The problems of the acceptance by Yi T`oegye of the philosophy of Chu Hsi(朱熹), and Neo-Confucianism, in the Sung (宋) era, and the nature of the philosophy he himself established are closely connected with the development of Chu Hsi`s philosophy in East Asia and its historical features. From this perspective, I attempt in this paper to investigate Yi T`oegye`s thoughts in the Cheonmyeongtoseol (天命圖說), which engendered a famous controversy concerning the Four Beginnings-Seven Emotions Thesis (四端七情論) between Yi T`oegye and Ki Kobong (奇高峰). Yi T`oegye`s view of human being, especially his theory of the interrelation between heaven and man found in the Cheonmyeongtoseol, which he himself established consequent upon his acceptance of traditional Confucianism and Neo-Confucianism in the Sung era, remains an important point in his philosophy. Firstly, he asserted that $quot;Heaven has the identity of Ultimate Principle$quot; (天卽理, cheon jeuk ri). ana recognized the functions of won, hyon, ri, and jeong (元亭利貞) both as the four virtues (四德, sa deong) and the four fundamental principles (四理, sa ri). Further, his elaborate theories specified the relationships between the four virtues-four fundamental principles, the functions of ki (氣), eum (陰), and yang (陽), and the five elements(五行 o haeng). Thus, secondly, he clearly explained the derivation of all things and affairs (all phenomenal existence) through his rational theory of i and ki. Consequently, although he retained the concept of the $quot;Mandate of Heaven$quot; (天命) as a mere word, its literal meaning, as the functions of Heaven, appeared to become rare or extinct. This was a typical argument, and may be contrusted with Chu Hsi`s logic of T`ien-ming (天命), which is commented on in the first phrase of the Doctrine of the Mean (中庸). Thirdly, Yi T`oegye indubitably imported dynamic characteristics to i and original human nature. Thus he argued that i, in the human mind, had four virtues, and established the five basic virtues (五常) and the four innate moral senses (the so called Four Beginnings), which he called original human nature, and ki, in human mind, formed the nature of physical despositions or material nature, from which arose the seven emotions. In this logical process, he argued that $quot;the names of human nature or emotion are identical, but their functions appear in various ways.$quot; Thus, the controversy between Yi T`oegye and Ki Kobong arose from the theory of nature and emotion in human being. This lead Yi T`oegye to formulate his specific theories of practice.