Augustine starts book 9 looking at the philosophers’ understandings of differences between demons. Are there good demons and bad demons? How might that be the case? For all his love for the Platonists, Augustine is being very thorough in his deconstruction of their ontology.
In chapters 1-3, he argues that there really aren’t major differences between demons, but there are differences between humans and demons. Demons are torn by their passions, while humans seem to have the God-given ability to master their passions, even though passions do affect even wise men. Demons do not have “in any part of their soul the truth and virtue by which such turbulent and depraved passions might be repulsed.” While humans have the ability to resist the passions and display virtue. Also, the passions might be used toward virtuous ends: “Within our discipline, then, [that is, among Christians] we do not so much ask whether a pious soul is angry, as why he is angry; not whether he is sad, but whence comes his sadness; not whether he is afraid, but what he fears. For I do not think that any right-minded person would condemn anger directed at a sinner in order to correct him; or sadness on behalf of one who is afflicted, in order to comfort him; or fear for one in peril, lest he perish.” The Christian may be moved to virtue by the passions. As we know, we may also be moved to vice by the passions, but humans do not need to be controlled by them. And so, humans are above the demons.