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With leaders of the Catholic Church about to gather in the Vatican to consider the future of the Church's teaching on the family, the BBC's director of news and current affairs, James Harding, asks whether Pope Francis is the moderniser progressives hope for, or an orthodox pontiff with a personal touch.

Just over a year ago, a phone rang in the offices of La Repubblica - Italy's main centre-left newspaper. Stella Somma, personal assistant to the editor, answered.

The man at the end of the line said he would like to speak to Eugenio Scalfari, the founder and former editor of the paper, a 90-year-old atheist, and a hero of the secular left.

"Who's speaking?" Stella asked. "Papa Francesco," the man said.

"Ah, the Pope," Stella replied - and put the call through to Scalfari. "Listen, I have the Pope on the line."

Scalfari picked up the phone at home and told Stella: "You're crazy, it must be a joke."

"No, it's not a joke, I can't make the Pope wait, so let me put you through."

Scalfari remembers a voice saying, "'Good morning, this is Pope Francis… you asked me for a meeting, and I want to do that. Let's fix a date.' And with the phone on his ear, he tells me, 'Wednesday I can't. Maybe Monday? Is that OK for you?' And I told him: 'Any day is fine for me. Monday is fine.'"

Image copyright Other Image caption Eugenio Scalfari: The Pope is "a revolutionary"

Eugenio Scalfari is not the only person to have received a call out of the blue from Pope Francis, who has made outreach to the unexpected one of the hallmarks of his papacy.

Pope Francis is not a doctrinal radical - this is not Che Guevara in a cassock John Allen, Boston Globe

And their unlikely dialogue about faith and conscience, paedophilia and celibacy, corruption and the Church produced an intriguing insight into the character of the man who has transformed expectations of the Catholic Church.

After further phone calls and a series of private meetings with Francis, Scalfari concluded: "He is a revolutionary Pope."

The man the Italians dub the "cold-call Pope" has, in little over a year, lifted the mood of the Vatican and raised new expectations of the Catholic Church.

But can he meet them? Is he the radical moderniser that progressives have hoped for or, rather, an orthodox priest with a ready smile and a knack for outreach to the unexpected?

From Sunday, 5 October, the world will begin to get some answers. Cardinals, bishops, priests and lay Catholics from around the world will arrive at the Vatican to consider how Church teaching on the family relates to the reality of modern life.

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The "extraordinary Synod" - the third of its kind in the modern history of the Catholic Church - is part of a process of reflection that will last more than a year. It's likely to reveal both the nature and, most likely, the limits of the change heralded by Pope Francis.

When I visited Scalfari, he recounted his conversation with the Pope. "I told him all popes have reformed the Church, for better or for worse, but you are not reforming this Church, you are not a reformist. You are a revolutionary." According to Scalfari, the Pope told him he is not revolutionising the Church, that his task is just to apply the conclusions of the Second Vatican Council.

The Second Vatican Council - commonly known as Vatican II - was, in theory at least, the seismic event in the modern history of the Catholic Church. It ran from 1962 to 1965.

Vatican II

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Convened by Pope John XXIII, the Second Vatican Council was concerned with Catholicism's renewal in the modern world

The world's 2,800 Catholic bishops gathered in St Peter's Basilica four times in the autumn of four consecutive years starting 11 October 1962, ending in 1965

Changes brought about include the celebration of mass in vernacular language (although Latin remains the liturgical language of Catholicism) and the positioning of the priest during services facing the congregation ("versus populum")

It was supposed to set the Church on a course to meet the modern world - not by rewriting doctrine, but by spelling out a fundamental change in the Church's outreach to other religions, in the conduct of the Mass, in the role of the laity in the running of the Church and much more.

Not long after the destination had been set, the Church stalled. Cardinal Cormac Murphy O'Connor, the head of the Catholic Church in England and Wales from 2000 to 2009, says Pope John Paul II "pressed pause" on Vatican II, while under Pope Francis "we have a push… the button is being pushed again".

Pope Francis seems to specialise in causing confusion on certain issues Joseph Shaw , Chairman of Latin Mass Society

The Synod will address what Cardinal Murphy O'Connor describes as some "neuralgic questions" - contraception and homosexuality for example. And, the one that's generated most debate - and the greatest expectation of change - is whether Catholics who divorce and then remarry civilly should be allowed to take communion.

Church teaching is that they can only do so if their first marriage has been officially annulled by the church - civil divorce doesn't count. But obtaining an annulment can be a lengthy and expensive process.

The problem has led to an unusually public spat as conservative cardinals have lined up to argue that Church teaching must not change.

John Allen, a long-time Vatican reporter for the Boston Globe, expects that the outcome will not be new doctrine, but new practice. "Pope Francis is not a doctrinal radical. This is not Che Guevara in a cassock," he says. He predicts annulment will be made faster, simpler and less expensive.

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There seems to be agreement among Vatican watchers that on all issues before the Synod, radical doctrinal change isn't on the agenda. Instead, Pope Francis has changed the emphasis.

Jane Livesey, General Superior of the Congregation of Jesus - a global religious order of some 2,000 nuns - says Pope Francis's message is: "There are different ways of interpreting the doctrine, and my way of doing it is through the prism of mercy and forgiveness."

Find out more For Radio 4's The Report, the BBC's director of news and current affairs James Harding set out to understand one of the world's most fascinating and charismatic leaders. You can listen to the programme on the BBC iPlayer. Download the podcast More investigations from The Report

In this, she says, the Pope leads by example. "Francis is a man who completely gets that - that you can preach all you like, but actually most of the important things in life are caught, not taught."

John Allen says this is because, at heart, Francis is not a theologian or a politician, but a pastor. "When he picks up the phone and calls a mother in southern Italy whose son is in the hospital," he says, "part of that is just genuine pastoral outreach, but part of it is also recalibrating the model of what leadership in the Catholic Church looks like."

The Bishop of Rome, as Francis likes to call himself, has positioned himself as one among many. He has made it clear he's in favour of decentralising the Church, and that means that while the rules may stay the same, he's giving bishops and priests more room to interpret them. "Every parish priest has to make these kind of judgements," says Cardinal Murphy O'Connor. "In moral theology there's what's called the objective truth and subjective, and sometimes you have to take account of the subjective situation of various people. And a good priest does just that and I think a good pope does that too."

Image copyright Getty Images Image caption Pope Francis surprised some observers by choosing a compact car on his recent visit to South Korea

But, of course, leaving the teachings of the Church to that kind of subjective interpretation by bishops and priests - making that age-old tradition of ambiguity the guiding principle of the papacy - threatens to disappoint and frustrate people across the Catholic spectrum.

Joseph Shaw, a Catholic blogger and fellow of St Benet's Hall, Oxford, argues there's a danger that the Pope's approach will obscure the Church's teaching. "Pope Francis seems to specialise in causing confusion on certain issues," he says. "It's upset people who appreciated having very, very clear teaching, even when it was unpopular, which is what we got from Pope Benedict."

To judge his papacy so far, Francis has behaved like a man who watched his predecessor - encrusted by the Vatican machine and defined by doctrinal argument - and has chosen, quite conspicuously, to be a different kind of pope.

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How is it working? Well, it's clear St Peter's is busier, Catholics have a renewed spring in their step and, if the issues of child sex abuse and financial wrongdoing have not yet been fully resolved, the Vatican story is nowadays about more than that. Then again, there's no solid evidence yet that the pews are fuller.

Francis has proved a surprise as Pope, even to those who thought they knew him, and he has demonstrated the power of a priest with a personal touch. But, by his own admission, he is not a revolutionary. He is, though, a herald of change. A pope with a deliberately different approach to his calling.

Behind the story

For a number of years, I watched, fascinated, by the apparent paralysis inside the Vatican as Pope Benedict's papacy was engulfed by scandals of child sex abuse, financial wrongdoing and court intrigue. His resignation, the first in 600 years, confirmed that the Holy See was in crisis. Then Jorge Bergoglio succeeded him in March 2013, becoming the first Jesuit and the first priest from the New World to become Pope. From his first evening on the balcony overlooking St Peter's, Pope Francis seemed to take the world by storm.

Although not a Catholic myself, I, like thousands of journalists the world over, was intrigued - and started angling for an interview for the BBC. I began to discuss the possibility with a range of senior figures in the Church and then went to Rome to make the case to Father Federico Lombardi, the Vatican spokesman, that the Pope should consider the BBC, given its audience of 250 million people around the world. Father Lombardi, plainly inundated with such requests, smiled and with some charm left me with the impression that the Pope was having no trouble reaching a global audience.

So, after that, I went for lunch with Ezio Mauro, the editor of La Repubblica, whom I'd met some years before. (We got to know each other, oddly enough, interviewing Vladimir Putin and, since then, had tried to help each other out getting access to interesting interviewees.) He could barely contain his excitement. His predecessor, Scalfari, had just been called by the Pope and gone for a meeting at the Santa Marta Convent. From then on, I kept in touch with Mauro and La Repubblica watching, if you like, the unusual drama from the wings.

Then, when I was on holiday in Italy over the summer, I asked whether I could visit Scalfari in Rome and discuss what he'd learned of Pope Francis. It was a way of trying to understand the man who presides over a global congregation of 1.2 billion people. And, in turn, it prompted a more concerted effort to answer the question: what, really, is the calling of Pope Francis?

You can listen James Harding's documentary for BBC Radio 4's The Report on the BBC iPlayer.

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