I wish I could quote Tony's post, so I'll just write:
Tony said: "This idea of replacing all the parts of something and wondering if it is still the same thing actually seems to by a paradox mentioned by the Ancient Greeks in a thought experiment known as
The Ship of Theseus, "
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Define "same".
Heraclitus's ship, 500 years after Theseus, may be made from different timbers, different ropes and different sails, but in spirit it may still be the Ship of Theseus.
This is like the "my grandfather's axe" argument in "The Fifth Element - er, Elephant".