What kind of religion is this? How can Islam be used to justify both peace and war?

The recent terrorist attacks, which authorities have blamed on Islamic extremists, have highlighted the tensions and contradictions in the practices of the world's 1 billion Muslims. Muslim leaders quote Koranic verses against aggression, while Osama bin Laden ignores such commands and cites other exhortations in the book to slay the infidels. Muslim women have ruled countries like Pakistan, while the Taliban of Afghanistan denies them the right to work or attend school

The religion has produced world empires, a civilization of stunning beauty and a theology of peace and submission to God. But it is also plagued with images of ruthless jihadi warriors, chopped-off hands, forced conversions — and now, hijacked airplanes blasting into the World Trade Center and Pentagon.

Since the Ottoman Empire collapsed after World War I, diverse Islamic practices have flourished in the absence of a central religious authority. Extremist ideology has flourished as well.

"The crumbling of the Islamic civilization has removed the established institutions to seriously challenge the extremists," said Khaled Abou El Fadl, UCLA acting professor of Islamic law. "Extremists have always been there in the Islamic tradition, but they tend to be very powerful when the institutions of society weaken and crumble."

Most Muslims — and non-Muslim experts on Islam — are quick to say that extremists are distorting the faith and violating its fundamental principles of peace for political gain.

"Nothing in the Koran, Islamic theology or Islamic law in any way, shape or form justifies ramming two airliners into civilian buildings," said Hamid Dabashi, chairman of the Middle Eastern languages and culture department at Columbia University. "In every great religious tradition, you can launch the most humanistic, loving ideas, or the most violent terrorist actions."

He and others say Islam is no more inherently violent than Christianity, which produced followers who carried out brutal campaigns of extermination during the Crusades and the Inquisition. Violence in Northern Ireland between Roman Catholics and Protestants is not a product of the religion, experts note. Judaism did not produce the strife in Israel, any more than Hinduism is at fault for fundamentalist violence against Christians in India.

But Dabashi and other experts said the Islamic religious texts lend themselves to manipulation by extremists because they are filled with fiery references to war, exhortations to fight oppression and mandates to mobilize against the enemy.

In the Koran's ninth chapter and fifth verse, for instance, Muslims are exhorted to "fight and slay the pagans wherever ye find them. And seize them and beleaguer them and lie in wait for them," according to an English translation. (The passage also instructs that Muslims must embrace those who repent, "for Allah is oft-forgiving, most merciful." And, in other verses, Christians and Jews are explicitly exempted from attack, embraced as kindred "people of the book" qualified for paradise.)

The militant verses are a product of the times in which the faith emerged in the Arabian desert almost 1,400 years ago. The leading city of Mecca was in chaos, with drunken orgies, a scarcity of goods, political deadlock and a prevailing religion of animistic polytheism, according to Huston Smith, a scholar of world religions.

"Islam naturally includes a lot more material in its most classic, basic sources that are militant because that is the world they lived in — a world of successful military campaigns," said Reuven Firestone, a professor of medieval Judaism and Islam at Hebrew Union College in Los Angeles and USC.

The Islamic sacred texts not only include exhortations to fight, they also lay out detailed rules of engagement. Experts say the terrorists broke every rule in the Islamic sacred books. The tradition expressly prohibits the killing of noncombatants: women, children, the aged, hermits, even trees. It forbids suicide. It even requires notice before attack.