Full Idea
Main criticisms of mereology: we don't mean 'part' as improper; transitivity of 'part' is sometimes not transitive; no guarantee that there are 'sums'; the identity criteria for individuals are false; we are forced into materialistic four-dimensionalism.
Gist of Idea
Criticisms of mereology: parts? transitivity? sums? identity? four-dimensional?
Source
Peter Simons (Parts [1987], 3.2)
Book Reference
Simons,Peter: 'Parts: a Study in Ontology' [OUP 1987], p.105
A Reaction
[Compressed summary; for four-dimensionalism see under 'Identity over Time'] Simons says these are in ascending order of importance.