Since his election six months ago, Pope Francis has proved himself a pontiff of surprises. He has chosen to live in a modest Vatican hotel room instead of the grandeur of the apostolic palace; and he has dropped some of the papal pomp, while preaching the Roman Catholic church's need to identify with the world's poor.
Signs are, moreover, that he is about to clean up the scandal-ridden state of the Vatican bureaucracy and its dubious finances.
But last week he went beyond gestures and good housekeeping.
In a 12,500-word Q&A article published on the website of America magazine – a popular Catholic journal run by Jesuits – he challenged two crucial mission statements of the last two pontificates.
At the heart of the interview he evokes an image of the church that drastically contradicts a favoured metaphor of his predecessor, Benedict XVI.
For Catholics, with their 1.2bn membership spread in every part of the world, imagery is everything. Francis says: "This church with which we should be thinking is the home of all, not a small chapel that can hold only a small group of selected people. We must not reduce the bosom of the universal church to a nest protecting our mediocrity.''
When he was the Vatican's watchdog of orthodoxy, Benedict – as Cardinal Joseph Ratzinger, and later as pope – urged precisely and repeatedly a version of that "small chapel" image.
He declared that the church would benefit from scaling down, to exclude dissidents and the barely practising. He drew a parallel with the church of the persecuted early Christians who preserved their orthodoxy in the catacombs.
Benedict argued that the church will survive by becoming a smaller obedient Church, a just "remnant".
As recently as last year he attacked Catholic critics, likening them to Judases.
But the Catholic church, avers Francis, is not an exclusive community of the just, but a big tent of sinners.
In another remarkable image he refers to the church as a "field hospital after battle", a place of healing for the lapsed, the doubting and the conflicted.
When asked to describe himself, he replies: "I am a sinner. This is the most accurate definition. It is not a figure of speech, a literary genre. I am a sinner." His besetting sin, as a young church leader, he confesses, was being "authoritarian".
In a profound critique of papal infallibility, he asserts that the church avoids error when it listens, and "thinks with" the entire faithful rather than dispensing top-down dogma.
Francis then goes on to dismiss a central feature of Pope John Paul II's 27-year pontificate.
Almost daily John Paul inveighed against the "culture of death" – abortion, contraception, homosexuality, divorce, sex before marriage, and the use of condoms even between partners with HIV.
But Francis says: "We cannot insist only on issues related to abortion, gay marriage and the use of contraceptive methods. This is not possible. I have not spoken much about these things, and I was reprimanded for that."
He adds, as if to avoid accusations of rank heresy: "The teaching of the church, for that matter, is clear and I am a son of the church."
Then he hammers home his point: "But it is not necessary to talk about these issues all the time."
This is good news for those Catholics who believe that there should be more to being Catholic than an obsession with what happens between the sheets.
The conservative Catholic media, led by the Catholic Herald in the UK, have been quick to
argue, at times as if through gritted teeth, that Francis has only endorsed authentic Catholic teaching.
In the US, where the Catholic divide is more shrill, conservative church apologists have accused the secular media, not least the New York Times, of distorting Francis's words. But conservative Catholic opinion is clearly rattled.
In America's National Catholic Register one commentator admits: "I'll be honest; I was disturbed. While it's clear that the pope is not changing church teaching, he is clearly changing the emphasis. The pope with a few words has unsettled so much."
The pope's interview is set to create tensions in the church's right-left divide. The liberals, now with Francis on their side, argue that Catholicism should be collegial, pluralist, ecumenical, inclusive, engaged with the secular world and other faiths. Their image of the church is of a pilgrim people on the move.
The conservatives promote a triumphalist church, which Francis clearly rejects. They deplore the loss of ancient liturgy and Latin; they are sticklers for the rules, especially on sexual morality, and prize top-down authority over individual conscience.
They are quick to see the least criticism of the church as defamation.
Francis clearly has the conservatives in mind when he says that the church "has locked itself up in small things, in small-minded rules".
The conservatives are unlikely to acquiesce without a fight, and Francis now risks criticism of his papacy up to the highest level, including the bishops – who have so far kept their counsel.
But Francis insists that failure to create a new emphasis threatens greater damage than inaction.
"We have to find a new balance," he says, "otherwise even the moral edifice of the church is likely to fall like a house of cards, losing the freshness and fragrance of the Gospel."
The image of the church – the Rock of Ages – as a "house of cards" is unprecedented in any era.
Should non-Catholics be impressed by a more compassionate and pluralist church?
The power and scope of Catholicism's moral voice in the world – on issues as diverse as the environment, war, terrorism, world hunger and the homeless – has plummeted as a consequence of the clerical child abuse scandal.
While priests abused their young sexually, bishops and even the Vatican often failed to act.
At the same time, non-stop papal denunciations of the sexual sins of consenting adults gave an impression of hypocrisy right up to the papacy.
Pope Francis's powerful admission that even "His Holiness" is a sinner, and that the Church of Rome is manifestly fallible and vulnerable to the point of collapse through its own faults and complacency, may shock the traditionalist faithful.
But it may signal the beginning of a slow and painful restoration of moral authority both within the Catholic church and beyond.