The Ship of Theseus
If every plank on a ship is replaced—is it still the same ship?
This thought experiment is recounted by Plutarch in his biography of Theseus. For centuries, the Athenians maintained the ship that Theseus supposedly sailed, replacing rotten planks with new ones. The question arises: once all the original parts have been replaced, is it still the same ship? And if someone gathered all the old planks and built a ship out of them—which one is the real one? The problem touches on identity, continuity, and what makes an object the object that it is.
The cells in your body are continuously being replaced. After a few years, you are physically made of almost entirely new material. Yet you experience an unbroken sense of identity. In what way are you the 'same' person as ten years ago?
The question is far from trivial. It resurfaces in debates about personal identity, consciousness, restoration ethics, and even software upgrades.
There is no single 'right' answer. The point is that our everyday concepts of identity are not as self-evident as they feel.
Which part of yourself would you have to replace to no longer be you? Your body? Your memories? Your values?
Identity over time is less straightforward than it seems.
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