"I wouldn't have accepted that they were human beings. You would see an infant who's just learning to smile, and it smiles at you, but you still kill it." So a Hutu man explained to an incredulous researcher, when asked to recall how he felt slaughtering Tutsis in Rwanda in 1994. Such statements are shocking, yet we recognize them; we hear their echoes in accounts of genocides, massacres, and pogroms throughout history. How do some people come to believe that their enemies are monsters, and therefore easy to kill?

In Making Monsters, David Livingstone Smith offers a poignant meditation on the philosophical and psychological roots of dehumanization. Drawing on harrowing accounts of lynchings, Smith establishes what dehumanization is and what it isn't. When we dehumanize our enemy, we hold two incongruous beliefs at the same time: We believe our enemy is at once subhuman and fully human. To call someone a monster, then, is not merely a resort to metaphor - dehumanization really does happen in our minds. Turning to an abundance of historical examples, Smith explores the relationship between dehumanization and racism, the psychology of hierarchy, what it means to regard others as human beings, and why dehumanizing others transforms them into something so terrifying that they must be destroyed.