Abstract
This chapter takes up issues to do with Peter van Inwagen's (1990a) general composition question: what is it for one thing to be a part of another? The chapter begins with some background to do with formal mereology, the study of parts and wholes. In discussing the metaphysics of parts and wholes, it is helpful to have some specialized vocabulary, as well as a well thought‐out mathematical model of a very broad, inclusive theory. The theory of mereology, proposed by the logician Stanislaw Lesniewski and introduced to the widerworld by Goodman and Leonard in an article in the Journal of Symbolic Logic, provides that vocabulary and such a model. These mereologists proposed some basic axioms for the part‐whole relation. Alternatively, the Composition as Identity (CAI) theorist could try to build transitivity into their definition of the part‐whole relation. Finally, the chapter provides some answers to the General Composition Question and considers whether those answers can supply a ground for the correct principles of mereology.