Scholarship has recognized fifteenth-century speculative thinker Nicholas of Cusa for his early contributions to conciliar theory, but not his later ecclesiastical career as cardinal, residential bishop, preacher, and reformer. Richard Serina shows that, as bishop in the Tyrolese diocese of Brixen from 1452 to 1458, and later as resident cardinal in Rome, Nicolas of Cusa left a testament to his view of reform in the sermons he preached to monks, clergy, and laity. These 171 sermons, in addition to his Reformatio generalis of 1459, reflect an intellectual coming to terms with the challenge of reform in the late medieval church, and in response creatively incorporating metaphysics, mystical theology, ecclesiology, and personal renewal into his preaching of reform.