The final controversy that influenced Augustine's writings was with the pagans, which was brought about by the fall of Rome in 410. The Roman Empire had been Christian for almost a century. Pagans blamed the fall of Rome to barbarians on Christian influence To combat this, Augustine wrote the City of God , a massive work begun in 412 and completed in 426 In it Augustine contrasted the earthly city (the state) with the city of God (the church). The earthly city was built on the love of self while the city of God was built on the love of God The two would always coexist. Yet earthly cities came and went as greed for power led to a cycle of conquest and decline. Only the city of God, where people lived in submission to God, would endure
Augustine was aware of corruption in the church but still felt that it was superior to the state. Even though the state was to be endured for the good of society, the church was to instruct it in the "ways of the heavenly city" These ideas were the basis for the church's involvement in politics, an involvement that would be an important part of life in the Middle Ages.
Augustine's City of God was completed near the end of his life as the Vandals were besieging Hippo. In many ways his work is the final contribution of a dying age to the empire. Still his ideas were powerful enough to make him the teacher of the new, emerging age.