Getting back in shape: Persistence, shape, and relativity

In this paper, we will introduce a novel argument (the “Region Argument”) that objects do not have frame-independent shapes in special relativity. The Region Argument lacks vulnerabilities present in David Chalmers' argument for that conclusion based on length contraction. We then examine how views on persistence interact with the Region Argument. We argue that this argument and standard four-dimensionalist assumptions entail that nothing in a relativistic world has any shape, not even stages or the regions occupied by them. We also argue that endurantists have viable ways of preserving shape despite the Region Argument. The upshot of these arguments is that contrary to conventional wisdom, considerations about shape in relativity support endurantism rather than four-dimensionalism. We conclude by examining the implications of our discussion for the debate over Edenic shapes, noting that endurantists have a satisfying response to skeptical arguments about Edenic shapes similar to the one they have against the Region Argument.