This first full-length study of the thought of Wu Ch’eng (1249-1333), who was the foremost classical scholar and philosopher during the century of Mongol rule in China, incorporates translations of his seminal essays on metaphysics, ethics, and the mind. Trained in the teachings of the Sung thinker Chu Hsi, who emphasized broad learning to understand moral principles, Wu's reflections on the Confucian tradition and his experiences in official position and as a private teacher led him toward moral introspection and the intuitionism of Chu's contemporary Lu Hsiang-shan. Wu believed that metaphysical discourse was limited by language, that only through experience could one assimilate moral truth to illuminate the mind. In synthesizing Sung Confucian ideas, Wu foreshadowed trends in Ming and Ch’ing thought. Ming thinkers who developed the philosophy of mind, such as Wang Yang-ming, endorsed Wu’s path to moral enlightenment, and Wu’s synthesis of scholarship and introspection, as well as his creative approach to learning and intellectual freedom, had an impact on thinkers well into the Ch'ing era.