Milan Kundera

Why in fact should one tell the truth? What obliges us to do it? And why do we consider telling the truth to be a virtue? Imagine that you meet a madman, who claims that he is a fish and that we are all fish. Are you going to argue with him? Are you going to undress in front of him and show him that you don't have fins? Are you going to say to his face what you think?...If you told him the whole truth and nothing but the truth, only what you thought, you would enter into a serious conversation with a madman and you yourself would become mad. And it is the same way with the world that surrounds us. If I obstinately told the truth to its face, it would mean that I was taking it seriously. And to take seriously something so unserious means to lose all one's own seriousness. I have to lie, if I don't want to take madmen seriously and become a madman myself.