Ancient fantasies inspire suicide bombers

My local Islamic bookshop is a ramshackle place whose volumes are barely visible through a mist of dust and burnt spices. Here the jovial staff - "All right, mate?" - will sell you commentaries on the Koran, hanging lamps, copper teapots and phone cards. They will also dispense, equally cheerfully, copies of a paperback which explains that Jews ritually murder Christian children and use their blood to season Passover matzo balls.

The Protocols of the Elders of Zion is a version of the medieval "blood libel" cooked up by the tsarist secret police a century ago. It is a work of the blackest propaganda, its every assertion demonstrably false. Yet it is circulating in 21st-century Britain, through bookshops, online book services and websites, nearly all of them Islamic but by no means all of them readily identifiable as the "extremist" outlets that Tony Blair proscribed at his press conference yesterday. The audience for the Protocols stretches far beyond fanatical jihadists; no one has surveyed "moderate" Muslims to discover how many accept its central tenet, but my guess is that community spokesmen would have a hard time accounting for the results on the Today programme.

Before we raise our hands in horror, however, it is worth scanning the shelves of the chain bookstore in a nearby shopping mall. For most of the past year, its best-selling title has been The Da Vinci Code, a thriller based on a myth about the Merovingian bloodline of Jesus that its author, Dan Brown, believes to be true. He is thus presenting secret "facts" in the form of fiction, which is also the technique adopted by an Egyptian television soap opera based on the Protocols.

If you prefer your conspiracy theories au naturel, there are books arguing the complicity of the United States in the September 11 atrocities, and at least one suggesting that President Bush planned them. The health section, meanwhile, stocks as many titles rubbishing medical science as those explaining it. These, too, are conspiracy theories, and not as harmless as they appear. (A musician friend of mine will walk with a stick for the rest of her life after natural healers identified the emotional roots of a "virus" that turned out to be a near-fatal bacterial infection.)

For centuries, a stream of "hidden wisdom" has flowed alongside the river of Western progress, absorbing empirically discredited ideas such as demonology and astrology. Paradoxically, the greater the accumulation of scientific evidence, the more the guardians of alternative wisdom cited science as the basis of their theories. The difference lay, and still lies, in methodology. A Victorian engineer might accurately measure the dimensions of the Egyptian pyramids - and then align them ingeniously with the numbers in the Book of Revelation. In our own day, Graham Hancock et al have used similar data to demonstrate the existence of an Antarctic Atlantis, the ruins of life on Mars or, my personal favourite, an ancient Roman colony in Arizona.

One effect of these books is the pollution of intellectual life: intimidated by the success of Pyramids of the Gods and The Da Vinci Code, real archaeologists and historians are increasingly presenting the past as a succession of mysteries. But it is the broader methodology of this "hidden wisdom" that poses the real threat - because it is employed, among others, by British suicide bombers.

All conspiracy theories collect supposed facts to bolster an existing thesis: the reverse of scientific method. Political conspiracy theories, alleging a global plot by the powers of Satan, have circulated in their modern form since the 18th century - "circulated" being the operative word, since they have depended on literature being passed from hand to hand. Television speeded up this process in the Middle East, thanks to the Arab world's Jew-obsessed state broadcasters. But it was the internet that really opened up the apocalyptic possibilities of what the American historian Richard Landes calls "self-brainwashing".

In the past few weeks, too much attention has been given to the effect of radical mosques on British-based suicide bombers; not enough has been given to the broadband connection between the bombers and websites that repeat medieval anti-Semitic fantasies and Islamic End Times prophecies. Tens of thousands of Muslim youths regularly view these sites in their bedrooms and internet cafés. Blocking access to them is a near-impossible task, even for this control-freak Government.

In any case, the problem goes deeper than that, as the Prime Minister indicated when he retreated into waffle yesterday on being asked about political correctness. It is not just that multiculturalism, whether in Britain, France or America, teaches students to be ashamed of the history of their host society. It also declines to challenge the conspiracy theories to which ethnic minorities - including the non-Muslim black community - are susceptible. I was once at a conference at Boston University at which a panel of mixed-race academics discussed the proposition (accepted by 30 per cent of black Americans) that the United States government manufactured Aids as a weapon of genocide. After a respectful debate, I asked each member of the panel if he or she was prepared to denounce the theory. Nobody was, on the grounds that it might constitute "disrespect".

The situation is little better in the British higher education system, through which a surprising number of actual or suspected suicide bombers have passed. Afro-centric history and feminist economics are constructed of little lies built on the foundation of a much bigger post-modern lie: that there is no such thing as objective truth - so you might as well grab that mouse and brainwash yourself.

That this world view should have been embraced so enthusiastically in Britain is particularly sad and poignant, given the proud empirical traditions of British philosophy and this country's astonishing contribution to scientific knowledge. It is this heritage that we urgently need to recover. We can block websites and expel ranting preachers, but we will not protect ourselves against the virus of self-brainwashing until young Muslims acquire the intellectual tools to evaluate conspiracy theories and - like Dr Johnson kicking a stone to disprove Bishop Berkeley's theory that we cannot know that things exist - refute them.