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.