A Flaw in Sider's Vagueness Argument for Perdurantism: Endurantism Endures

ABSTRACT Sider's vagueness argument for perdurantism (2001: 126ff.) has long been seen as one of the most powerful, or perhaps the most powerful, in the perdurantist's arsenal. In its absence, the case against endurantism is significantly weakened. Despite its age, there is still no generally agreed view on its worth. I shall show that this argument fails. It is an extension of a modification Sider gives of David Lewis's argument for unrestricted mereological composition. I shall first set out Lewis's argument for unrestricted mereological composition, Sider's modification, and the problem with it. I will then turn to Sider's extension of the argument into an argument for perdurantism and show that it suffers from the same problem. As I shall explain, though Sider's modification of Lewis's argument for unrestricted mereological composition fails, this is not a crushing blow for proponents of that thesis, since Lewis's original argument is still available, which is valid and plausibly sound. But there is no available retreat for the perdurantist to a Lewisian form of Sider's argument for perdurantism.