Yu Dae-chi

Yu Dae-chi (given name Yu Hong-gi, 1831–c. 1884) was a reformist thinker of the late Joseon period who came from the middle (jungin) class and worked as a practitioner of traditional Korean medicine. Together with Oh Gyeong-seok and Park Gyu-su, he played a major role in shaping the early Enlightenment Party, and he mentored young reformers such as Kim Ok-gyun and Park Yeong-hyo, earning him the nickname the "prime minister in plain clothes." Never holding official office, he was a teacher outside the government who, transcending the limits of his social status, helped lay the intellectual foundation of Joseon's reform movement.