This was not a steady or obvious matter, since during the first quarter-century of its evolution the imperial Church had been part of the empire that had been reunified by the emperor Constantine, and Constantine attempted to create a Christian Church that would be a unifying force within the empire. For it to be so, the Church had to be universal, and so Constantine began dismantling the old state religion and turning its buildings, assets and functions over to the Christian Church. As an aside, however, he confiscated the gold owned by the other religions and used it to restore the gold currency, a reform that Diocletian had attempted but failed to institute. With its greatly expanded material base, the Church needed more financial and administrative skill than its personnel was able to provide.

This difficulty solved itself, by and large. Constantine established that, like many other Roman administrative functions, the Church should operate as a local institution with its centers located in the civitates, the municipalities that formed the basic governmental unit of the empire. These positions were filled, at least at first, through the election of bishops by members of the local community, approved by a representative of the imperial government and confirmed by a ceremony called investiture in which the candidate was "clothed" in the symbols and uniform of his office. The ceremony of investiture was conducted by two or more neighboring bishops and so represented the Church's ratification of the selection. This concentration of Church authority in urban centers made little difference in the East, where the population was denser and more sophisticated, and where there was little distinction between urban dwellers and residents of country villages. This was not the case in the West, however, and placing the focus of Christianity in the urban centers of this region effectively delayed the conversion of the inhabitants of the rural areas of the civitates, called the pagus. It was not until the seventh and eighth centuries that appreciable progress was made in converting the country- dwellers, pagans, of the West to Christianity.

On the whole, however, this practice allowed local communities to choose the sort of man they needed as bishop. Some chose spiritual leaders unversed in the ways of the secular world, and others chose rich and experienced men from the Roman nobility. In the West, at least, this had the side effect of reintegrating the Roman senatorial nobility -- who had been exempt from almost all civil responsibility -- back into society. It also had the effect of placing direction of the Church into the hands of men with little knowledge of the nature or meaning of the Christian faith.

Consequently, one of Constantine's primary concerns was to establish a clear and commonly accepted definition of the Christian faith, especially since there appeared to be considerable dispute among the early Christians over the nature and status of Jesus. Although the details are complex, the basic division was between the followers of a priest by the name of Arius, who supported Arianism. Very roughly, the Arians held that Jesus was a human being endowed with divine powers. Their opponents, followers of Bishop Athanasius, believed that Jesus was made out of the same substance as God the Creator and so was equal to and identical with both Him and the Holy Spirit. In order to settle this dispute, Constantine called an assembly of the Christian bishops to meet in the city of Nicaea (the eastern imperial capital at the time) in 325. Although the Council of Nicaea decided on a definition of Christianity that followed the beliefs of the followers of Athanasius, this did not settle the conflict within the Church. Constantine and some of his successors tried to move the Church to a compromise position closer to Arianism, but, by 381, the Church finally and firmly embraced the Athanasian Creed. Only for a short time during this period, had the Church accepted Arianism, but it was during this period that a missionary by the name of Ulfilas carried the Christian message to the Germans. The result was that, even as the imperial Church settled on the Athanasian form of Christianity, their German neighbors in the West were adopting the Arian form.

The bishops who had assembled at Nicaea also realized that they needed some less cumbersome organization, although Constantine might have preferred dealing with a quite decentralized Church. They decided to establish the bishops of Jerusalem, Antioch, Alexandria, and Rome as patriarchs, leaders of the bishops in their regions. As soon as Constantinople had been as established as the new Roman capital, its bishop was admitted to this select group. If Constantine had hoped that the Council of Nicaea would establish a uniform faith that would help unify the empire, he was disappointed. He failed to obtain an accepted and universal definition of Christianity, and he saw his assembly adopt a regional organization that would almost guarantee that the Church would evolve in different directions in different parts of the empire.

There was another area that needed regularization, however. Over the years, a vast collection of "Christian" literature had grown up. Some of these works were copies of accounts from the period around 60 A.D. and represented authentic records of the early Church, while others were fragmentary or even fabulous stories, some written with pious intent and others as mystic revelations, adaptations of tales of pagan heroes, or books of miracles and wonders. Constantine appointed a commission of scholars to sift through these materials, choosing those that they believed to be authentic, editing out spurious or unwanted materials, and preparing a standard edition of their canon, or accepted collection of works. The work they produced was the Septuagint, written in the form of Greek that was the common language of the Eastern empire, and the basis of what is generally called the New Testament.

This lasted a bit longer than the emperor's attempt to establish a common definition of the Faith and something other than a regionalized Church, but it too finally succumbed to the forces that were driving the East and West in different directions. Between 385 and 415, a resident of Rome by the name of Jerome, who had taken up the monastic life in Judaea, devoted himself to preparing translating the Greek and Hebrew books of the Bible into Latin. This translation, the famous Vulgate (meaning "common"), although differing in certain important respects from the Septuagint, became the standard form of the Bible used in Western Europe and established yet another significant difference between eastern and western Christianity.

Constantine had succeeded in one respect, however, he had established, for a time, the principle that the emperor played the leading role in Church affairs. This principle, known as caesaro-papism, seemed acceptable to the eastern patriarchs, but was opposed by the bishop of Rome and other western leaders, who rejected the idea that the Church was primarily a secular institution or that the practice of the Faith could be regulated by someone without a spiritual mandate such as Jesus and the Holy Spirit on the day of Pentecost had given the disciples and their successors. By 390, Ambrose, bishop of Milan, required the emperor Theodosius (379-395) to do penance for executing a number of Christians. In the West, not only was caesaro-papism rejected, but there was a strong belief that the emperor was subject to Church leaders in spiritual and moral matters.

The Council of Nicaea had made another decision with unforeseen consequences. By proclaiming only one patriarchate in the West, that of Rome, they had virtually assured that there would be a greater unity in the western Church that in the East. Moreover, the ecclesiastical politics of the day elevated the position of the bishops of Rome within the Church as a whole. Constantinople and Jerusalem usually were on the other side of any dispute from Antioch and Alexandria, so the bishop of Rome generally held the balance of power and eventually gained the reputation of "ever-orthodox," and never supporting a position that was eventually discarded

In the course of the early fourth century, the bishops of Rome became the accepted secular rulers of the city of Rome itself. The city had decayed materially, its population had diminished, and it was quite indefensible, as the sack by the Visigoths under Alaric in 410 had shown. So the capital was moved elsewhere, to more defensible positions closer to the frontiers where the emperor would be better situated to lead his armies and defend the empire's borders. Sirmium in modern Croatia, Triers near the French-German border, and Milan and Bologna in northern Italy all served as the imperial capital until, at the opening of the fifth century, it was established at Ravenna, a small town located on an "island" in the midst of the marshes of the Po River's delta, where it was protected from land attack and had a port to accommodate naval reinforcements if the need should arise. Here it remained until the very end of the Roman empire in the West.

Rome itself was forgotten and when, in 453, Attila the Hun appeared before the city, it was Pope Leo I the Great (440-461) who negotiated with the Hunnic Chieftain on behalf of the city of Rome and arranged the tribute that purchased his withdrawal. Leo did more than that, however. He claimed that the bishops of Rome were the heirs to Peter, who had died in the city, and so had inherited Peter's preeminence in spiritual affairs, which Jesus had granted in the famous words "Thou art Peter and on this rock, I will found my Church," going on to grant Peter the power to "bind and loose" in both Earth and heaven. Later popes would use this principle, known as the "Petrine Doctrine" to claim a supreme position among all other churchmen.

Other things were happening in the West. Throughout the fourth century, a series of excellent scholars and philosophers had arisen to deal with some of the basic problems facing the Church as it was drawn into the political structure of a decaying western imperial administration. Three of these men stand out as the Latin Fathers: Jerome (345-420), who translated the Greek and Hebrew Bibles into a standard Latin bible for the western Church; Ambrose (340-397), who devoted himself to defining the roles and function of bishops, and presented and defended the position that bishops were superior to emperors in spiritual and ecclesiastical affairs. This direct rejection of caesaro-papism was perhaps a reflection of the lesser power exercised by western emperors, but it effectively differentiated the western Church from its eastern counterpart. The most important of the Latin Fathers was doubtless the philosopher, Augustine of Hippo (354-430), who considered and formulated the most basic of Christian doctrine, answering such questions as: If God is wholly good and made all things, where did evil come from? If God is whole good and is all-powerful, why do the virtuous suffer and the evil prosper? If God is all-knowing, does that mean that the future is already fixed, and He knows who will achieve salvation and who will be damned? But if he is all powerful, couldn't he change that future and save the sinners from damnation? But if everything is already determined and God will not interfere, and it is already decided who will be saved and who will be damned, why should the individual worry? He can't do anything to change matters. These three men, together with other western thinkers, gave the western Church a unique character.

During the first half of the sixth century, the Church had to face the difficulty of preserving itself under the rule of Germanic kings who were all too often followers of Arianism. Although this situation caused the western Church great trouble, it also placed the western Christians in a position in which they could not afford the weakness of disunion, so its persecutions at the hands of the Arians may actually have strengthened the western Church, It had to be strong to survive.

After the reconquest of the West by the emperor Justinian, the Church had to face and determined Byzantine effort to establish the principle of caesaro-papism in the West, and this ended only with the invasion of Italy by the rather unsophisticated Lombard tribes. Byzantine control over Italy disintegrated, and the bishops of Rome found themselves the sole champions of Roman culture, or what was left of it, and "true" Christianity in the entire West. This power vacuum was filled by Pope Gregory I the Great (590-604). Trained in law, as many of the other western churchmen, he was a masterful administrator, who used his family's not inconsiderable wealth, mainly in the form of fertile lands in Sicily, to endow the Church and to put its operations on a firm financial basis. In addition, he wrote voluminously, always trying to establish a more unified western Church and a better-equipped and more aware episcopacy to lead the western Church. Perhaps even more important, he set the conversion of the pagans as the primary function of the Church and sent missionaries out to convert the English, among others. Although there would be problems in the future, the western Church had now established its peculiar identity. It was a centralized church, headed by a pope who was secure in ruling the land on which his capital was located, and so it was less prone to religio-political strife than the eastern Church. It was less interested in theological disputes of fine points of doctrine that in establishing a rational and coherent set of rules and regulations to govern its affairs. Finally, it had a sense of active purpose. The clergy of the West might yearn for the solitary life spent in mortification of the flesh and seeking God in some desert waste, but there was little time for such self-indulgence when pagan nations were waiting to hear the Good News and to have their sins of scarlet washed as white as snow in the waters of baptism.