Are you the same person you were several years ago?
Are you the same person you were several years ago? You think so, of course, because you are you. But think about the fact that virtually every atom in your body has changed over the years. Are you still you? A similar question was asked with regard to the Ship of Theseus, reported by Plutarch:
The ship wherein Theseus and the youth of Athens returned [from Crete] had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place, insomuch that this ship became a standing example among the philosophers, for the logical question of things that grow; one side holding that the ship remained the same, and the other contending that it was not the same.
Many philosophers, ancient and contemporary, have weighed in on this fundamental question of ontology and flux, as reported by Wikipedia.