Yi Hwang (Toegye)

Yi Hwang, known by his pen name Toegye, was a leading scholar of the mid-Joseon period who developed the "principle-centered" (juri) school of Neo-Confucianism, which emphasized li (principle). He wrote the Seonghak sipdo (Ten Diagrams on Sage Learning), a distilled guide to the learning a ruler should pursue, and founded the Dosan Seowon academy in his hometown to teach later generations. His thought became a major current in Joseon Neo-Confucianism, and today he appears on the 1,000-won banknote.