<P> During the reign of the Roman Emperor Constantine the Great (AD 306--337), 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, encouraged her to convert to the faith himself . Some scholars question the extent to which he should be considered a Christian emperor: "Constantine saw himself as an' emperor of the Christian people' . If this made him a Christian is the subject of...debate," although he allegedly received a baptism shortly before his death . </P> <P> 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 the notion 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 ." </P> <P> The first recorded official persecution of Christians on behalf of the Roman Empire was in AD 64, when, as reported by the Roman historian Tacitus, Emperor Nero attempted to blame Christians for the Great Fire of Rome . According to Church tradition, it was during the reign of Nero that Peter and Paul were martyred in Rome . However, modern historians debate whether the Roman government distinguished between Christians and Jews prior to Nerva's modification of the Fiscus Judaicus in 96, from which point practicing Jews paid the tax and Christians did not . </P>

Who legalized the practice of christianity in the roman empire