There is a real chance that we live in the sort of branching universe Ted Chiang portrays in “Anxiety is the Dizziness of Freedom.” I’ve studied this question for a couple of decades, arguing back and forth with some of the world’s experts on the subject. Although there are some strong arguments against the many-worlds picture of quantum mechanics, the reasons in favor are impressive as well. My own paper on many-worlds is an argument against it, so I’m hardly a partisan, but still I would give it 30 or 40 percent odds of turning out to be true.