趙光祖
Yi I (; December 26, 1536 – February 27, 1584) was a Korean philosopher and writer. He was one of the two most prominent Korean Confucian scholars of the Joseon Dynasty, the other being his older contemporary, Yi Hwang (Toegye). Yi I is often referred to by his pen name Yulgok ("Chestnut valley"). He is not only known as a scholar but also as a revered politician and reformer. He was academical successor of Jo Gwang-jo.