In 1098, a sickly girl was handed over to the church by her German noble family and, by age eight, literally walled inside a stone hermitage attached to a monastery. By every measure of her era, her life should have ended in silent, forgotten obscurity. Instead, Hildegard of Bingen emerged from those walls to become a composer, a medical writer, a linguist who invented her own secret alphabet, and a public preacher who spent her sixties and seventies traveling Germany by river and horseback — openly condemning clerical corruption — at a time when women were explicitly forbidden from doing any of it. Her weapon was the same institution that confined her: she claimed to be a weak, empty vessel unworthy of credit, which made every word she wrote the undeniable voice of God, impossible for any bishop or abbot to silence without arguing directly with  ...