“The able and the disabled aren’t two different kinds of people but the same people at different times,” the journalist Tom Scocca wrote in a recent article in New York magazine. Whoever has health one day can be deprived of it the next. Scocca was writing at the time about stunning changes to his own health. Sickness, even when easily or quickly healed, brings with it suffering or pain; prolonged illness stirs up uncertainty, loss, and grief. One can so easily cross from the realm of the healthy...