Accordingly, we can show from an examination of the sacred Scriptures, that the Jewish prophets, who were enlightened as far as was necessary for their prophetic work by the Spirit of God, were the first to enjoy the benefit of the inspiration; and by the contact— if I may so say— of the Holy Spirit they became clearer in mind, and their souls were filled with a brighter light. And the body no longer served as a hindrance to a virtuous life; for to that which we call “the lust of the flesh” it was deadened.
For we are persuaded that the Divine Spirit “mortifies the deeds of the body,” and destroys that enmity against God which the carnal passions serve to excite. If, then, the Pythian priestess is beside herself when she prophesies, what spirit must that be which fills her mind and clouds her judgment with darkness, unless it be of the same order with those demons which many Christians cast out of persons possessed with them? And this, we may observe, they do without the use of any curious arts of magic, or incantations, but merely by prayer and simple adjurations which the plainest person can use.
Because for the most part it is unlettered persons who perform this work; thus making manifest the grace which is in the word of Christ, and the despicable weakness of demons, which, in order to be overcome and driven out of the bodies and souls of men, do not require the power and wisdom of those who are mighty in argument, and most learned in matters of faith.
Source: Against Celsus (New Advent)