METAPHYSICS – AN OVERVIEW : Identity and Persistence

Personal Identity - Realist and Reductionist Alternatives:  (1) The diachronic unity relation is an irreducible relation, both in the case of persons, and in the case of inanimate objects;  (2) The diachronic unity relation is an irreducible relation in the case of immaterial egos, and so there would be a fact of the matter in fission cases;  (3) Bodily identity is a necessary and sufficient condition of personal identity;  (4) Brain identity is a necessary and sufficient condition of personal identity;  (5) The unity relation is a matter of relations between occurrent psychological states;  (6) The unity relation is a matter of relations between psychological states, both occurrent states and underlying powers;  (7) The unity relation is a matter of relations between psychological states, both occurrent states and underlying powers, and also a matter of those states' being instantiated in the same underlying stuff, where the latter might be either the same brain, or the same immaterial substance.

Important Thought Experiments and Test Cases:  (1) Interchanging psychological states between different brains;  (2) The transference of psychological states and powers to a different immaterial substance;  (3) The destruction of all psychological states, together with the continued existence of brain and body;  (4) Shoemaker’s brain transplant case;  (5) The case where one hemisphere is destroyed;  (6) The case where one hemisphere is destroyed, and the other hemisphere is transplanted;  (7) The case where both hemispheres are transplanted into different bodies;  (8)  Derek Parfit's fusion cases;  (9) The reprogramming case; (10) Teletransportation cases, (a) with the same matter arranged the same way, (b) with the same matter arranged a different way, and (c) with completely different matter.

Issues Raised by Derek Parfit:  (1) Is it possible to make sense of the notion of "surviving" in a case where the resulting person is not identical with the original person?  (2) Must there always be a true answer to any question concerning identity in any conceivable case?  (3) Is identity an important matter?  (4) Is what matters an all-or-nothing matter, or a matter of degree?  (5) Can one set out an account of memory, which is such that it is not an analytic truth that if A has a memory of experience E, then E is an experience that A had?  (6) Can all mental states be described impersonally - that is, in a way that does not presuppose the existence of any person at all?  (7) Does personal identity just consist in bodily and psychological continuity, or is it a further fact, independent of the facts about these continuities?  (8) If there is a further fact, is it (a) a deep fact, and (b) an all-or-nothing fact?