Oration to the Greeks 16

The demons who give orders to human beings are not the souls of human beings. For how could souls become active after death? Only if a human being were senseless and powerless while alive, and after becoming a corpse could be believed to acquire more active power. But this is not so, as we have shown elsewhere. And it is hard to suppose that the immortal soul, hindered by the parts of the body, becomes wiser when it has moved out of it. For the demons, raging against human beings in their malice, divert their minds, which are bent downward, by various lying stage-shows, so that they are unable to rise up for the journey to the heavens. But the things of the world have not escaped us, and the divine is easily grasped by us, since the power that makes souls immortal has come to us. The demons are seen even by the merely natural, when they sometimes show themselves to people, either so that they may be thought to be something, or to do some harm, like friends who are ill-disposed toward enemies, or to give those who are like them occasions to honor them. If they could, they would certainly have dragged down heaven too, together with the rest of creation. But as it is they do not do this at all, for they cannot; instead, with the lower matter they make war on matter that is like themselves. Whoever wishes to conquer them, let him reject matter. For armed with the breastplate of the heavenly spirit, he will be able to save everything it encloses. There are diseases and disturbances of the matter within us; but when these occur, the demons ascribe their causes to themselves, coming upon a person whenever sickness seizes him. And sometimes they themselves shake the condition of the body with a storm of their folly; but struck by the word of God's power they depart in fear, and the sick person is healed.