As 1.1 billion Roman Catholics turn their eyes to Rome, awaiting the selection of their next pope, the other four-fifths of humanity also has much at stake in the choice the cardinals will make.
Although modern popes don't enjoy the preeminent political clout of their medieval predecessors, they arguably exert more influence on moral issues - reaching far beyond the ranks of Catholic faithful.
Indeed, Pope John Paul II, who will be buried here Friday in a ceremony expected to draw millions of people - including as many as 80 heads of state - shaped the papacy into a global institution, projecting his personality through the media to extend the authority of his office.
The next pope is expected to build on that media outreach to spread the Catholic Church's message. And he will be bolstered in that effort by the presence of Vatican embassies in 175 of the United Nations' 192 member states - one more than the United States maintains.
This geographic spread makes the church "more germane to this age than any political structures" says Jonathan Sacks, chief rabbi of England. "The imperative of the 21st century is 'think global, act global,' and that is exactly what the Catholic church does."
Before the Iraq war, for example, the pope was one of the few figures to talk to leaders on both sides of the conflict, receiving Iraqi Deputy Prime Minister Tariq Aziz and British Prime Minister Tony Blair in the Vatican, and sending envoys to Baghdad and Washington in a bid to avert violence. [Editor's note: The original version misstated Aziz's title.]
John Paul II gave voice to the concerns of millions, warning President Bush that he was assuming "a grave responsibility before God, his conscience, and before history."
That illustrated what Rabbi Sacks calls the pope's role as a kind of moral global positioning or navigation system. "The most important thing is that you key in the destination," he says. "However many wrong turns you take, it recalculates your route. Politicians hold the steering wheel and can take wrong turns, but the satellite navigation ... reminds you of your destination."
The next pope will hold "an extraordinary position of moral influence and soft power," says Joseph Nye, former dean of the John F. Kennedy School of Government at Harvard University in Cambridge, Mass., who invented the term "soft power" to describe the force of suasion by example. "How he chooses to use that position can be of great importance."
That will probably be a key consideration for the 117 cardinals who will meet in a conclave on April 18 to select the next pope, hoping to pick a man who can repeat Karol Wojtyla's feat of earning respect from a diverse range of figures, from President Ronald Reagan to Cuba's Fidel Castro.
Though the pope no longer commands armies - prompting Joseph Stalin's famously dismissive question "The pope! How many divisions has he got?"- his authority can stop armies in their tracks: Hitler kept his troops out of Vatican City. And the late pontiff's 26-year reign offered considerable evidence of the power of ideas to change political landscapes just as radically as infantry.
Nowhere was this clearer than in John Paul's homeland, Poland, where his homilies during a visit in 1979 inspired opponents of Communist rule to organize Solidarity, the dissident trade union movement that eventually brought down the government in Warsaw. That unexpected victory sparked similar revolutions in neighboring countries, dismantling the Soviet Empire in Eastern Europe.
Likewise, leaders of the "People Power" uprising in the Philippines that ousted dictator Ferdinand Marcos in 1986 later said that they had drawn strength from the pope's sermons on human rights during his trip to Manila five years earlier.
Those successes for the pope, however, were bluntly offset by his impotence during the run-up to the 2003 Iraq war, when Messrs Bush and Blair set aside his admonitions against going into battle. "Where was the impact of the pope's declarations on Iraq?" asks John Cornwell, author of a critical biography of the pope. "He was listened to but ignored."
That, perhaps, is as it should be, says Rabbi Sacks. "Religious leaders are not democratically elected," he points out.
But a pope's moral weight can put a price on such political decisions when they run counter to his will, argues Professor Nye. "A pope cannot dictate to [political] leaders, but he can raise public opinion that makes decisions more costly" for them, he says.
Ever since the institutional papacy arose from the ashes of the Roman Empire, pontiffs have not hesitated to throw their weight into secular matters.
In 452, when Attila the Hun threatened Rome, it was Pope Leo I who went out to meet him, and, legend has it, so impressed the invader that he withdrew.
Popes have also exerted power through their annual encyclicals, some of which shaped history by influencing public debate and inspiring sea changes in global politics and society.
Twelve Leos later, in 1891, Pope Leo XIII wrote "Rerum Novarum," which called for organized labor and a minimum wage for all, accusing "a small number of very rich men" of harnessing the masses with "a yoke that is very little better than slavery itself." That encyclical spurred the emergence of labor unions worldwide.
In 1968, Paul VI's "Humanae Vitae" - which called contraception "evil" - gave immense moral boost to antiabortion movements worldwide, nowhere more so than in the United States.
"John Paul II's continued emphasis on pro-life issues manifestly affected American politics to the point of dramatically influencing legislation. And that's in a country that is not Catholic," says Eamon Duffy, a papal historian at Cambridge University in England.
At the same time, John Paul II's anti-condom message - once the Vatican announced that condoms have tiny holes in them and so do not provide protection against disease - is seen as holding back efforts to prevent the spread of HIV/AIDS in the developing world. "It has complicated things and made the task of getting information to people who need it much harder," says Ben Plumley, spokesman for UNAIDS in Geneva, who says "rethinking the role of condoms" should be a "major priority" for the next papacy.
Centuries ago, the pope had decisive political power as head of the Papal States, and no compunctions about backing it up with his army. Medieval popes "combined the two offices of secular prince of a large state and spiritual leader of Western Christendom," says Kenneth Pennington, a professor of history at Catholic University in Washington. "That gave them enormous power and authority in a number of areas."
At the same time, popes sought to control European politics, sometimes by arranging royal marriages, on other occasions by plotting murder, according to Professor Pennington.
Since the 1929 accord between the Vatican and the Italian government, the church has restricted its temporal ambitions to the Vatican walls. But "the loss of papal authority was turned into an enormous worldwide spiritual presence," says Anthony Majanlahti, a historian in Rome who wrote "The Families Who Made Rome."
Where the next pope chooses to make that presence felt will decide a number of critical questions for Catholics and non-Catholics alike: how to combat the HIV-AIDS plague; how to reduce poverty for the three billion people living on less than $2 a day; and how relations between Islam and Christianity develop.
"This pope was a kind of hero; he redefined what being a pope is," says Fuad Nahdi, editor of Q News, a Muslim magazine based in London. "He initiated a dialogue between the church and the Muslim world."
At the same time, when a pope takes a position on a social issue, he endows that stance with moral weight that strengthens and encourages those who share it - whether it be opposition to abortion or protests against the death penalty. "When the pope's message overlaps with other global messages such as antiglobalization ... it acts to reinforce them," suggests James Walston, who teaches International Relations at the American University of Rome.
Many observers say that Blair's recent commitment to make development in Africa a top priority was inspired by the pope's call to reduce poverty.
The next pope could make a great impact "if he were to focus on social justice and economic equality in the developing world," says Pennington. "Such policies might transcend sectarian religious boundaries."
Not that he would set such policies. Rather, says Professor Nye, a pope can "help to set the agenda ... dramatize issues, and direct attention to them."
He enjoys that authority well beyond his own church, says Mr. Nahdi. The late pope "was attractive to Muslims who lack their own spiritual focus," he says, especially since "his stance was identical to Muslim views on issues such as family morals and sex. It was an inspiration to many Muslims ... This pope had strong opinions and he was not afraid to be unfashionable," he adds.
Those strong opinions found little echo in liberal Western Europe. "I don't think he has anything more than sentimental value for non-Catholics" there, says Mr. Cornwell. "Intelligent Northern Europeans don't really like the pope."
To critics and followers alike, however, a pope wields unique authority to act as a moral compass.
"If Stalin had made his comment to me," says Rabbi Sacks, "I would have replied that to defend a country you need an army. To defend a civilization you need a vision. We need a pope with vision."