Would the answer to this question still be the same had Dan erased from his memory ONLY the crime -but recalled everything else (in an act of selective dissociation)? Do our moral and legal accountability and responsibility spring from the integrity of our memories? If Dan were to be punished for a crime he doesn't have the faintest recollection of committing - wouldn't he feel horribly wronged? Wouldn't he be justified in feeling so?
There are many states of consciousness that involve dissociation and selective amnesia: hypnosis, trance and possession, hallucination, illusion, memory disorders (like organic, or functional amnesia), depersonalization disorder, dissociative fugue, dreaming, psychosis, post traumatic stress disorder, and drug-induced psychotomimetic states.
Consider this, for instance:
What if Dan were the victim of a Multiple Personality Disorder (now known as "Dissociative Identity Disorder")? What if one of his "alters" (i.e., one of the multitude of "identities" sharing Dan's mind and body) committed the crime? Should Dan still be held responsible? What if the alter "John" committed the crime and then "vanished", leaving behind another alter (let us say, "Joseph") in control?
Should "Joseph" be held responsible for the crime "John" committed? What if "John" were to reappear 10 years after he "vanished"? What if he were to reappear 50 years after he "vanished"? What if he were to reappear for a period of 90 days - only to "vanish" again? And what is Dan's role in all this? Who, exactly, then, is Dan?
II. Who is Dan?
Buddhism compares Man to a river. Both retain their identity despite the fact that their individual composition is different at different moments. The possession of a body as the foundation of a self-identity is a dubious proposition. Bodies change drastically in time (consider a baby compared to an adult). Almost all the cells in a human body are replaced every few years. Changing one's brain (by transplantation) - also changes one's identity, even if the rest of the body remains the same.
Thus, the only thing that binds a "person" together (i.e., gives him a self and an identity) is time, or, more precisely, memory. By "memory" I also mean: personality, skills, habits, retrospected emotions - in short: all long term imprints and behavioural patterns. The body is not an accidental and insignificant container, of course. It constitutes an important part of one's self-image, self-esteem, sense of self-worth, and sense of existence (spatial, temporal, and social). But one can easily imagine a brain in vitro as having the same identity as when it resided in a body. One cannot imagine a body without a brain (or with a different brain) as having the same identity it had before the brain was removed or replaced.
What if the brain in vitro (in the above example) could not communicate with us at all? Would we still think it is possessed of a self? The biological functions of people in coma are maintained. But do they have an identity, a self? If yes, why do we "pull the plug" on them so often?
It would seem (as it did to Locke) that we accept that someone has a self-identity if: (a) He has the same hardware as we do (notably, a brain) and (b) He communicates his humanly recognizable and comprehensible inner world to us and manipulates his environment. We accept that he has a given (i.e., the same continuous) self-identity if (c) He shows consistent intentional (i.e., willed) patterns ("memory") in doing (b) for a long period of time.