Zhu Xi’s Theory of Heterodoxy and King Sejong’s Thinking of Zhongyong: Focusing on the Arguments over the Sarigak at Heungcheonsa Temple

King Sejong practiced faithfully the Confucian policies that had been established with the foundation of the new Joseon dynasty. He was a typical Confucian king who repressed Buddhism, which had been the state religion in the preceding Goryeo dynasty. When he expressed support for a Buddhist event of repairing the sarigak at Heungcheonsa temple in the capital in the 17th year of his reign (1435), however, King Sejong came into conflict with his Confucian subjects. The opposition assumed various aspects in the process until the conflict came to an end, and the will of King Sejong was accomplished in the 24th year of his reign (1442). Previous studies have interpreted the Buddhismfriendly events of the Confucian King Sejong from the viewpoints of social, national, and religious necessity as well as of functionalism, usefulness, and practicability. This paper, however, pays attention to the reasoning structure of King Sejong. It aims to show that while Confucian subjects argued on the basis of Zhu Xi's theory of heterodoxy, King Sejong employed zhongyong (doctrine of the mean) in the conflicts with his subjects on Buddhist events. In addition, this paper examines the relationship between Zhu Xi's theory of heterodoxy and the theory of zhongyong, and gives ideological meaning to the arguments between King Sejong and his subjects. [PUBLICATION ABSTRACT]