Abstract

The author expounds critically Roderick Chisholm's theory of modal mereology and undertakes to redeploy and reconcile this with the Lesniewski-Tarski theory of part-whole, modally augmented. An argument is presented for the principle that what belongs to an aggregate as a part belongs essentially to it. This principle is argued not to imply that every part of an ordinary substance is essentially part of it (such substances not being aggregates), and to give no particular support to Roderick Chisholm's postulation of entia successiva in substitution for ships, trees, and houses as ordinary conceived. Entia successiva are not good candidates for identification with these.