Mark Twain's short "On the Decay of the Art of Lying" he tells a story about how he takes to task a morally righteous woman, who swears that she is honest and true, always, by revealing her lie about the efficacy of her child's nurse to properly care for the child. The child has since come down with a cold due to the nurse's negligence, and is in danger of catching pneumonia, thereby exposing the child is in imminent danger of serious sickness.
This revelation causes the sanctimonious mother rushing off to rescue her child from the incompetent nurse. All turns out well in the end.
Except for the fact that, according to that devious Mark Twain, it was all just a lie.
According to Twain, ever critical of the brutal truth, he informs, "An injurious truth has no merit over an injurious lie. Neither should ever be uttered."
But he goes on to say, "No fact is more firmly established than that lying is a necessity of our circumstances.... Judicious lying is what the world needs."
In the anecdote, Twain shows that by lying to the woman, he cleverly exposes her two faced nature, has her face the moral consequences of her own lies, and helps a child regain the long overdue affection of his real mother. Twain thus proved that a single lie could do far more good than the brutal truth of her bad parenting and poor example.