This is the age of the conspiracy theory. In the interstices of the internet, no global event happens by accident - or as it seems at first glance - any more. While the truth is slowly getting its boots on, a paranoid counter-narrative is broadbanded across the world in a flash. We can all offer a list of conspiracies we have been told in a confidential whisper, backed up by a blizzard of small incongruent questions that are scraped together to make a fantastical answer. The 9/11 massacres were the Bush Administration's Reichstag fire, carried out by the CIA to provide a pretext for invading the Middle East. The 2004 tsunami was caused by secret Israeli nuclear tests. Diana was killed for carrying a Muslim foetus. Swine flu is a bioweapon developed to kill Barack Obama. And on, and on, into the shadows.
The British journalist David Aaronovitch has been "obsessed" by conspiracy theories, he writes, since an intelligent, likeable young man he was working with told him a few years ago that the 1969 moon landings were faked by NASA in a TV studio. All of Aaronovitch's common sense responses - why wouldn't any of the thousands of people needed for such a hoax have gone public by now? - were met by that weary conspiracists' nod. The lack of evidence, he was told, is simply more proof of how devious the conspiracists are. They can hide anything. They can kill anyone.
In his weighty, gloriously readable new book, "Voodoo Histories: The Role of the Conspiracy Theory in Shaping Modern History', he traces how these "voodoo histories" began - and where they could be leading us.
He begins with an admission that will disarm the moderate conspiracists. Quoting the writer Robin Ramsay, he says: "By far the most significant factor in the recent rise of conspiracy theories is the existence of real conspiracies." We know that the Vatican really did cover up the rape of children - so many more people suspect they are covering up the "true lineage" of Christ. We know that President Lyndon Johnson really did fake the 1965 Gulf of Tonkin "attack" to give himself a pretext to start bombing North Vietnam - so many more people suspect the Roosevelt or Bush II administrations did the same.
Yet real conspiracies are, he notes, "dogged by failure and discovery." Richard Nixon couldn't even "wipe a few incriminating tapes" without being caught out. In open societies, you can't keep the thousands of people you need for a big conspiracy quiet for long. He defines a conspiracy theory - as opposed to a real conspiracy - neatly: it is "the attribution of deliberate agency to something that is more likely to be accidental or unintended."
He takes as the archetype of conspiracy theories the Protocols of the Elders of Zion. In the shattered Europe that staggered out of the First World War, a document began to circulate offering an overarching explanation for how this evil happened - and how it could be expunged from the face of the earth. It was an eighty page booklet that claimed to be the leaked memo of a meeting of "the Elders of Zion" - a group of senior Jews that met once a decade in a graveyard in Prague to plot the destruction of existing societies and their replacement with a Jewish-run empire.
Aaraonovitch begins each chapter about conspiracies by describing the theory vividly, as if it were true. He then shows how it was invented. The Protocols were in fact cobbled together by the Russian secret police, who plagiarised it from a novel published back in 1868. But a rubble-strewn Europe was eager for a scapegoat - and they latched onto the Jews. Even now, a thousand facts later, the anti-Semitic smears refuse to die: Aaronovitch follows them from the trenches of Europe to the cable channels of Iran.
He traces over a dozen other conspiracy theories in the same way, from the Moscow Show Trials to the World Trade Center. Each time, conspiracy theories emerge at a time of confusion and trauma, to allow people to fit terrible new events into their existing world-view. The Bolsheviks couldn't accept that their way of running a society produced famine and catastrophe - so they preferred to believe in a vast conspiracy of Trotskyist "wreckers" plotting to bring it down from within, and they tortured their comrades into "confessing" to it. It offered, Aaronovitch says, "a painless explanation for massive failure... If it were true, then the great problems of state socialism could be solved by rooting out the plotters." So many people across the world were invested in believing that the Soviet Union offered a better world that they preferred to something - anything - but the truth.
Whenever a big event happens, we all have an intuitive expectation that it will have a big cause. So when, say, a President is shot, it seems impossibly empty for the cause to be one lone and lonely lunatic - but it is almost always the case. Ronald Reagan really was shot by a man who wanted to impress Jodie Foster; and John Kennedy really was shot by Lee Harvey Oswald, acting alone.
We know Oswald's motive. He was a lonely and troubled kid who, as Aaronovitch puts it, "defected to Russia in 1961 hoping to discover a better form of society - and discovered instead the Soviet Union." When he returned to America, he was bitter and angry, and determined that the only solution left was to tear down all forms of authority. He wanted to build an anarchistic society "without any centralized state whatsoever." All the endless theories that he couldn't have done it melt on examination. Take the nonsense of the "magic bullet": Aaronovitch talks the reader through how it has been shown by scientists studying the Zapruder footage to be not just possible but highly probable that Oswald's shots were responsible.
Conspiracy theories are theology disguised as investigation: no facts can permeate their certain stories about the world. Aaronovitch gives the example of the Irish film-maker Shane O'Sullivan, who claimed to have spotted in the footage of the Bobby Kennedy assassination senior three CIA agents mulling menacingly. He investigated the backgrounds of these CIA operatives and built an elaborate theory about why he was killed by them. The documentary was shown by the BBC and released in cinemas.
Then a small flaw emerged - the men in the footage turned out to be watch salesmen who were having a conference in the hotel that night. Oh, and one of the CIA agents he accused of committing the murder had in fact died of a heart-attack six years earlier. O'Sullivan didn't miss a beat. He said the watch salesmen must be other CIA stooges, because their company was chaired by a former advisor to Lyndon Johnson. And they must have stolen the dead agent's identity. Obviously. The theory - the CIA killed Kennedy - was an a priori belief; the facts will always slot into it somewhere.
When Korey Rowe, the producer of the huge 9/11 conspiracy "documentary" Loose Change, was challenged about the huge number of blatant factual errors in the film, he replied: "We know there are errors in the documentary, and we've actually left them in there so that people can discredit us and do the research for themselves."
When a conspiracy theory is finally, fatally debunked, its adherents often simply fall silent and find another target. Aaraonovitch offers the case of Hilda Murrell, a 78 year old British woman who murdered in 1984 when she was in the middle of investigating the threat a nuclear power station posed to public safety. The case became a cause celebre - there were three plays, a novel, and several documentaries detailing the "cover up." And then in 2003 - when the case was largely forgotten - the police used new DNA technologies on the old evidence. It led them to a 37 year old labourer with a long criminal record, who claimed that - although he was at the scene - it was his brother who killed her. He is now serving a life sentence for murder.
Aaronovitch fillets conspiracy theories brilliantly - but ultimately for the wrong reason. He complains they "eventually add up to an idea of the world in which the authorities, including those who we elect, are systematically corrupt and untruthful." In the place of excessive incredulity, he offers an unnecessary credulity. Some of the fiercest critics of conspiracy theories have been the very writers who are boldest and best at exposing real conspiracies - I.F. Stone, Noam Chomsky, and George Monbiot, for example. They know that by swallowing any old anti-government nonsense, activists waste their energy - and fail to expose real crimes by governments. You can be equally sceptical of authority and scornful of empty conspiracy theories: there is no contradiction.
Indeed, it is this flaw that leads Aaronovitch to leave a hole in his otherwise-compelling book. 'Voodoo Histories' purports to be an account of how conspiracy theories shape history - but it leaves out the most history-scarring conspiracy theory of our age. The Bush administration concocted a story that Saddam Hussein's agents had met with 9/11 hijacker Mohammed Atta. In order to get "proof", we now know they tortured captured Islamists into "confessing." On the basis of this conspiracy theory, a war was launched.
Yet Aaronovitch doesn't peer into this theory - or even mention it. He supported the war, and it would have added an extra layer of depth if he had admitted that he too fell for a conspiracy theory, as we all do sometimes, and teased out the reasons why. Instead, he charges off to condemn the Liberal Democrat MP Norman Baker for claiming Dr David Kelley was murdered for his views on Iraq - a theory that is ridiculous, but has harmed nobody.
Aaronovitch returns to form in his conclusion. He argues that we keep returning so obsessively to conspiracy theories because they are, paradoxically, reassuring. "Paranoia", he writes, "is actually the sticking plaster we fix to an altogether more painful wound": the knowledge that life is chaotic and random and nobody is in charge. Drive into a wall, and you will die, even if you are a Princess. Get shot by a maniac, and your story will end, even if you are a President. Sit in a tower in Manhattan when a plane hits, and you will burn, no matter how rich you are. We can all be killed in a second, for nothing, by next-to-nothing.
Faced with this fact, it is actually more soothing to fantasize that there is a force ordering the universe and controlling it all - even if that force is demonic. As Susan Sontag said: "I envy paranoids. They actually feel someone is paying attention to them."