Looking at the world today it is easy to be awed by the pace and scale of global change. From America's recent, brief moment of unipolar pre-eminence, we have suddenly stepped into a new and uncertain age, with big, fast-growing new actors, China and India chief among them, rising to claim a place on the world stage. Meanwhile, as the global furniture is rearranged, many regard whole regions, even all of Africa, as coming into play. And yet the change, for all its dramatic implications, has been remarkably mild in execution. For a sense of historical perspective on how convulsive things might have been, it helps to cast...