Every group of people has a worldview, and every worldview is based on stories that are at least partly mythical. For example, a key part of the progressive worldview is the idea that social change driven by appeals to science and reason is (a) good and (b) irreversible.

Exhibit A is usually the fate of institutional racism: Once upon a time, the story goes, racism was a given. Since the dawn of civilization, the superiority of some races over others was a basic assumption — until at some point in the 19th or 20th century, people, moved by the spirit of the Enlightenment, recognized that racism was false and moved to abolish it. Progress!

This background assumption colors so much of our public debate. For example, when opponents of same-sex marriage warn that social change that is completely unprecedented in the history of human civilization doesn't sound like a good idea, the race card is inevitably thrown down. Thus, in a recent column subtly mocking Alabama Supreme Court Justice Roy Moore for his opposition to same-sex marriage, my colleague Damon Linker rhetorically asks: "Can you point to any socio-cultural revolution — in race, gender, and now sexual orientation — that’s ever been halted or reversed?" and answers his own question: "Me, neither."

Well, actually, race itself is a "socio-cultural revolution" that's been "halted or reversed."

As people on the left of the left, who usually care more about the history of ideas than milquetoast progressives, never tire of pointing out (and rightly), race is a social construct.

Now, prejudice against out-group members, in one form or another, has always been with us, still is, and always will be. And often out-group membership was linked to ancestry or ethnicity — but just as often, it was not. The word "barbarian" which ancient Greeks used as a slur against foreigners referred to their language, not their skin color. The Roman Empire was famously multicultural and multiethnic. Christianity came on the scene proclaiming that "there is neither Jew nor Greek, neither male nor female, but all are one in Christ Jesus," and Ethiopia was one of the earliest countries to be evangelized.

While some forms of distinctions and prejudice based on ancestry have always existed, the specific idea of race and the ideology of racism — the linkage of skin color with natural, immutable, and global essential traits — is an idea that has a very specific history, whose birth can be dated, which came to dominate the cultural worldview, and thence changed law and behavior. In other words, it was a socio-cultural revolution.

Like other socio-cultural revolutions, it started out as a fringe idea and became mainstream seemingly overnight. The idea of studying and classifying "races" as such appears as mostly a sidebar in scientific inquiry in the mid-part of the 18th century, but by the end of the 18th century it's all over the place and by the 19th century the idea of races is pretty much received wisdom. In the American Colonies, the first person to be legally recognized as a slave was owned by a free black man. While some colonies had laws banning marriage between free persons and slaves, none of them originally had anti-miscegenation laws. These laws were passed in a sudden wave, in a matter of a generation.

Like other socio-cultural revolutions, it draped itself under scientific accoutrements. To many people, theories of evolution seemed to naturally indicate that there were different races and that these races had intrinsic traits. "Scientific racism" was all the rage. While we hear about people like James Henley Thornwell, the Southern white Calvinistic preacher who backed slavery, we hear much less about figures like Louis Agassiz, the Swiss-born deist scientist who built a profitable public speaking career in the South promoting scientific racism.

Like other socio-cultural revolutions, it advanced under the banner of moral progress. Racism is inseparable from colonialism and the "white man's burden" to colonize the lesser races to teach them civilization (at the barrel of a gun if need be — for their own good, of course). Another form of so-called moral progress, enthusiastically embraced by progressive elites and coevally linked with racism, is eugenicism. Margaret Sanger, the doyenne of the family planning movement and great advocate of eugenicism was, like the Ku Klux Klan, a sworn enemy of both inferior races and the Catholic Church (and in fact, spoke at a KKK event and was well received).

Like other socio-cultural revolutions, some Christians jumped on the bandwagon, and those who stuck to traditional teachings were branded as backward fundamentalists. It is still ill remembered that, in the infamous Scopes Monkey Trial, William Jennings Bryan's main objection to a school textbook teaching evolution was that it presented evolution as proving a hierarchy of races. One of the main scientific theories used to advance racism was polygeny, or the idea that the different races evolved from different origins; Christians who objected on the grounds that the Bible describes the entire human race as descending from Adam and Eve were dismissed as obscurantists.

Now, it's important for me to make clear what I am not saying. I am not saying that today's progressives are "the real racists." I am not saying that same-sex marriage or any other progressive social movement is the equivalent of racism. Today's progressives have at best a fuzzy lineage with yesteryear's, and all of us are implicated in this civilizational enormity; as one who is "conservative" by today's political standards but firmly in the camp of Enlightenment liberalism, i.e., a "progressive" on the scale of millennia, I don't exculpate myself from this legacy. Not all racists were progressives and not all progressives were racists (it was the French Revolutionaries who banned slavery in the French colonies, for example). No group — ideological, religious, or otherwise — comes out of that complex history looking good (which itself should warn us off easy narratives of Progress vs. the Dark Ages).

What I am saying, however, is that the conventional wisdom on social change is wrong. The conventional wisdom sees our civilization's still-incomplete turn away from racism over the past 50 years as the cornerstone case for the inevitability, goodness, and irreversibility of socio-cultural revolution. In fact, it was not a "socio-cultural revolution"; it was the halting and reversing of a socio-cultural revolution.

Can we draw any lessons from this? Well, that's risky business. But one potential lesson is that while socio-cultural revolutions are reversible, they take a long time to play out — 150 years in this case.

In any case, it turns out, not all social change is irreversible, and some social changes are good, but others are bad. And maybe, just maybe, history is on the side of orthodox Christians after all.