Material Constitution is Ad Hoc

The idea that two objects can coincide—by sharing all their proper parts, or matter—yet be non-identical, results in the “Problem of Coincident Objects”: in what relation do objects stand if they are not identical but share all their proper parts? One solution is to introduce material constitution. In this paper, I argue that this is ad hoc since, first, this solution cannot be generalized to solve similar (real) problems, and, second, there are pseudo cases of coincidence that should not trigger the introduction of material constitution and these cannot be distinguished in any principled way from the allegedly real cases of coincidence.