Full Idea
I propose that parthood essentially involves causation. Too many philosophers have supposed that objects compose something when and only when they stand in some (more or less stable) spatial relationship to one another.
Gist of Idea
I think parthood involves causation, and not just a reasonably stable spatial relationship
Source
Peter van Inwagen (Material Beings [1990], 09)
Book Reference
Inwagen,Peter van: 'Material Beings' [Cornell 1995], p.81
A Reaction
I have to say that I like this, even though it comes from a thinker who is close to nihilism about ordinary non-living objects. He goes on to say that only a 'life' provides the right sort of causal relationship.