Chinul （1158-1210）; Korean monk of the Koryo period， who is considered to be the most influential figure in the formation of Korean Son Buddhism. Chinul entered the world at a time when the sangha was in a state of crisis， in terms of external appearance as well as internal issues of doctrine. Deeply disturbed at the degree of corruption that had crept into the sangha， he sought to establish a new movement within Korean Son which he called the "sama^dhi and prajn~a^ society" （定慧社） whose goal was to establish a new community of disciplined， pure-minded practitioners deep in the mountains. Chinul eventually accomplished this mission with the founding of the Songgwangsa monastery （松广寺） at Mt. Chogye （曹溪山）.
One major issue that had fermented long in Chinese Ch'an and which had received special focus from Chinul， was the relationship between so-called "gradual" 渐 and "sudden" 钝 methods in practice and enlightenment. Drawing upon various Chinese treatments of this topic， most importantly those by Zongmi （宗密; 780-841） and Dahui， （大慧; 1089-1163） Chinul came up with his famous "sudden enlightenment followed by gradual practice" 顿悟渐修 dictum. From Dahui Chinul also incorporated the kwanhwa （观话 "observing the key phrase of the kong'an"） method into his practice. This form of meditation is the main method taught in Korean Son down to modern times.
Chinul did not undergo his enlightenment experiences as the result of the classical so-called personal "mind-to-mind transmission" between teacher and student as characterized in the Son school. Rather， each of his three enlightenment experiences came in connection with the contemplation of a passage in a Buddhist text. In his final articulation of the issue， Chinul was highly influenced by the explanation of the relationship between Son and Kyo provided by the Tang Huayan master Li Tongxuan （李通玄; 635-730）. Chinul's phi^osophical resolution of this issue brought a deep and lasting impact on Korean Buddhism. Chinul produced a number of important disciples who passed on his teaching and continued to work within his discourse. His major works include: Encouragement to Practice: The Compact of the Sama^dhi and Prajn~a^ Community 劝修定慧结社文（one fasc.）， Moguja's Secrets on Cultivating the Mind 牧牛子修心诀 （one fasc.）， Straight Talk on the True Mind 真心直说 （one fasc.）， The Complete and Sudden Attainment of Buddhahood 圆顿成佛论 （one fasc.）， Resolving Doubts About Observing the Hwadu 看话决疑论 （one fasc.）， Admonitions to Beginning Students 诫初心学人文 （one fasc.）， Afterword to the Sixth Patriarch's Dharma Jewel Platform Sutra 六祖法宝坛经跋， Excerpts from the Dharma Collection and Special Practice Record 法集别行录节要并入私记， Essentials of the Flower Ornament Scripture 华严论节要 （three fascicles）. For background on Chinul and translations of most of the above works， see Buswell （1983）; see also Keel （1984）.