While the Roman Emperor Constantine the Great reigned (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 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 himself. Some scholars question whether he should be considered a Christian at all: "Constantine saw himself as an 'emperor of the Christian people'. If this made him a Christian is the subject of ... debate.", and he did not receive baptism until shortly before his death.