This is one of my favorite philosophical questions. At what point is something different? [quote]The ship of Theseus, also known as Theseus' paradox, is a thought experiment that raises the question of whether an object that has had all of its components replaced remains fundamentally the same object. The paradox is most notably recorded by Plutarch in Life of Theseus from the late first century. Plutarch asked whether a ship that had been restored by replacing every single wooden part remained the same ship.[/quote] https://en.wikipedia.org/wiki/Ship_of_Theseus