Clinical cases and metaphysical theories of personal identity.

In this article, we consider three metaphysical theories of personal identity: the soul theory, the body theory, and the psychological theory. Clinical cases are discussed as they present conceptual problems for each of these theories. For the soul theory, the case of Phineas Gage, and cases of pedophilic behavior due to a brain tumor are discussed. For the body theory, hypothetical cases of cephalosomatic anastomosis and actual cases of dicephalic parapagus and craniopagus parasiticus are discussed. For the psychological theory, cases of delusions and memory impairments are discussed. After a discussion of all these cases, we conclude that it is very difficult to unequivocally favor one of these theories, yet we argue that this discussion must be based not on abstract armchair speculation, but rather, consideration of real clinical cases.