Full Idea
If composition just requires contact, that tells us that the bricks of a house compose at least one thing; it does not tell us that they also compose at most one thing.
Gist of Idea
If bricks compose a house, that is at least one thing, but it might be many things
Source
Peter van Inwagen (Material Beings [1990], 04)
Book Reference
Inwagen,Peter van: 'Material Beings' [Cornell 1995], p.39