According to the Gospel of John, peace was Christ's principal bequest to his apostles and through them to his church: “Peace I leave you, my peace I give you” (John 14:27). The context makes it clear that this peace was a tranquillity of the heart, not a peace of the world. Yet as Augustine saw, the church was necessarily a political society, existing in the world even while waiting for it to end. What, then, did the peace of God mean for the church on earth, a mixed community of saints and sinners?

There were two basic answers. One was a Stoic idea which was taken over by Neo-Platonists, from whom it was received by Augustine, who gave it its most famous formulation.

This was a kind of Grand Unified Theory of peace. It brought together microcosm and macrocosm in a single whole, so that cosmology, political theory, and psychology all obeyed the same principle: in peace, the inferior willingly conformed itself to the superior. Throughout the entire history of the Middle Ages, no learned person would have disputed the truth of this formulation. On the other hand, simply because it was a Grand Unified Theory, Augustine's notion of peace was not particularly helpful in solving the problems of real life and so was not often explicitly discussed, even though it was nearly everywhere assumed.