YI YULGOK, pen name of Yi I (1536–1584), Korean Neo-Confucian thinker whose stature in the tradition is equalled only by that of Yi T'oegye. Yulgok is credited with having established the Kiho ("material force") school in Korea. Born in Kangnŭng in Kangwon Province in western central Korea, not far from the capital, Yulgok began his studies with his mother, Sin Saimdang, a well-known poet and painter. Her death when he was sixteen seems to have brought about a profound personal crisis. After three years of mourning, Yulgok retreated into a Buddhist mountain temple intending to become a monk. Although he changed his mind after a year of studying the Buddhist scriptures, his resulting familiarity with Buddhism supposedly influenced his scholarship. In 1564 he placed first in both the preliminary and final civil service examinations and thus acquired the nickname Lord First Candidate of the Nine Examinations. His...