Abstract: Why are lies wrong? The answer bears on continuing disputes about freedom of speech and the protection of lies and falsehoods. One answer, rooted in the work of Immanuel Kant, sees lies as a close cousin to coercion; they are a violation of individual autonomy and a demonstration of contempt. By contrast, the utilitarian answer is that lies are likely to lead to terrible consequences, sometimes because they obliterate trust, sometimes because they substitute the liar's will for that of the chooser, who has much better information about the chooser's welfare than does the liar. The utilitarian objection to paternalistic lies is akin to the utilitarian embrace of Milll's Harm Principle. It is possible to see the Kantian view as a kind of moral heuristic, welcome on utilitarian grounds. The Kantian and utilitarian objections to lying have implications for the family, the workplace, advertising, commerce, and politics, and also for constitutional law.