It was an unbearably steamy August afternoon in New York City, the kind of sweaty day that makes people sullen with discomfort. I was heading back to a hotel, and as I stepped onto a bus up Madison Avenue I was startled by the driver, a middle-aged black man with an enthusiastic smile, who welcomed me with a friendly, “Hi! How you doing?" as I got on, a greeting he proffered to everyone else who entered as the bus wormed through the thick midtown traffic. Each passenger was as startled as I, and, locked into the morose mood of the day, few returned his greeting.