The next major influence to traditional Korean medicine is related to Sasang typology (사상의학). Lee Je-ma and his book, "The Principal of Life Preservation in Oriental Medicine" (東醫壽世保元, 동의수세보원) systematically theorized with the influence of Korean Confucianism and his clinical experiences in Korea. Lee Je-ma said that even if patients suffer the same illness, patients need to use different herbal applications to treat the same illness due to the pathophysiologies of individuals. He stresses that the health of human body had a close relationship with the state of mind. He believed that the human mind and body were not separate and they closely reflected each other, and the aspect of mind needed to be considered when examining the causes of disease. Thus, not only food and natural environment but also emotional changes in humans can be another major reason for illness. He believed that medical diagnosis and treatment should be based on person's typology rather than on symptoms alone and each person should be given different prescriptions depending on the constitution of the individual. Sasang typology (사상의학) focuses on the individual patients based on different reactions to disease and herbs. Treat illness by the treatment of the root cause through proper diagnosis. Key to this diagnosis is to first determine the internal organs or pathophysiology of each patient.