When you hear someone described as a "member of al-Qaeda", what image comes to mind? A wide-eyed fanatic brought up on the dusty backstreets of Cairo, or in the wilds of rural Pakistan, hell-bent on revenge against the rich, secular, decadent west?
You'd be wide of the mark. Marc Sageman, a forensic psychiatrist at Pennsylvania University and counter-terrorism adviser to the US government, has pored over the profiles of some 380 individuals linked directly or indirectly to al-Qaeda. He found that a majority are well-off, well-educated, middle class, cosmopolitan, professional, married and sane - not unlike the average New Statesman reader, perhaps.
Using data from government documents, police wire-taps, news reports, academic publications and transcripts from trials in the US, France, Germany, Egypt, Indonesia and Morocco, Sageman collated biographies of 382 terrorists or suspected terrorists. He included known members of al-Qaeda, such as Osama Bin Laden and Ayman al-Zawahiri, and members of other groups known to share al-Qaeda's goals, including the Egyptian Islamic Jihad, Jemaah Islamiyah in Indonesia, Malaysia's Abu Sayyaf and others. He tells me he focused exclusively on the "global Salafi jihad" network, whose aim is to take the jihad to the "far enemy" - that is, to western governments and their populations.
He found that the jihadists are young, intelligent and respectable. Of the 306 for whom he had family background, 17.6 per cent were upper class, 54.9 per cent middle class and 27.5 per cent lower class.
Most had received a good education, too. Of the 264 for whom he had information, 16.7 per cent were educated to a level lower than high school, 12.1 per cent got at least as far as a high school education, 28.8 per cent had some college education, 33.3 per cent had a college degree and 9 per cent had a postgraduate degree. Only 9.4 per cent received a religious education.
Sageman had information on the careers of 268 individuals. Of these, 42.5 per cent worked in professional careers (as doctors, lawyers, teachers and so on), 32.8 had semi-skilled jobs and 24.6 per cent were unskilled. The average age of the jihadists was 25.7 years; 73 per cent were married and most of these had children.
There was little evidence of mental illness or criminality - there were only four cases of possible thought disorder and one case of mild mental retardation. Sageman says that, before turning to terror, the jihadists were mostly "good kids", apart from some from North Africa who lived a life of petty crime.
One thing widely shared among the jihadists was the experience of travel: 70 per cent "joined the jihad" while away from home in a foreign country. Some signed up while living and learning in the west - in cities such as Hamburg, London, Paris and Montreal, rather than in the Islamist hotbeds of Kandahar, Karachi or Tehran. "We're talking about the elite of the country sent abroad to study, because the schools in Germany, France, England and the US are better," Sageman says. He thinks that something about the isolating experience of travelling to the west may have pushed some towards radical Islam. They became homesick, he suggests, "feeling lonely and marginalised and perhaps rejected by their new host society". They drifted to the mosques, "more for companionship and friendship than for religion".
So how did these people become the mass killers of 9/11, Bali and Madrid? Sageman does not pretend he has the answers. However, he is clear that the "war on terror" is misconceived if it concentrates on distant parts of the world.
"We now have this diffuse social movement," he says, "made up of people like us, some of whom have lived among us. The war on terror should be a war of ideas: if we try to understand how they transform from normal people into terrorists, then we can start intervening and perhaps make a difference."
Brendan O'Neill is assistant editor of Spiked (www.spiked-online.com)
Marc Sageman's Understanding Terror Networks is published by University of Pennsylvania Press