Yi I

(1536–1584), Korean philosopher and statesman. Yi I, whose honorific is Yulgok, forms with Yi Hwang (1501–1570) the most famous pair in the intellectual history of the Choson dynasty (1392–1910). Yi I was educated in his youth by his mother, Shin Saimdang, who is as famous as her son in Korea and is regarded as the paragon of Korean motherhood. Yi became famous by placing first in the civil service examination nine times. After entering officialdom, he was engaged in a wide scope of activities, from historian to diplomat.

However, Yi is mainly remembered for his contributions to Neo-Confucian thought. He participated in what was known as "Four-Seven Debate," arguing for the position that li and ki, ("principle" and "material force"—a pair of key terms in Neo-Confucian metaphysics) were ultimately inseparable. His position has often been interpreted as reflecting the practical character of his thinking, for Yi was also actively engaged in the effort to reform governmental institutions and strengthen the military system.

Chung, Edward Y. J. (1995) The Korean Neo-Confucianism of Yi T'oegye and Yi Yulgok: A Reappraisal of the "Four-Seven Thesis" and Its Practical Implications for Self-Cultivation. Albany: State University of New York Press.

Kalton, Michael C., et al. (1994) The Four-Seven Debate: An Annotated Translation of the Most Famous Controversy in Korean Neo-Confucian Thought. Albany: State University of New York Press.

Ro, Young-Chan. (1989) The Korean Neo-Confucianism of Yi Yulgok. Albany: State University of New York Press.