Certainty is not what it used to be. Our ancestors had the certainty of their gods, myths and rituals, then of one God, his purposes and the orderliness of all that he had created. The Enlightenment promised a world freed from the lore of the past by the power of human reason; the industrial age, a world endlessly made better by the force of Progress. Few such absolute certainties survive in the twenty-first century and yet, it seems, we cannot resist...