Capital punishment, serial killings, war, terrorism, abortion, honour killings, euthanasia, suicide bombings, war, and genocide: all involve the taking of life. Put most simply, all involve killing other people. However, cultural context heavily influences heavily how people perceive these acts, and most people reading this paragraph will likely disagree on the extent to which these "count" as killing.

For such an evolved species, humans can be violent far beyond the point of humanity. Why We Kill examines this violence in its many forms, exploring how culture plays a role in people’s understanding and definition of violent action. From the first chapter, which examines "conventional" homicide, to the final chapter’s bone-chilling account of the Rwandan genocide, this fascinating book makes compelling reading.