As a form of Confucian development, "Neo-Confucianism" basically appeared in the reception of the philosophical impact that metaphysical learning and Mahayana Buddhism had brought since the Wei and Jin dynasties. Several theory systems were achieved in the Song Dynasty in reaction to the new situation and demands. Among related debates, the ones between Zhu Xi and Lu Jiu-Yuan have received the most attention. This article re-examines the tangled issues lying under the basic structures of these theories when regarding them both as philosophies and as an academic discipline in Confucian tradition