This paper, as part of a project to understand Korean Buddhist history within the broader context of East Asian Buddhism - coming after several studies on the thought of Wonhyo and Chinul - seeks to adopt a comparative approach to the interpretation of the Ch`ont`ae sect founded by Uich`on. I considered therefore Uich`on`s activities within the background of East Asian Buddhism, and examined their relation to the Tiantai sect in China. At a time when the Hwaom and Popsang sects were polarised and opposing each other, Uich`on - though sticking fast to the Hwaom precepts - established a third sect, namely the Tiantai, with the objective of weakening the Son sects (Nine Mountains) by attracting their monks to the newly founded Ch`ont`ae. Due to Uich`on`s ideological background the ideals of "harmonization of the Ch`ont`ae and Hwaom sects" from the doctrinal point of view, and of the "simultaneous cultivation of theory and practice" (kyogwan pyongsu) were both perceived as of the utmost importance. Therefore the process of adopting the Tiantai sect of the Song dynasty implied two aspects: while on one side it claimed officially to adopt the tenets of the orthodox Shanjia pai, on the other side in terms of content it was actually closer to the Shanwai pai, which was generally considered heretical and retained a strong Huayan influence. As the Ch`ont`ae sect was based on a clergy exclusively composed of Son masters, it remained Ch`ont`ae only in name after the death of Uich`on. Its contents and character were heavily laden with Son elements. Thus, the establishment of the Ch`ont`ae sect led to a division of the Son sects of Koryo into the Ch`ont`ae and the Chogye orders. Consequently, the Ch`ont`ae sect was thereafter officially classified as a Meditation sect also by the State. Yose (1153-1245) understood the problems of the Ch`ont`ae sect as deriving from its Son character and tried to solve them through the adoption of the Tiantai teachings of Siming Zhili, a representative of the Tiantai sect during the early Song dynasty. He emphasized a type of faith centered on the Lotus Sutra and the Pure Land teachings, thereby trying to establish the true character of the Ch`ont`ae sect, as distinct from the Hwaom and Son sects. In view of the above it seems obvious that in order to understand the doctrinal contents and historical character of the Ch`ont`ae sect of Uich`on we need to adopt a comparative approach and analyse Uich`on`s Ch`ont`ae in conjunction with the Tiantai sect of China, and particularly that of the Song dynasty. We also need to mention that Japanese Tendai followed quite a different path of development. It came under the strong influence of esoteric Buddhism, while in Korea and China, as mentioned above, the Ch`ont`ae tradition developed under the influence of both the Hwaom and Son doctrines.