Personal identity: bodily, psychological and no-self theories

What this dot point is asking

This dot point belongs to the metaphysics strand of the TASC Philosophy course. You are asked to explain the main criteria of personal identity, test them with thought experiments, and assess which best survives the objections.

The problem

You change constantly: your cells replace themselves, your beliefs shift, your appearance ages. Yet we ordinarily assume the person reading this is the same person who was a child years ago. What grounds that sameness? A good theory of personal identity must explain why a single person persists through such change, and the answer matters for responsibility, survival and what we should care about.

The bodily theory

The simplest view is that you are the same person because you have the same body, or more precisely the same living organism. This fits everyday practice, since we reidentify people by their bodies. But it faces problems. Thought experiments about brain transplants suggest that if your brain were moved to a new body, you would go with your brain, not stay with your old body. This pushes many toward locating identity in the brain or, more abstractly, in the mind the brain supports.

Locke's psychological theory

John Locke argued that personal identity consists in continuity of consciousness, especially memory. You are the same person as someone in the past if you can remember their experiences from the inside. This neatly explains why we hold people responsible only for what they did as the same conscious self. Thomas Reid objected with the brave officer paradox: a general remembers being a brave officer who remembers being a boy who stole apples, but the general does not remember the apple theft. By memory alone the general is and is not identical to the boy, which is contradictory. Later theorists repair this by appealing to overlapping chains of psychological connections rather than direct memory.

Parfit and what matters

Derek Parfit used teleportation and fission cases to argue a radical conclusion. Imagine your brain is split and each half placed in a new body, yielding two people each psychologically continuous with you. They cannot both be you, since they are two and you are one, yet there is no reason to favour either. Parfit concludes that personal identity is not what fundamentally matters. What matters is psychological continuity and connectedness, which can hold to degrees and can branch. On this reductionist view, the question of whether a future person will literally be you can be empty.

The no-self view

Buddhist philosophy, through the doctrine of anatta, denies there is any enduring self underlying experience. What we call a self is a bundle of constantly changing physical and mental processes, an idea strikingly echoed by David Hume, who reported that when he looked inward he found only particular perceptions and never a self. On this view the search for a criterion of identity rests on a mistake, since there is no single persisting thing to track.

Evaluating the theories

A strong answer recognises a trade-off. The bodily theory is concrete but yields the wrong verdict in brain-swap cases. The psychological theory matches our intuitions about responsibility but struggles with duplication. Parfit dissolves the puzzle but at the cost of denying that survival matters in the way we assume. For the exam, run a thought experiment, state what each theory predicts, and argue which result is least revisionary or most defensible.