while we fear snakes, spiders, darkness, open spaces and closed spaces, we do not fear the more likely instruments of danger — knives, guns, cars, electrical sockets — because, he says, “our species has not been exposed to these lethal agents long enough in evolutionary time to have acquired the predisposing genes that ensure automatic avoidance.” Which is to say, fear, real fear, deep fear, the kind that changes our habits and actions, is not something on which we are likely to follow sensible instruction.