Correspondence between the churches was an early custom. Circular letters from the heads of the great churches, read on Sunday in the re-unions of the faithful, were a sort of continuation of the apostolic literature. The ecclesiastical province, questioning the precedency of the great churches, appeared in germ. The Church, like the synagogue and the mosque, is essentially a citadel. Christianity, like Judaism and Islamism, is a religion of cities. The countryman, the _paganus_, will be the last resistance which Christianity will encounter. The few rural Christians came to the church of the neighboring city. The Roman municipality thus enclosed the church. Among the cities, the _civitas_, the grand city, was alone a veritable church, with an _episcopos_. The small city was in ecclesiastical dependence on the great city. This primacy of the great cities was an important fact. The great city once converted, the small city and the country followed the movement. The diocese was thus the unity of the conglomerate Christians. As for the ecclesiastical province, it corresponded to the Roman province: the divisions of worship of Rome and Augustus were the secret law which ruled all. Those cities which had a flamen, or _archiereus_, are those which later had an archbishop: the _flamen civitatis_ became the bishop. After the third century, the flamen held the rank in the city which was later that of the bishop in the diocese. Thus it happened that the ecclesiastical geography of a country was very nearly the geography of the same country in the Roman epoch. The picture of the bishops and the archbishops is that of the ancient _civitates_, according to their line of subordination. The empire was as the mould in which the new religion was formed. The interior framework, the outlines, the hierarchical divisions, were those of the empire. The ancient archives of the Roman administration, and the church-registers of the middle ages, and even those of our own day, are nearly the same thing. Thus the grand organisms which have become so essential a part of the moral and political life of European nations were all created by those _naïve_ and sincere Christians, whose faith has become inseparable from the moral culture of humanity. The Episcopate under Marcus Aurelius was fully ripe: the Papacy existed in germ. [OE]cumenical councils were impossible. The Christian Empire alone could authorize great assemblies; but the provincial synod was used in the affairs of the Montanists and of the Passover. The bishop of the capital of the province was allowed to preside without contest. II.