The City of God

Augustine began this enormous work, in twenty-two books, after the sack of Rome by the Visigoths in 410, when pagans blamed the disaster on the abandonment of the old gods. The first ten books answer them: the gods never protected Rome's morals or its safety, and neither civic religion nor the Platonists' worship of lesser divinities can bring true happiness. The last twelve trace the origin, course and destinies of two cities, intermingled in history: the earthly city, formed by love of self to the point of contempt for God, and the heavenly city, formed by love of God to the point of contempt for self. Along the way Augustine treats evil as privation rather than substance, free will and foreknowledge, time and creation, the fall, the limits of politics, and peace as the tranquillity of order. He famously asks what kingdoms are, without justice, but great bands of robbers.

It is the foundational Christian philosophy of history and politics, and its sober view of what states can and cannot achieve has shaped political thought from medieval kingship to modern realism.