Parmenides: If anyone, with his mind fixed on all these objections and others like them, denies the existence of ideas of things, and does not assume an idea under which each individual thing is classed, he will be quite at a loss, since he denies that the idea of each thing is always the same, and in this way he will utterly destroy the power of carrying on discussion... Then what will become of philosophy? To what can you turn, if these things are unknown?