Yi Hwang (Toegye)

Yi Hwang, known by his pen name Toegye, was the greatest Korean neo-Confucian philosopher, often called the "Zhu Xi of Korea." He spent his life refining the metaphysics of Cheng-Zhu Neo-Confucianism, developing a sophisticated theory of the relationship between principle (i) and material force (gi) that diverged significantly from his Chinese predecessors.

His most famous philosophical contribution was the Four-Seven Debate, in which he argued that the Four Moral Beginnings are activated by principle alone, while the Seven Emotions are activated by material force. His extensive correspondence with Ki Daeseung on this question is one of the great philosophical exchanges of East Asian history. His image appears on the Korean 1000-won note, and his academy at Dosan became the model for Korean Confucian learning.