Yi Hwang (Toegye) on Li and Qi

Yi Hwang (1501-1570), known by his pen name Toegye ("retreating creek"), is generally regarded as the most systematic and influential metaphysician of the Korean Neo-Confucian tradition. Born in Yeongnam province, he passed the higher civil service examination in 1534, held a series of court and provincial posts, and repeatedly withdrew from active office to devote himself to teaching and writing, eventually settling near Andong, where he built the Dosan Seodang, the precursor to the later Dosan Seowon academy. His major works include the Seonghak sipdo (Ten Diagrams on Sage Learning, 1568), a compact visual and textual summary of Neo-Confucian self-cultivation presented to the young King Seonjo, and an extensive correspondence, particularly the letters exchanged with Gi Dae-seung (Gobong, 1527-1572) between 1559 and 1566, which constitutes the founding documents of the Four-Seven Debate.