It is uncertain when this method of interpretation began to be applied to ancient literature. It was part of the general intellectual movement of the fifth century B.C. It is found in one of its forms in Hecatæus, who explained the story of Cerberus by the existence of a poisonous snake in a cavern on the headland of Tænaron.[82] It was elaborated by the sophists. It was deprecated by Plato. “If I disbelieved it,” he makes Socrates say,[83] in reference to the story of Boreas and Oreithyia, “as the philosophers do, I should not be unreasonable: then I might say, talking like a philosopher, that Oreithyia was a girl who was caught by a strong wind and carried off while playing on the cliffs yonder; ... but it would take a long and laborious and not very happy lifetime to deal with all such questions: and for my own part I cannot investigate them until, as the Delphian precept bids me, I first Know myself.” Nor will he admit allegorical interpretation as a sufficient vindication of Homer:[84] “The chaining of Hera, and the flinging forth of Hephæstus by his father, and all the fightings of gods which Homer has described, we shall not admit into our state, whether with allegories or without them.” But the direct line of historical tradition of the method seems to begin with Anaxagoras and his school.[85] In Anaxagoras himself the allegory was probably ethical: he found in Homer a symbolical account of the movements of mental powers and moral virtues: Zeus was mind, Athené was art. But the method which, though it is found in germ among earlier or contemporary writers, seems to have been first formulated by his disciple Metrodorus, was not ethical but physical.[86] By a remarkable anticipation of a modern science, possibly by a survival of memories of an earlier religion, the Homeric stories were treated as a symbolical representation of physical phenomena. The gods were the powers of nature: their gatherings, their movements, their loves, and their battles, were the play and interaction and apparent strife of natural forces. The method had for many centuries an enormous hold upon the Greek mind; it lay beneath the whole theology of the Stoical schools; it was largely current among the scholars and critics of the early empire.[87] Its most detailed exposition is contained in two writers, of both of whom so little is personally known that there is a division of opinion whether the name of the one was Heraclitus or Heraclides,[88] and of the other Cornutus or Phornutus;[89] but both were Stoics, both are most probably assigned to the early part of the first century of our era, and in both of them the physical is blended with an ethical interpretation.