The idea might seem ludicrous at first. Ricky Gervais and Woody Allen? Yet both are writers and stand-up comedians who got their big start in television. Each is obsessed with his inability to get the girl. While Allen has long traded on his puniness, Gervais trades on his portliness. Each portrays a character much like themselves, taking that character from project to project, allowing self-deprecation and embarrassment to lead the way. And each has become the writer, director and star of his best work.

It doesn’t end there. Allen has always divided audiences in a big way, and so does Gervais. People love them and hate them in equal measure. Allen has always had an ambiguous relationship with Hollywood, and so will Gervais. Allen’s appeal crossed easily to Europe and Gervais’s crossed easily to America. So, apart from Jewishness, what’s the difference? Before today you would have said Gervais has been interested in portraying small professional mortifications and not the problems of metaphysics and death and sex which have been making Allen’s films art-house hits and flops for more than 40 years. Yet The Invention of Lying might persuade you that Gervais, as much as Allen, is happy to step into the ring with the moral philosophers and tell us what life is actually about.

To insist on the connection, The Invention of Lying’s titles come up in Allen’s famous signature typeface. And the story is Woody-ish, too. Gervais plays Mark Bellison, a writer who lives in a world without lies. It is an American world, so the concept is quite hard to imagine, but the film deftly and funnily lays out what it would be like if everybody just said what was on their minds, without obfuscation, diversion, cover-up or lying. It is a world without adverts.

We first meet Mark when he is going out on a date with Anna (Jennifer Garner), who is out of his league, as even the waiter at the restaurant tells him. When he turns up early to meet her, she says she’s not quite ready yet, as she’s been upstairs masturbating. When he asks her how she is, she says “a little frustrated at the moment. Also equally depressed and pessimistic about our date tonight.”

The truth makes everybody a little tense. There’s nowhere to hide. Mark works for a film company that only makes historical movies about things that happened in the past. In a society without lies they don’t understand the concept of fiction, and in his work Mark has a tough beat — the 14th century — so he has to come up with an interesting way to narrate the truth of the Black Death. He is about to be fired. But things begin to look up when he tells a lie while withdrawing money from the bank. He discovers that lying can make life bearable. His mother is dying in an old people’s home — or, as it’s named in the truthful world, A Sad Place for Hopeless Old People — and Mark, in her final moments, feels he can’t bear to agree with her when she says she’s going into an eternity of nothingness. He makes up a great lie on the spot about how everybody she loves will be waiting for her and that she’ll be looked after by the man in the sky.

Bingo! The metaphysical lie. Every kind of complication in the world comes from this and soon we find that Mark’s simple life of quiet uselessness is upended. Lying has made life complicated and he must deal with what he has created, which is either the end of innocence or the birth of delusion, or both.

This is a fantastic, wild and funny premise, the kind of moral conundrum that made a movie like Allen’s Zelig such fun to watch. It is also the kind of scenario that would have delighted Billy Wilder, a great believer in unexpected reversals leading to great truths. There are a few problems. Wilder was often unable to stop his movies from sliding towards sweetness but even he might have worried at the way Gervais and co-writer/co-director Matthew Robinson allow their great idea to give itself over too slickly to more standard romantic comedy. Never mind: the production never stops showing you laughs and the moral trapeze, and I found myself applauding the size of Ricky Gervais’s ambition.

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Another difference with Allen is that he was always, fundamentally, a student of film. Gervais needs to take more of an interest in the texture of what can be captured on camera. The Invention of Lying has brilliant strengths but none of them are visual. Gervais and Robinson don’t really establish a memorable style, often allowing the film to seem a little made-for-TV. But you also feel that, like every other film-maker worth following and paying real attention to, this will all get stronger with future projects.

And there should be many of them. Despite its flaws, The Invention of Lying is Gervais’s best film outing to date. It draws his talent into alignment with some comedy classics, and shows that he has the intelligence to go for invention and originality, for screwball comedy and good writing, where others might have stuck with the safer plainness of The Office.

Great comedy needs to find new causes, new places, new moral occasions — and Gervais is now showing he can do that while still remaining close to himself.