sometimes thought to have been a teacher of Plato before Socrates. He is famous for capping the doctrine of Heraclitus that you cannot step into the same river twice by adding that you cannot step into the same river once: the river is changing and gone even as a single event of stepping occurs. The point is that reality is utterly particular (one individual event, one moment of time, one individual thing after another). Any adequate thought would have to match the flux with change of its own, so any attempt to categorize reality is like trying to cage the winds. He is also represented in Plato’s dialogue Cratylus as holding a doctrine of the ‘right name’ of things, although the proper conclusion of his views was that the flux cannot be captured in words. According to Aristotle (Metaphysics Γ‎, iv. 1010) he eventually held that since ‘regarding that which everywhere in every respect is changing nothing could truly be affirmed’, the right course is just to stay silent and wag one’s finger. Plato’s theory of forms can be seen in part as a reaction against the impasse to which Cratylus was driven.