I remember a friend telling me only a few days after the Sept 11 attacks that the World Trade Centre had been wired with bombs either by the government or by the owner. It was also pointed out to me that the dust around the World Trade Centre had fallen in the shape of Satan’s visage. I wouldn’t have predicted it at the time, but the crackpot impulse behind these ideas has become common currency. In one American poll, a third of respondents registered their belief that the Bush Administration either aided the attacks or declined to stop them.

More recently the cult of Zeitgeist: The Movie, made by someone called Peter Joseph, has been brought to my attention. Its argument – if it could be called that – is that the world is divided between the manipulators, the suckers, and the truth-telling dissenters. In the first group, you’ll find international bankers, American presidents, and the Internal Revenue Service. (According to Zeitgeist, income tax is “nothing less than the enslavement of the entire country”.) The suckers, meanwhile, are those who are none of the above and who are also none of the following: America First hero Charles Lindbergh and the 9/11 “truthers”.

Watch the film as closely as you like; you will not discover what Mr Joseph believes actually occurred on Sept 11. You will, however, find a general spray of points culminating in the assertion that the attacks were part of a “false flag operation” orchestrated by the Government in order to frighten the public, crush civil liberties, and launch wars in the Middle East (as well as “the war against you” – and why not, when the going’s good?).

This, honestly, is as nicely as I can put it. Because when the “arguments” are put together, they create rather a lot of friction. For instance, it is suggested that the Pakistani intelligence agency, the ISI, had a hand in funding the hijackers, and that the Bush Administration has failed to investigate because of its cosiness with the Pakistanis. In itself, this is not a crazy claim. (I first read it in Bernard-Henri Lévy’s book Who Killed Daniel Pearl?, which argues that Pearl was murdered by ISI types because he knew too much about the relationship between the Pakistani regime and Al-Qaeda.)

But it suggests that 9/11 was not an “inside job”, doesn’t it? Or could the American war-mongers not scrape together enough dosh to fund their own hijackers? Zeitgeist goes on to tell us that “At least 12 Countries warned the US regarding intelligence about an eminent [sic] attack on America”. Well, again: did the American Government organise this attack or not? Anyway, if Pakistan and the United States were co-plotters, then the former did not get much bang for its buck: the war against the Taliban unseated the ISI’s closest international ally. Nor could such close co-operation buy the Americans any Pakistani support for the Iraq War. Still, by missing the fairly significant point that a major American “ally” is also apparently funding a major enemy of open society, the “truthers” have managed to neglect this real scandal, preferring to feast on a half-baked non-theory.

There is no dearth of evidence that United 93 crashed in Shanksville, but suppose Zeitgeist’s claim is correct, and this evidence does not exist: how careless can one government get! All that scheming and no one remembered to plant any wreckage. I hope someone was fired for that foul-up. This contradiction – America as both Iago and Bottom – might loom larger in the thoughts of the “truthers”. Most obviously, why would the mastermind make its plot so difficult to execute? These fake hijackings and fake phone conversations and fake building collapses and fake planes and fake people seem to be needlessly complex. The “plot” to unseat Saddam Hussein might have been greatly assisted by making the culprit someone with more obvious ties to that dictator.

All this can be said without even mentioning the factual howlers that make up Zeitgeist’s gooey core. None of the extraordinary claims are backed up by even tokenistic evidence. Precisely zero experts agree that flying a plane into a wall of the Pentagon was beyond the wit of the hijackers, pace Mr Joseph. Nor is there “extraordinary secrecy” surrounding the collapse of WTC 7: you can find the National Institute of Standards and Technology’s working hypotheses by doing a Google search. And it is true to say that no evidence exists of a plane crashing into the Pentagon only if you discount all the pictures of a crumpled plane next to the Pentagon, and deny the existence of eye-witnesses like Allyn E Kilsheimer: “I picked up parts of the plane with the airline markings on them. I held in my hand the tail section of the plane, and I found the black box. … I held parts of uniforms from crew members in my hands, including body parts. Okay?”

Okay, but did you know that experts agree the way the WTC buildings collapsed could only have been caused by a controlled demolition? You didn’t know that because it’s not true. Although, unless you have considerable knowledge of civil engineering, you’re unlikely to be able to provide a rapid-fire response when someone says, “Explain how WTC 7 collapsed!”

For those who are genuinely curious, the best and most easily available elucidation of these supposed abnormalities is the March 2005 report published by Popular Mechanics. According to the PM journalists, “[W]e were unable to find anyone with any degree of authority, in the public or private sector – first responders or university professors, engineers or flight instructors – who agreed with the claims made by 9/11 conspiracy theorists.”

It’s all very well to know that reports like this exist. But if you wanted to respond quickly to the claim that jet fuel does not burn hot enough to “melt” steel and that therefore the WTC buildings should not have collapsed, you would have to know that steel frames do not have to “melt” for a building to collapse, and that steel can expand, crack, and buckle at much lower temperatures than those caused by burning jet fuel. You would also need some knowledge of the fact that the spray-on fireproofing insulation was damaged by the initial impact of two Boeing 767s, which left the metal vulnerable. Plus you would need to know a bit about the WTC’s steel bar joists, centre-core columns, outer frame-tubes, and bearing walls.

In the same way, if a creationist collars me and demands to know how I explain the development of immune systems in vertebrates, I will not be able to provide an immediate answer. But I don’t consider this a crushing defeat. I can of course give my reasons for rejecting creationism, and these reasons are good enough that my inability to explain every detail of evolutionary biology does not cause me to spiral into a crisis of doubt and angst.

But to the paranoid mind everything should have a rapid explanation. “The mistaken belief that a handful of unexplained anomalies can undermine a well-established theory lies at the heart of all conspiratorial thinking”, writes Michael Shermer in Scientific American. “Such notions are easily refuted by noting that scientific theories are not built on single facts alone but on a convergence of evidence assembled from multiple lines of inquiry.”

The quickest way to refute the Sept 11 fantasist is not to trawl through the detailed reports, but to point out the existence of a jihadist movement with a life well beyond North America and a history that stretches back to at least 1928. Given these facts, it would be far more surprising if a group like Al-Qaeda had not managed to attack America. Reading “truther” screeds, you’ll find waves of quasi-physics and hearsay circling around some meagre scraps of gossip, but usually no mention of Islamism. That’s like charging into a debate on Darwinism and ignoring the fossil record. What good are the receipts if all the debits are blanked out?

But to reason against Zeitgeist is to miss the point; the point is to get angry. And Mr Joseph, like most fans of the racist demagogue Charles Lindbergh, seems to be an angry guy. What’s interesting here is that, while Lindbergh is quoted as an oracle throughout the film, Bush is depicted in no uncertain terms as a new Hitler. So, in between shrieks that America is a dictatorship, Zeitgeist invokes the authority of the man who did most to encourage a Roosevelt-Hitler pact. How must it feel to adore the moral leader of the anti-Jew America First movement while pretending to oppose fascism?

Turning to Afghanistan and Iraq, it emerges that the United States has really overthrown the Taliban and Baath dictatorships for oil. Odd, given that America never had any trouble purchasing oil from these countries when it wanted to, and could have saved itself a lot of trouble by simply removing the trade sanctions. Apparently “other non-conforming countries like Iran and Syria” are next. Who knew that the defining characteristic of the Baath Party has been non-conformism? But now that you mention it, it makes sense: America can’t handle having such chilled-out individualists in the region because it’s a threat to the American project of crushing diversity and unconventional behaviour. Right on.

The movie ends with some nugatory uplift – the power of one, the oneness of our power, the togetherness of our all, etc. Apparently “when the power of love overcomes the love of power, the world will know peace”. And that’s what you get from a group who believe that the Jews run the world.

A further irony, in a film that has a brief and ham-fisted section on religion, is the extreme similarity between inside-jobbers and creationists. Both have adopted silly titles – “9/11 Truth Movement” and “Intelligent Design Network” – that are supposed to give them an air of scrupulous objectivity. Both are political movements originating on the extreme Right (with sympathisers on the reactionary Left) masquerading as disinterested truth-seekers. Neither can distinguish between criticism and persecution; anyone who criticises the argument is said to be “silencing dissent”. Their methods – supposition posing as fact, hearsay treated as proof, early factual mistakes repeated as if they had never been discredited, quoting phoney sources, ignoring or distorting the opinions of experts – are the same. Then there is the laziness. It takes more work to understand the theory of natural selection than to chant “creation”. And if America can have a fundamentalist enemy, then certain comfortable political assumptions might have to be reconsidered; it might even be necessary to learn something about Kashmir and Waziristan.

In some cases, the connection is more than metaphorical: the most prominent “truther”, David Ray Griffin, is a Christian theologian who sees Sept 11 as “a religious issue”. The film’s other idol is the creepy Jordan Maxwell, who bores on about “the true and divine presence in the universe called God”. His website sells DVDs including Magic Dominates the World and Signs of Destiny II: The Hidden Hand in World Affairs. One has to wonder whether these people truly believe their propaganda: why are we not seeing an exodus of “truthers” fleeing the American dictatorship before it’s too late? Why are they reporting for duty to their IT jobs and attending pep-rallies instead of making plans to save their families?

In Saul Bellow’s novella Seize the Day, the anxious Tommy Wilhelm is surrounded by men who know and know and know. The “psychiatrist” Dr Tamkin is one, styling himself as an otherworldly mystic, always ready to dish out ready-made advice, full of pseudo-profundities. “I deal in facts. Facts always are sensational. I’ll repeat that a second time. Facts always! are sensational”, Tamkin insists. In his eyes, everyone leads a squalid double-life, “like the faces on a playing-card, upside down either way.” “I guess I am a sucker for people who talk about the deeper things of life, even the way he does”, reflects Wilhelm.

The Tamkins of the world are stubborn. But, encouragingly, there is always resistance. Whatever your opinion of the American military, one thing it deserves credit for is the development of the Internet, which makes it infinitely easier to check facts. The freely available investigations by Skeptic, Popular Mechanics, and NIST make it that much harder to sucker the credulous. For every David Ray Griffin there is a Michael Shermer. When you look at the “sources” listed on Mr Joseph’s Zeitgeist website, it turns out that there are quite a few and that almost all of them are crank publications with titles like Rule by Secrecy and The Shadows of Power. Following Wilhelm, you find yourself asking, “With all the books he reads, how come the guy is so illiterate?”