Commonsense ontology contains both continuants and occurrents, but are continuants necessary? I argue that they are neither occurrents nor easily replaceable by them. The worst problem for continuants is the question in virtue of what a given continuant exists at a given time. For such truthmakers we must have recourse to occurrents, those vital to the continuant at that time. Continuants are, like abstract objects, invariants under equivalences over occurrents. But they are not abstract, and their being invariants enables us toinfer both their lack of temporal parts and that non-invariant predications about them must be relativized to times.
[E]ndurance is the property of finding its pattern reproduced in the temporal parts of the total event.
Whitehead, Science and the Modern World, 189.