The question is whether the emperor is justified in what he said. His main thrust was at least partly justified. There is a real problem about the teaching of the Koran on violence against the infidel. That existed in the 14th century, and was demonstrated on 9/11, 2001. There is every reason to discuss it. I am more afraid of silence than offence.

The Pope's actual quotation is not just a medieval point of view. It is a common modern view; even if it seldom reaches print; it can certainly be found on the internet. "Show me just what Muhammad brought that was new, and then you shall find things only evil and inhuman, such as his command to spread by the sword the faith he preached."

Is it true that the Koran contains such a command, and has it influenced modern terrorists? The answers, unfortunately, are "yes" and "yes".

The so-called Sword Verse from Chapter 9 must have been in the emperor's mind: "So when the sacred months have passed away, Then slay the idolaters wherever you find them.

"And take them captive and besiege them, and lie in wait for them in every ambush."

This does shock many Muslims: extremists are angered by the implied criticism of those who quote it, while moderates who cannot disavow the terms of the Koran prefer more evasive interpretations. The shock it creates shows the importance of the doctrine.

One man who does not question the meaning of the verse is Osama bin Laden. His attitude is discussed at some length in Chapter 14 of an excellent new book, The Qur'an, a Biography, by Bruce Lawrence, who is the Professor of Islamic Studies at Duke University, North Carolina. Lawrence observes the use of this verse as a central argument for jihad in Bin Laden's manifesto in 1996; that was a declaration of war against native and foreign infidels.

Lawrence makes several relevant points. Bin Laden selects only those verses that fit his message, and then cites them exclusively for his own purposes. He ignores both their original context and also the variety of historical differences between committed Muslims about how to apply their dicta. He collapses the broad spectrum of Koranic teaching into a double requirement: first to believe; and then to fight.

Lawrence also draws attention to the qualifications that surround the Sword Verse; particularly that those infidels who repent should be allowed to go free: "For God is most forgiving; most merciful."

It is impossible to reconcile the consistent Koranic teaching that God is most merciful with suicide bombing, which is indiscriminate and murders faithfuls and infidels alike.

It is a mistake to think that all the major religions are identical: they have real differences of doctrine that have real impacts on human society. What is true, however, is that no religion shall survive for more than a generation or two unless it has a substantial element of truth in it. The diabolical cult of Nazism lasted for only one generation. It is natural for Christians of different denominations to love what they have in common without ceasing to be aware of their differences.

A Christian should also rejoice in the positive spiritual values of the other major religions. It is natural for a Christian to feel enriched by Judaism, which was the religion of Jesus; or by Platonism, the philosophy of the opening chapter of St John's Gospel and of St Augustine. Yet Christians also find spiritual truths in Buddhism, Confucianism, Daoism, Hinduism, Sikhism and Islam itself. There is a significant link between aspects of Islamic Sufi mysticism and the Christian mystical tradition.

When one lists these religions it becomes obvious that there are two problems: violence and the influence of reason, both of which Pope Benedict identified in his lecture. Violence is a fault from which no major religion has historically been free. St Patrick's conversion of Ireland is sometimes given as a unique example of the conversion of a nation without the loss of a single life. It is one of the great scandals that so many persecutions have taken place in the name of Jesus.

This has been more or less true of all the great religions: human beings are the most savage of beasts, and they will kill each other in any cause, however noble.

Yet nowadays Islam is the only major religion in which violence is a serious doctrinal issue. It is true that tribalised Roman Catholics and Protestants in Ireland have only recently stopped killing each other and vengeful Sikhs assassinated Indira Gandhi in India, but neither the Catholic nor the Protestant churches believe in terror; nor do the Sikhs.

A significant proportion of the Islamic community does believe that suicide bombers are martyrs carrying out a religious duty. Suicide bombing causes Islamophobia. There are varying degrees of authority and uniformity in different religions; rather low in most cases. This pluralism has its own virtues, but in Islam they are outweighed by the disadvantages. Those imams who preach al-Qaeda's view of the duty of jihad are not required to answer to any authority, even the authority of reason.

Islam has only partially experienced the modern process of enlightenment and reform, which was, after all, resisted by a number of pre-Vatican II Popes. Pope Benedict will have done Islam a service if he has started a debate within Islam and between Islam and the critics.

END