At the beginning of the Christian era, the greatest attempt ever made to gather all peoples into a universal society was actually in progress. The Roman Empire was founded on the basis of a common administrative system, and a common law--the _jus gentium_. It needed a common religion. The effort to supply this passes through three stages. The earliest of these is the stage of universal toleration which was made possible by polytheism. A second stage soon follows. The various religions of the Empire overflow one another's frontier-lines and a synthesis begins, leading to the Stoic idea of the universal truth expressed in many forms. But the popular mind was unable to rise to this high conception, and the third stage begins towards the end of the first century in the formal adoption of the worship of the Emperor as the religious expression of the unity of the Empire. It was the opposition of the Christian Church that did most to bring to naught this effort to give a religious foundation to the unity of the Empire, and the attempt of Constantine and Theodosius to make Christianity an Imperial religion came too late to save the Empire from disintegration. For the unity of the Christian Church had been undermined. When Christianity shook itself free from the shackles of Jewish nationalism, it came under the influence of Greek thought. The theology and language of the early Church were Greek. Even in Rome the Church was for at least two centuries "a Greek colony." Hence the growth of Christianity was slow in those western parts of the Empire that had not come under the influence of Greek culture--Gaul, Britain, Spain, North Africa. Latin Christianity found its centre in North Africa, where Roman culture had imposed itself on the hard, cruel Carthaginian world. It is Carthage, not Athens, that gives to Tertullian his harsh intolerance and to St Augustine his stern determinism. So the way was prepared for what I regard as the supreme tragedy of history--the falling apart of Eastern and Western Christianity. Then, in the West, the unity of the Church is broken by the conversion of the Teutonic peoples to Arianism, so that the contest between the dying Empire in the West and the tribes pressing on its frontiers is embittered by religious antagonism. The sword of Clovis secured the victory of orthodoxy, but at what a cost!