Experiment #14 · Thought experiment

Parfit's Teletransporter

What matters in survival

Derek Parfit · 1984 · Personal identity, ethics

First published: D. Parfit, *Reasons and Persons* (1984), Part III.

Scan, destroy, rebuild on Mars. Is the person who steps out you, or someone exactly like you?

A teletransporter scans every cell of your body, transmits the data to Mars, and reconstructs an exact duplicate there while destroying the original. Subjective experience appears continuous from the duplicate's side. Parfit asks two questions: is the Martian person you, and — more importantly — does the answer matter? In the "branch-line" variant, the scan is non-destructive and there are *two* of you. Parfit concludes that personal identity is not what matters; what matters is psychological continuity, which can hold without identity. The case is the lever for his reductionism about persons and the source of much subsequent thinking on what survival is.

Formulation

(Branch line) Subject is scanned non-destructively; a duplicate is constructed on Mars; the original survives one week, then dies of scan-induced organ failure. Question: should the original regard the Martian as themselves, as a continuator, or as a stranger? Parfit's answer: identity may not be determinate, but what matters (psychological continuity) is preserved either way.

Compare this experiment

Dimensions Engaged

◎

Observer

Targets Observer · Number and Observer · Physicality: is a single self preserved across the scan, multiplied, or replaced? Parfit's answer (none of the above; the question is empty) is itself a thesis.

◉

Matter

Bears on Matter · Ontological Status: if a person is identical with their material body, fission and reconstruction are decisive disruptions; if they are a pattern, material continuity matters less.

⧖

Time

Forces a choice on Time · Traversability: endurantist readings (the self is wholly present at each moment) and perdurantist readings (the self is a four-dimensional process) make different verdicts on the branch-line case.

Responses — How Schools Engage

Affirms / takes the bait 2

Buddhism

A natural fit for anatta: there is no persistent self to be teleported in the first place. The case reproduces, in a science-fictional register, what Buddhist analysis already concludes about ordinary persistence.

Structuralism

Identity supervenes on structural pattern; the Martian is the same person because they instantiate the same cognitive-psychological structure. Material substrate is incidental.

Denies / rejects the premise 2

Hylomorphism

The Martian is a different individual: the soul / substantial form is what individuates persons, not pattern, and form is not transmissible by data link. The teletransporter is a copying machine, not a transport.

Dualism

If the mind is non-physical, scanning the body cannot transfer the mind. The Martian has a new soul or no soul; the original dies in the scanner.

Reframes the question 2

Analytic Metaphysics / Logical Atomism

Parfit's reductionism: persons are nothing over and above their physical and psychological continuants. Identity questions can have indeterminate or empty answers without anything morally important being lost.

Process Philosophy

Persons are processes, not enduring substances. Fission cases reveal the artificiality of insisting on a unique continuant; the two-branch outcome is metaphysically tractable, just not classically describable.