In the controversy that followed his speech, the Pope told Muslim leaders there should be no doubt about his commitment to the dialogue launched by the Second Vatican Council or of his "esteem and profound respect" for Muslim believers.

At the same time, the Pope is not hesitating to raise some uncomfortable questions about the religious foundations of Islam and its cultural and political influences today.

"It is important that (interreligious) dialogue take place with much patience, much respect and, most of all, in total honesty," the Pope wrote several years ago.

For the Pope, the honest approach to dialogue with Muslims means not simply talking about the shared belief in one God but also facing sensitive issues like that of violence and religion. Against a backdrop of global tensions, the Pope believes that question cannot be ignored and that moderate voices must be heard.

"Many people, including the Pope, are asking whether there is not perhaps a link between certain interpretations of the foundations and sources of Islam, and what is being done by Islamic extremists," said Jesuit Father Christian W. Troll, a professor of Islamic studies  in Frankfurt, Germany.

While the Pope would not fall into the mistake of overly generalizing about radical Islam, he would like Muslim dialogue partners to take a closer look at the interpretation of the Islamic heritage, in particular those elements that can be misused in the direction of violence, Troll said.

In his first major encounter with Islamic representatives in 2005, the Pope asked Muslim elders to make sure their young are formed in attitudes of tolerance and co-operation.

"I am profoundly convinced that we must not yield to the negative pressures in our midst, but must affirm the values of mutual respect, solidarity and peace. The life of every human being is sacred, both for Christians and for Muslims," he said.

During his first 18 months in office, Vatican officials say Pope Benedict has adopted a new style of dialogue with Islam, but without setting off in an entirely new direction.

"Pope Benedict XVI is carrying on the work of John Paul II with a style of his own: It's a work of continuation, not imitation," said Cardinal Paul Poupard, head of the Pontifical Council for Interreligious Dialogue.

In fact, over the course of his pontificate, Pope John Paul frequently spoke to Muslims about interreligious tolerance, cultural co-operation and reciprocal respect for religious freedom. Pope Benedict has touched on the same points, but with more direct language. He has also tended to avoid the public gestures of interreligious friendship that were a trademark of his predecessor.

"We are facing two different approaches to dialogue," Fr. Justo Lacunza Balda, an official of the Pontifical Institute for Arabic and Islamic Studies in Rome, told CNS.

For Pope John Paul, Lacunza said, encounters with Muslims were a key part of papal travels abroad and special ceremonies at the Vatican. Pope Benedict is less a "stage person" and more analytical, he said.

"His approach is one in which you have to identify issues that are absolutely relevant and important to discuss in our modern times," Lacunza said.

At the University of Regensburg in September, the Pope touched on several of these themes in language that he later acknowledged was open to misinterpretation. Most of the Muslim criticism focused on the Pope's quotation of a medieval Byzantine emperor, who said the prophet Mohammed had brought "things only evil and inhuman, such as his command to spread by the sword the faith." The Pope afterward clarified that he was not endorsing the emperor's words.

Much less attention was given to a broader question the speech posed about Islam: whether God is absolutely transcendent for Muslims and therefore not bound up with "any of our categories, even that of rationality."

That echoed a question that arose last year, when the Pope hosted a two-day, closed-door seminar on Islam with some of his former graduate students: If Muslims understand the Quran's revelation as literally divine and unadaptable, can Islam really engage the modern world and accept concepts like democracy?

According to one participant, Jesuit Father Samir Khalil Samir, the Pope believes Islam and democracy are compatible, but not without difficulty.

Troll said the Pope avoided categorical judgments about Islam. But he said the Pope understands that the traditional, mainstream theology of Islam may make it difficult for Muslims to critically evaluate how their faith interacts with history.

The Pope has long held that Islam's all-encompassing approach makes it a challenging dialogue partner. As he said in the 1997 book, Salt of the Earth, the Quran is "a total religious law, which regulates the whole of political and social life and insists that the whole order of life be Islamic."

Samir, an Egyptian-born expert on Islam, said in a recent article that Pope Benedict is one of the few figures to have understood Islam's struggle to find a place in modern society. He said this awareness has led the Pope to broaden Christian-Muslim dialogue, emphasizing cultural issues above strictly religious aspects.

"The essential idea is that dialogue with Islam and with other religions cannot be essentially a theological or religious dialogue, except in the broad terms of moral values; it must instead be a dialogue of cultures and civilizations," Samir said.

In promoting what he calls a "dialogue of cultures and religions," the Pope also has outlined a potential area of Christian-Muslim co-operation — the struggle against secular trends in contemporary society. As the Pope said in Regensburg, it's a society that risks becoming "deaf to the divine" and that "relegates religion to the realm of subcultures."

Poupard said the Pope was, in effect, offering "an outstretched hand" to Islam in the battle against an oversecularized global culture.

But the Pope has also made it clear that for Christians, the struggle against a godless society is based on a rational approach, one that rejects violence, that does not see faith and reason in conflict, and that affirms the centrality of the person. His Regensburg speech, then, could be viewed as an invitation for Muslims to clarify the teachings of Islam on the same points.

The strong initial criticism of the Regensburg speech has given way to more thoughtful evaluation by Islamic scholars. Even though the Muslim commentary is still largely unfavourable, Vatican officials now say the papal speech may turn out to be providential in promoting a frank, in-depth look at Christian-Muslim issues.

One problem demonstrated by the controversy, however, was that Islam speaks with many voices. In the absence of a Muslim hierarchy, a small group burning an effigy of the Pope may make a greater global impact than a group of Islamic scholars calmly dissecting the Pope's arguments.

An important issue the Pope and his aides have raised with diverse Muslim audiences is the need for mutual respect for religious rights, including those of minority Christian populations in majority Muslim countries.

But reciprocity is not seen at the Vatican as a prerequisite for dialogue, nor is it a Pope Benedict invention. Pope John Paul repeatedly raised the issue, notably in his 1985 speech in Morocco.

Pope Benedict has said he wants to build on the work of his predecessor and the relations of trust that have developed between Christians and Muslims. He has described his own approach as recognizing with joy the shared religious values and respecting "with loyalty" the differences.

His recent prodding on some of the differences, his aides say, only illustrates the crucial importance he gives to this dialogue.