The occurrence is variously described, and is not without serious difficulties. Lactantius, the earliest witness, some three years after the battle, speaks only of a dream by night, in which the emperor was directed (it is not stated by whom, whether by Christ, or by an angel) to stamp on the shields of his soldiers 'the heavenly sign of God,' that is, the cross with the name of Christ, and thus to go forth against his enemy. Eusebius, on the contrary, gives a more minute account, on the authority of a subsequent private communication of the aged Constantine himself under oath—not, however, till the year 338, a year after the death of the emperor, his only witness, and twenty-six years after the event. On his march from Gaul to Italy (the spot and date are not specified), the emperor, while earnestly praying to the true God for light and help at this critical time, saw, together with his army, in clear daylight toward evening, a shining cross in the heavens above the sun, with the inscription: 'By this conquer;' and in the following night Christ himself appeared to him while he slept, and directed him to have a standard prepared in the form of this sign of the cross, and with that to proceed against Maxentius and all other enemies. This account of Eusebius, or rather of Constantine himself, adds to the night dream of Lactantius the preceding vision of the day, and the direction concerning the standard, while Lactantius speaks of the inscription of the initial letters of Christ's name on the shields of the soldiers. According to Rufinus, a later historian, who elsewhere depends entirely on Eusebius, and can therefore not be regarded as a proper witness in the case, the sign of the cross appeared to Constantine in a dream (which agrees with the account of Lactantius), and upon his awaking in terror, an angel (not Christ) exclaimed to him: 'Hoc vince.' Lactantius, Eusebius, and Rufinus are the only Christian writers of the fourth century, who mention the apparition. But we have besides one or two heathen testimonies, which, though vague and obscure, still serve to strengthen the evidence in favor of some actual occurrence. The contemporaneous orator Nazarius, in a panegyric upon the emperor, pronounced March 1, 321, apparently at Rome, speaks of an army of divine warriors and a divine assistance which Constantine received in the engagement with Maxentius; but he converts it to the service of heathenism by recurring to old prodigies, such as the appearance of Castor and Pollux.
This famous tradition may be explained either as a real miracle implying a personal appearance of Christ, or as a pious fraud, or as a natural phenomenon in the clouds and an optical illusion, or finally as a prophetic dream.
The propriety of a miracle, parallel to the signs in heaven which preceded the destruction of Jerusalem, might be justified by the significance of the victory as marking a great epoch in history, namely, the downfall of paganism and the establishment of Christianity in the empire. But even if we waive the purely critical objections to the Eusebian narrative, the assumed connection, in this case, of the gentle Prince of peace with the god of battle, and the subserviency of the sacred symbol of redemption to military ambition, is repugnant to the genius of the gospel and to sound Christian feeling, unless we stretch the theory of divine accommodation to the spirit of the age and the passions and interests of individuals beyond the ordinary limits. We should suppose, moreover, that Christ, if he had really appeared to Constantine either in person (according to Eusebius) or through angels (as Rufinus and Sozomen modify it), would have exhorted him to repent and be baptized rather than to construct a military ensign for a bloody battle. In no case can we ascribe to this occurrence, with Eusebius, Theodoret, and older writers, the character of a sudden and genuine conversion, as to Paul's vision of Christ on the way to Damascus; for, on the one hand, Constantine was never hostile to Christianity, but most probably friendly to it from his early youth, according to the example of his father, and, on the other, he put off his baptism quite five and twenty years, almost to the hour of his death.
The opposite hypothesis of a mere military stratagem or intentional fraud is still more objectionable, and would compel us either to impute to the first Christian emperor, at a venerable age, the double crime of falsehood and perjury, or, if Eusebius invented the story, to deny to the 'father of church history' all claim to credibility and common respectability. Besides, it should be remembered that the older testimony of Lactantius, or whoever was the author of the work on the Deaths of Persecutors, is quite independent of that of Eusebius, and derives additional force from the vague heathen rumors of the time. Finally the Hoc vince, which has passed into proverbial significance as a most appropriate motto of the invincible religion of the cross, is too good to be traced to sheer falsehood. Some actual fact, therefore, must be supposed to underlie the tradition, and the question only is this, whether it was an external, viable phenomenon or an internal experience.
The hypothesis of a natural formation of the clouds, which Constantine by an optical illusion mistook for a supernatural sign of the cross, besides smacking of the exploded rationalistic explanation of the New Testament miracles, and deriving an important event from a mere accident, leaves the figure of Christ and the Greek or Latin inscription, 'By this sign thou shalt conquer!' altogether unexplained.
We are shut up, therefore, to the theory of a dream or vision, and an experience within the mind of Constantine. This is supported by the oldest testimony of Lactantius, as well as by the report of Rufinus and Sozomen, and we do not hesitate to regard the Eusebian cross in the skies as originally a part of the dream, which only subsequently assumed the character of an outward objective apparition, either in the imagination of Constantine or by a mistake of the memory of the historian, but in either case without intentional fraud. That the vision was traced to supernatural origin, especially after the happy success, is quite natural and in perfect keeping with the prevailing ideas of the age. Tertullian and other ante-Nicene and Nicene fathers attributed many conversions to nocturnal dreams and visions. Constantine and his friends referred the most important facts of his life, as the knowledge of the approach of hostile armies, the discovery of the holy sepulchre, the founding of Constantinople, to divine revelation through visions and dreams. Nor are we disposed in the least to deny the connection of the vision of the cross with the agency of Divine Providence, which controlled this remarkable turning point of history. We may go farther and admit a special providence, or what the old divines call a providentia specialissima; but this does not necessarily imply a violation of the order of nature or an actual miracle in the shape of an objective personal appearance of the Saviour. We may refer to a somewhat similar, though far less important, vision in the life of the pious English Colonel James Gardiner. The Bible itself sanctions the general theory of providential or prophetic dreams and nocturnal visions through which divine revelations and admonitions are communicated to men.
The facts, therefore, may have been these: Before the battle, Constantine, leaning already toward Christianity as probably the beat and most hopeful of the various religions, seriously sought in prayer, as he related to Eusebius, the assistance of the God of the Christians, while his heathen antagonist, Maxentius, according to Zosimus, was consulting the sibylline books and offering sacrifice to the idols. Filled with mingled fears and hopes about the issue of the conflict, he fell asleep, and saw in a dream the sign of the cross of Christ with a significant inscription and promise of victory. Being already familiar with the general use of this sign among the numerous Christians of the empire, many of whom no doubt were in his own army, he constructed the labarum,[A] afterward so called, that is, the sacred standard of the Christian cross with the Greek monogram of Christ,[B] which he had also put upon the shields of the soldiers. To this cross-standard, which now took the place of the Roman eagles, he attributed the decisive victory over the heathen Maxentius.
Accordingly, after his triumphal entrance into Rome, he had his statue erected upon the forum with the labarum in his right hand, and the inscription beneath: 'By this saving sign, the true token of bravery, I have delivered your city from the yoke of the tyrant.' Three years afterward the senate erected to him a triumphal arch of marble, which to this day, within sight of the sublime ruins of the pagan Colosseum, indicates at once the decay of ancient art and the downfall of heathenism; as the neighboring arch of Titus commemorates the downfall of Judaism and the destruction of the temple. The inscription on this arch of Constantine, however, ascribes his victory over the hated tyrant, not only to his master mind, but indefinitely also to the impulse of Deity; by which a Christian would naturally understand the true God, while a heathen, like the orator Nazarius, in his eulogy on Constantine, might take it for the celestial guardian power of the urbs æterna.
At all events the victory of Constantine over Maxentius was a military and political victory of Christianity over heathenism; the intellectual and moral victory having been already accomplished by the literature and life of the church in the preceding period. The emblem of ignominy and oppression[C] became thenceforward the badge of honor and dominion, and was invested in the emperor's view, according to the spirit of the church of his day, with a magic virtue. It now took the place of the eagle and other field badges, under which the heathen Romans had conquered the world. It was stamped on the imperial coin, and on the standards, helmets, and shields of the soldiers. Above all military representations of the cross the original imperial labarum shone in the richest decorations of gold and gems; was intrusted to the truest and bravest fifty of the body guard; filled the Christians with the spirit of victory, and spread fear and terror among their enemies; until, under the weak successors of Theodosius II., it fell out of use, and was lodged as a venerable relic in the imperial palace at Constantinople.
Before this victory at Rome (which occurred October 27, 312), either in the spring or summer of 312, Constantine, in conjunction with his Eastern colleague, Licinius, had published an edict of religious toleration, now not extant, but probably a step beyond the edict of the still anti-Christian Galerius in 311, which was likewise subscribed by Constantine and Licinius as co-regents. Soon after, in January, 313, the two emperors issued from Milan a new edict (the third) on religion, still extant both in Latin and Greek, in which, in the spirit of religious eclecticism, they granted full freedom to all existing forms of worship, with special reference to the Christian. This religion the edict not only recognized in its existing limits, but also—what neither the first nor perhaps the second edict had done—allowed every heathen subject to adopt it with impunity. At the same time the church buildings and property confiscated in the Diocletian persecution were ordered to be restored, and private property-owners to be indemnified from the imperial treasury.