The triumph of the great Constantine established the security of the Christian Church from the attacks of the pagans.  Converted in 306, Constantine, as soon as he had achieved the conquest of Italy, issued the Edict of Milan (313), declaring that the places of worship which had been confiscated should be restored to the Church without dispute, without delay, and without expense.  Though himself never received by baptism into the Church, until his last moments, his powerful patronage of the Christians, and his edicts of toleration, removed all the temporal disadvantages which had hitherto retarded the progress of Christianity.

The faith of Christ became the national religion of the empire.  The soldiers bore upon their helmets and upon their shields the sacred emblem of the Cross.  All the machinery of government was employed to propagate the faith, not only within the empire, but beyond its borders.  Confirmed in his new religion by the miraculous vision of the Cross, Constantine, who was the master of the world, consented to recognise the superiority of the ecclesiastical orders in all spiritual matters, while retaining himself the temporal power.

The persecution of heresy was carried out by Constantine with all the ardour of a convert.  An edict confiscated the public property of the heretics to the use either of the revenue or the Catholic Church, and the penal regulations of Diocletian against the Christians were now employed against the schismatics.  The Donatists, who maintained the apostolic succession of Donatus, primate of Carthage, as opposed to Caecilian, were suppressed in Africa, and a general synod attempted to regulate the faith of the Church.

The subject of the nature of the divine Trinity had early given rise to discussion.  Of the three main heretical views, that of Arius and his disciples was the most prevalent.  He held in effect that the Son, by whom all things were made, though He had been begotten before all worlds, yet had not always existed.  He shone only with the reflected light of His Almighty Father, and, like the sons of the Roman emperors, who were invested with the titles of Caesar or Augustus.  He governed the universe.

The Tritheists advocated a system which seemed to establish three independent deities, while the Sabellian theory allowed only to the man Jesus the inspiration of the divine wisdom.  The consubstantiality of the Father and of the Son had been established by the Council of Nicaea in 325, but the East ranged itself for the most part under the banner of the Arian heresy.  At first indifferent, Constantine at last persecuted the Arians, who later, under Constantius, were received into favour.

Constantinople, which for forty years was the stronghold of Arianism, was converted to the orthodox faith under Theodosius by Gregory Nazianzen.

IV.—­The Conversion of the World