“Stone Soup,” an old tale with many versions, tells of a starving man who comes to a village, but no one there can spare a crumb of food for him. He puts a stone and water in a pot over a fire. Intrigued, the villagers watch him as he begins to stir his “soup.” Eventually, one brings a couple of potatoes to add to the mix; another has a few carrots. One person adds an onion, another a handful of barley...