Responds to comments made by Rhemtulla and Xu on the current authors' original paper Concepts of individual objects (e.g., a favorite chair or pet) include knowledge that allows people to identify these objects, sometimes after long stretches of time. In an earlier article, the authors set out experimental findings and mathematical modeling to support the view that judgments of identity depend on people's beliefs about the causal connections that unite an object's earlier and later stages. This article examines M. Rhemtulla and F. Xu's (2007) critique of the causal theory. The authors argue that M. Rhemtulla and F. Xu's alternative sortal proposal is not a necessary part of identity judgments, is internally inconsistent, leads to conflicts with current theories of categories, and encounters problems explaining empirical dissociations. Previous evidence also suggests that causal factors dominate spatio-temporal continuity and perceptual similarity in direct tests. The authors conclude that the causal theory provides the only existing account consistent with current evidence.