Full Idea
It is the hierarchical conception of sets and their members, rather than the linear conception of set and subset or of aggregate and component, that provides us with the better model for the structure of part-whole in its application to material things.
Gist of Idea
Hierarchical set membership models objects better than the subset or aggregate relations do
Source
Kit Fine (Things and Their Parts [1999], §5)
Book Reference
-: 'Midwest Studs in Philosophy' [-], p.72
A Reaction
His idea is to give some sort of internal structure. He says of {a,b,c,d} that we can create subsets {a,b} and {c,d} from that. But {{a,b},{c,d}} has given member sets, and he is looking for 'natural' divisions between the members.