Every year at the Metropolitan Museum of Art in New York, there is displayed, beneath the great Christmas tree, a beautiful eighteenth century Neapolitan nativity scene. In many ways it is a very familiar scene. The usual characters are all there: shepherds roused from sleep by the voices of angels; the exotic wise men from the East seeking, as Auden once put it, "how to be human now"; Joseph; Mary; the babe all are there, each figu…