All links below are to .pdf files.
According to one view about the nature of persistence, four-dimensionalism, our world and everything in it consists of stages or temporal parts; moreover, where an object exists at various times, it does so, according to the four-dimensionalist, in virtue of having distinct temporal parts at those times. While four-dimensionalism is often motivated by its purported solutions to puzzles about material objects and their persistence through time, it has also been defended by more direct arguments. Three such arguments stand out: (1) the argument from temporary intrinsics, (2) the argument from vagueness and (3) the argument from recombination, Humean supervenience and causal constraints. Not surprisingly, each of these arguments originates in the work of four-dimensionalism’s most prominent modern defender, David Lewis. The third of these arguments has received, by far, the least attention, critical or otherwise; it is now time to begin to address this imbalance.
I show that the nature of the fundamental mereological relation can decisively influence the outcome of this debate. In short, if the fundamental mereological relation is proper parthood-at-a-time then four-dimensionalism is false. Recognizing this does two things for us: (i) It makes room for three-dimensionalists to say at least one of the things they have tended to say all along: persisting things do not have (proper) temporal parts, and (ii) it re-focuses the debate over persistence on a narrower and perhaps more tractable question—“What is the nature of the fundamental mereological relation?”