Islamic radicals hijacked airplanes to attack and undermine the West. They killed thousands of innocents without a single moral qualm. But their enmity is not just directed against us. They also mean to hijack Islam itself and to destroy 13 centuries of Islamic civilization. We are not in a war between two civilizations. We are fighting an enemy of two civilizations.

Osama bin Laden has a strikingly simple and violent conception of the world. It is bipolar. Taking his lead from ancient Islamic legalists who wrote when the world knew nothing but empires, bin Laden divides the earth into the dar al-Islam (the realm of Islam) and the dar al-harb (the realm of war). Between the two there is unceasing conflict.

But for bin Laden, the dar al-Islam is no longer the realm of Islam, or as is sometimes translated, the realm of peace. In common with many Islamic radicals, bin Laden believes that the Islamic world has fallen into perfidy and apostasy. He makes civil war on Islam as much as he makes international conflict with the United States.

He targets moderate Islamic leaders like Egyptian President Hosni Mubarak, former Pakistani President Benizir Bhutto, and Jordan King (then Prince) Abdullah. He has no respect for the Saudi government because it permits the stationing of Western troops, contrary to his view of the ancient Shari’a’s prohibition of non-Muslims living on the holy soil of Arabia.

Bin Laden and other Islamic radicals claim they represent ancient Islam. It is true that they do represent one tradition in Islam, but it is a tradition that Islam early on rejected as opposed to the universal message of its Prophet. In the earliest centuries of Islam, a great civil war was fought over who should be the successor to Muhammad. The battle was between the partisans of the assassinated third Caliph, Uthmann, and those who supported the fourth Caliph, ’Ali. This was the conflict that ultimately led to the division between Sunni and Shi’a Islam. But there was a moment when a truce and an arbitration promised a possible peaceful resolution to the conflict.

One group was adamantly opposed to any arbitration and any compromise. Later called the Kharajites, this sect believed that only God could determine who should be the proper successor, and God would let his will be known in battle. The Kharajites withdrew and made war on both factions. They held that any person who strayed from the perfect practice of Islam was ipso facto an apostate and could be killed. And they believed that only they had the true notion of what Islam required. They applied their doctrine with a ferocity against both the developing Sunni and Shi’a traditions of Islam, even assassinating ’Ali. Their tactics were frightfully violent, and it took centuries before they were put down.

Today, radicals like bin Laden replicate that ancient sect that threatened to destroy Islamic civilization at its inception. They copy that sect that stood against what came to be a civilization known in its time for its learning, science, openness and toleration. They engage in tactics that are far beyond what is acceptable in the Islamic moral tradition. They insult the vast multitudes of Muslims who abhor such actions.

Partly because of the timidity of the West, these radicals have gained influence. Some regimes protect them. Some apparently even sponsor them. . Many leaders in the West, bereft of and often hostile to their own Christian roots, have patronizingly assumed that radical violence was an essential part of the Islamic faith. Our own weak responses have helped to legitimate those whom Islam fought so earnestly to rid itself of at its beginning. If we have respect for ourselves, if we have respect for Islam, we can no longer tolerate the evil they represent. Two civilizations hang in the balance.

David F. Forte is a Professor of Law at Cleveland-Marshall College of Law in Cleveland, Ohio and the author of Islamic Studies: Classical and Contemporary Applications. He is an Adjunct Fellow of the John M. Ashbrook Center for Public Affairs at Ashland University, Ashland, Ohio.