Near the climax of the movie Indiana Jones and the Last Crusade, a villain shoots Indiana’s father to motivate the distressed son to enter a booby-trapped temple and retrieve the Holy Grail. “The healing power of the Grail is the only thing that can save your father now,” he said. “It’s time to ask yourself what you believe.” I deplore what the evil man did, but he was on to something: What we believe determines what we do.