Philosophers often think that scientific concepts should refer to natural kinds. It has been suggested that this requirement not only holds in the natural sciences but also applies in the social and behavioral sciences, including the cognitive sciences, because inductive success in the special sciences requires that the used categories must somehow track the objective structures of reality. 1 In the philosophy of psychology, debates concerning cognitive natural kinds have recently surfaced, for example, in discussions on scientific eliminativism and on extended cognition: scientific eliminativism presupposes a view of concepts in the psychological sciences as natural kinds, and in the extended cognition debate, especially defenders of intracranialist positions have alluded to properties of natural kinds in their arguments against cognitive extension. 2