In Greece, too, an idea akin to this found lodgment both in the popular belief and in the philosophy of Plato and Socrates; and though, as we have seen, the great leaders in medical science had taught with more or less distinctness that insanity is the result of physical disease, there was a strong popular tendency to attribute the more troublesome cases of it to hostile spiritual influence.( 344) (344) For the exorcism against disease found at Ninevah, see G.Smith, Delitzsch's German translation, p.34.For a very interesting passage regarding the representaion of a diabolic personage on a Babylonian bronze, and for a very frank statement regarding the transmission of ideas regarding Satanic power to our sacred books, see Sayce, Herodotus, appendix ii, p.393.It is, indeed, extremely doubtful whether Plato himself or his contemporaries knew anything of evil demons, this conception probably coming into the Greek world, as into the Latin, with the Oriental influences that began to prevail about the time of the birth of Christ; but to the early Christians, a demon was a demon, and Plato's, good or bad, were pagan, and therefore devils.

The Greek word "epilepsy" is itself a survival of the old belief, fossilized in a word, since its literal meaning refers to the SEIZURE of the patient by evil spirits.
From all these sources, but especially from our sacred books and the writings of Plato, this theory that mental disease is caused largely or mainly by Satanic influence passed on into the early Church.

In the apostolic times no belief seems to have been more firmly settled.

The early fathers and doctors in the following age universally accepted it, and the apologists generally spoke of the power of casting out devils as a leading proof of the divine origin of the Christian religion.
This belief took firm hold upon the strongest men.

The case of St.
Gregory the Great is typical.