What is the theme in Pope Joan by Donna Cross?

Knowledge over superstition is the main theme. Joan's early ability to reason through problems and questions reflects the dawning of a new age. She is not willing to settle for the accepted stories which people concoct to try to explain their world, but chooses to look underneath for the real truth. The author presents the Dark Ages as a time during which people locked themselves into a fearful belief system so rigid that it prevented them from looking beyond it. Without the means to determine the truth of natural phenomena, such as the weather, they resort to stories and, once a story is accepted, it becomes sinful, or unlawful, to think otherwise.