This article covers the events of, reaction to, and historical legacy of Emperor Constantine I's legalization, legitimization, and eventual conversion to Christianity.

Note on Period Historical Sources

It should be noted that historical sources of the 4th century Roman Empire seem to be unusually rich in omens, magic, hexes and spells, while lacking in critical inquiry. A suspicion of literacy and higher learning which began at least a century before had grown. These may have been the results of the fear and high mortality rates caused by the first and second outbreak of the Antonine Plague (165 - 180 and 251 - 266 respectively).

Constantine's Vision

Constantine is perhaps best known for being the first Roman Emperor to freely allow Christianity. The traditional story of Constantine's reasoning for toleration, and his later conversion (officially he did not convert until he was on his deathbed, according to most sources) is presented as Constantine seeing an omen in the sky — two Greek letters, chi and rho (the first two letters of the name of Jesus Christ in Greek) with the inscription In hoc signo vinces (with this sign, you will conquer) before his victory in the Battle of Milvian Bridge on October 28, 312. Upon seeing this vision, Constantine is said to have instituted a new standard to be carried into battle called the labarum. There are at least 3 different surviving ancient versions of this battle in greater detail.

See: Of the Manner in Which the Persecutors Died, Chapter 44, by Lactantius, The Life of Constantine, Chapters 24-31, by Eusebius of Caesarea, and New History, Book 2 43,44 by Zosimus; this version seems to have numerous owls as an omen of victory.

Christianity's Status in the Empire before the Edict of Milan

Contrary to popular imagery, hunting Christians was not the first priority of the Roman Empire. Only under the specific direction of reigning emperors were persecutions enforced.

• Caesar Nero, who sponsored rumors of cannibalism at Christian gatherings
• Septimius Severus (193-211) ordered provincial governors to round up Christians and punish
  
  
  
  them according to the local governor's preference
• Emperor Alexander, who was friendly to the Christian movement and built a shrine to Jesus in his own home next to his shrines to the Roman gods
• The persecution of Diocletian (251–312?) was probably the most extreme; he ordered Christian buildings (and the homes of Christians) torn down, their sacred books collected and burned, and Christians themselves were denied the protection offered other citizens by Roman law. Christians were arrested, tortured, mutilated, burned, starved, and forced to gladiatorial contests to amuse spectators.

In the end, many Christians kept their religion to themselves even during times of peace, because it was all too likely that the peace would soon be replaced by violence, and that those who had revealed themselves as Christians might be remembered as such during later trials.

Constantine's Edicts and Actions

Constantine and Licinius' Edict of Milan (313) neither made paganism illegal nor made Christianity a state-sponsored religion, rather it granted religious freedom. It legalized Christianity, returned confiscated Church property, and established Sunday as a day of worship.

The Practical Effects of Constantine's Actions

The effects of the legitimization of Christianity, and the Roman public's reaction to it, were mixed. For the Christians themselves, it was an unprecedented boon. After the Edict of Milan, all manner of new avenues were opened to Christians, including the right to compete with pagan Romans in the traditional cursus honorum for high government positions, and greater acceptance into general civil society. New churches were allowed to be constructed, including the Church of the Nativity in Bethlehem and the Church of the Holy Sepulchre in Jerusalem. Church leadership became increasingly bold — Christian bishops took aggressive public stances that were unheard of among other religions.

Though the church prospered under Constantine's patronage, its controversies, which had been lively within the Christian communities since the mid-2nd century, now flared in public schisms often accompanied by riotous violence — see, for example, the Donatist schism in Africa. Constantine, who as all Roman emperors believed himself divinely appointed, saw quelling religious disorder as the emperor's duty and eventually called the First Council of Nicaea (May 20 - July 25, 325) to settle some of the doctrinal problems plaguing the early church.

Likewise, not all segments of Roman society reacted positively either. The tendencies towards public prominence of church leaders lead to the outlawing of public Proselytism. And in the Roman legions, considered a critical component of Roman society, Christianity was unpopular both because it accepted women, and because the soldiers generally were members of other religions such

Also, as Christianity began to move from a position of toleration to one of preference, followers of the old religion turned to appeals to the state to protect their own traditions. For example, when the Altar of Victory was desecrated and removed from its place of honor in the Senate, the Senate deputized Symmachus, prefect of Rome, to appeal to the Emperor for its return. Symmachus publicly characterized the late Emperor Constantine's policy, in a plea for freedom of religion:

" diminished none of the privileges of the sacred virgins, he filled the priestly offices with nobles, he did not refuse the cost of the Roman ceremonies, and following the rejoicing Senate through all the streets of the eternal city, he contentedly beheld the shrines with unmoved countenance, he read the names of the gods inscribed on the pediments, he enquired about the origin of the temples, and expressed admiration for their builders. Although he himself followed another religion, he maintained its own for the empire, for everyone has his own customs, everyone his own rites. The divine mind has distributed different guardians and different cults to different cities. As souls are separately given to infants as they are born, so to peoples the genius of their destiny." (Possible Christian insertion in italics.)

—. (The Memorial has been emended to address three emperors, Valentinian II (died 392), Theodosius I, and Arcadius. Arcadius was named co-ruler of his father and Augustus in January, 383. So the address to the three Augusti could have been written anywhere between 383 and 392. There may be Christian adulterations of the text. The reply of Ambrose, Bishop of Milan, is appended, which is highly revealing in the character of his argument in rebuttal.)

See: Diocletian's Edicts against the Christians, Galerius Maximianus, and Lactantius' Of the Manner in which the Persecutors Died, Chapters 21-24). (MacMullen, 1990 & 1966, Wilken, 1984)

Persian Reaction

Beyond the limites, east of the Euphrates, the Sassanid rulers of the Persian Empire had usually tolerated their Christians. A Letter supposedly from Constantine to Shapur II of Persia (both lived and reigned from 310 to 379), written in c. 324 urged him to protect the Christians in his realm… With the edicts of toleration in the Roman Empire, Christians in Persia would now be regarded as allies of Persia's ancient enemy, and were thus persecuted. Shapur II wrote to his generals:

You will arrest Simon, chief of the Christians. You will keep him until he signs this document and consents to collect for us a double tax and double tribute from the Christians … for we Gods have all the trials of war and they have nothing but repose and pleasure. They inhabit our territory and agree with Caesar, our enemy. (quoted in Freya Stark, Rome on the Euphrates 1967, p. 375)

It was not a surprising demand in the circumstances. The Sassanids were perennially at war with Rome, (which incidently raises further doubt on the authenticity of this letter). Christians were now suspected for potential treachery. The "Great Persecution" of the Persian Christian churches occurred in a later period, 340 to 363, after the Persian Wars that reopened upon Constantine's death. In 344 came the martyrdom of Catholicos Shimun bar Sabbae, with five bishops and 100 priests.

Historical Reflections on Constantine's Actions

Christian historians ever since Lactantius have adhered to the view that Constantine "adopted" Christianity as a kind of replacement for the official Roman paganism. Though the document called the "Donation of Constantine" was proved a forgery (though not until the 15th century, when the stories of Constantine's conversion were long-established "facts") it was attributed as documenting the conversion of the Roman Empire to Christianity for centuries. Even Christian skeptics have accepted this formulation, though seeing Constantine's policy as a political one, unifying and strengthening the Empire, rather than a spiritual move. Still the Edict of Milan indicated that reverence to the Divine, as shown by past events, was for the good of the Roman Empire. The Roman Emperor has become more responsible to the Divine for giving religious guidance to its people than in the past.

Despite the questions surrounding Constantine, he is celebrated as a major Saint of Eastern Orthodoxy, together with his mother Helena (both feasted on 21 May). The emperor is not only considered an example of a "Christian monarch" (isapostolos - "equal to the Apostles"), he is associated, albeit in retrospect, with the idea of a "Second Rome" - the Byzantine one.

See also

• Constantinian shift