Abstract

"Parts of Classes" tries to separate the unproblematic part of set theory (mereology) from the problematic part (singletons). In the process several things get lost: an empty set which is really empty; a satisfying account of the paradoxes; and the motivation for the iterative conception of set. Lewis' attack on the coherence of singletons makes it puzzling what he sees his book as doing. Nor is it clear that mereology is as ontologically innocent as Lewis would have us believe.