Attributed to Aesop, Greek fabulist, c. 620-564 BCE.
A shepherd boy, watching a flock of sheep near his village, grew lonely. He devised a way to get some attention and companionship by playing a trick on the villagers. One morning he yelled: "Wolf! Wolf!" When his neighbors ran to help save their flock and livelihood, they found the sheep placidly cropping grass. The boy laughed and laughed. The villagers were angry at the boy and warned him not to call them if there was no danger. And yet the next day he did it again. "Wolf! Wolf!" he shouted. The villagers came running. When they found the boy had tricked them again, they were even angrier than the day before. Warning him not to lie again, they went back to their work. The next day as the shepherd boy lay watching the sheep on the hillside a wolf came out of the woods. The boy shouted in terror: "Help me! The wolf is killing the sheep!" But no one paid any attention to his cries and no villager came to help. The wolf destroyed the whole flock. The moral of the story is: There is no believing a liar, even when he speaks the truth.