An important but overlooked essay on Christianity and culture is Massey H. Shepherd’s “Before and After Constantine.” In reaction to assertions by historians like Arnold Toynbee that Christianity has been becoming gradually obsolete or, at least, losing its influence, he suggests that the real predicament for Christianity is in another area. The actual problem, asserts Shepherd, is not that Christianity is losing influence, only that it is losing influence in society. It’s possible that in certain small pockets of the West, a vibrant, virile Christianity survives — and even flourishes. But it does not survive as a culturally dominant force.
Whatever one may think of the product of Constantine’s Edict of Milan (313), it ushered in an astoundingly extensive era of Christian culture. In fact, in the East, the longest-lived human empire in the history of the world was Christian — I am speaking, of course, of that centered in Byzantium. Constantine’s edict, it is sometimes presumed, explicitly established Christianity as the official religion of the Empire. This is not correct, as Charles Norris Cochrane observes in his great Christianity and Classical Culture. Constantine granted religious liberty. The Edict of Milan truly was an act of political toleration, canceling persecution of the church and restoring its confiscated lands and other possessions. The fact that Christianity soon became the dominant cultural force in the ambiance of such relative political toleration lends credence to the idea that what is necessary for such dominance is not official political establishment, but only the absence of official political hostility. If given genuine religious freedom, all other factors being equal, Christianity tends to rise to the top.
Christian culture requires religious liberty
Today’s Western world, including its preeminent nation, the United States, does not in practice accord Christianity such freedom. Expressions of orthodox, Biblical Christianity are officially or unofficially outlawed or censured in politics, the major media, the educational institutions, the artistic community, and so on. Note carefully that while the profession of Christianity is permitted to exist in many of these spheres, the practice of such Christianity is often outlawed. No Christian teacher in any state school in the United States may teach Biblical Christianity as absolute, divine truth or evangelize his students. No civil magistrate may enforce the law of God as it relates to aborticide (elective abortion). No local, orthodox church may treat its physical property as though it were an extraterritorial Christian outpost and as a legal haven for those wrongfully persecuted for their faith, race, and so on. It is questionable whether Bible-believing churches will be permitted to discriminate against practicing homosexuals who apply for church membership. The George W. Bush administration elicited a media firestorm when it was thought that it had cut a deal with the Salvation Army to protect this organization from local laws that forbid discrimination in hiring homosexuals. The Boy Scouts, hardly an overt Christian organization, wished simply to maintain its traditional policy of forbidding homosexual Scout leaders; and it was subjected to merciless assaults, even publicly at the Democratic National Convention. In July 2015, under immense pressure, the Scouts ended their ban on openly gay Scout leaders.
If the present trend is not reversed, it is possible that soon in the United States orthodox Christian ministers will not be permitted publicly to declare the Biblical teaching regarding homosexuality, regarding the uniqueness of Jesus Christ as the only way of salvation, and regarding false religion. These will be considered “unprotected” speech in that they offend “good, hard-working Americans.” The problem is not that Christianity as such is becoming less virulent (though this likely also is true), but that it is becoming less relevant in the society at large.
Some jeremiads speak of a “post-Christian” world. It’s more accurate to speak of a post-Constantinian world. Christianity still survives (even, in small pockets, some orthodox Christianity!); but it decreasingly influences education, politics, media, the arts, and so forth. When the present administration in Washington, D.C., for example, floats policies reflecting even the slightest degree of even the most generic Christian faith, the liberal elite in Congress and the media mercilessly shouts them down. While this is inexcusable, it is perfectly understandable, given the present dominant secular culture rabidly hostile to anything that smacks of Biblical faith.
Christian culture is the only viable culture
The only legitimate culture the Bible knows anything about is a godly culture under divine authority mediated in the Bible. It was this culture spawned by Constantine’s act which, however, imperfectly, laid the foundation for a medieval and Reformation Europe Christian culture which, by and large, reflected a sincere, widespread attempt to please God in all things, not merely at church on Sunday. This culture was the fruit (from a human standpoint) not only of vigilant prayer and labor in the family and church, but also in the wider society. It repudiated (or rather, did not even consider) the idea that there could be zones of life impervious to Christianity, the Bible, and the church. This culture is fully compatible with (and, I believe today demands) constitutional democracy and republican forms of government, which tend to check the growth of tyranny.
It is only when Christians recover a full-orbed, liberty-loving faith that we can expect manumission from the slavery of secularism under which we presently languish. We will recover this faith. As my friend Dr. Joseph Boot likes to say, we live not in a post-Christian world but a pre-Christian world: the world of the cultural prevalence of true Christianity uncontaminated by elements of ancient Greek philosophy that blighted medieval Christian culture is ahead of us. Future Christian culture will surpass past Constantinian culture.
via Doc Sandlin
 Massey H. Shepherd, “Before and After Constantine,” in The Impact of the Church Upon Its Culture, Jerald C. Brauer, ed. (Chicago and London: University of Chicago Press, 1968), 17–38.
 Charles Norris Cochrane, Christianity and Classical Culture (New York: Oxford University Press, 1957), 178–179.