Historian William Naphy asks how the actions of an obscure German monk are still shaping our modern world. When Martin Luther nailed 95 criticisms of the Catholic Church to the door of his local church in 1517, he sparked not just a religious reformation, but an unending cycle of political, social, and economic change that continues to this day. By challenging the authority of the Pope, Luther inadvertently unleashed a revolutionary force--the power of the individual to determine his or her own thoughts and actions. Naphy demonstrates how more than four centuries later, Protestant minister Martin Luther King, Jr. was acting on the same revolutionary principle when he rejected racial discrimination and spearheaded the civil rights movement. The legacy of the Reformation is all around us, influencing our work life, family life, sex life, and political views. From literature to science, from gay marriage to the "War on Terror," a vibrant struggle for Protestant principles is alive.