Let’s be honest . . .

The scene being filmed called for Ricky Gervais to clear up the question of whether or not he was the Messiah.

Despite the weighty confusion, the British comedian looked every bit himself -- barrel-waisted, sheepish and wearing a dark suit -- as he stood on the stoop of an apartment building in this Industrial Revolution-era city northwest of Boston.

Though “The Invention of Lying,” which opens Oct. 2, is technically not a comedic period piece, it stars Gervais (of “The Office” and “Extras” fame) as a significant historical figure -- a man who discovers the ability to lie in a world where humankind has evolved without producing a single fibber or serial fabricator (hold your sarcasm until the end, please).

On the one hand, the repercussions of this deceit-less world are chilling. Without lying, there is no art, no literature, no music (at least not the kind with lyrics or stories). Most important for this movie, films are not willful entertainments; instead, they’re lectures, spoken by actors who read dry, provable facts to a camera, written by screenwriters who have credits like “The History of Nuclear Weapons.”

Gervais’ character, Mark, is one such lecture writer, and when we meet him he’s down in the dumps. He’s out of favor at work, where he’s mocked by his (brutally honest, of course) secretary (Tina Fey). Soon he’s on the verge of going broke. Meanwhile, his big crush (Jennifer Garner) is (to be honest) way out of his league.

Then Gervais utters a lie, a small one, and soon he’s like Bill Murray with his deja vu all over again in “Groundhog Day” -- both elated and plagued by the God-like status his special talent confers upon him.

As with Murray, Gervais has a sneakily expressive face that tends to set itself in deadpan; much of the joy in watching him comes from observing the way he can subtly modulate his eyes and mouth, as if seeking out the precise volume at which his comedy should be played.

And unlike his more daredevil fellow Brit Sacha Baron Cohen, Gervais allows himself, in his comedy, to wade into true sentiment. As much as making people laugh at David Brent in “The Office” or Andy Millman in HBO’s “Extras,” Gervais believes the audience has to care what will happen to them.

And so it is in “The Invention of Lying,” where Gervais sees his character as influenced not just by Woody Allen in “Sleeper” but also by Jack Lemmon in “The Apartment.” An Everyman, acting normally in a world that’s otherwise gone strange -- but not so strange that the audience is overwhelmed.

“What you want [the audience] to do, once they get it, is forget about it,” Gervais was saying in his trailer during a lunch break from filming. “Once they know ‘The Office’ is a fake documentary, forget about it. Follow the drama, and if they know it and they’ve understood, they never have to question it again. We have to make sure that jokes don’t keep happening. Then people are just watching everything, thinking, ‘Is that a joke?’ They’ve just got to relax.”

Gervais was sitting on adjoining loungers with his co-writer and co-director, Matt Robinson.

They did not know each other when Robinson, a 31-year-old, L.A.-based screenwriter who grew up in Westwood and went to Santa Monica’s Crossroads School, wrote the initial draft of “The Invention of Lying.”

In the shotgun marriage that developed, Robinson gave “The Invention of Lying” to veteran Hollywood producer Lynda Obst, the mother of Robinson’s college roommate at Sarah Lawrence College. Obst in turn got it to Gervais, and the next thing Robinson knew he was boarding a plane for London to write a script with one of his comedic heroes.

“It feels like I won the Make-a-Wish Foundation,” Robinson said, “without having to have that annoying cancer.”

Hearing this, Gervais cracked up. He laughs easily and generally has the air of a comedian unburdened by the vagaries of the Hollywood machine.

“Don’t let him write that; stand up for yourself,” Gervais said when Robinson readily agreed that their collaboration could be subtitled “Obsessed Comedy Nerd Writes Script, Gets to Work With Hero.”

“He’s got other influences as well,” Gervais insisted merrily.

He proceeded to heap praise on the script, perhaps to further emphasize that he wouldn’t be here had the material not grabbed him the way it did.

“I loved it [by] Page 10,” Gervais said of the script. “I felt at home.” So he called Robinson right away. “Then I read the scene [in which Mark] invents religion -- gotta do this. Gotta do this film.”

Though he starred in the 2008 film “Ghost World” and has been in both “Night at the Museum” comedies, Gervais maintained that he is not one who casts around for other people’s material (his next film is “Cemetery Junction,” set in 1970s England, which he is making with his regular collaborator and “Office” costar, Stephen Merchant).

“The Invention of Lying” costars Garner and comedian Louis C.K., but its cast sprawls to include Fey, Christopher Guest, Rob Lowe, Jonah Hill and Jason Bateman (with cameos by Edward Norton and Philip Seymour Hoffman).

Garner, as the apple-cheeked love interest, has a memorable first line, delivered when Gervais picks her up for their first date.

“Hi,” she greets him at the door, unable to lie, “you’re early. I was masturbating.”

Garner, relaxing in a nearby trailer filled with scented candles and children’s toys, said she’d had to practice the line a few thousand times before getting comfortable with it.

Growing up, she said, she had not been exposed to much edgy comedy.

“We weren’t allowed to watch Carol Burnett because my mom thought it would encourage us to be loud,” she said.

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