Some fears, of course, are universal. Even a rat whose ancestors forty generations deep were lab animals will freeze at the scent of a cat. And people fear the dark, the rattlesnake’s rattle, and not just their own deaths but those of the people they love. These latter, seemingly elemental fears, of course, rise partly from the imagination and foresight that can make us neurotic or phobic. But LeDoux, who has suffered his own share of shocks and grief, feels these fears affirm the things we live for. “The backside of every positive emotion,” he says, “is the fear you’ll lose what makes you happy. Not only do you love your wife, even after thirty years, but you’re also afraid of what life would be like without her. How much should you trust your positive emotions? How do you focus on and enjoy them and not give in to the fear? These are things we all wrestle with. I’m afraid fear is terribly basic.