C+

Bold but in the final analysis not bold enough, Ricky Gervais’ second attempt at a star vehicle—following the charming but underappreciated “Ghost Town”—starts with a clever premise and raises the prospect of really biting satire, only to trail off into weakly sweet comedy that falls far short of its potential. There are some big laughs in “The Invention of Lying,” but it’s front-loaded, and one gets the feeling that its makers suffered a failure of nerve as they went along.

The premise is that the world’s population has never learned deception, always speaking the truth and nothing but, often bluntly and—some would say—cruelly. In a small town in such a world, Mark Bellison (Gervais, again the likable schlub, a role he fits perfectly) is a sad-sack screenwriter for Lecture Films, an outfit that, since fiction has never been invented, makes movies in which readers (the “stars”) intone what are effectively history lessons into the camera. Mark’s been assigned the fourteenth century, the downbeat age of the Black Death, and as a result his pictures have tanked and his dithering boss (Jeffrey Tambor) fires him, much to the delight of his obliviously nasty secretary (Tina Fey) and his successful, arrogant colleague Brad (Rob Lowe).

In danger of being evicted for non-payment of rent, Mark goes to the bank to withdraw his final $300 but instead takes advantage of a computer glitch to suggest that his account contains the full $800 he needs; and to his amazement, the teller assumes he’s telling the truth and forks it over. Mark has discovered the possibilities of deceit, something that’s never occurred to anyone else before, and takes advantage of it, penning a phony “old” account of a fourteenth-century close encounter with aliens that gets him his job back and makes him the toast of the industry.

These relatively innocuous lies are followed by something more serious. To console his dying mother (Fionnula Flanagan) on her deathbed, he counters her statement that she’s going into oblivion with a made-up story about an afterlife in which everyone gets a mansion and is reunited with deceased family and friends. He’s overheard by people who believe what he says, and before long he’s besieged by mobs wanting to know more. That turns him into a modern-day prophet, and in the movie’s best scene he delivers the messages he says he’s received from “The Man Who Lives in the Sky,” which he’s written down on the backs of two pizza boxes that look suspiciously like tablets Charlton Heston might have carried. They include the revelation that The Man is responsible for everything that happens, both good and bad (which occasions some prickly questions), but that he rewards those who live good lives with happiness after death while punishing those who do wicked things (three or more “sins” bring down his wrath).

This is obviously a riff on organized religion, or monotheism at least, and even the most fervent believer might admit that it might have been the start of a really sharp, edgy satire. But the picture fails to take that route. Instead it retreats into the conventions of romantic comedy, wasting most of its running-time on Mark’s pursuit of the lovely Anna (Jennifer Garner), with whom he’s had one date, but who rejects him even after his celebrity for genetic reasons—she informs him directly that she doesn’t want chubby kids with snub noses. The script even has her about to marry the noxious Brad instead, only changing her mind at the last moment in “Graduate” style.

One can only imagine “The Invention of Lying” without that whole romantic angle (and you must admit that without it, it probably would never have been green-lit). But it seems like an opportunity lost. There are moments when you can glimpse the possibilities. A scene in which Bellison, distraught over Anna’s rejection, lets his hair and beard grow and, waddling around in a bedsheet, looks like an overweight Jesus, has a promise that’s never fulfilled. And I take it as a signal of the makers’ personal attitudes that in the wedding scene, the minister (John Hodgman) at the chapel dedicated to The Man is wearing a silver cross (something that, in the religion-free society, would be meaningless). But the ribbing of faith turns out to be pretty toothless for the age of Dawkins and Hitchens, all wind-up without much follow-through. Of course, going whole hog on the matter might have been the movie’s kiss of death with the mass audience, and it should come as no surprise that Gervais isn’t Bunuel. But one’s left with the feeling that this movie could have been this generation’s “Life of Brian,” had he tried a bit harder.

So what one’s left with are a few crackling good moments, especially in the early going, followed by a long, sad letdown in the second half. Matters aren’t helped by the casting of stand-up comics like Louis C.K., who plays Mark’s best pal and mostly just looks lost, and the many others who fill lesser roles—like his co-writer Matthew Robinson in a flashback about Bellison Sr., who plays the scene with all the subtlety of an English music-hall sketch—come across as amateurish. Among the real actors, Garner is one-note, Lowe is awful, and Fey and Tambor are wasted. But Jonah Hill gets a few laughs as a colleague of Mark’s who’s always contemplating suicide, and Jason Bateman has a nice bit as a disconcertingly honest emergency-room doctor. But overall Gervais does not seem to have exercised a very firm directorial hand over the proceedings, and most of the picture has an overly loose, lackadaisical feel. On the technical side, too, the picture’s just okay.

So what Ricky Gervais has delivered in his second outing are some solid throwaway laughs, but what one comes away from “The Invention of Lying” with is mostly regret over what might have been.