Oriental medicine which is based on internal activeness has constantly been developed for over thousands years and during that time it has encountered Western medicine that has the different system. Because of a lot of different viewpoints of how to understand human and nature, there exist lots of problems to cope with for the integration of two medicines as follows: (1) Oriental medicine regards each person as a cosmos in miniature but Western medicine is based on dualism, substantialism and mechanism. (2) Oriental medicine thinks much of totality as a cosmos in a miniature but Western medicine investigates individual structure and function of human organ and system. (3) Oriental medicine considers that organs are the core of the Oriental medical physiology and makes much account of their functions and their relationships with fundamental texture, but Western medicine gives much emphasis on the structure than functions. Despite of these differences, Oriental medicine and Western medicine should develop mutual understanding and this will facilitate the achievement of the third medicine that is suitable for the primary object of medicine that is to enhance human health and cure diseases.