He has made history by being the first head of the Roman Catholic Church to pray in a mosque, and he has sought to heal the ancient wounds between Christians and Jews.
But in spite of the general feelings of goodwill towards other religions that the Holy See has sought to generate since the groundbreaking Second Vatican Council in the 1960s, there is still concern about interfaith marriages.
This was illustrated by a document issued by the Vatican on 14 May on the subject of world migration. In it, the head of the Pontifical Council for the Pastoral Care of Migrants and Refugees, Cardinal Stephen Fumio Hamao, warns women in traditionally Catholic countries about the risks of marrying Muslim men.
The tone of the warning is unusually direct for today's ecumenical climate, in which organized religions are at pains to express their tolerance of other cultural backgrounds. Referring to women as the "least-protected member of the Muslim family," it says that "bitter experience" shows the difficulties facing European women who marry Muslim men. It says those difficulties are compounded in cases where the couple goes to live in a Muslim country.
The document further says that such marriages need to be very carefully prepared for. And it urges Muslims to show "a growing awareness that fundamental liberties, the inviolable rights of the person, the equal dignity of men and women, the democratic principle of government, and the healthy lay-character of the state are principles that cannot be surrendered."
Muslim scholars are expressing surprise at the tone of the Vatican's assessment. The registrar of the Markfield Institute of Higher Education in Britain, Nizam Muhammad, took issue with the Vatican's view. He said that a distinction must be made between religious belief and social custom.
He acknowledged that some countries that are mainly Muslim have customs and cultures in which women are not treated as they should be. But he also said, "The teachings of Islam are totally against [the suppression of women]; in Islam, women have all the dignity given to them, perhaps even more so than in Western societies, and they are not to be given second-class status, nor be trampled upon; they have rights of inheritance; they have freedom, they are really head of the family; so the unfortunate thing with the Vatican statement is that it gives the impression that this is the teaching of Islam, which it is not."
Another scholar, Ghayasuddin Siddiqi of London University's Muslim Institute, also found the Vatican's lecture on human rights condescending toward Muslims. "I think it is just playing on the existing Islamophobia, which is taking a grip on our society. I think we have to detach ourselves. I mean this whole Islamophobia, the war on terror, has come about as a result of political reasons," he said.
Muhammad said that he, as a Muslim with a Catholic wife, has personal experience of a life spent in harmony with Catholicism, and he feels that the church is making too much of the mixed-marriage issue. "I am a Muslim, I am married to a Catholic, I have never once tried to convert my wife, she has never tried to convert me. Unfortunately we do not have children, but if we did have children, I would have allowed them to go both to the mosque and the Catholic church, and let them decide by themselves which one they want to follow," he said.
In referring to children, he has touched on one of the most difficult aspects of a mixed marriage, namely the religion of the children. Both Catholic and Islamic faiths are alike in wanting the children of such unions to be part of their own flock.
Rome insists that the children must be baptized and brought up as Christians. Part of the church's worry about marriage with Muslim men is that the dominating position of the man in many Islamic households makes it impossible in reality for the wife to bring up the children as Catholics.
In Islam, there are similar concerns. Muslim men are allowed to marry Jewish or Christian women with the proviso their children are brought up as Muslims. Islam does not allow a Muslim woman to marry a non-Muslim man -- probably originally for the same reason, namely that the husband is likely to take the dominant role in deciding what religion the children will take.
Catholic theologian Richard Puza, of Tuebingen University in Germany, added a few words to the debate. He noted that regardless of the tone of the Vatican statement, the fact remains that the church does at least allow marriage between Catholics and Muslims.
Second, he said, the latest Vatican document can be viewed as an assembly of facts, not as a religious standpoint that detracts from Muslim-Catholic relations. He said that on a purely factual level, there have been cases of troubles reported between mixed-faith couples who have gone to live in Muslim countries. The fact that the Vatican document refers to that should not be seen as a criticism of Islam, but merely as a word of caution for Catholic women. And Puza said, "It is perfectly clear to me that in most of the Islamic countries, rights and justice are just as paramount as with us here [in Europe]."
In any event, given today's trend toward globalization and world travel, it seems that the practice of mixed marriages will continue, and increase, regardless of what religious leaders say.