Augustine thinks that he's written more than enough to counter the claims of paganism concerning the dominance of the gods:
And who does not know that, in the face of excessive stupidity and obstinacy, neither these five nor any other number of books whatsoever could be enough, when it is esteemed the glory of vanity to yield to no amount of strength on the side of truth,—certainly to his destruction over whom so heinous a vice tyrannizes? For, notwithstanding all the assiduity of the physician who attempts to effect a cure, the disease remains unconquered, not through any fault of his, but because of the incurableness of the sick man.Such, however, is the nature of sin that one can never write enough to argue men out of it. Our natures must first be changed by grace.
We've seen Augustine refute the claims that the gods should be worshiped in exchange for worldly power and glory, now he is going to tackle the idea that the pagan deities should be worshiped so that one may achieve eternal life.
To some extent, the pagan philosophers and playwrights (especially the comic ones) have done our work for us as they have argued and mocked away the open idolatry and superstition of the crowd of the common people. Yet, we cannot wholly endorse what the philosophers have done, because they have brought with them a more subtle paganism that itself requires a response.
Whether for the sake of the life which is to be after death, we ought to worship, not the one God who made all creatures spiritual and corporeal, but those many gods who, as some of these philosophers hold, were made by that one God, and placed by Him in their respective sublime spheres, and are therefore considered more excellent and more noble than all the others?In other words, are not the pagan gods merely representatives of the one true God, and so to be at least respected (if not openly worshiped) as the bearers of His will and as His agents in creation?
What we see in fact is that these gods are the inventions of men, and as such rulers over nothing. As we've seen in the last five books they do not control even the affairs of mankind here on earth, why would we ever extend to them the power to control eternal matters?
Wherefore, if, when we were inquiring what gods or goddesses are to be believed to be able to confer earthly kingdoms upon men, all things having been discussed, it was shown to be very far from the truth to think that even terrestrial kingdoms are established by any of those many false deities, is it not most insane impiety to believe that eternal life, which is, without any doubt or comparison, to be preferred to all terrestrial kingdoms, can be given to any one by any of these gods?But we've already answered this in the preceding books--the gods cannot provide even happiness (if they could, we should worship Felicity and no one else), so even the intangible rewards of eternity are beyond the reach and control of created beings.