In Liar Liar , Jim Carrey gains the superpower of not being able to lie for 24 hours. Wikipedia defines lying as ... a statement used intentionally for the purpose of deception. The practice of communicating lies is called lying, and a person who communicates a lie may be termed a liar. Does this mean he just wasn't able to say anything deceptive, or does it mean he wasn't able to say anything that was false? I always thought it was the former, but there is one scene in the movie where he says... I'm a bad father ...then looks shocked that he was able to say it on the day he wasn't able to lie, indicating that, according to the movie's logic, he cannot utter false statements. In short, my questions are, in Liar Liar, can Jim Carrey say a statement if: It is true but he genuinely believes it to be false? It is false but he genuinely believes it to be true? It may be true or false but he has no idea either way? Answer In the original script , we see that Fletcher...