Questions hidden inside
- Would the person who appears at the destination be you, a perfect copy, or a successor related in another way?
- What happens to the identity claim if the original body survives and two people continue?
- Could survival matter even when strict numerical identity is absent or indeterminate?
Philosophical lenses
Psychological continuity
Do memory, character, intention, and projects carry the person forward?
Psychological approaches explain why the destination person may seem continuous with the traveler, but duplication creates competing continuers.
Bodily continuity
Must the same living organism persist?
Animalist and biological approaches deny that copied information can move the original organism, even when the copy is exact.
Survival and practical concern
Is strict identity what matters most?
Reductionist approaches ask whether continuity, connectedness, and preserved relationships can justify anticipation and concern without a further identity fact.
Begin with a choice
A teletransporter destroys your body and creates an exact counterpart on Mars. Who arrives?
The scenario
A teletransporter scans the complete physical state of your body, transmits the information to Mars, and uses new matter to construct a person exactly like you. The destination person remembers entering the machine, recognizes your friends, continues your projects, and expects to be treated as you.
In the standard destructive version, the scanning process eliminates the original body. From the outside, one continuous life appears to end on Earth and resume on Mars, but the mechanism involves copying and reconstruction rather than ordinary travel.
What the experiment is for
The case pulls psychological continuity apart from bodily and material continuity. In ordinary life these largely coincide, allowing memory, organism, social recognition, and causal history to support one identity judgment.
The teletransporter asks which connection is necessary for persistence and whether identity is a further fact beyond the continuities that can be described. It also tests what grounds anticipation, responsibility, ownership, promise, and relationship.
Competing approaches
A psychological-continuity view can treat the Mars person as the continuer because memories, intentions, character, and projects are preserved through the right causal process. A bodily or animalist view holds that the living organism remains on Earth and is destroyed, so the person on Mars is a new being.
Reductionist approaches argue that no additional hidden fact may determine identity once all physical and psychological relations are fixed. The practical question may then become whether the relation preserves what matters for survival, not whether it satisfies an all-or-nothing label.
| Approach | What must continue | Pressure from teleportation |
|---|---|---|
| Psychological continuity | Memory, character, intention, and other mental connections | Two equally continuous copies cannot both be numerically identical to one original |
| Bodily or biological continuity | The same living organism | An exact psychological successor still appears to continue the life in important ways |
| Brain-based continuity | Enough of the same functioning brain | The case replaces rather than transports the original brain |
| Reductionist | Specified physical and psychological relations | Ordinary practices may still demand a single legal and social answer |
The duplication problem
Now suppose the machine malfunctions and the original body survives while the Mars counterpart is created. Both remember the same past, claim the same relationships, and intend to continue the same projects. They cannot both be one numerically identical person if they immediately become two.
Branching suggests that psychological continuity can be one-to-many even though identity is one-to-one. Responses include privileging the original organism, denying identity to the copy, revising the psychological criterion to exclude branching, or concluding that identity is not the only relation that matters.
- Ask who owns property and remains bound by promises after duplication.
- Distinguish qualitative similarity from numerical identity.
- Separate fear of death from concern that projects and relationships continue.
- Consider whether social and legal practices need a sharper answer than metaphysics provides.
Change one fact
Does the existence of two equally continuous people change the original identity judgment?
Your earlier choice: Treat the person reconstructed on Mars as the same person because the original body is destroyed and the psychology continues.
Continue with personal identity, moral responsibility, authenticity.
Continue with Ada
Professor Ada Rowan
Test an idea or objection
Compare perspectives, test an assumption, or develop an objection using this reviewed page as context.
Related paths
Sources
- Reasons and Persons — Derek Parfit (1984)
Major philosophical work on psychological connectedness and continuity, reductionist accounts of persons, branching cases, and the claim that identity may not be what matters most for survival and practical concern.
View source - Personal Identity — Eric T. Olson (2023)
Scholarly overview of distinct personal-identity questions, including characterization, personhood, persistence, evidence, psychological-continuity accounts, animalism, bodily continuity, fission, and the practical importance of survival.
View source - The Human Animal: Personal Identity Without Psychology — Eric T. Olson (1999)
Academic defense of animalism and biological continuity as an alternative to psychological and memory-based accounts of personal identity, useful for presenting bodily continuity as a serious competing view.
View source - An Essay Concerning Human Understanding — John Locke (1975)
Primary source for Book II, chapter XXVII, where Locke distinguishes the identity of persons from the identity of substances, links personal identity to consciousness across time, and treats person as a forensic term connected with action and accountability.
Last modified 2026-07-30. Reviewed by Thinking Paths editorial team.