MODERNITY has left nearly every religious tradition in the Western world divided.

The specific issues vary with the faith, but there is an essential sameness to what separates Reform Judaism from Orthodox Judaism, evangelical churches from mainline Protestantism, the liberal Episcopal Church from the conservative Anglican Church in North America.

In each case, disagreements about the authority of tradition, the reliability of Scripture, and eventually the proper response to the Sexual Revolution have made it impossible for liberal and conservative believers to remain in community or communion.

Roman Catholicism, however, remains officially united. The church has a conservative wing, a liberal wing, and a low-grade civil war. But the church’s left and right have found ways to coexist, and since the 1970s any kind of rupture has seemed relatively unlikely.

That coexistence depends on a tension between doctrine and practice, in which the church’s official teaching remains conservative even as the everyday life of Catholicism is shot through with disagreement, relativism, dissent.

Because the teaching is consistent, conservatives are reassured that the church is still essentially unchanging, still the faith of the church fathers, Nicaea and Trent as well as Vatican II.

At the same time, the flexibility and soft heterodoxy of many pastors and parishes and Catholic institutions enables liberal Catholics to feel reasonably at home while they wait for Rome to “evolve” in their direction.

Of course many Catholics on both sides have been dissatisfied with this arrangement. And from the outset of his pontificate, it was clear that Pope Francis was one of them, and that he was determined to renegotiate its terms — in liberal Catholicism’s favor.

The question wasn’t just how far he would go in encouraging flexibility. It was how far he could go without hitting a kind of self-destruct button on his own authority, by seeming to change the church in ways that conservative Catholics deem impossible.

Now we have an answer, of sorts. In his new letter on marriage and the family, the pope does not endorse a formal path to communion for the divorced and remarried, which his allies pushed against conservative opposition at two consecutive synods in Rome, and which would have thrown Catholic doctrine on the indissolubility of marriage (and sexual ethics writ large) into flagrant self-contradiction.

But what he does seem to encourage, in passages that are ambiguous sentence by sentence but clearer in their cumulative weight, is the existing practice in many places — the informal admission of remarried Catholics to communion by sympathetic priests.

This move means that the truce is still in effect, but its terms have distinctly changed. There is still a formal teaching that remarriage without an annulment is adultery, that adultery is a mortal sin, that people who persist in mortal sins should not receive communion. And there is no structure or system in church life that contradicts any of this. This much conservatives still have, and it’s enough to stave off a sense of immediate theological crisis.

But there is also now a new papal teaching: A teaching in favor of the truce itself. That is, the post-1960s separation between doctrine and pastoral practice now has a papal imprimatur, rather than being a state of affairs that popes were merely tolerating for the sake of unity. Indeed, for Pope Francis that separation is clearly a hoped-for source of renewal, revival and revitalization, rather than something that renewal or revival might enable the church to gradually transcend.

Again, this is not the clear change of doctrine, the proof of concept for other changes, that many liberal bishops and cardinals sought. But it is an encouragement for innovation on the ground, for the de facto changes that more sophisticated liberal Catholics believe will eventually render certain uncomfortable doctrines as dead letters without the need for a formal repudiation from the top.

This means that the new truce may be even shakier than the old one. In effectively licensing innovation rather than merely tolerating it, and in transforming the papacy’s keenest defenders into wary critics, it promises to heighten the church’s contradictions rather than contain them.

And while it does not undercut the pope’s authority as directly as a starker change might have, it still carries a distinctive late-Marxist odor — a sense that the church’s leadership is a little like the Soviet nomenklatura, bound to ideological precepts that they’re no longer confident can really, truly work.

A slippage that follows from this lack of confidence is one of the most striking aspects of the pope’s letter. What the church considers serious sin becomes mere “irregularity.” What the church considers a commandment becomes a mere “ideal.” What the church once stated authoritatively it now proffers tentatively, in tones laced with self-effacement, self-critique.

Francis doubtless intends this language as a bridge between the church’s factions, just dogmatic enough for conservatives but perpetually open to more liberal interpretations. And such deliberate ambiguity does offer a center, of sorts, for a deeply divided church.

But not one, I fear, that’s likely to permanently hold.

<ROSS DOUTHAT>