My father replaced the lenses on his glasses. Then he replaced the frame when it later broke. Same type of lenses and same model of frame. He claims they're still the same pair of glasses. When I argue he's wrong and that they're now a different pair, he claims the same could therefore be said of him as he's replaced all his cells several times since he originally bought the glasses but, since he's still him, the glasses are still the glasses. Who's right?