City of God

As to the demons, these false and deceitful mediators, who, though their uncleanness of spirit frequently reveals their misery and malignity, yet, by virtue of the levity of their aerial bodies and the nature of the places they inhabit, do contrive to turn us aside and hinder our spiritual progress; they do not help us towards God, but rather prevent us from reaching Him. Since even in the bodily way, which is erroneous and misleading, and in which righteousness does not walk—for we must rise to God not by bodily ascent, but by incorporeal or spiritual conformity to Him—in this bodily way, I say, which the friends of the demons arrange according to the weight of the various elements, the aerial demons being set between the ethereal gods and earthy men, they imagine the gods to have this privilege, that by this local interval they are preserved from the pollution of human contact.

Thus they believe that the demons are contaminated by men rather than men cleansed by the demons, and that the gods themselves should be polluted unless their local superiority preserved them. Who is so wretched a creature as to expect purification by a way in which men are contaminating, demons contaminated, and gods contaminable? Who would not rather choose that way whereby we escape the contamination of the demons, and are cleansed from pollution by the incontaminable God, so as to be associated with the uncontaminated angels?