Parfit's psychological continuity theory, the fission problem, and the claim that identity is not what matters

What this dot point is asking

VCAA wants you to explain Derek Parfit's reductionist account of personal identity, work carefully through his thought experiments (the teletransporter and fission), and assess his startling conclusion that identity is not what matters in survival. The top response keeps the technical terms straight (continuity versus connectedness, the further fact, Relation R), uses the fission case to drive the argument rather than just describing it, and reaches a reasoned verdict on whether Parfit has shown what he claims.

Parfit's reductionism

Derek Parfit, in Reasons and Persons, defends two linked claims. First, the criterion of personal identity is psychological: I continue to exist so long as there holds Relation R, psychological connectedness (direct memory, intention, belief and desire links) and continuity (overlapping chains of such connections). This refines Locke by replacing single memories with overlapping chains, repairing the transitivity problem.

Second, and more radically, Parfit is a reductionist: the fact of personal identity just consists in more particular facts about brains, bodies and interrelated mental events. There is no separate, deep further fact, no Cartesian ego or bare self, whose presence or absence is all-or-nothing. Persons are, in his phrase, less deep than we ordinarily assume.

The teletransporter

Parfit imagines stepping into a scanner that records the exact state of every cell, destroys the original body, and builds an exact replica on Mars from new matter, with all psychological states continuous. Is the person on Mars you, or have you died and been replaced by a copy? Our intuitions waver. Parfit's point is that once we know every physical and psychological fact about the case, there is no further question left whose answer we are missing. Asking whether it is really me adds nothing. This sets up the deeper case.

The fission argument

The decisive thought experiment is fission. Suppose my brain is divided and each half is transplanted into a different body, each resulting person being fully psychologically continuous with me (the empirical basis is the relative independence of the two hemispheres). Call them Lefty and Righty. Now ask: what happens to me?

1. I cannot be identical to both Lefty and Righty, since they are two distinct people and identity is one-one.
2. There is no reason to say I am Lefty rather than Righty; they are symmetrical.
3. So I am not identical to either.
4. But fission preserves everything I normally care about in survival (memories, intentions, character) twice over. It is surely not as bad as ordinary death.
5. Therefore identity is not what matters in survival. What matters is Relation R, which fission preserves.

The conclusion is that the question what matters and the question of identity come apart. Ordinarily Relation R coincides with identity, so we never notice; fission prises them apart.

Parfit's further claims

Parfit draws practical morals. Because what matters is a matter of degree, and because there is no deep further fact, the boundary of a person is less sharp than we think. He argues this should reduce egoistic self-concern, soften the fear of death, and support a more impartial morality, since the gap between persons is shallower than the metaphysics of the ego suggested.

Evaluation

The fission argument is among the most influential in the field, and its logic is hard to escape once the empirical possibility is granted. It cleanly refutes the view that identity is the relation that carries what we care about.

But there are replies. The multiple occupancy view holds that there were two people present all along, sharing a body before fission, so identity is preserved; Parfit answers that this is an ad hoc rescue with strange consequences. A second worry attacks premise 4: a critic may insist that having a duplicate genuinely is worse than ordinary survival, because the existence of a rival who is equally me changes the prudential situation. If fission is not as good as survival, the argument is blocked. Third, the reductionist denial of a further fact is contested by those who hold that the unity of consciousness is a deep fact, not reducible to physical or psychological relations.

Judgement: Parfit succeeds in showing that identity and what matters can come apart, a real and surprising result; the fission case is genuinely hard to answer without paying a cost. His stronger conclusions about the fear of death rest on the contested claim that Relation R alone fully captures what matters, and an opponent who values identity itself can resist them. The metaphysics is convincing; the consolation is optional.