What’s Wrong With Lying?

Immanuel Kant's categorical imperative states in effect that we're only morally permitted to do things that we could reasonably will everyone to do. So it's immoral to lie, because if everybody always lied, then communication would become impossible and society would collapse. So for Kant, lying is always wrong, because it violates the categorical imperative.

For a utilitarian, an action is wrong if it has bad consequences. Lying tends to cause bad things and unhappiness — people are disappointed when promises aren't kept, people get angry when they discover they've been lied to, people feel ashamed about having lied, people count on others' word, and suffer from them not following through, etc. For a utilitarian, it's usually wrong to lie, because usually, lying has bad consequences (and it's very difficult to recognize the situations where it won't). In some extreme cases, though, a utilitarian will encourage lying. If, for example, a gun-wielding maniac who is trying to murder your children asks you where they are, you should lie to him. (Kant famously thought you should tell the truth even then.)