“ST. AUGUSTINE'S work of “The City of God” was, like all his books, a livre de circonstance, written with definitely controversial aim in response to a particular need. But during the fourteen years—from 412 to 426—during which he was engaged upon it, the work developed from a controversial pamphlet into a vast synthesis which embraces the history of the whole human race and its destinies in time and eternity. It is the one great work of Christian antiquity which professedly deals with the relation of the state and human society in general to Christian principles; and consequently it has had an incalculable influence on the development of European thought. Alike to Orosius and to Charlemagne, to Gregory I and Gregory VII, to St. Thomas and Bossuet, it remained the classical expression of Christian political thought and of the Christian attitude to history. And in modern times it has not lost its importance. It is the only one among the writings of the Fathers which the secular historian never altogether neglects, and throughout the nineteenth century it was generally regarded as justifying the right of St. Augustine to be treated as the founder of the philosophy of history.”
~Christopher Dawson: from St. Augustine and the City of God.