Woei-Ahm is an Inmoolsungdongronja (a scholar who supports the theory that human being and an animal have same nature). His idea of Silsa (Practical Affairs) is the core of his whole philosophy. To Woei-Ahm, the Practical Affairs is the method to reach the pure good, the state of true Mibal (not-yet actualizes consciousness). In his view, true Mibal is not mere state which one's feeling is not expressed, but which disordered disposition could reveal the pure Principle of Heaven through being led by enlightening, pure and brilliant Virtue passes through body and mind. It is also definite meaning of ”Ligidongsil” (both the Principle and Material Force are substantial, real) and ”Simsungilchi” (mind and nature are one and same). In this light, Kongbu (disciplinal study, learning and cultivating one's mind) which enable the Virtue to manifest itself has to become very important. At the same time, the brilliant Virtue becomes a fundamental basis for putting morality into practice. However' despite not being same with disposition, the brilliant Virtue is subjected to Gi (Material Force, Ether). It cannot be purely good, but can control and preside over human being as a remarkable cognitive ability. Therefore, there is a separate and ultimate basis of ethical behaviours: the very Sung (human nature), bestowed universal Principle of all existence, Li. More definitely saying, its substance Osang (Five Constancies).Woei-Ahm's philosophy developed entirely based on the Zhu-Xi school, especially Youlgok sector school. Osang theory is the Sung theory based on Youlgok's Litonggigook (the Principle applies universally, Ether does individually.), his Mibal debate is Simron (the Mind theory) based on Simzeukgi (Mind is Ether) and Zhu-Xi's brilliant Virtue which is regarded as the origin of Mind, and Silsa theory is his disciplinal study theory which progressed from Gibal-Liseung-Ildo (there is no different way except Gi arouses and Li rides). Therefore Woei-Ahm's philosophy can be regarded as the most satisfying system of Zhu-Xi's ethic, c least of Youlgok sector's.