The same thing is true of the Kingdom of the earth. It has the same ambiguity. On the one hand it is the state of power, compulsion, arbitrariness, tyranny, the gangster-state (as Augustine called it); it has all the imperialistic characteristics we see in all states. On the other hand,(there) is the unity which overcomes the split of reality, and from this point of view it is a work of love. And if this is understood by the emperor, he can become a Christian emperor. Here again we have the ambiguous valuation: the state is partly identical with the Kingdom of the Devil; partly it is different from it because it restricts the devilish powers.

History has three periods: that before the law, that under the law, and that after the law. In this way we have a fully developed interpretation of history. We are in the last period, in the third stage, and it is sectarian heresy to say that another state must be expected. This heresy was expressed, of course, by the medieval sects, and from that point of view the fight between the revolutionary attempts of the sectarian movements and the conservatism of Augustine’s philosophy of history, becomes visible.

Paul Tillich, A History Of Christian Thought – Table of Contents