Cratylus—Athenean philosopher, a contemporary of Socrates and Plato. Cratylus taught a radical form of scepticism. He was a disciple of Heraclitus, whose most famous aphorism is You cannot step in the same river twice. Cratylus amended that aphorism, making it You cannot step into the same river once. He believed there is no point even to speak, because as we speak we and the world change, rendering all that we say into useless babble about nothing real. See Scepticism.