Full Idea
Classical extensional mereology won't extend well to temporal and modal facts, because of 'mereological extensionality', which is the thesis that objects with the same parts are identical (by analogy with the extensionality of sets).
Gist of Idea
'Mereological extensionality' says objects with the same parts are identical
Source
Peter Simons (Parts [1987], Intro)
Book Reference
Simons,Peter: 'Parts: a Study in Ontology' [OUP 1987], p.1
A Reaction
Simons challenges this view, claiming, for example, that the Ship of Theseus is two objects rather than one. I suppose 'my building bricks' might be 'your sculpture', but this is very ontologically extravagant. This is a mereological Leibniz's Law.