Category: identity
Associated thinker(s): Derek Parfit
Original publication or approximate period: Reasons and Persons (1984), modern influential presentation
Difficulty: Intermediate
Themes: survival, copying, continuity
Related experiments: fission, ship-of-theseus
Kind: thought experiment
Research checked: 2026-10-30
A scanner records your body and brain in exhaustive detail, destroys the original, and constructs an exact counterpart elsewhere. The arrival remembers entering the scanner and continues your projects. Now change one condition: the scanner fails to destroy you, while producing the arrival as usual. The person who stayed behind meets the person who arrived. Both have the same apparent claim to your remembered past.
Does perfect psychological reconstruction preserve you, or merely produce someone much like you?
The contrast between ordinary transport and duplication tests whether a pattern of information is sufficient for personal identity. It also separates the question of strict identity from questions about what someone should care about in a future successor.
The duplicate version is a useful stress test because the arrival’s internal state need not change when the original remains alive. If your verdict about the arrival changes solely because another person exists elsewhere, explain why identity is sensitive to that fact. If it does not change, explain how one predecessor could be identical to two distinct later people. Either answer exposes a commitment that the simpler destruction-and-reconstruction story can conceal. You may also conclude that the practical value of continuation is clearer than the question of strict numerical identity.
Psychological-continuity approaches may regard the arrival as a continuer, while adding nonbranching conditions when copies compete. Animalist approaches locate persistence in the continued life of the human organism. Parfit’s reductionist treatment suggests that psychological relations can matter even where strict identity fails to track what we ordinarily value.
The case does not show that actual teleportation is technically possible. Quantum teleportation transfers quantum states under specified conditions and is not this imagined transport of a person. A duplicate’s sincere recollection is evidence of psychological resemblance, not automatically proof of numerical identity.
The branch-line variant preserves the original and thereby forces rival claims into view. Gradual replacement and partial reconstruction cases test continuity differently; they are recognized neighboring debates, not solutions by definition.
Historical association: Reasons and Persons (1984), modern influential presentation. The sources above support the scenario and its intellectual context. Where an original work was not retrieved in full, its account is mediated by the named academic reference; no claim of full primary-source verification is made. The explanation and reflection questions here are original editorial prose.