Nancy Koehn, a Harvard Business School historian, tells the life stories of three influential leaders: the abolitionist Frederick Douglass, the pacifist Dietrich Bonhoeffer, and the ecologist Rachel Carson. They all overcame personal challenges to achieve and inspire social change. In Koehn’s new book, "Forged in Crisis: The Power of Courageous Leadership in Turbulent Times," she argues that tomorrow's leaders of social change will come from the business world.