Suicide bombing cannot be explained by poverty and disadvantage. The London bombers were not the wretched of the earth. They came from working-class but comfortable backgrounds, living in one of the world's most prosperous countries. For all the talk of their being marginalized, none were living in hellish ghettos. Britain today does a decent job of assimilating its immigrants, certainly better than any other European country. If anyone had cause for rage, it was not the bombers but their parents. Muslim migrants from Pakistan (in three cases), they arrived in Britain in less multicultural times. They were dirt-poor and probably ostracized and persecuted. And yet they did not become murderers; they started fish-and-chips shops.

Like all ideologies, radical Islam is a phenomenon of the educated class. From Muhammad Atta to Mohammed Sidique Khan, almost all suicide bombers have been men who read and write. In V. S. Naipaul's book "A Million Mutinies Now," the author interviews a young Hindu fanatic. The man explains his fascistic views, and then Naipaul asks the man's father, who happens to be sitting there, what he thinks. The old man explains that he works at a factory from morning till night and doesn't really have time for these kinds of ideas.

Extremist ideology is a leisure-time pursuit.

Nor can foreign policy really explain such rage. The invasion of Iraq clearly has greatly enraged many Muslims, radicalizing some deeply. But can a disagreement over foreign policy really make a Briton like Germaine Lindsay, who had never even visited Iraq, kiss his pregnant wife and child goodbye and go out and blow himself and others up?

There is something deeper at work here. Last week Egypt, which sent no troops to Iraq and condemned the invasion, was targeted. Turkey and Indonesia—which are both opponents of the war—have also been attacked. (Besides, the demands keep changing. Osama bin Laden's primary one was that American troops leave Saudi Arabia, which they have done. Bin Laden seems not to have noticed.)

The good news is that in the heart of the Muslim world, this ideology is not doing so well. The bombings, increasingly of civilians, are showing Al Qaeda and its ilk in their true light. Arabs are finally denouncing terrorism and also the ideologies that feed it. They need to do much more, and far more forcefully. It's a cliché, but true, that ultimately only Muslims can win this fight.

But Western countries can do more as well. We're fighting a military battle against a phenomenon that is largely nonmilitary. In a battle of ideas, no one bullet will win. We must present a positive vision for Muslim societies, be seen as a friendly and progressive force by them and thus strengthen the moderates and liberals.