A group of conservative clerics has accused Pope Francis of heresy for his attempts to liberalise the church’s treatment of divorced people. This raises an interesting question: how long must a pope be dead before his opinions can safely be ignored? For many people the answer is “no time at all”: it is not just humanists, Muslims and Protestants, but the vast majority of the world’s Catholics who take little notice of Catholic doctrine when they disagree with it. The Catholic right ignores more than a hundred years of consistent papal teaching against the excesses of capitalism, along with more recent denunciations of the death penalty, of wars of aggression and of environmental destruction. The Catholic left ignores the pope’s teachings on sexuality – and everyone ignores the ban on contraception.

Popes themselves, however, are meant to take their predecessors very seriously even though neither party is writing infallibly. Papal encyclicals read like legal documents, buttressed with footnotes to prove that doctrine has not changed, and that they are just repeating what their predecessors meant, even when they contradict what was plainly said. Those magnificent robes conceal some very fancy footwork at times. It is an article of faith – literally – that doctrine can never change, only develop, and the eye of faith can clearly see the subtle differences between change, development and decay. So the 19th-century denunciations of democracy and freedom of thought and conscience are now ignored, but pope John Paul II’s refusal to admit women priests looks certain to stand for another couple of centuries at least.

What, though, of Pope John Paul II’s equally clear denunciation of divorced and remarried couples taking communion, restated forcefully only 14 years ago? “Those who obstinately persist in manifest grave sin”, as he referred to remarried divorcees, are to be banned from participation in the central rite of the church. Even at the time, this was widely ignored – his letter is one of those laws from which historians can conclude that the conduct banned was commonplace. There can be very few Catholic congregations in the west without divorced and remarried communicants and everyone knows this. To turn them away at the altar rails would cause a public scandal, and that is also banned. So it’s unlikely that the letter had any effect on the facts on the ground.

But the efforts of the present pope, Francis, to reverse his predecessors’ policy have provoked a vigorous backlash. Whether he is changing doctrine, as his opponents charge, or merely the interpretation of doctrine, as his supporters claim, there is no doubt that he wants the church to encourage some of the people who are in breach of its regulations on sexuality to take communion. The issue is simply no longer controversial in any other church, despite Jesus’s clear statement of principled opposition to divorce.

Only the Catholic church has the combination of bureaucracy and authoritarianism that makes it so difficult for the clergy to learn from the experience of their flocks. The very idea that the church should learn from the world and not teach it outrages some Catholics. The most recent development is the publication of a long letter accusing the pope of heresy for his beliefs about remarriage, signed by 62 conservative clergy, who appear keen on refighting the Reformation 500 years on: they also accuse Francis of various Lutheran heresies incomprehensible to the untrained mind. Francis sees the church as a hospital; his enemies see it (as Luther did) as a kind of fortress against error and infidels. The important thing, though, is that Francis after years of debate is winning the argument. There are 4,000 bishops in the worldwide church; only one, who is 94, has signed it. Plenty of Catholics may disagree with Francis. But no one in the hierarchy dares publicly ignore him, at least while he’s alive.