Introduction: Nonviolence on Trial -- The Expert Witnesses for the Prosecution -- Niccolo Machiavelli: Renaissance War Realism -- Max Weber: Modern Realism -- Reinhold Niebuhr: Christian Realism -- The Expert Witnesses for the Defense -- Mahatma Gandhi: Militant Idealism -- Martin Luther King, Jr.: Christian Idealism -- The Mothers of the Plaza de Mayo: Anarchist Idealism -- Considering Further Evidence -- Modern Nonviolence Movements -- Scientific Evidence on Human Violence: Nature or Nurture?