A 2006 poll by the Pew Research Centre asked Muslims in Indonesia, Egypt, Turkey, Jordan and Pakistan whether Arab terrorists carried out the September 11 attacks. A majority in all countries — and a huge majority in Pakistan — replied that they did not. More than half of British Muslims (56 per cent) agreed that the hijackers were innocent stooges of a devilish plot, and one-quarter went on to say that "the British government was involved in some way" with the 7/7 atrocities on the London Transport system. More than 100 million people have watched Loose Change, a slick and mendacious documentary which opines that a missile, not an airliner, hit the Pentagon, and that a secret government agency faked the recordings of panicked calls from the doomed passengers. 

Meanwhile, around the Middle East, and increasingly among western intellectuals, anti-Semitic conspiracy theories that ascribe supernatural power to Jewish influence are so prevalent no one has found a way to measure them. 

With the collapse in the authority of elected politicians in Britain, the first — and often, the second and third reaction — to the untimely death of a significant figure or unexpected disaster is to mutter "cui bono" rather than "how sad". The British Left thought in the 1980s that the Tory press kept Labour in opposition by brainwashing the gullible population. In the 1990s, the Right followed suit and decided that the liberal BBC stopped voters realising that the Conservative Party best represented their interests. All paranoid belief systems hold that a powerful conspiracy controls the media, turning the masses into the victims of what 20th-century Marxists called "false consciousness" and Noam Chomsky calls "manufactured consent". It is fair to say that the conviction that democracy is a sham because hidden forces control the flow of information to the electorate extends far beyond the old Left and the cultish disciples of Professor Chomsky. Most politically committed people would be lucky to get through their lives without slipping into this version of conspiratorial thinking in moments of despair. 

Until recently, examining paranoid politics was not a respectable occupation for serious writers. Stephen Jay Gould once wrote that few of his scientific colleagues wanted to spend years looking for fraudulent science when they could be concentrating on making their own discoveries. The same unwillingness to waste precious time protected fraudulent history. The effort needed to go through the shifting assertions of, say, the 9/11 "truth" campaigners would question the researcher's sanity as much as the sanity of his or her targets. Such studies of paranoia as there have been followed the format of Louis Theroux's Weird Weekends, where the role of the journalist is to confirm the audience's sense of its own superiority by inspecting American survivalists or racial supremacists, much as Georgian gentlemen examined the lunatics of Bedlam.