The oldest identity puzzle on record: Theseus's ship, preserved by replacing each rotting plank until none of the original wood remains. Is it still his ship? And Hobbes's follow-up: rebuild the discarded planks, and which one is?
Documented
Plutarch's report and the philosophical fleet
Documented: Plutarch's Life of Theseus (c. 100 AD) describes the Athenians preserving the ship by plank-swapping, sparking debate he calls ongoing among the philosophers. Hobbes added the reassembly case (De Corpore, 1655); Locke made it about personal identity, pinning sameness to consciousness rather than matter; Hume dissolved the self into a bundle in flux. Two millennia of solutions: spatiotemporal continuity, the four-dimensional worm view, identity as convention, identity as narrative.
Assessment: Documented as philosophy's most durable open file. No solution commands the field because the puzzle is not empirical, it asks which of our concepts of sameness we actually mean, and we mean several at once.
Stories
Grandfather's axe, Trigger's broom
Every culture stocks the folk version: my grandfather's axe, three new heads and two new handles; the Japanese shrine rebuilt identically every twenty years for thirteen centuries; the band touring with zero original members. The instinct the puzzle exposes: we grant identity to continuity of story and function, not to matter, and we grant it gladly.
Assessment: Documented across cultures as the default human answer, which is itself data: identity is a social technology, and the ship stays Theseus's because the city agrees it does. The Ise Shrine renews its identity by replacing everything; that is the feature, not the bug.
Interesting claims
The teleporter clause
The interesting claims modernize the stakes: teleportation that scans, destroys, and rebuilds you is plank-swapping with a commute; uploading minds inherits the entire paradox; and the Ship of Theseus now sits in legal scholarship, does a nation survive total constitutional replacement, and in biology, clonal colonies older than their cells. Wherever continuity is claimed, the ship is docked.
Assessment: Documented applications, zero resolutions. The puzzle persists because it works: it is the universal adapter between metaphysics and every practical identity dispute humans actually fight about. File as the archive's oldest unsolved object.
Sources and further reading
Plutarch, Life of Theseus (c. 100 AD), the original report
Hobbes, De Corpore (1655), the reassembly case
Locke, An Essay Concerning Human Understanding (1689), identity as consciousness
Hume, A Treatise of Human Nature (1739), the bundle dissolution
Ise Grand Shrine rebuilding records, the living folk answer
Worth asking
You are the third or fourth ship by now. What, precisely, kept sailing?