In this world, everyone always tells the truth, so everyone always trusts everything you say. Gervais's character's life is circliing the drain when he invents lying out of pure desparation: since Gervais considers using his new skill to exploit his fellow man for money, sex, and social status. The movie hits the heart (and made me weepy) when Gervais consoles his mother on her deathbed. There is no God and no Heaven in this world, so Gervais "makes up" a higher power to save her from eternal oblivion. Quickly word spreads of his "man in the sky who watches everything you do" and he becomes a prophet for the God he just invented.
There's also a romantic triangle between Gervais, Jennifer Garner, and Rob Lowe. Garner refuses to date Gervais because he is unsuitable genetically: apparently love is not blind in this world? It's a thin excuse to keep their characters apart. Only because Garner is so sweet and wholesome can we stand to listen to her complain about how fat their kids would be if they mated.
I tried to treat this as a parable and not an alternate universe. The concept of this entire world without lying was taken too literally in some places. For example, Gervais is happy to mine comedy from his short, fat, and ugliness, so there's too many scenes of people making insulting observations about each other. Also, in this world, fiction does not exist so all entertainment is in the form of historical documentaries, which does not yield too many laughs. One of many plot holes: they never address the idea that people could say things that are untrue because they are misinformed, drunk, crazy, etc.
To sum up: some interesting ideas about atheism, religion, and God, but the script needed a fresh perspective. (Entertainment Cinemas Fresh Pond)