New York Times columnist Ross Douthat is no one's idea of a radical. In the five and a half years since joining the op-ed page of the paper, he's proved himself to be a thoughtful, measured, and nuanced social-conservative commentator on political and cultural events.

That's why I was surprised when six months ago Douthat responded rashly to reports that Pope Francis had told an Argentine woman that she could receive the sacrament of communion even though she was married to a divorced man. Roman Catholic Church doctrine holds that the woman's marriage is adulterous unless the man's original marriage is annulled — and that someone living in a state of persistent (adulterous) sin should not present herself for communion. The possibility that Francis may have indicated otherwise — that he might have given her a green light to receive the sacrament — led Douthat to warn that any fundamental shift in church teaching on such matters "wouldn't just provoke conservative grumbling; it would threaten outright schism."

That's right: Ross Douthat indicated that any move to reform doctrine on marriage and divorce could well spark the first institutional rupture in the church in nearly 600 years. (The last schism ended in 1417.)

Any ambiguity about whether Douthat was merely predicting a schism or actively threatening one was settled with his column this past Sunday, in which he weighed in on the recently concluded Synod on Marriage and the Family. The synod was chaotic, with reformist bishops (handpicked by the pope) at first seeming to propose significant alterations in church teaching on marriage, divorce, and homosexuality, and then backing off after an outcry from more conservative prelates. After discussing these events and the history of the doctrine of papal infallibility, Douthat concluded that a time may soon come when conservative Catholics will have to decide whether or not to "protect the church from self-contradiction" by choosing to "resist" the pope.

With that remark, the culture war has finally come to the Catholic Church.

Allow me to explain.

Since the mid-1970s, the United States has been embroiled in a culture war over the legacy of the sexual revolution. That war has split our politics — social issues are what most deeply divide Democrats and Republicans, not economics or foreign policy — just as it has split our churches. Over the past two generations, nearly every major Protestant denomination has broken apart into conservative (orthodox) and liberal (progressive/reformist) factions.

Until now, the Catholic Church has avoided that level of rancor. Yes, the church underwent tumultuous reform with Vatican II. But when Pope Paul VI in 1968 upheld the church's traditional ban on the use of artificial contraception even among married couples, he placed the papacy and its teaching authority firmly on the conservative side of the sexual revolution. This was strongly reinforced during the pontificates of John Paul II and Benedict XVI, which together lasted 34 long years. Reformist Catholics could still be found, but they were clearly on the defensive, and over time, increasingly powerless. The institution itself spoke with a united voice against change. That made the church a powerful (and perhaps the most intellectually formidable) combatant on the right-wing side of the culture war. But it also meant that there was no culture war within the church itself.

Not anymore.

Reformist Catholics have their first champion at the top since John XXIII presided over the start of Vatican II in 1962. (He died before it ended three years later.) It's still unclear whether Pope Francis hopes to institute immediate doctrinal changes or merely prepare the way for future change by urging pastors to stop proclaiming and enforcing doctrines he'd like to sweep aside. What is perfectly clear is that he wants some form of liberalization. And that means that for the very first time, the culture war has broken out within the Catholic Church itself.

That's the proper context for understanding Douthat's remarkable Sunday column.

His side's arguments aren't frivolous. Jesus Christ himself declared that marriage is indissoluble — in words found in all three synoptic gospels (Matthew 19:7-9; Mark 10:9-12; Luke 16:18). That's why the church officially teaches that divorce is an impossibility, that a second civil marriage is inevitably adulterous, and that civilly divorced Catholics who are remarried cannot receive communion (since they are living in a state of grave sin with no intention of reforming their behavior). Given the roots of these doctrines in the explicit words of Jesus of Nazareth, and the fact that the doctrines have been infallibly affirmed by numerous popes, a change in the doctrine by Pope Francis would seem to indicate either that he's in error (meaning that he's not a true pope) or that the doctrine of papal infallibility is a crock.

But of course, reformist Catholics disagree — and they, too, have a point. As theologian Natalia Imperatori argued on Twitter in response to Douthat's claims, the context of Christ's statements about marriage was very different from our own. Jesus was talking about the practice of men abandoning their wives at a time when women had no independent rights and were considered their husband's property. In that context, Christ's commands protected women from abuse, but today, abuse is more likely to result from a woman being trapped in a bad marriage. Hence, the genuinely Christian approach would be to stop penalizing people for ending unhappy marriages. Then there's the fact that Eastern Orthodox Christians already permit second marriages (while simply refusing to treat them as sacraments). All together, Catholic reformists claim, it adds up to a strong case for allowing church doctrine on marriage and the family to develop in a progressive direction.

And that's where we are — conflicting views squared off against each other on opposite sides of an unbridgeable divide, just like in the broader culture war. And as Douthat rightly points out in his column, the opposing sides are far more evenly matched today than they were, for example, during Vatican II, when the most sweeping reforms were passed by a margin of roughly 22 to 1. In the United States and Latin America today, conservatives and reformers can each claim the support of millions of parishioners. In Europe, by contrast, the reformers far outnumber their opponents, while in Africa (where the church is growing rapidly) the situation is reversed, with conservatives in a very strong position. Everything's in place for a cultural war of attrition played out across the globe, within nations, between regions — with the possibility of the outright schism that Douthat appears prepared to endorse looming ominously in the background.

Pope Francis may fashion himself a reformer. He appears at least as likely to end up known as the pontiff who provoked a cultural conflagration with the potential to tear the church apart.