Source: Zen and the Art of Motorcycle Maintenance (1974), Ch. 29
Context: The Immortal Principle was first called water by Thales. Anaximenes called it air. The Pythagoreans called it number and were thus the first to see the Immortal Principle as something nonmaterial. Heraclitus called the Immortal Principle fire and introduced change as part of the Principle. He said the world exists as a conflict and tension of opposites. He said there is a One and there is a Many and the One is the universal law which is immanent in all things. Anaxagoras was the first to identify the One as nous, meaning "mind."
Parmenides made it clear for the first time that the Immortal Principle, the One, Truth, God, is separate from appearance and from opinion, and the importance of this separation and its effect upon subsequent history cannot be overstated. It's here that the classic mind, for the first time, took leave of its romantic origins and said, "The Good and the True are not necessarily the same," and goes its separate way. Anaxagoras and Parmenides had a listener named Socrates who carried their ideas into full fruition.
