Activists and politicians have long recognized the power of a good story to move people to action. In early 1960 four black college students sat down at a whites-only lunch counter in Greensboro, North Carolina, and refused to leave. Within a month sit-ins spread to thirty cities in seven states. Student participants told stories of impulsive, spontaneous action--this despite all the planning that had gone into the sit-ins. "It was like a fever,"...