Diagrams (Chinese tu, Korean to) played an important role in both Chinese and Ko-rean Confucian discourse, providing a special tool of argumentation in so far as they brought together visual image, structural concept and non-linear text. In 16th century Korea, diagrams served as a highly efficient instrument for the concise recording of philosophical concepts and their dissemination within the community of literati. The aim of this study is to present a brief survey of the role of diagrams within the Korean Confucian discourse, to indicate the strategies of their composition, reading, and inter-pretation, and to explain why Korean Confucians often used this unusual medium as opposed to that of simple texts. The focus of the analysis will be Chŏng Chiun’s (1509‒1561) Ch’ŏnmyŏng to (Diagram of Heavenly Mandate) and the discussions surrounding this diagram. The story of this picture, as it circulated among the literati, shows how a single diagram was able to connect various thinkers and play a crucial role in sparking the Four-Seven debate.