The Rwandan genocide, the Holocaust, the lynching of African Americans, the colonial slave trade: these are horrific episodes of mass violence spawned from racism and hatred. We like to think that we could never see such evils again—that we would stand up and fight. But something deep in the human psyche—deeper than prejudice itself—leads people to persecute the other: dehumanization, or the human propensity to think of others as less than human. This book looks at the mechanisms of the mind that encourage us to see someone as less than human. There is something peculiar and horrifying in human psychology that makes us vulnerable to thinking of whole groups of people as subhuman creatures. When governments or other groups stand to gain by exploiting this innate propensity, and know just how to manipulate words and images to trigger it, there is no limit to the violence and hatred that can result.