Why are identity disorders interesting for philosophers?

"Identity disorders" constitute a large class of psychiatric disturbances that, due to deviant forms ofself-modeling, result in dramatic changes in the patients' phenomenal experience of their own personal identity. The phenomenal experience of selfhood and transtemporal identity can vary along an extremely large number of dimensions: There are simple losses of content (for example, complete losses of proprioception, resulting in a "bodiless" state of self-consciousness, see Cole 1995, Gallagher and Cole 1995, Sacks 1998). There are also various typologies of phenomenal disintegration as in schizophrenia, in depersonalization disorders and in Dissociative Identity Disorder (DID), sometimes accompanied by multiplications of the phenomenal self within one and the same physical system. It is important to not only analyze these state-classes in terms of functional deficits or phenomenology alone, but as self-representational content as well. For instance, in the second type of cases just mentioned, we confront major redistributions of the phenomenal property of "mineness" in representational space, of what is sometimes also called the "sense of ownership". Finally, there are at least four different delusions of misidentification (DM1; namely Capgras syndrome, Frégoli syndrome, intermetamorphosis, reverse intermetamorphosis and reduplicative paramnesia). Being a philosopher, I will discuss two particular types of identity disorder in this contribution - disorders, which are of direct philosophical relevance: A specific form of DM, and the Cotard delusion. Why should philosophers do this? And why should psychiatrists care?