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What makes something remain itself?

The Ship of Theseus asks whether an object is still the same object after every part has gradually been replaced.

The idea

The thought experiment tests competing ideas of identity: continuity through time, physical material, structure, function, or the story we attach to an object.

An example

If every component of a restored aircraft is eventually replaced, is it still the original aircraft—or a successor carrying its identity?

Put it into practice

Notice which kind of continuity matters most when you call a person, organisation, or object “the same.”