The close analogy between Pythagoreanism and Orphism has been recognized from Herodotus (ii.
Both inculcated a peculiar kind of ascetic life; both had a mystical speculative theory of religion, with purificatory rites, abstinence from beans, &c.; but Orphism was more especially religious, while Pythagoreanism, at least originally, inclined more to be a political and philosophical creed.
It does not appear, however, that a regularly organized or numerous Orphic sect ever existed, nor that Orphism ever became popular; it was too abstract, too full of symbolism.
Of more modern writings on Orpheus and Orphism the following may be consulted.
The doctrine established itself in Greek theology under the influence of Orphism, and supplied Plato with mythic forms for his " criticism of life."