The accomplishment that Constantine the Great is known for more than any other is his official recognition of Christianity and the Christian church. For some this was momentous for all the wrong reasons: it signalled the beginning of the end. As soon as the state acknowledges the Christian faith, the church becomes worldly, looking more to the favour of government than to God.
But it begs an inevitable question: what is the proper and biblically legitimate face of the state towards Christ and the Christian church? As long as the Church remains a small minority amidst a sea of paganism this question may be avoided, since it is speculative and irrelevant to actual circumstances. But when the Christian population grows to double figure percentages the issue can no longer be avoided.
A legitimate question then is where ought we to stand with respect to the Constantinian solution?
First off, we had better understand what Constantine's solution was. Upon assuming control of the Empire, Constantine did not "legalize" Christianity. Back in 306 when he was proclaimed Augustus of the West at York in Britain, he ended the persecution of Christians. From that time on it was legal to be a Christian and to live out the Christian faith in the western portions of the Empire.
Seven years later, in 313 Constantine and his fellow Augusti, Licinius signed two letters after discussing religious policy in general and Christianity in particular. These letters did not make Christianity the official religion of the Empire. Instead they declared religious liberty for all.
Considering it "highly consonant to right reason," they adopted the policy that "no man should be denied leave of attaching himself to the rites of the Christians, or to whatever other religion his might directed him." Thus all Christians "are to be permitted, freely and absolutely to remain in it, and not to be disturbed in any ways, or molested." [Peter Leithart, Defending Constantine: The Twilight of and Empire and the Dawn of Christendom (Downers Grove, Illinois: IVP Academic, 2010), p. 99.]This policy of religious liberty for all drew heavily on the teaching of Lactantius, who was very close to Constantine and his family. He argued that God does not want force to be used in religion; force is always inimical to true belief.
. . . one cannot be chaste and pious in religion if one is coerced to worship. Force pollutes rather than purifies religion. "For religion is to be defended, " he wrote, "not by putting to death, but by dying; not by cruelty, but by patient endurance; not by guilt, but by good faith: for the former belong to evils, but the latter to goods; and it is necessary for that which is good to have place in religion, and not that which is evil. For if you wish to defend religion by bloodshed, and by tortures, and by guilt, it will no longer be defended, but will be polluted and profaned." (Ibid., p. 108)Lactantius and Constantine were arguing that this was the true Christian position. True faith in God is inimical to force and compulsion. Liberty of conscience is necessary to true faith. Without it, faith cannot be true. Practically, this meant the toleration of paganism.
Now this did not mean that Constantine was a pagan sympathiser, or that he adopted a mien of neutrality towards all religions. Rather, he overtly and deliberately spoke against paganism and idolatries of all kinds: devotees of such were imprisoned in temples of lies. He also publicly favoured and supported the Church. But he allowed pagans to worship and believe as they chose, whilst at the same time calling them to come into the light. In an edict to the Eastern Provinces in 324 he
. . . attacked the irrationality of polytheism and defended monotheism. He recalled his father's kindness to the church with fondness and recounted the arrogance and stupidity of the persecuting emperors, "unsound in mind" and "more zealous of cruel than gentle measures." . . . .The official position, then, was that paganism and idolatry were clearly wrong in so many ways, but pagans were free to practise their faith. Constantine expressed fervent hope that in time they, too, would come to faith in Christ. And that faith could not be forced: such measures would destroy faith. In the meantime, Constantine encouraged and promoted the Christian faith. His public square was never neutral. Nor is our own, despite protestations to the contrary.
Having exposed the error, savagery, and the political evils of paganism, and just as the reader is ready for the hammer to fall, Constantine revealed the thrust of his edict. Insisting that his desire was "for the common good of the world and the advantage of all mankind, that your people should enjoy a life of peace and undisturbed concord," he declared that "anyone who delight(s) in error, [should] be made welcome to the same degree of peace and tranquillity which they have who believe." . . . .
As it comes to a close, the edict modulates from imperial pronouncement to prayer: "We"--he meant "we Christians"--"have the glorious edifice of your truth, which you have given us as our native home. We pray, however, that they [the pagans] too may receive the same blessing, and thus experience that heartfelt joy which unity of sentiment inspires". . . . Constantine is less a theocrat imposing Christianity than Billy Graham issuing an altar call. (Ibid., p. 110f)
The Constantinian "establishment" was very different from popular misunderstandings and misrepresentations.