If you want a reference point for al-Qaida, suggests Faisal Devji, some other movement that channels the same impulses for similar reasons, look no further than environmentalism. Devji, a New York-based historian and author of the new book Landscapes of the Jihad, is unafraid of provocative statements about Islamist terrorism. Another is that al-Qaida and the other groups pursuing the global jihad provide a mirror image of industrial globalisation, so the atrocities they commit are, as one reviewer of Devji's book put it, an "Islamic auto-immune response" to the Coca-Cola machine in Riyadh.

Devji's thesis - that al-Qaida represents, essentially, an "ethical" rather than a politically militant ideology. It might quite soon, he thinks, "tip over" into something non-violent. Picture Osama bin Laden not with that AK47 in his lap, but alongside Gandhi's spinning wheel.

Devji sees nothing paradoxical in such a notion. "One of the reasons this movement is so violent," he argues, "is because it is so inherently unstable and it could flip at any moment into the opposite. There is no political form which defines them at the global level." Because of this inherent formlessness, in Devji's analysis, "actions like suicide bombings are not actions that can be seen in strategic or instrumental terms. They are not means to an end. There is no 'end', as such."

Martyrdom should be linked not to any political wish list but "ethical practice". That doesn't, of course, mean "there are no strategic aims at all, but the act always folds back into itself because the movement is incapable of controlling anything at the global level. Of course, on one level, the rhetoric is all about policy - but when you look at that rhetoric more carefully you realise that any political or strategic aims dissolve. For instance the Islamic demand 'get out of our lands' is completely unclear. It could mean anything. Such a programme ceases to have any real-world political or strategic relevance. It dissolves into something else."

We should, for our own wellbeing Devji believes, think carefully about that "something else". Starting, for example, by reading what Bin Laden actually says. "I was surprised," Devji recalls, "when I went to the trouble after 2001 of looking at his speeches and statements and communiques at how coherent they were." More than that, how effectively they were picked up and absorbed as a coherent message across the Muslim world.

"It's not as if people were educated to think as he thinks. It's spread amazingly fast. So if you look at the video tape by Mohammad Sidique Khan, the London bomber, it contains the most important elements in Bin Laden's discourse. The stress on 'ethics', for instance - Khan actually uses that word and defines his impending suicide bombing as an 'ethical act'."

So where do we go from here? "As I see it, al-Qaida's actions are typically 'symbolic' - they can be seen as 'effects' rather than political interventions. This is because they have no way of planning what they want to achieve. They have no blueprint for the future. This, of course, is also true of other global movements like environmentalism. They, too, have no coherent political programme."

So how should the west adjust its approach to al-Qaida? First, Devji advises, don't be so afraid. "I tend to think that violence is the least important of al-Qaida's many effects. First, because it will inevitably come to an end. No movement based on violence of this sort has survived for any length of time. Second, violence is the least important thing about al-Qaida because the violence is ethical in origin and will quite likely flip into its opposite. The most important feature of al-Qaida is fragmentation and dispersal of Islamic thought globally."