Philosophy
The Metaphysics of Identity and the Problem of Change Over Time
Quick fact
The 'paradox of change' troubled philosophers for millennia: if an object changes, it seems to both be and not be the same thing. Ancient Greek philosopher Heraclitus claimed you cannot step into the same river twice, while Parmenides denied change entirely, arguing that reality is unchanging and our senses deceive us.
Why this is interesting
You are not the same person you were ten years ago—your cells have been replaced, your memories have shifted, your personality has evolved. Yet you still think of yourself as 'you.' How can that be?