The movie (written by and starring Ricky Gervais) is funniest in the early going, when we see what life is like in a scrupulously candid society where there is no tact, because there is no need for it.
Gervais plays Mark, a dumpy bachelor who endures a humiliating date with a gorgeous girl (Jennifer Garner). She informs him, with congenital frankness, that he is too short, fat and poor to rank as a suitable mate. (The waiter who delivers their drinks confesses that he sipped from them.)
This World of Truth, as conceived by Gervais, is a cruel and a dull place - Mark works for a movie studio that makes only documentaries, because there is no storytelling. No artful lying.
Act 2 commences when Mark has a brain malfunction that makes him the first of his kind to lie. He immediately starts to fabricate history in order to make better movies - becoming a kind of protean Oliver Stone.
It's one thing to suggest that Hollywood is full of beans, another to say the same of religion, which "The Invention of Lying" does in due course.
Gervais goes to comfort his terrified, dying mother, and spins for her (in a truly startling scene) a soothing tale of eternal life, full of opulent mansions were residents are surrounded by everyone and everything they've ever loved.
His mother believes him and so does the attendant medical staff. Word spreads. Since no one has ever lied, the credulous population assumes Gervais is telling the truth, and clamors for more revelations, forcing him to embellish his story by concocting an omniscient power and accompanying rules, which he lists on a pair of pizza boxes, in lieu of stone tablets.
This cheeky satire of religion looms so large that its accompanying satire of Darwinism goes almost unnoticed. Mark continues to pursue Garner's goddess, who continues to naturally not select him based on his obviously substandard genes (she prefers Rob Lowe).
The problem with "Invention" is that it ultimately rests not on critiques of religion or evolution, but the nuts and bolts of romantic comedy. It botches the fitful attraction between Gervais and Garner, whose character is attractive only in the physical sense.
Gervais, meanwhile, has now made two romantic comedies that keep him, literally, at arms' length from his love interest. "Invention" argues that true love is blind, but the movie will not let the sighted look upon the image of Gervais kissing Garner.
That alternate universe wherein short, fat, plain men cannot be matched (on screen) with beautiful women?
It's called Hollywood.