 The Four-Seven Debate continued in one form or other down to the beginning of the twentieth century. T’oegye and Yulgok and their opposed strategies for dealing with this challenge tower over the history of Korean Neo-Confucian thought. As a matter of fact, the Four-Seven Debate later spilled over to another debate (“Horak 湖洛 Debate”) where Han Wŏnjin (1681–1751) and Yi Kan (1677–1727) had a lengthy discussion over whether there is any difference between human nature and sub-human nature, and also over what, and how much, shelter human nature can provide from evil in the context of moral community (R. Kim 2015). It also ignited the Heart/mind (Simsŏl 心說) Debate from the middle of the nineteenth century well into the twentieth century.