 It is the sixth diagram in T’oegye’s collection where we find his view of the “Four-Seven” issue that was first mentioned by Kwŏn Kŭn, but which really addressed the questions: if human nature is completely good—why do people do things that are “not good” and how/why are there negative feelings? Is this due to Principle or the material force? This was a conundrum for Neo-Confucians just as good and evil was for the Scholastics in Europe trying to explain why there was evil if their God was good. Michael Kalton (1985: 119) describes the subsequent debate, outlined below, as “the single most important intellectual controversy of the Yi dynasty”, ultimately related to the different roles of Principle and material force, their interactions and significance in regard to one’s human nature and the mind. T’oegye’s sixth diagram is actually divided into three parts, relating to the saying The Mind Combines and Governs the Nature and the Feelings (心統性情圖) and they describe different but interrelated aspects of the mind: