The Pulitzer-winning writer Tony Horwitz has a new book out about anti-slavery crusader John Brown (Midnight Rising: John Brown and the Raid that Sparked the Civil War), and we consider the challenge that Brown still poses for American history. Was Brown right to spill blood fighting slavery? When is violent resistance to manifest inhumanity justified? I talk history and morality with Tony Horwitz, with my friend and John Brown buff Andrea Monroe, and with ethicist Peter Singer.