Korean Confucianism went further than the Chinese original in seriousness and in institutional reach, and Yi Hwang, known by his pen name Toegye, is its central figure. His long correspondence with Gi Daeseung — the Four-Seven debate, conducted over eight years with a scholar twenty-six years younger — concerns whether the four moral sprouts of Mencius and the seven ordinary emotions of the Book of Rites arise from principle or from vital force, and it became the defining problem of Korean philosophy, generating schools and factional alignments for centuries afterwards. He founded Dosan Seowon, now a UNESCO World Heritage site, and repeatedly declined or resigned high office to teach. His portrait is on the 1,000-won note. That a technical metaphysical dispute about the origins of emotion could organise a nation's intellectual life for three hundred years is a reasonable measure of how thoroughly Chosŏn Korea committed to this tradition.