Full Idea
The modern theory of parts and wholes was intended primarily to replace set theory; in this way, wholes came out looking as much like sets as they possibly could, without set theory's commitment to an infinite hierarchy of abstract objects.
Gist of Idea
Wholes in modern mereology are intended to replace sets, so they closely resemble them
Source
Kathrin Koslicki (The Structure of Objects [2008], Intro)
Book Reference
Koslicki,Kathrin: 'The Structure of Objects' [OUP 2008], p.4
A Reaction
A very nice clarificatory remark, which explains well this rather baffling phenomenon of people who think there is nothing more to a whole than a pile of parts, as if a scrap heap were the same as a fleet of motor cars.