  While Aristotle does not saddle Heraclitus himself with the rejection of PNC, he notes that Heraclitus’s followers thought that there is so much change in the world that it is impossible to say anything true, and so Cratylus, one of their number, was reduced to wagging his finger. Cratylus was mistaken, according to Aristotle, because there is no radical flux. When things change, something persists, and even if the quantity of a thing is not constant, we know each thing by what sort of thing it is. Presumably, even if its water is constantly flowing, we can still identify a river. Aristotle points out that if there were radical flux, this would be tantamount to everything being at rest, so the idea of radical flux is contradictory.