THE Archbishop of Canterbury must just now be feeling the force of a remark by Pope John XXIII, who once said: "I have to be pope both for those with their foot on the accelerator, and those with their foot on the brake." Homosexuality is again on the agenda, revealing much deeper division than the controversy over women bishops. Archbishop Welby has to find a way of keeping within the Anglican Communion two sides whose positions are fundamentally incompatible.

His predicament came to mind this week, during the latest Westminster Faith Debate, which was tackling the question: "Can historic global Churches maintain central authority, or must they devolve?" Now that more Christians live in the Global South than elsewhere, are the historic Roman Catholic and Anglican ecclesial formulae still sustainable?

Classically, there is a balance to be struck between an authoritarian magisterium, which safeguards the orthodoxy of the faith, and a lively authentic expression of Christianity which acts in the lives of individual believers.

There are dangers at both extremes. At its most disciplinarian, a central authority can stifle personal religious integrity with rules and dogma. Cynics might call that Roman Catholicism. At its most chaotic, unregulated individualism can become utterly relativist. The appeal to sola scriptura, which we might parody as Protestantism, only dodges the thorny problem of how the Bible is to be interpreted, by whom, and how prescriptively.

The suppression of dissent in the Roman Catholic Church under John Paul II and Benedict XVI shows the downside of an over-rigid magisterium. The current hokey-cokey over same-sex relationships in the Anglican Communion shows the obverse. Archbishops Welby and Sentamu have appealed for compassion from Anglicans in Africa, and then issued, the day after St Valentine's Day, without evident irony, their own document of cold exclusion to gay Christians in the Church of England. No wonder African church leaders rebuffed their admonition, and then applauded them for their legalism.

The polar dangers here are that, in one case, the tail wags the dog, and, in the other, there is no dog, just the tail.

In the Vatican, Pope Francis is moving to redress a historic imbalance. He recalls vividly his 18 years as a bishop and archbishop in Buenos Aires, when junior Curia officials routinely rejected his recommendations for new Argentinian bishops.

All the eight members of his new Council of Cardinal Advisers have their own unhappy experience of being treated by Curia underlings with an infantilising disregard. This is why new mechanisms for restoring collegiality are top of its list of reforms. It is also why, of 19 men made cardinals last week, only a few were from Europe, and most were from the developing world.

Conservatives are wary. Cardinal Gerhard Müller, the chief watchdog of the Congregation for the Doctrine of the Faith, is no doubt reminding Pope Francis of history's repeated lesson that revolutions come when authoritarian regimes liberalise. But Francis seems determined to let a thousand flowers bloom.

The Archbishop of Canterbury has a similar solution. At the General Synod, he urged the Church not to be afraid of "incoherence and inconsistency", and said that "untidy" arrangements were better than splits (News, 21 February). I suspect that Pope Francis - who famously said he preferred a Church that goes out and risks accidents to a closed one that stays safe and sterile - would agree. He concluded those remarks by saying: "God is always creative, never closed, and this is why he is never rigid. . . To be faithful, one must be creative, one must be able to change."

Pope Francis - Untying the knots by Paul Vallely is published by Bloomsbury.