Constantine the Great and Christianity

During the reign of the Roman Emperor Constantine the Great (306–337 AD), Christianity began to transition to the dominant religion of the Roman Empire. Historians remain uncertain about Constantine's reasons for favoring Christianity, and theologians and historians have often argued about which form of early Christianity he subscribed to. There is no consensus among scholars as to whether he adopted his mother Helena's Christianity in his youth, or, as claimed by Eusebius of Caesarea, encouraged her to convert to the faith he had adopted.

Constantine ruled the Roman Empire as sole emperor for much of his reign. Some scholars allege that his main objective was to gain unanimous approval and submission to his authority from all classes, and therefore he chose Christianity to conduct his political propaganda, believing that it was the most appropriate religion that could fit with the imperial cult. Regardless, under the Constantinian dynasty Christianity expanded throughout the empire, launching the era of the state church of the Roman Empire.^[1] Whether Constantine sincerely converted to Christianity or remained loyal to paganism is a matter of debate among historians.^[2] His formal conversion in 312 is almost universally acknowledged among historians,^[1][3] despite that it was claimed he was baptized only on his deathbed by the Arian bishop Eusebius of Nicomedia in 337;^[4][5][6] the real reasons behind it remain unknown and are debated also.^[2][3] According to Hans Pohlsander, professor emeritus of history at the University at Albany, SUNY, Constantine's conversion was just another instrument of realpolitik in his hands meant to serve his political interest in keeping the empire united under his control:

The prevailing spirit of Constantine's government was one of conservatism. His conversion to and support of Christianity produced fewer innovations than one might have expected; indeed they served an entirely conservative end, the preservation and continuation of the Empire.

— Hans Pohlsander, The Emperor Constantine^[7]

Constantine's decision to cease the persecution of Christians in the Roman Empire was a turning point for early Christianity, sometimes referred to as the Triumph of the Church, the Peace of the Church or the Constantinian shift. In 313, Constantine and Licinius issued the Edict of Milan decriminalizing Christian worship. The emperor became a great patron of the Church and set a precedent for the position of the Christian emperor within the Church and raised the notions of orthodoxy, Christendom, ecumenical councils, and the state church of the Roman Empire declared by edict in 380. He is revered as a saint and isapostolos in the Eastern Orthodox Church, Oriental Orthodox Church, and various Eastern Catholic Churches for his example as a Christian monarch.