The idea of Augustine of societas (society) as a community identified and held together by its loyalties and love became an integral part of the general tradition of Christian social teaching.
Augustine wrote the City of God while the Roman Empire was falling into ruin under the barbarian invasions and the Church was rising from the imperial ashes. There was need of justifying these two events, which disturbed not only those who did not believe in Christ but also those who did believe in him. With this purpose in mind, Augustine undertook this major work over a period of thirty years.
The City of God can be considered the first in the philosophy of history. Until the late Middle Ages a thousand years later, the City of God influenced the politics and government of Christian nations, and in the relations between the Church and the civil government. It was an influence in the creation of the Holy Roman Empire, and had little in the way of rival theories until Nicola Machiavelli in the year 1513 wrote a very secular work, The Prince, that appealed to the more base desires of power and cunning. The world view of Augustine and his history of humanity is organic and unified, but it is also ascetic and Christian. Christ is the very soul of history. The coming of Christ presupposes another truth of the Christian faith, original sin. In consequence of original sin, people are divided into two distinct cities: one of God, the other of the earth. Both, however, are at the service of Christ.
The city of God, prior to the coming of Christ, was represented by the people of Israel; the city of this earth was represented by the Roman Empire. The two cities had a different purpose, the one religious and the other political. The first had the task of preparing for the coming of Christ through the prophetic men in the Bible; the second was to prepare for his coming politically. After the coming of Christ and the founding of the Church, the purpose of the Roman Empire had been fulfilled, and hence it fell under the assaults of the barbarians. If in the Christian era the Church represents the city of God, moral evil, wherever it be found, will be the representative of the city of the earth. These two cities now are not politically separated and are only religiously diverse, for the Church has a universal task and must embrace the elect of all times and of all races. The complete division will be made on the Great Sabbath, when the good will forever be citizens of the city of God, the eternal Jerusalem, and the evil will be confined forever to the city of Satan, which is hell.
But who are those who will end in heaven and who are those that will end in eternal pain? This, too, was one of the many problems on the mind of Augustine. The answer to this is among the secrets of God. The view of Augustine on the shape and process of human history has been more influential than any other single source in the development of the Western tradition which regards political order as inextricably involved in moral order.
His conception of a societas (society) as a community identified and held together by its loyalties and love has become an integral part of the general tradition of Christian social teaching and - it would not necessarily have been to his liking - of the Christian vision of the historical Christendom of the Middle Ages.