Ship of Theseus, explained.
The Ship of Theseus explores how an object can persist as its material parts change. Reassembling its removed parts adds a rival claim grounded in original material rather than maintenance history.
Why it happens
Continuous repair preserves one chain of use while relocating old components. When the components form a second ship, continuity of history and continuity of matter no longer identify the same candidate.
The Ship of Theseus asks what allows an object to persist when its parts change. Reassembling the removed parts sets material continuity against the continuity of the maintained object.
Read the result
Replace original planks and reassemble the stored originals in the second hull. Follow each material transfer before choosing an identity criterion. The board reports part counts but never equates them with percentages of identity.
A worked example
Two ships and one history
Replace all eight planks of the maintained ship over the sequence of repair actions.
Use the eight stored originals to build the second hull, so the original material is conserved rather than duplicated.
Choose a criterion and compare the two ships. Material continuity and maintained history now support different candidates.
OPTIONAL DEEPER DETAILGo deeper: inside the model
Inside this model
Eight original planks start aboard a ship. Clicking a plank replaces it and moves its original to storage. Each original can be reassembled in a second hull. Counts track original material aboard and in the reconstructed ship. Identity choices remain open to revision; the software supplies no numerical identity percentage.
Where this idea is useful
A practical use
A repaired tool or continually maintained organisation can preserve a history while changing its components.
A common misconception
“The ship with more original planks must be the original by definition.”
That conclusion already adopts a material criterion. The puzzle asks why that criterion should govern instead of another account of persistence.
What this explanation leaves out
- A wooden ship is a thought experiment, not a model proving personal identity or consciousness. Different identity criteria are not assumed to be interchangeable, and counting material does not resolve the philosophical dispute.
Does this settle who a person is after changing over time?
No. Artefact identity and personal identity involve different questions. The ship can clarify a tension without proving a theory of persons or consciousness.
When something changes, which continuity are you actually relying on when you call it the same thing?
Associated thinkers
Associations marked provisional are awaiting source review.
Further reading
Explore the original research or the teaching reference behind this experiment.