Imagine a world where no one could lie. Ricky Gervais and Matthew Robinson have created this parallel universe in the film they wrote and directed, “The Invention of Lying.” This romantic comedy of infinite opportunity is set in a society in which lying is mentally and physically impossible – in fact, there isn’t even a word for it. There doesn’t seem to be a word for “truth,” either; everything is simply a black-and-white case of what is and what isn’t. For a good part of the movie, Gervais and company get some great mileage out of this premise, but in the long haul the idea falls short and feels drawn out. With so much truthfulness, the society in “The Invention of Lying” has more or less become impervious to embarrassment. Mark Bellison, played by Gervais, is the only character in the film that has the ability to lie. In this world, the concept of lying is so nonexistent that no one is able to do anything but believe what Bellison says. He gets money and plays with sexual exploitation before realizing that he can use his newfound gift to help people. This element of helping people also appeared in Gervais’ last film, “Ghost Town,” in which he acted as a medium between the dead and the living. However, having great power leads to trouble when the public catches wind and Bellison suddenly finds himself at the center of attention as “the man with the answers.” Encouraged by a now-interested female companion, he sets out to bring hope to the rest of the world. It’s a hilarious concept, as he plays a modern day Moses, dictating 10 self-written truths – scribed onto pizza boxes – about the afterlife and the man in the sky who controls everything. “The Invention of Lying” has a great premise, and in its opening half it raises a great deal of laughs. The forced element of speaking the truth plays out like a Monty Python sketch, and when it turns to religious matter, it reminds us of the wonderful Monty Python film “The Life of Brian.” Gervais, in his now-customary unassuming and flustered way, plays it all brilliantly. He has a knack for getting laughs from the quietest sigh of frustration. Unfortunately, for such a great premise, the film loses direction at the halfway point, as it turns into a run-of-the-mill romantic comedy about people finding inner beauty – love – instead of focusing on the superficial. Overall, this film might have been better as a short film: It’s funny but it burns out fast.