The only reason people lie is because they don't want someone to know the truth for various reasons. Lie as a word, is really too vague. Calling someone a liar is meaningless, because everyone is a liar. No exceptions (that I've ever ran across). If someone said they were not a liar and was truthful, they would be isolated and socially inept. Lying is the only personal filter left to us which cannot always be breached.