Yi Yi (Yulgok)

Yi I (1536-1584) was a scholar-official and Neo-Confucian philosopher of the mid-Joseon period, remembered as a leading representative of Korean Neo-Confucianism for his emphasis on the active role of material force (gi) within the theory of principle and material force. He wrote the Seonghak jibyo, a compilation of the learning a ruler should master, and is widely known for advocating national defense through the so-called "Ten Thousand Soldiers" proposal. In recognition of his stature, he appears today on South Korea's 5,000-won banknote.