Their best was not enough, however, and later, at the hospital, the terrible sadness settled in.

As Mr. Monson filled out his report, the mother sat in the trauma room’s designated “bereavement rocking chair,” rocking her dead son, saying her goodbyes, while family members filed in and wailed at the sight.

An image of that mother in her rocking chair comes to Mr. Monson’s mind every time he answers another “bad kid” call, spurring him to keep going, to never give up or grow sloppy or cynical, to simply do his job; and through doing his job, he has saved far more lives than he has lost.

Only once did he allow the furniture connection to spook him  when his own wife was at the same hospital having emergency surgery for a ruptured ectopic pregnancy, and his young daughter happened to climb onto the bereavement seat. “I knew it was a totally irrational thing to do,” he said, “but I made her get out of that chair.”

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.

A new report in the journal Current Biology describes the case of a woman whose rare congenital syndrome has left her completely, outrageously fearless, raising the question of whether it’s better to conquer one’s fears, or to never feel them in the first place.