Jeong Yak-yong is a representative Confucian intellectual of the latter 18th century Joseon. His time was a period when various thoughts and books of foreign countries were being introduced through diplomatic envoys sent to China and Japan. New thinking such as the doctrines of Wang Yangming from the end of Ming and early Ching Dynasties, the Ching Dynasty’s study of ancient documents, the medieval thoughts and Catholicism of the West, and the classic doctrines of Japan were accepted, and Dasan tried to intellectually deal with such circumstantial changes. During this period, the books of Western learning translated into Chinese by Western missionaries represented by Matteo Ricci had a very important impact on the formation of Dasan’s philosophy.
Ricci’s concept of God provided the philosophical basis for Dasan’s argument for a personal Sangje(Ruler of Heaven) while criticizing Zhu Xi’s Neo-Confucian Theory of Li Ki. Furthermore, through this, Dasan moved beyond the moral metaphysics of Zhu Xi’s Neo-Confucianism that explained nature and man with the same principles. He argued that the nature of man is different from that of animals and plants and only man has the heart of spiritual clarity to communicate with Sangje, that is, only man has the spiritual clarity embodied. The spiritual clarity embodied is composed of three elements: the nature of innate liking of good and disdain of evil, the balance determining the choice of good and evil, and the process of acting where it is difficult to do good and easy to do evil.
That Dasan understood the human heart with the concept of spiritual character or spiritual clarity, considered this as the common link between God and man, and saw there is in the human heart a free will to choose good have all been judged be perspectives resulting from the impact of Western learning. But this impact of Western learning is difficult to explain with the logic of one-sided conveyance or acceptance. The reason is that Dasan as a Confucian intellectual has already learned Zhu Xi’s doctrines in his own way through exchanges with Sungho School scholars, scholarly encounters with Jeongjo at Gyujanggak, and his particular intellectual experience.
Hence Dasan’s interest regarding Western learning and Cheon-ju-sil-ui resulted in finding only what he himself wanted to find within his inner tradition. This is different from Matteo Ricci’s position and Zhu Xi’s, and in fact, is premised on the distinct philosophical perspective of Jeong Yak-yong himself. Particularly when considered from the overall structure of Dasan philosophy that connects the concept of innate nature as regarded as making preferences and the perspective on spiritual clarity and God with the interpretive studies of Confucian classics and politics, Dasan’s viewpoint has a distinctiveness that is difficult to explain with just the impact of Western learning. Therefore, Dasan’s position on the books of Western learning, including Cheon-ju-sil-ui, should be understood not as simple acceptance,but as a Confucian thinker’s intellectual response, that is, as philosophical action toward a changed era.