Constantine’s most radical innovation was in the sphere of religious policy. He permanently altered the Roman policy toward Christianity. There is a story here Shortly after he had gained control of the West, Constantine met with Licinius at the city of Milan in north Italy. The purpose of the meeting was to conclude their agreement to share the imperial office. But they also issued jointly what is commonly misnamed the Edict of Milan (314). It was really a series of administrative orders. To a large extent, the Great Persecution started by Diocletian had already ended by 311 with a return to the traditional policy of ignoring Christians unless they caused problems. But the new policy went much further. The rulers proclaimed complete toleration. Christianity was to be legal, just like any other religion in the Empire.

One of the most hotly debated historical issues about Constantine's reign is why this new policy was adopted. The only ancient explanation was given by various Christian writers of the Late Empire. In the later part of his life, Constantine is said to have claimed that Christ appeared to him in a vision and offered to help him in winning the Battle of the Milvian Bridge. Constantine is supposed to have said that after the battle he had granted Christians toleration in gratitude for Christ's help.

By the Middle of the fourth century, the Roman Empire was gradually falling apart. One institution that changed in this period more profoundly than any other was the Christian Church. In the next two lectures I want to look at changes in the church more closely. Constantine’s decision to tolerate Christianity had solved the most serious external problem of the church, government persecution. But internal problems remained. In particular, conditions in the early 300’s produced two major new heresies.

In the western church, the principal heresy arose at Carthage. Many factors led to the split in the North African Church, but the main religious issue typically dealt with a legal and administrative problem arising from the Great Persecution under Diocletian. The question was what to do about those North African Christians who had abandoned or betrayed the Church in that period. These persons had renounced the faith, surrendered copies of the scriptures to authorities, or had merely refused to show the strength of their beliefs by hiding to avoid arrest.

Such persons were called lapsi (back-sliders) or traditores (surrenderers). They had betrayed the faith. There was a moderate faction in the Church that proposed to forgive such persons. They believed that Christianity was a forgiving faith and that the Church had to accept all sinners and former sinners. But the North African Church had a strong tradition of puritanical harshness (remember that Tertullian came from there). It also had a tradition of glorifying martyrs who died for the faith. A rigorist faction argued that the lapsi should be excluded from the Church forever. They were permanently tainted because they had refused to be martyrs and die for the faith.

The dispute broke into the open in 311. The bishop of Carthage died, and the moderates were able to get one of their leaders elected as the new bishop. His name was Caecilian. But the rigorist faction decided to protest the election. They were led by a bishop from Numidia named Donatus (d. c. 347). The splinter movement is called Donatism after him.

The grounds that they gave for opposing the election had far-reaching theological implications. The supporters of Donatus argued that Caecilian had been ordained as bishop by a traditore. They claimed that this made his ordination invalid. This argument came from the basic tenet of the Donatist heresy. Donatists argued that the sacraments are not valid if they are administered by a sinful man; in fact, they are religiously harmful. In other words, they argued that a bad man cannot be a good priest.

The main problem of the Donatists was to find someone to hear their case. They wanted bishops in other parts of the West to meet and review Caecilian's election, but it was hard to get them together. Then, in 313, Constantine got control of the West and began making friendly noises toward the Church. That gave them an idea. They wrote to the Emperor and asked him to help them settle the dispute. It was a momentous step. For the first time, a ruler was being asked to intervene in an internal Church matter. Constantine responded by helping to organize two separate synods of bishops to hear the case, one at Rome in 313 and another at Arles in Gaul in 314. Both meetings rejected the Donatist claims. Constantine probably wanted to secure peace, but his effort failed. The Donatists refused to give in for the next two hundred years.

Eventually, the person who probably did the most to end the Donatist controversy was St. Augustine, the Bishop of Hippo. In his City of God (c. 420), Augustine stressed the idea of original sin, which under Donatist doctrine would mean that no one could perform the sacraments since all humans are tainted by Adam’s sin at birth. As the doctrine of Original Sin became a central doctrine of the Church, Donatism should have faded away. But the Carthage Donatists were a hard-headed bunch!  Donatism survived the Vandal occupation in the 400s and even the Byzantine reconquest under Justinian I in the 500s. It is unknown how long this belief persisted into the Muslim period, but some Christian historians believe the Donatist schism and the discord it caused in the Christian community made the military takeover of the region by Islam easier.

The most serious heresy in the Church before the Middle Ages began in the East. It was typically Eastern in that it dealt with an abstract theological problem—the old question of the exact relation of God and Christ in the Trinity. In the 200s, this issue took on added urgency with the teaching of a new group of rigid monotheists, called “Monarchians.”  There were several different flavors of them, but all Monarchists agreed that the three members of, the Trinity were all different “modes” or forms of a single, unified “monarchian” divinity.

In the West, Tertullian successfully refuted these doctrines in the West by arguing that the Trinity consisted of three “persons” with the same basic “substance” or nature. This formulation raised several logical questions, but Western Christians were not all that concerned over the fine points. In the East, Origen provided a position similar to that of Tertullian, but he also tried to reason out the details more fully. Origen's argument was more complete logically, more philosophically refine, but it did not go far enough for many Easterners, whose Greek philosophical inclinations made them more sophisticated, of course, more obnoxious, and more demanding of a perfect rational explanation for something that defied rational explanations. For the most part, though, Christians, East and West, were willing to accept the explanations proffered by Tertullian and Origen.

But, the issue was reopened after 310 by a priest and theologian at Alexandria named Arius (d. 336). He thought that he detected a particular strain of Monarchist thought in the teaching of the Egyptian Church. He tried to correct this by elaborating Origen’s views more fully, as he understood them. None of his doctrinal writings has survived, so we can only piece together his thought from his critics and his later followers, both dangerous propositions.

It seems clear that Arian relied heavily of the philosophical systems of the Neo-Platonists, especially Plotinus. Plotinus had argued that all things came from a perfect Unity — the One. It was self-sufficient, eternal, and immutable. Since the One did not change or move itself, it had to generate from itself an active, creative principle to create the World. This principle Plotinus called Mind (or perhaps, the Word). Arius adopted this same distinction to define the relation of God to Christ. God was the eternal, unchanging, self-sufficient One; and Christ was the Word, the creative principle or power.

Christians had long thought of Christ in this sense. One of the oldest Christian writings, the Book of John, states that Christ is the incarnation of the Word through which God creates the World. John stresses a sameness in time and space between God and Christ (the Word):

1:1 In the beginning was the Word: and the Word was with God: and the Word was God.

1:2. The same was in the beginning with God.

But by Neo-Platonist reasoning, God the Father must have logically existed prior to Christ. God came first; then he had to create the Word in order to create the World. So, Christ was not eternal as God was. He was created by God at some point in time. Additionally, Christ was not self-sufficient, since He relied on God to create Him. Nor was Christ unchanging, since He had changed from not existing to existing when he was created. Arians argued that God the Father and Christ were different in substance and in being. God was eternal, perfect, unchanging, and Christ was none of those, but a creature (a created being) separate from God. 

This doctrine provoked a sharp response from the leaders of the Alexandrian Church. It was led by the bishop Alexander (d. 328) and by one of his closest religious advisers Athanasius (d. 373). They contended that Arius had relegated Christ to a subordinate position. He had become a mere intermediary between God and the World. That was unacceptable because it meant that God might send other intermediaries, other Christs, in the future. They argued that Christ had always existed with God and was just as divine as God was. That was why his becoming a man was so miraculous. This position was placed far more emphasis on authority and on faith than on reason. Many of the more philosophically inclined leaders of the Eastern Church did not like it as well as the Arian position at first.

Arianism and Donatism increased the need to solve the two major internal questions of the early church: what should Christians believe and who will decide what Christians should believe? But the improved relations with the state now made possible a new effort to answer these questions. The man who took the initiative in this effort was Constantine. With the resources of the state at his disposal, he was able to achieve more apparent success than had ever been achieved before.

Constantine apparently felt that disputes in the Church weakened the unity of the Empire as a whole. He became increasingly concerned about Arianism because it caused a split the Eastern Church. He had already intervened in the Donatist controversy. The fact that he had not been successful did not deter him.  He decided to arrange an ecumenical or worldwide meeting of Church leaders from all over the Christian world to resolve these various differences once and for all.

Early in 325, right after he had gotten control of the whole Empire, he called the meeting. It occurred at Nicea in Asia Minor. It was the first ecumenical council, a major event in Church history. Constantine’s paid the expenses of those attending, he came to the meetings, and he even participated in some of the discussions himself. Three hundred and eighteen churchmen attended, including some from Christian areas outside the Empire itself. The bishop of Rome did not come, but he sent representatives.

The council addressed both the problem of doctrine and the problem of defining lines of authority in the Church. On doctrine, they adopted the Nicene Creed, a brief definition of the basic beliefs required for all Christians. The Creed specifically rejected the suggestion that Christ was not eternal. Then, they came to a harder problem. They had to choose a term to describe the exact relation of Christ to God. Finally, Constantine himself proposed a term that had been suggested to him by one of the Western bishops. The term was homoousios, having the same substance. It was based on Tertullian's theory of three persons with one nature. The term was very vague and raised almost as many questions as it answered. Moreover, it was not used in the Scriptures anywhere. After the Council, many Easterners began to have second thoughts about the term and some even believed that it should be changed. But, anyone who wanted to change it was labeled an Arian, including many who were not real Arians.

The Nicene Council also issued a series of directives clarifying lines of authority and jurisdiction within the Church. The bishop in the capital city of each province of the Roman Empire was to have general authority over all other bishops in the province. These men came to be called metropolitans or archbishops.

Four men were recognized as patriarchs, men with the highest authority in the Church. Each had general jurisdiction over the churches in one part of the Empire. The bishop of Rome had highest authority in the West; the bishop of Alexandria in Egypt; the bishop of Antioch in the remaining Eastern churches. The Bishop of Jerusalem was an honorary patriarch. These men did not have absolute power. It was assumed that major policy decisions would be made by future councils.

When the decisions were made, Constantine wrote letters to all Church leaders informing them what had been determined and calling on them to accept what the Council had said. Anyone who refused was to be deposed from Church office, and the Emperor undertook to use his power to see to it that they were.

The legalization of Christianity had brought significant changes in the life of the early Church. In the long run, the most important change was in the cooperative relationship between the Church to the Imperial government.  Cooperation made it possible for the Church to address the major problems that had plagued the Church internally. But there was a price for this, Constantine probably saw Christianity as a way of unifying the Empire more closely. But the Church itself was not united, and Constantine had not really done enough to heal that split.