Courage is something that we want for ourselves in gluttonous portions and adore in others without qualification. Yet for all the longstanding centrality of courage to any standard narrative of human greatness, only lately have researchers begun to study it systematically, to try to define what it is and is not, where it comes from, how it manifests itself in the body and brain, who we might share it with among nonhuman animals, and why we love it so much. ... The theme of courage claims a long and gilded ancestry. Plato included courage among the four cardinal or principal virtues, along with wisdom, justice and moderation.