Voodoo Histories, By David Aaronovitch

This is the age of the conspiracy theory. In the interstices of the internet, no global event happens by accident any more – or as it seems at first glance. 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 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 was invented "in a lab", as a "high-tech way to assassinate Barack Obama". And on, and on, into the shadows.

The 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 conspiracist's nod. The lack of evidence is simply more proof of how devious the conspirators are. They can hide anything. They can kill anyone.

In his gloriously readable new book, Aaronovitch 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 George W Bush 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 80-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 cobbled together by the Russian secret police, who plagiarised it from a novel published in 1868. But a rubble-strewn Europe was eager for a scapegoat – and latched onto the Jews. A thousand debunking facts later, rhe anti-Semitic smears refuse to die. Aaronovitch follows them from the trenches of Europe to the cable channels of Iran.

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 turned out to be watch salesmen who were having a conference in the hotel. One of the CIA agents accused of committing the murder had died of a heart attack six years earlier. O'Sullivan did not 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. The theory – the CIA killed Kennedy – was an a priori belief; the facts will always slot into it.

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 – IF 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.

Indeed, it is this flaw that leads Aaronovitch to leave a hole in his otherwisecompelling 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 Kelly 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 more soothing to fantasise that there is a force ordering the universe and controlling it – even if that force is demonic. As Susan Sontag said: "I envy paranoids. They actually feel someone is paying attention to them."

The father of lies: the 'Protocols'

The 'Protocols of the Elders of Zion', purportedly written by a secret group of Jews, 'revealed' a Jewish and Masonic plot to achieve world domination. It has long been proven to be the most infamous of forgeries, believed to have been authorised by factions of the Russian aristocracy in the late 1870s. By 1905, they began disseminating the document as part of their fight against the Bolsheviks in an attempt to link the revolutionaries, with a number of Jews among their leadership, to the 'conspiracy'.