Liberty and freedom are frequently invoked to justify political action. Presidents as diverse as Woodrow Wilson, Franklin Delano Roosevelt, John F. Kennedy, Ronald Reagan, and George W. Bush have built their policies on some version of these noble values. Yet in practice, idealist agendas often turn sour as they confront specific circumstances on the ground. Demonstrated by incidents at Abu Ghraib and Guant namo Bay, the pursuit of liberty and...