Trying to proselytize a Muslim was cause for on-the-spot decapitation, but Kamil was a wise and moderate man, who was deeply impressed by Francis’ courage and sincerity and invited him to stay for a week of serious conversation. Francis, in turn, was deeply impressed by the religious devotion of the Muslims, especially by their five daily calls to prayer; it is quite possible that the thrice-daily recitation of the Angelus that became current in Europe after this visit was precipitated by the impression made on Francis by the call of the muezzin (just as the quintessential Catholic devotion of the rosary derives from Muslim prayer beads).  It is a tragedy of history that Kamil and Francis were unable to talk longer, to coordinate their strengths and form an alliance. Had they been able to do so, the phrase “clash of civilizations” might be unknown to our world.  Francis went back to the Crusader camp on the Egyptian shore and desperately tried to convince Cardinal Pelagius Galvani, whom Pope Honorius III had put in charge of the Crusade, that he should make peace with the sultan, who, despite far greater force on his side, was all too ready to do so. But the cardinal had dreams of military glory and would not listen. His eventual failure, amid terrible loss of life, brought the age of the crusades to its inglorious end.  Donald Spoto, one of Francis of Assisi’s most recent biographers, rightly calls Francis “the first person from the West to travel to another continent with the revolutionary idea of peacemaking.” As a result of his inability to convince Cardinal Pelagius, however, Francis saw himself as a failure. Like his model, Jesus of Nazareth, Francis was an extremist. But his failure is still capable of bearing new fruit.  Islamic society and Christian society have been generally bad neighbors now for nearly 14 centuries, eager to misunderstand each other, often borrowing culturally and intellectually from each other without ever bestowing proper credit. But as Sir Jonathan Sacks, chief rabbi of the British Commonwealth, has written, almost as if he was thinking of Kamil and Francis, “Those who are confident of their faith are not threatened but enlarged by the different faiths of others. ... There are, surely, many ways of arriving at this generosity of spirit and each faith may need to find its own.” We stand in desperate need of contemporary figures like Kamil and Francis of Assisi to create an innovative dialogue. To build a future better than our past, we need, as Rabbi Sacks has put it, “the confidence to recognize the irreducible, glorious dignity of difference.”  May the Lord give you peace.  Thomas Cahill is the author of “Mysteries of the Middle Ages: The Rise of Feminism, Science and Art From the Cults of Catholic Europe.”  A version of this op-ed appears in print on , on Page A25 of the New York edition with the headline: The Peaceful Crusader. Today's Paper|Subscribe
Amid the useless bloodshed of the Crusades, the story of the early 13th-century friar Francis of Assisi suggests an extended clash of civilizations between Islam and the West was not preordained.