The controversy provoked by Pope Benedict XVI's lecture, "Faith, Reason and the University," delivered on September 12 at the University of Regensburg, may prove to be, in the long run, a salutary development. It could be the occasion for greater openness about the growing rift between Christians and Muslims worldwide, and for a renewed determination to enter into meaningful and mutually respectful dialogue with one another.

To be sure, this latest incident could push us in the opposite direction as well. The pope's lecture, coupled with a number of other events (including the continuing war in Iraq and the now-concluded armed conflict between Israel and Hezbollah in Lebanon), could poison relations for generations to come, and with terrible consequences for everyone concerned.

What is needed more than ever now are the calm voices of leaders on both sides of the divide --- honest leaders who can speak the truth to the other side, and courageous leaders who can speak the truth to their own side.

One such Christian leader is Lord Carey of Clifton, the previous Archbishop of Canterbury and, as such, the former spiritual leader of some 80 million Anglicans around the world. George Carey happens to be a personal friend, and that must be said up front.

Unlike too many others in the West who tend to speak glibly about Islam, whether negatively or positively, without any extensive experience of Muslims nor of the countries in which millions of them live, Lord Carey knows what he is talking about and is not afraid to speak the truth both to his friends in the Muslim world and to his fellow Christians as well.

In a recent lecture entitled, "The Cross and the Crescent: The Clash of Faiths in an Age of Secularism," given at Newbold College, a Seventh Day Adventist institution in England, Lord Carey characterized the present state of relationships between the Christian West and Islam as "the most dangerous, most important and potentially cataclysmic issue of our day."

While disagreeing with Harvard Professor Samuel Huntington's well-known thesis that we are in the midst of a "clash of civilizations," Archbishop Carey concedes that it would be "foolish" to claim that the thesis "lacks total validity." Indeed, Islam and Christianity, the Muslim world and the Western world, have clashed in the past and are doing so again.

Carey's even-handedness will not satisfy people on either side who can only think in simplistic categories, as if their side is completely in the right, while the other side is not only wrong, but evil as well.

The archbishop acknowledges in his typically straightforward manner that the Crusades "remain a shameful episode in Christian history." At the same time, he is not reluctant to remind us that the Crusades were launched to recover lands taken by force and to reopen pilgrimage routes to the Holy Land.

Indeed, it is "undeniably the case that [Islam's] expansion was largely due to military conquest, reaching at times the heart of Europe," including Spain and Portugal. In the 16th and 17th centuries there were invasions of Hungary, Poland, Ukraine and all the way to the gates of Vienna.

Neither Christians nor Muslims, therefore, "can take the high moral ground and accuse the other of violence."

Lord Carey agrees that, while Pope Benedict's address last month in Germany was a powerful call for reasonableness in religion and for a greater role for faith in society, the quotation from the 14th-century Byzantine emperor should have been deleted before delivery. It is a mystery why it was included in the first place, and a tragedy that it remained in the final text.

However, the controversy those few lines provoked may provide an opportunity for leaders on both sides to raise what Lord Carey calls "awkward" questions, one of which is: "Why is Islam associated with violence?"

"We are told," he noted, "that true Islam is not a violent religion and the true Muslim condemns violence. I understand and agree. My many Muslim friends tell me so."

Nevertheless, "We need to bring the issue much more into the open," Carey continued. "Perhaps the Pope's unguarded words may encourage a "global conversation" on the matter without [leading] either to polemics or, ironically, violence"

"The Muslim world," he insisted, "must address this matter with great urgency"

In other words (mine, not the archbishop's), Islam is in need of the same kind of honest self-criticism that is now common in mainline Christian denominations, and within Catholicism in particular, especially since Vatican II.

To be sure, internal critics are rarely popular with co-religionists and almost never enjoy completely tranquil lives. History is often kinder on them, however.

Father Richard P. McBrien is the Crowley-O'Brien Professor of Theology at the University of Notre Dame.