Mark Gregory Pegg's history of the Middle Ages opens and closes with martyrdom, the first that of a young Roman mother in a North African amphitheater in 203 and the second a French girl burned to death beside the Seine in 1431. Both Vibia Perpetua and Jeanne la Pucelle died for their Christian beliefs, yet that for which they willingly sacrificed their lives connects and separates them. Both were divinely inspired, but one believed her deity shared...