1989) (with Boolos (1971) in the background), to which reference will in any case be essential, should suffice.