This study is focused on the explanation of how a great Confucian scholar Lee Hwang (pen name Toegye) who lived in the middle of the Chosun Dynasty thought of Cho Sik (pen name Nammyeong). Most agree that the two scholars have an outstanding status in the history of Chosun Confucianism. The legion of followers of Lee Hwang was classified as Namin, while ones of Cho Sik as Bukin respectively, where that separation was due to in part political reasons, but basically their differences in disposition and learning had largely affected such division. The two scholars did not nearly have common thing in every aspect of tendency, learning, attitude, view of reality and life style. Toegye lived both as a scholar and a governmental official, while Nammyeong representing only a typical scholar with noble character. They exchanged letters and showed respect for each other and wanted more social intercourse, but, nevertheless, their different lifestyle and thought had them fail to recognize each other's learning or accept easily counterpart's attitude of life. That led eventually to disharmony between the two parties, furthermore making the differentiation of school and party and largely influencing the history of thought and politics in the late period of the Dynasty. From this, it could be said that the study of how they understood and evaluated each other has itself an important meaning.