Abstract
This paper is written in order to investigate how Lee Je-Ma changed traditional Zhu Xi's philosophical view on Way(Tao; 道) Virtue(De: 德) Nature(Xing;性) and Imperative(Ming; 命), which was general concepts of his contemporary age, to practical philosophy and created new medical theories of Sasang(4 symbols) science from it. Lee emphasized the true thing which is able to be done in one's living not the concepts of Sasang. So he induced the concepts of Way and Virtue from the easy and simple way(易簡之道) in the Classic of Changes(I'Ching) for the purpose of practice by anyone. Because Nature and Imperative are derived from Way and Virtue in the context logically, human life is virtual in itself, so the substance of Nature and Imperative became equal with Way and Virtue. Herein the names and concepts of original 'Sasang' were substituted to Business(事), Mind(心), Body(身), Thing(物) which is able to be directly related with human being in his daily life. And he explained variously about the responses of Mind and Body of individuals onto Business and Thing. So it could be applied in medical aspects like emotional, symptomatical, characteristic features. Conclusively man is virtual being, so Nature and Imperative in the level of Human being are based on Way and Virtue in the level of Heaven. For that reason the new concepts of Sasang Business. Mind. Body Thing or Heaven. Human. Nature and Imperative were proposed.