Was his conversion sincere- was it ail act of religious belief, or a consummate stroke of political wisdom? Probably the latter. His mother Helena had turned to Christianity when Constantius divorced her; presumably she had acquainted her son with the excellences of the Christian way; and doubtless he had been impressed by the invariable victory that had crowned his arms under the banner and cross of Christ. But only a skeptic would have made so subtle a use of the religious feelings of humanity. The Historia Augusta quotes him as saying, “it is Fortuna that makes a man emperor”- though this was a bow to modesty rather than to chance. In his Gallic court he had surrounded himself with pagan scholars and philosophers. After his conversion he seldom conformed to the ceremonial requirements of Christian worship. His letters to Christian bishops make it clear that he cared little for the theological differences that agitated Christendom- though he was willing to suppress dissent in the interests of imperial unity. Throughout his reign he treated the bishops as his political aides; he summoned them, presided over their councils, and agreed to enforce whatever opinion their majority should formulate. A real believer would have been a Christian first and a statesman afterward; with Constantine it was the reverse. Christianity was to him a means, not an end.
He had seen in his lifetime the failure of three persecutions; and it was not lost upon him that Christianity had grown despite them. Its adherents were still very much in the minority; but they were relatively united, brave, and strong, while the pagan majority was divided among many creeds, and included a dead weight of simple souls without conviction or influence. Christians were especially numerous in Rome under Maxentius, and in the East under Licinius; Constantine’s support of Christianity was worth a dozen legions to him in his wars against these men. He was impressed by the comparative order and morality of Christian conduct, the bloodless beauty of Christian ritual, the obedience of Christians to their clergy, their humble acceptance of life’s inequalities in the hope of happiness beyond the grave; perhaps this new religion would purify Roman morals, regenerate marriage and the family, and allay the fever of class war. The Christians, despite bitter oppression, had rarely revolted against the state; their teachers had inculcated submission to the civil powers, and had taught the divine right of kings. Constantine aspired to an absolute monarchy; such a government would profit from religious support; the hierarchical discipline and ecumenical authority of the Church seemed to offer a spiritual correlate for monarchy. Perhaps that marvelous organization of bishops and priests could become an instrument of pacification, unification, and rule? Nevertheless, in a world still preponderantly pagan, Constantine had to feel his way by cautious steps. He continued to use vague monotheistic language that any pagan could accept. During the earlier years of his supremacy he carried out patiently the ceremonial required of him as pontifex maximus of the traditional cult; he restored pagan temples, and ordered the taking of the auspices. He used pagan as well as Christian rites in dedicating Constantinople. He used pagan magic formulas to protect crops and heal disease. Gradually, as his power grew more secure, he favored Christianity more openly. After 317 his coins dropped one by one their pagan effigies, until by 323 they bore only neutral inscriptions. A legal text of his reign, questioned but not disproved, gave Christian bishops the authority of judges in their dioceses; other laws exempted Church realty from taxation, made Christian associations juridical persons, allowed them to own land and receive bequests, and assigned the property of intestate martyrs to the Church. Constantine gave money to needy congregations, built several churches in Constantinople and elsewhere, and forbade the worship of images in the new capital. Forgetting the Edict of Milan, he prohibited the meetings of heretical sects, and finally ordered the destruction of their conventicles. He gave his sons an orthodox Christian education, and financed his mother’s Christian philanthropies. The Church rejoiced in blessings beyond any expectation. Eusebius broke out into orations that were songs of gratitude and praise; and all over the Empire Christians gathered in festal thanksgiving for the triumph of their God. Three clouds softened the brilliance of this “cloudless day”: the monastic secession, the Donatist schism, the Arian heresy. In the interval between the Decian and the Diocletian persecution the Church had become the richest religious organization in the Empire, and had moderated its attacks upon wealth. Cyprian complained that his parishioners were mad about money, that Christian women painted their faces, that bishops held lucrative offices of state, made fortunes, lent money at usurious interest, and denied their faith at the first sign of danger. Eusebius mourned that priests quarreled violently in their competition for ecclesiastical preferment. While Christianity converted the world, the world converted Christianity, and displayed the natural paganism of mankind. Christian monasticism arose as a protest against this mutual adjustment of the spirit and the flesh. A minority wished to avoid any indulgence of human appetite, and to continue the early Christian absorption in thoughts of eternal life. Following the custom of the Cynics, some of these ascetics renounced all possessions, donned the ragged robe of the philosopher, and subsisted on alms. A few, like Paul the Hermit, went to live as solitaries in the Egyptian desert. About 275 an Egyptian monk, Anthony, began a quarter century of isolated existence first in a tomb, then in an abandoned mountain castle, then in a rock-hewn desert cell. There he struggled nightly with frightful visions and pleasant dreams, and overcame them all; until at last his reputation for sanctity filled all Christendom, and peopled the desert with emulating eremites. In 325 Pachomius, feeling that solitude was selfishness, gathered anchorites into an abbey at Tabenne in Egypt, and founded that cenobitic, or community, monasticism which was to have its most influential development in the West. The Church opposed the monastic movement for a time, and then accepted it as a necessary balance to its increasing preoccupation with government.
Within a year after Constantine’s conversion the Church was torn by a schism that might have ruined it in the very hour of victory. Donatus, Bishop of Carthage, supported by a priest of like name and temper, insisted that Christian bishops who had surrendered the Scriptures to the pagan police during the persecutions had forfeited their office and powers; that baptisms or ordinations performed by such bishops were null and void; and that the validity of sacraments depended in part upon the spiritual state of the ministrant. When the Church refused to adopt this stringent creed, the Donatists set up rival bishops wherever the existing prelate failed to meet their tests. Constantine, who had thought of Christianity as a unifying force, was dismayed by the chaos and violence that ensued, and was presumably not unmoved by the occasional alliance of Donatists with radical movements among the African peasantry. He called a council of bishops at Arles (314), confirmed its denunciation of the Donatists, ordered the schismatics to return to the Church, and decreed that recalcitrant congregations should lose their property and their civil rights (316). Five years later, in a momentary reminiscence of the Milan edict, he withdrew these measures, and gave the Donatists a scornful toleration. The schism continued till the Saracens overwhelmed orthodox and heretic alike in the conquest of Africa.