For Augustine the bishop, Christ and salvation were central realities, and it is in the Incarnation that we must look for the clue to History. Having dealt with the origin of the world and of man, Augustine goes on to talk about the fall of man. Pride is the primordial sin, and the fall of angels establishes the Civitas Terrena in the heavens, then the fall of man establishes it on earth. As the Civitas Dei came to earth with the creation of the first man, so the Civitas Terrena with his fall. Augustine's doctrine of the unity of History and of its providential characters indicates, first of all, a doctrine that mankind is by nature one, the world a comprehensive whole, their History quite intel igible, and the essence of sin is a spiritual act by which the will turns itself from God. In writng De Civitate Dei, he was endeavouring to describe the progressive revelation of a divine intention. If Christ was born at a certain place at a certain time, our History cannot be an illusion. Moreover Augustine argues that the universe itself is a harmony of numbers reflecting the divine One who, willing the fullness of being, wills it down to its most trifuling manifestation. God made all of them good and loves them best. Augustine admonishes that humility is the root of the virtues, and therefore a foundation-stone of the City of God, that is, the Christian sense of belonging to God's universe. Pride, then, is a loss of the power of living ordinately. Augustine's account of the two cities bases mainly upon Scripture and for him History is essentially religious history. He is ever trying to give us a glimpse of history sub specie aeternitatis. We can hold that both in good and in evil man is fundamentally social and there are two cities or societies (Civitas Dei et Civitas terrena) inextricably mingled and confused only by faith and both invisible in a fundamental way. They are kingdoms of wills distinguishable here and now only by Love (Caritas, Amor, Dilectio). Fecerunt itaque civitates duas amores duo, terrenam scilicet amor sui usque ad contemptum Dei, caelestem vero amor Dei usque ad contemptum sui. Denique ilia in se ipsa, haec in Domino gloriatur. We can say Amo ut intelligam in History.