Yi Hwang (1501-1570 C.E.) is one of the two most honored thinkers of the Korean Neo-Confucian tradition. His fully balanced and integral grasp of the complex philosophical Neo-Confucian synthesis woven by Chu Hsi during China's Sung dynasty marks the tradition's arrival at full maturity in Korea. His "four-seven debate" with Ki Taesŭng established a distinctive problematique that strongly oriented Korean Neo-Confucian thought towards exacting investigation of critical issues regarding the juncture of metaphysics and their all-important application in describing the inner life of the human heart-and-mind.