Religulous

In Umberto Eco's The Name Of The Rose (and for those who have neither read it nor seen the film adaptation, this is a spoiler), a blind, god-fearing monk is willing to kill to prevent the last known copy of Aristotle's treatise on comedy from ever coming to light. Both the lost Aristotelian text and Eco's work are, of course, just books (as is the Bible), but the point, nonetheless, holds true: there can be few greater threats to religious zealotry than the power of laughter or the quest for knowledge – which is what makes comedian Bill Maher such an effective champion for the cause of scepticism in an age of rising fundamentalism.

Maher has doubt in spades and the intellect to back it up, but most importantly, he is outrageously funny. Having already earned himself notoriety for his straight talk on the stand-up circuit as well as on his TV shows Politically Incorrect and Real Time, this is a man who takes his irreverence very seriously. Team him up with Larry Charles, who has directed television's Seinfeld and Curb Your Enthusiasm as well as the film version of Borat, unleash the pair to work their miracle of fearless debunkery on strong believers of every faith, and the result is Religulous, a scabrous, at times shocking assault on the more idiotic aspects of religion, and the dangers that they pose in a society capable for the first time of bringing about its own destructive Apocalypse.

Sure, when it comes to non-evidential beliefs, there is no shortage of easy targets for comic ridicule, and Maher makes light work of say, Scientologists, Mormons, or a slightly uncomfortable looking man called Jose Luis de Jesus Miranda who proclaims himself the Second Coming of Christ ("lots of people would like this job") – but such nuttiness is juxtaposed to the equally bizarre mythologies of more mainstream faiths.

"It worries me that people who are running my country believe in a talking snake," as Maher puts it to Mark Pryor, a devout evangelical who is visibly uneasy with the idea of evolution and who just happens to be Arkansas' Democrat Senator. Pryor's entirely unironic response is the sort of absurdist non sequitur comedians can only dream of penning themselves: "You don't have to pass an IQ test to be in the Senate." It's funny (and terrifying) because, gosh darn it, it's true – and no less than George W Bush, himself not known for his high IQ, is on record as stating that under his Presidency, parts of US foreign policy has been based on his personal beliefs about God - an extraordinary piece of file footage that Maher and Charles gleefully replay.

Maher has an impressive panoply of facts and arguments at his fingertips (the Problem of Evil, inconsistencies or astonishing omissions in the Bible, the historical unreliability and derivativeness of the Gospels, etc), but he is often at his best when he gives his interlocutors enough rope to hang themselves. In some cases, apparently, not much rope is required. One has only to hear Dr ("not a Dr", as a subtitle reveals) Jeremiah Cummings, one-time Muslim (and Blue Note) turned charismatic Christian televangelist, painfully mangling a quote from the New Testament as a justification for his love of bling ("Jesus dressed very well") to see a whole history of human corruption, charlatanism and self-serving greed played out in the name of a higher authority.

If Religulous has a flaw, it is the scattergun approach that it takes to organised religions. One can understand why Maher's journey takes him to Holland, recently a flashpoint for the increasingly violent collision between free speech and Islamic extremism, and it is hard not to be impressed by his brave adoption of the kind of public stance that can easily earn one a fatwa - but his meeting, while there, with one Ferre van Beveren, Can-theism churchleader and founder of the THC Ministry Amsterdam, comes across as just a dopy joke that risks diluting the force of Maher's more serious inquiry. Similarly, while he is admirably frank about his own views in the interviews, the effect of this is somewhat undermined by his decision to editorialise his footage with comic subtitles and post-interview commentary, to which his subjects are, of course, unable to respond. Even-handedness is one quality that Maher often lacks.

Still, Maher is both funnier and wiser than, say, Michael Moore, and he tends to treat what one might call 'conventional' or 'soft' religious beliefs with an easy-going respect, finding an unlikely (and remarkably canny) ally for his arguments in the jocular Father Reginald Foster, Senior Vatican Scholar and Principal Latinist to the Pope, who says of those who take the "nice stories" in the Bible literally: "You just have to live and die with their stupid ideas." Few people other than fundamentalists themselves will defend the substance of the fundamentalist viewpoint, but even fewer dare to speak out against them. It is what makes this mockumentary so important.

"Doubt", Maher concludes, "is humble, and that's what man needs to be, because human history is just a litany of people getting shit wrong." Amid the destructive dogmas underlying Jihadist militancy, Bush's 'crusade' against Terror, and the religious struggles of the Middle East, it is a viewpoint well worth hearing – and slap-your-thighs hilarious to boot. Laughter, it turns out, might just be the long-hidden weapon of mass destruction that we all need to find right now.