“Constantine [was] as an emperor born of an emperor, the pious son of a most pious and virtuous father, and Licinius next to him, were both in great esteem for their moderation and piety.” This is how Eusebius of Caesarea describes the emperor Constantine in his history of the church. Constantine was the first Roman emperor to be baptized as a Christian. The story of how he converted to Christianity and the impact that this had on Christianity has provided much debate ever since.
Christianity had been in conflict with Rome for much of the first three centuries with Christians suffering persecution by imperial decree culminating in Constantine’s predecessor Diocletian’s edicts. This situation was not directly a result of the teachings of Jesus or Paul, but possibly an inevitable consequence. When Jesus was tested by the Pharisees and Herodians over paying taxes to Caesar he replied, “Render to Caesar the things that are Caesar’s, and to God the things that are God’s.” Neuhaus’ analysis is that God is the power over all things and that Caesar’s role is temporary.
Neuhaus refers to Paul in Romans 13 where he says that those in authority have been “instituted by God” and “every person should submit to the governing authorities.” Neuhaus also points to Paul writing to the Corinthians where he “makes clear that Christians should as much as possible steer clear of Caesar’s jurisdiction and should not, for example, take their disputes to the secular courts.” Christians were to respect those in authority, obeying the law, but acknowledge that God was superior.
Christians were considered by Romans to be cannibals, incestuous and atheist. They refused to worship Caesar or the Roman gods. Jews were exempt and so this had not been a problem as long as Christians were seen as Jews. But in time Christians were seen as distinct and they seemed arrogant for not bowing down to the gods. Roman attitude hardened and waves of persecution began with many Christians martyred. Despite this, Christianity continued to grow until Christians were approximately 5-15% of the population of the empire by the start of Constantine’s reign.
Eusebius was a bishop from the fourth-century who wrote the first history of the church and about Constantine shortly after his death in 337. Eusebius tells the story of the “Vision of the Cross” that Constantine had in October 312 after which he defeated his rival Maxentius and became emperor in the west. Eusebius records “that about noon, when the day was already beginning to decline, [Constantine] saw with his own eyes the trophy of a cross of light in the heavens, above the sun, and bearing the inscription, CONQUER BY THIS.” This vision had a profound effect on Constantine.
In his writing Eusebius uses phrases like “excited by God,” “invoking the God of heaven,” and “divine assistance” to demonstrate that he saw Constantine as the instrument of God. Eusebius draws a parallel with God defeating Pharaoh and his army at the Red Sea, as Moses led the Hebrews out of Egypt, when he describes how Maxentius and his army were defeated fleeing “before the power of God that was with Constantine” and coming to a similar fate crossing a river outside Rome.
Eusebius records that after this victory Constantine had a dream in which Christ appeared to him “commanding him to make a likeness of the sign he had seen and to use it as a safeguard in all engagements with his enemies.” This symbol, known as Chi Rho, being the first two letters of the name Christ in Greek, is still used in churches today. Eusebius had no doubt that Constantine was God’s agent and that there was, as Neuhaus records, “a providential convergence between the history of Christianity and that of the Roman Empire.”
Constantine and Licinius
Constantine was allied to Licinius who, following their victory, would rule the empire in the east. In 313 they issued what became known as the “Edict of Milan” on the occasion of Licinius’ marriage to Constantine’s half sister Constantia. The edict gave legal standing to Christianity and, for the first time in the Western world, recognized the principal of the freedom of belief. Eusebius describes the events as God the protector of the pious removing a tyrant and favour being given to Christians by the emperor with the restoration of churches.
In 324 Constantine came into conflict with Licinius and invaded the eastern empire. According to Eusebius this was because it was necessary to protect Christians from persecution, the majority of whom lived in the eastern provinces. Drake suggests it is possible that Licinius’ “persecution” was his intervention in a Christian theological disagreement that became known as the Arian heresy.   Eusebius describes Licinius as plotting treachery against his benefactor Constantine. He calls God “the friend and vigilant protector and guardian of the emperor.” Constantine defeated Licinius and had him killed; as a result becoming the sole emperor of a unified empire.
Constantine and the church
Constantine’s subsequent attitude towards Christians is similar to the way Cyrus King of Persia had acted towards the Jews when he released them from captivity in Babylon and commissioned them to rebuild the temple in Jerusalem. God had brought to power a ruler who would show favour to His people. The difference in this case is that Constantine had converted to Christianity, whereas Cyrus had not converted to Judaism.
The church experienced increased favour by Constantine in the period that followed. He built many important churches, including St Peter’s in Rome, the Holy Sepulchre in Jerusalem, and Hagia Sophia in Constantinople. At the same time Constantine diverted the control of state resources into the hands of Christian bishops. He also gave the bishops “unprecedented legal and juridical privileges.” Drake writes “by one simple act – ordering that Sunday be observed as a day of rest and prayer – he gave a new rhythm and feel to the pace of ancient life.”
Sacrifices stopped and temples were closed and spoiled. Brown portrays this period in terms of power shifting from cities, with their identity linked to local gods and temples, to an “empire-wide patriotism” that was “centred on the person and mission of a God-given, universal ruler, whose vast and profoundly abstract care for the empire as a whole made the older loyalties to individual cities … seem parochial and trivial.”
This shift in power adds weight to the premise that Constantine was a skilled politician who used Christianity for his own ends. Not only had he unified the empire under his rule, but he had taken power from the cities and created a new power base by promoting the role of bishops in civic life.
Drake refers to Swiss historian Jacob Burckhardt writing 150 years ago who found “that at the same time that Constantine was lavishing favour on the Christian Church, the emperor continued to support pagan rites.” Burckhardt describes Constantine as “a calculating politician who shrewdly employed all available physical resources and spiritual powers to the one end of maintaining himself and his rule without surrendering himself wholly to any party.” 
Drake counters this argument by saying Burckhardt had applied a nineteenth-century worldview to support his thesis which could not fairly be applied to Constantine’s own time. He adds that Eusebius wrote, “[Constantine] wanted to find a god who would not only protect him from magical arts but also give him a secure and successful reign.”
The Council of Nicaea
After Constantine had defeated Licinius he became involved in the Arian dispute. This was not the first time Constantine had involved himself in such matters. He had intervened in an earlier heresy after a group from North Africa known as Donatists had appealed to him.  The emperor called a council at Arles in 314 and found against the Donatists.
In order to resolve the Arian heresy, Constantine called a council in Nicaea in 325 which was attended by over three hundred bishops, the majority of whom came from provinces in the empire. Constantine was in attendance for much of the Council which lasted for over a month. Many decisions came out of the Council of Nicaea including a statement of faith known as the Nicene Creed, an agreement on the date of Easter, possibly at the suggestion of Constantine himself, and twenty church laws called canons.
Drake describes the Council of Nicaea as “a watershed in the development of Christian theology.” Up until this point there was not one single church, but a number of churches, each led by their own bishop. There was no universal authority to which the bishops reported, and there was not always unity between the churches. Drake writes that “only subsequent to Constantine’s reign, and in large part as a reaction to it, do such mechanisms come into being.”
Constantine had decided to take a leading role in the development of the church. Barnes notes that “Constantine’s presence in Nicaea drew attention away from the events with Licinius.” He also says that Constantine participated in debates even though he had not been baptized. The Council of Nicaea had not resolved all disputes in the church and Constantine did not always impose his will. Barnes writes this was because he “believed the bishops spoke with divine authority.” 
Constantine was baptized by Eusebius of Nicomedia in May 337 shortly before his death. He left a much changed empire and Christianity had a new found confidence. Christianity had not completed routed paganism, Brown details accounts of polytheism continuing beyond the end of the sixth-century; but it was in the ascendant and had never exercised so much influence. Drake refers to Edward Gibbon in The Decline and Fall of the Roman Empire who suggests that Christianity, and in particular Christian organisation is inherently intolerant due to the exclusive nature of the Gospel message. This intolerance led to the coercion that was seen in the years after Christianity gained legal status in the empire.
Brown writes that in the last decades of the fourth-century, “Christian spokesmen, representing the needs of Christian congregations in the cities, began to intervene in the politics of the empire.” Emperors listened to bishops as they had previously listened to philosophers. Bishops became more powerful and gave voice to their congregations at the heart of empire. Brown adds that “by the fifth-century a Christian emperor could be taken for granted.”
Many philosophers became bishops, and arguably the system changed in name but not in method. Brown writes that Bishops were accused of spending money intended for the poor on the construction of “grandiose new churches,” and “the food of the poor was eaten up by stone, by the multicoloured marbles and gold mosaic of new basilicas.” This was a far cry from the first-century church and further evidence that Constantine had compromised Christianity.
Christianity took a different path because of Constantine. The history of Christianity became inexorably linked to that of the Roman Empire and its successors, giving it the platform to evangelize the Western world. At times this did compromise the mission and the power of the church. When Thomas Aquinas visited Innocent IV in Rome, he was amazed at the wealth he saw. The pope said to him “you see, Thomas, we cannot say as did St. Peter of old, ‘Silver and gold have I none.’” “No,” said Aquinas, “neither can you command, as did he, the lame man to arise and walk.”
Constantine was a man of faith who God used to save the church from persecution and the catalyst to begin the transformation of it from disparate local communities to a worldwide movement.
T. D. Barnes, Constantine and Eusebius (Cambridge, MA: Harvard University Press, 2006)
Biblos Bible Commentaries, ‘People’s New Testament’, http://pnt.biblecommenter.com/acts/3.htm, December 2009
P. Brown, Power and Persuasion in Late Antiquity: Towards a Christian Empire (Madison: University of Wisconsin Press, 1992)
C. F. Cruse, trans., Eusebius’ Ecclesiastical History (Peabody, MA: Hendrickson Publishers, 1998)
H. A. Drake, Constantine and the Bishops: The Politics of Intolerance (Baltimore: John Hopkins University Press, 2000)
R. J. Neuhaus, The Naked Public Square: Religion and Democracy in America (Grand Rapids, MI: Wm. B. Eerdmans, 1986)
Wikipedia, ‘First Council of Nicaea’, http://en.wikipedia.org/wiki/First_Council_of_Nicaea, December 2009
 Wikipedia, ‘First Council of Nicaea’, http://en.wikipedia.org/wiki/First_Council_of_Nicaea, December 2009
 Biblos Bible Commentaries, ‘People’s New Testament’, http://pnt.biblecommenter.com/acts/3.htm, December 2009