Following Wiggins’ seminal article, On Being in the Same Place at the Same Time, this article presents the first comprehensive account of the relation of material constitution, an asymmetrical, transitive relation which totally orders distinct ‘entities’ (individuals, pluralities or masses of stuff) which ‘spatially coincide.’ Their coincidence in space is explained by a recursive definition of ‘complete-composition’, weaker than strict mereological indiscernibility, which also explains the variety of logically independent similarities in such cases. This account is ‘analytical’, dealing with ‘putative’ (...) cases in general. The main strategy is to rationally reconstruct Aristotle’s notion of material cause. It is developed more fully with a theory of how to justify admitting generable and perishable things into the natural world, in The Kinds of Things: A Theory of Personal Identity Based on Transcendental Argument (Open Court, 1996). (shrink)