This was a second and further fulfilment of the vision, which as yet Augustine saw not, nor even anticipated; but after thus writing he set himself in the last years of his life to a great task, even that of comparing together from their origin to their end the course of the two societies, not national, but world-wide, which run out through human history, intermingled together, and claiming possession of the same man. First, the natural society of the human race played upon by all the passions and infirmities which are the effect of man's original Fall; and secondly, that other society chosen by God from the beginning in view of His Son's Incarnation, for the purpose of repairing and counterworking that Fall. It was the capture of Rome by Alaric, and the deep despondency which thence arose in the minds of many, both Christian and heathen, that moved him originally to this design, of which the first tracing is seen in the letter to Volusian just quoted. He sought to meet conclusions unfavourable to the Christian faith, which were drawn by weak, or narrow, or unbelieving minds from the fall of the imperial city. His plan accordingly led him to take a complete view of all human history; and the result has been that one of the last representatives of the old world, and certainly the greatest of all as thinker, philosopher, and theologian, the most universal genius of the patristic ages, whether among Greeks or Latins, has left us a Philosophy of History, the first in time, and as yet unequalled in ability; for it supplies a key to the acts of man and the providence of God in that masterly comparison between the City of God and the City of the devil in their origin, their course, and their end. The leading thought of this great work gives me a final text bearing on the subject of this volume.