Thinking about genocide is a challenge by itself; so much anger, horror, dread, and disgust flood the mind. People rather like us, who are not criminals in other ways, kill innocents because of the group to which they belong. Not to be horrified, not to be angry would be a failure of character, and yet horror and anger may drown out the thinking that the subject calls for. To be calm about it is to betray the many who have been killed; so how can I be clear enough about this terrible subject, and not betray its victims? How not betray the victims, while looking to explain what happened to their destroyers? The horror has two edges, one for those who are killed and one for those who, in a devastating moral catastrophe, become killers.