Albemarle Street, off Piccadilly, was London’s first one-way street. This historic moment in 19th-century traffic management was caused, hard though it is to believe in these days of The X Factor and Justin Timberlake, by the excessive popularity of the scientific lectures given at the Royal Institution, which still occupies No 21. The Christmas lectures in particular, delivering a secular creed at Christianity’s primary festival, created such a crush of people and vehicles that one-way traffic proved the only safe response.

How things have changed, despairs the bewildered humanist as he gazes at the alternative-therapy shelves in bookshops and pharmacies, while the religious divisions in Mumbai are writ large on the screens in the audiovisual departments. If it’s not new-age tosh, then it’s the rise of faith schools, the teaching of creationism and talk-show hosts complaining about the liberal “war on Christmas”. Where’s a humble rationalist to find succour in these dark days? Astonishingly, at the feet of stand-up comedians.

On Shaftesbury Avenue, in the West End of London, Eddie Izzard’s Stripped show constitutes a one-man pantomime with, sadly, no dame — Izzard’s not in drag this year. It plays through December, comes to an end on the day before Christmas Eve and starts with the premise “There is no God”. Izzard careers through history, wondering how a species that has existed for so little of the earth’s life could believe it was the purpose of a supreme being. What, he wonders, was God doing for the other billions of years? And why would anybody believe in the creative skills of a god who gave a cow four stomachs and made the poor creature eat its own poo?

Barely feet away from Izzard at the Lyric theatre squats the Gielgud, currently home to Bill Bailey, comedian of the enlightenment, whose show, Tinselworm, attacks numbskull beliefs from scientology to emo while drifting admiringly through the Hadron Collider, Kant’s categorical imperative and the thoughts of the French post-structuralist Jean Baudrillard.

And, as the crowning glory of comedy’s rationalist outreach, a series of nights coming up at the Bloomsbury theatre and the Hammersmith Apollo will feature a bewildering list of the great and the good from the worlds of comedy, music and science, delivering a show called Nine Lessons and Carols for Godless People.

From the laboratory come Richard Dawkins, Simon Singh and Dr Ben Goldacre. From the well of whimsy come Ricky Gervais, Dara O’Briain, Mark Thomas, Stewart Lee, Josie Long and — to roll out the cliché — many, many more. Meanwhile, breaking up the lectures and gags, there's music from, among others, Jarvis Cocker, the Australian musical comedian Tim Minchin and the former Auteurs and Black Box Recorder member Luke Haines, all accompanied by a 22-piece orchestra. It’s as if someone has taken the Royal Institution lectures and given them da funk.

The format of the Nine Lessons show is an affectionate apeing of the traditional Christmas carol service: nine songs divided up by nine sermons. For some, the existence of the night alone is going too far. Here’s the previewer for LondonTown.com, who wrote that this line-up would be “taking the piss out of faith of all kinds at the holiest time of the year. In many ways, it’s a tribute to the Church of England’s genial tolerance that this staggeringly offensive event can take place with so little complaint (you certainly can’t imagine them doing the same for Ramadan)”.

Yet the organiser of the event, the comedian Robin Ince — a self-proclaimed humanist who contributes to New Humanist magazine — is keen to stress that the comics were deliberately asked to avoid a full-scale assault on faith. Instead, they were invited to talk about something that fires them up, such as Chris Addison riffing around evolution.

“The show is not an attack on religion,” Ince explains. “Personally, I would like to see a world without religion, but the way to do that is not by saying: ‘Your book is stupid.’ It’s better to say: ‘There is something you may not know that shows how this wonderful world could come to be without a creator.’ ”

Indeed, it’s the scientists who are cocking the strongest snooks. Goldacre will rip into homeopathy, alternative therapies and the media with the kind of cracks and calculation familiar to readers of his book, Bad Science. Dawkins, who was a great friend of the out-and-proud atheist Douglas Adams, will throw in a few gags as he demolishes pro-creationism arguments, taking great delight in unpicking the recently published creationist atlas, which argued against natural selection using a fly-fishing fly for proof. (It wasn’t a real fly.)

The mathematician Simon Singh, meanwhile, will attempt to explain the entire Big Bang theory of the creation of the universe in about eight minutes, with the help of a pickled gherkin. “It’s to demonstrate ‘red shift’,” he explains with a shrug. “You put a current through the gherkin — do not try this at home, by the way — and the sodium it’s been pickled in glows yellow. If it were moving away from us, the light would suffer a sort of Doppler effect and seem bluer. The sodium burning in stars seems just that blue, so they must be moving away from us.”

It may seem odd that stand-up comedy should hoist its standard alongside that of scientific knowledge — although, as both groups were probably fairly spoddy schoolkids, they were likely to have spent a lot of time hiding in the classroom together during lunch break. Comedy, however, has a quasi-scientific role in any well-ordered society: where science dissects and tests the natural world, so comedy dissects and tests the culture. That which cannot withstand its mocking sneer is probably a bit rubbish and has bluffed this far. No right-thinking Brit can avoid a stab of pride when recalling that the Italian Northern League's plans, at the end of the last century, to march beside drops of water from Lake Garda as they flowed down the Tiber to Rome were abruptly dropped when the English-speaking press burst out laughing during the announcement.

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