Augustine’s late life would continue to struggle against forms of heretical movements; after the Donatists—mostly a North African phenomena—Augustine would turn his attention to another sect called the Plagenianists a group debated throughout the whole of the Roman Empire; Augustine’s arguments reinforced mass-psychological and social complexes already at work in the social-material reality of the Holy Roman Empire.
Augustine argued against the idea that people themselves could attain spiritual enlightenment without the help of a church. He also fought against the idea that babies didn’t need to be baptized and thought that the Plagenianists overestimated the ability of free will, which would ultimately fall apart under the heavy burden of attaining a heavenly disposition.
Eventually, Augustine got his way when the pope and the emperor got together to ban Plagenists.
Ultimately, Augustine’s outlook would become bleaker as time went on and he would come to emphasize more and more on the need of humanity to rely on God. His masterwork, The City of God, written after the sack of Rome by Goths and contains the mature Augustine theology.
Part of why Augustine wrote this book was, because, after the sack of Rome, contemporary pagans used the event to argue that the reason that it happened was because paganism was outlawed; that Rome was sacked was because Christianity had somehow stolen the ability of the Romans to be a victorious empire. Augustine, obviously, was keen on debating such reasoning.
Augustine’s masterwork, though giving some lip-service to the admirable qualities of some pagan philosophers and the early Roman Empire, quickly moves on to a blistering attack on paganism and the Roman Empire in general; in the former, Augustine seized on those aspects of paganism which seemed most ridiculous—the defense of pagan empires left to gods, the irrationality of divine productivity in the human world, etc.—while emphasizing the ‘evil’ of paganism in that since pagan Gods do not lay down commandments, then their followers behavior is entrusted to chaos and henceforth evil in that humanity is allowed to wander morally. In terms of the latter, he ‘lays the smack down,’ to use a colloquialism, on the empire and reduces them to an elaborate system of thugs in their subjugation of neighbors. His attack on classical philosophy, meanwhile, centered on pagan thinkers setting for themselves an unobtainable goal—to achieve happiness by their own efforts, without God.