The Prince and the Cobbler

The scenario

Locke asks you to imagine a prince, fully conscious with all his memories, ambitions, and sense of self, waking up in a cobbler's body. The cobbler's soul, if there is one, has gone elsewhere. The body is the cobbler's, but the person inside it remembers being a prince, thinks like a prince, and takes himself to be the prince.

Locke's answer is unambiguous: the prince is in that body. The person who wakes up is the prince, not the cobbler, because personal identity follows psychological continuity, not bodily continuity. The cobbler's family would be wrong to treat this person as their relative. The prince's creditors would be right to come calling.

Psychological continuity theory

Locke's argument established what philosophers now call psychological continuity theory: personal identity consists in the continuity of consciousness, especially memory. You are the same person as the child who attended your first day of school because you can remember being that child, or are connected through overlapping chains of memory to someone who can.

This was a radical departure from two alternatives. The soul theory says identity consists in the persistence of an immaterial soul. Locke thought the soul couldn't do the work: a prince could wake in a cobbler's body with the cobbler's soul and the prince's memories, and we'd still call him the prince. The body theory says identity consists in bodily continuity. The prince-and-cobbler case was designed to show that intuition runs the other way.

Reid's objection

Thomas Reid pressed a serious objection. Imagine an old general who, as a young officer, was flogged for stealing. As a boy, he had stolen the apples. The general can remember his time as a young officer but cannot remember being the boy who stole. On Locke's view, the general is the same person as the young officer (he remembers that), and the young officer is the same person as the boy (the officer could remember the flogging). But the general is not the same person as the boy, because he cannot remember it.

This is a problem because identity should be transitive: if A is the same as B, and B is the same as C, then A must be the same as C. Locke's memory criterion produces a case where that fails. Derek Parfit later tried to fix this with a more sophisticated version of psychological continuity, but Reid's challenge showed that memory alone is not a sufficient account.