Chapter 4 from that book I was reading a while ago

The Christian tradition was very dualistic: a kingdom of God, and a kingdom of Caesar. It was reinforced in the West by the Augustinian philosophy of history. His book, City of God, speaks about the struggles between two worlds, which are separate, but do intertwine and mix here on earth. The Christian people were the second Israel. To the barbarians, kinship was the most important aspect of life. It was what held together their social lives. The new barbarian kingdoms had double purpose. 1) They'd inherited some traditions of heroic races and 2) they were allies of the Roman Empire. They made excellent rulers; ruling with justice and leading their countries in wise decisions. Nevertheless, it was cities and kingdoms like these who would get wiped away in 711-13. Throughout the ages, we can clearly see the different tribes and cultures continuing to preserve their traditions and origins. It was not always the ruler that defined the culture, but rather the people and how well they held together. The king was merely the one who held the strands together somewhat. The coming of Christianity brought a revolution socially. "However small was the political power of the king, he was the keystone of the social structures and his conversion to Christianity was the symbol and pledge of the conversion of his people." "All the faithful must know is that the universal church is the body of Christ who is its Head, and in it there are two figures which stand out supreme - the priest and the king." the people are bound to obey the king and the king is bound to obey God. The priest and the king were often in tension with each other because they each wanted the ultimate power over the people.