The Ship of Theseus

In short: The Ship of Theseus is a thought experiment about identity: if you gradually replace every plank of a ship, is it still the same ship at the end?

In more detail: The ancient writer Plutarch reports that the Athenians kept the ship of their hero Theseus for a long time and kept replacing rotten planks with new ones. Even then, philosophers argued about whether it was still the original ship.

In detail

• The basic question: It is about what makes a thing the same thing over time, even though its parts change.
• Hobbes’s extension: Thomas Hobbes sharpened the puzzle: what if someone kept the old planks and built a second ship from them, which of the two would then be the real one?
• Continuity: A common answer is that the gradually repaired ship remains the same because it continued to exist as a ship without interruption and kept its function.
• Matter as the yardstick: Anyone who ties identity to the original material would rather consider the ship built from the old planks to be the real one.
• A linguistic solution: Some think the puzzle mainly shows that our word “same” has several meanings, which have to be distinguished in each case.
• Everyday examples: Similar questions arise with buildings that are restored again and again, with bands whose members change, or with a club that has existed for over a hundred years.
• Personal identity: The human body also renews many of its cells over a lifetime, and memories and character change; yet we still speak of the same person.
• No clear result: The thought experiment has no generally accepted solution, but it is a classic tool for thinking more precisely about concepts such as identity and change (logische-paradoxien-grundlagen, leib-seele-problem, was-ist-philosophie).