The Yi King is in Korean DNA — and on a banknote

Yi Hwang: the philosopher who engraved the Yi King in Korean DNA

Among the hundreds of scholars who enriched the Yi King tradition in Korea, one name dominates all others: Yi Hwang (이황), known by his pen name Toegye (退溪), born in 1501, died in 1570.

His face appears on the 1,000 won banknote — the most common denomination in South Korea. Fifty-two million people handle daily the effigy of a Yi King commentator. The symbol is powerful.

Toegye is to Korean neo-Confucianism what Thomas Aquinas is to medieval scholasticism: the thinker who gave the tradition its most accomplished and influential form. His major work, the Seonghak sipto (聖學十圖, Ten Diagrams on the Learning of the Sage), presented to the young King Seonjo in 1568, is a masterpiece of philosophical synthesis where the Yi King runs through every page. His commentary on the Book of Transformations follows in the lineage of Zhu Xi (朱熹), the great Song neo-Confucian, but Toegye brings to it a meditative depth and analytical rigor that are his own.

Toegye's originality lies in his theory of li (理, principle) and gi (氣, material energy). Where Chinese thinkers tended to subordinate one to the other, Toegye insists on their dynamic interaction — a vision deeply aligned with the logic of the Yi King, where yin and yang continually engender each other. His famous Four-Seven Debate (사단칠정논쟁) with Ki Daeseung, one of the greatest philosophical controversies in Korean history, is essentially a debate about how the principles of the Yi King manifest themselves in human nature (Chung, Edward Y.J., The Korean Neo-Confucianism of Yi T'oegye and Yi Yulgok, 1995).

Toegye's influence does not stop at Korea's borders. His writings profoundly shaped Japanese neo-Confucianism — Fujiwara Seika and Hayashi Razan, founders of the Tokugawa neo-Confucian school, explicitly acknowledge their debt to the Korean master. Through an ironic twist of history, it is via Korea that the Yi King found its most elaborate form in Japan.

When the master's house burned: the Cultural Revolution and the Chinese rupture

To understand why Korea became the guardian of the Yi King, we must look at what happened on the other side of the Yellow Sea.

In 1966, Mao Zedong launches the Great Proletarian Cultural Revolution. The stated objective: destroy the "Four Olds" — old ideas, old culture, old customs, old habits. In practice, it is total war against China's Confucian heritage.

The Red Guards burn books. Not metaphorically — literally. Entire libraries of Confucian classics go up in smoke. The Confucius Temple in Qufu, a sacred site of Confucianism for two millennia, is ransacked. The tomb of Confucius is desecrated. Thousand-year-old steles are smashed with hammers (Spence, Jonathan, The Search for Modern China, 1990).

Scholars who devoted their lives to studying the Yi King are publicly humiliated, forced to wear dunce caps, forced to kneel before howling crowds. Some are beaten to death. Others commit suicide. Most simply abandon the practice and teaching, out of pure terror. For ten years (1966-1976), the transmission of Confucian knowledge is actively and systematically interrupted in mainland China.

What the Cultural Revolution destroyed is measured not only in burned books or ransacked temples. It broke the chain of transmission — that unbroken lineage from master to student which, for three millennia, had carried the Yi King tradition from generation to generation. You can reprint a book. You cannot reprint a master.

Post-Mao China certainly undertook to rebuild. Since the 1980s, Confucian studies have experienced spectacular revival in China. But there is a generational gap — and in a tradition where oral transmission and the master-student relationship are essential, this gap is a chasm.

The student who never stopped studying

Meanwhile, in Korea, nothing of the sort occurred.

Korea experienced its own traumas — Japanese occupation (1910-1945), the Korean War (1950-1953), decades of military dictatorships. These trials were terrible. But none specifically targeted the Confucian tradition or the Yi King. Japanese occupation attempted to erase Korean identity, but paradoxically, Korean Confucianism became a vector of cultural resistance. The Korean War devastated the country materially, but intellectual structures remained intact.

The result is striking. In 2026, South Korea possesses what China lost: an unbroken tradition of study and practice of the Yi King. The seowon still exist. Confucian rituals (jerye) are still celebrated. Direct descendants of Confucius living in Korea — and there are some — still maintain ancestral ceremonies. And the flag, that flag with its trigrams, still flies.

The irony is dizzying. The Yi King was born in China, probably during the era of the Western Zhou (circa 1000-750 BCE). For two millennia, China was its natural home, its center of interpretation, its undisputed guardian. Then, in the span of a decade, that bond was violently broken. And it is the student — Korea, who had received the text as a gift from its imperial neighbor — who became guardian of a heritage the master had attempted to destroy.

As in a hexagram of the Yi King itself: the reversal. What was above goes below. What was at the center finds itself at the periphery. Transformation is the only constant.

Sources and references

- Lee, Ki-baik. A New History of Korea. Translated by Edward W. Wagner. Cambridge: Harvard University Press, 1984.

- Chung, Edward Y.J. The Korean Neo-Confucianism of Yi T'oegye and Yi Yulgok: A Reappraisal of the "Four-Seven Thesis" and Its Practical Implications for Self-Cultivation. Albany: State University of New York Press, 1995.

- Spence, Jonathan D. The Search for Modern China. New York: W.W. Norton, 1990.

- Kalton, Michael C. To Become a Sage: The Ten Diagrams on Sage Learning by Yi T'oegye. New York: Columbia University Press, 1988.

- Kim, Yung Sik. The Natural Philosophy of Chu Hsi (1130-1200). Philadelphia: American Philosophical Society, 2000.

- Koh, Byong-ik. "The Impact of the Chinese Cultural Revolution on Korea." Journal of Korean Studies, vol. 3, 1981.