"The view that the soul is a "harmony," or... attunement, is intimately connected with the theory of the four elements. It cannot have belonged to the earliest... Pythagoreanism; for... in Plato’s Phaedo, it is... inconsistent with the idea that the soul can exist independently of the body. It is... opposite of the belief that "any soul can enter any body." ...[F]rom the Phaedo... it was accepted by Simmias and Kebes, who had heard Philolaos at Thebes, and by Echekrates of Phleious, who was the disciple of Philolaos and Eurytos."