Cao-Dong School
The establishment of Soto zen during the 13th century by Dogen Zenji marks not only the beginning of a new school of Buddhism in Japan, but also the decline of its predecessor sect in China, called Cao-Dong School, (Caodong zong). When Dogen studied as a young man with the Cao-Dong Master Rujing [Tendo Nyojo] at Tiantong Temple, he was following a practice tradition which had already existed in China for at least 400 years; one which had always emphasized zuo chan [zazen], "sitting zen," as its central practice, but one which had also developed characteristic teachings in relation to the philosophical ideas and methods presented by the other chan sects. Thus the teaching of mo zhao chan [mokusho zen], "'silent illumination zen," which Dogen learned from Rujing and accepted as a basis for Soto zen, is a view of zen practice associated with the celebrated 12th-century Cao-Dong master Hongzhi Zhengjue, likely as a reaction to what was viewed as an overemphasis on the study of gong an, [koan] as a means of producing intuitive insight. Although silent illumination zen clearly centers upon the practice of zazen, it is also true that there is no mention of it in the founding period of the Cao-Dong school. In those distant times, other ideas and concerns prevailed.
The primary source of information about the founding of Cao-Dong School, as well as of the other chan schools during the Tang period (600-907 CE), known later collectively as the Five Houses of Chan, are the numerous Song-period (960-1279) chan histories. The first of these that has survived is called Zu tang ji (Collection from the Ancestral Hall), which appeared after 952. Arranged according to teaching lineages, all the Song histories present biographies and conversations held between masters and students, and also some occasional information about the origin and activity of the various schools.
These histories agree that Cao-Dong School was founded in the second half of the 9th centuryby Caoshan Benji (840-901) and his teacher Dongshan Liangjie (807-869), whose first or "mountain" names taken together probably provided the name by which the school became known. Both masters were active in the modern province of Jiangxi in central China. Jiangxi Province and adjacent Hunan Province, both of which lie north of Guangdong Province, where Huineng, the Sixth Patriarch (683-713), lived and taught, formed the heartland for the further development of the Southern School and for the Tang-period in general.
But unfortunately the Song histories don't give us any details about the organization of early Cao-Dong, nor do they tell us anything at all about the meditation practices associated with it. We can guess that the rise of the school derived from the obvious ability of Caoshan and Dongshan to attract students and appoint disciples, and that like the earlier Hongzhou school which formed around the great 8th-century master Mazu, it was due to the organizational efforts of these students and disciples that the sect itself began to spread and attract further students. It may be that neither Caoshan nor Dongshan had the intention to found a new zen school. Although the formation of each of the Five Houses certainly had much to do with creating characteristic methods of responding to koans, each school advancing its own distinctive approach, koan practice as such did not exist in the 9th century. In the absence of further information, we have to view the specific teachings of Caoshan and Dongshan as the real source and origin of Cao-Dong School.
Happily we are well-provided in this respect. The Song histories give extensive coverage to both masters, and in addition there is a separate discourse record in the Chinese Canon entitled Juizhou Dongshan Liangjie chan shi yu lu (The Record of Dongshan Liangjie), translated into English by Prof. William Powell. Leaving aside for a moment the question of textual authenticity, these records present many conversations, poems, and discourses of both Cao-Dong founders. In addition to the various statements regarding emptiness, Buddha-nature and thusness, which conform in every respect to the commonly accepted teachings of all the chan schools, Dongshan also develops the teaching of the Five Ranks, represented in the Song histories as the characterizing philosophical doctrine of the emergent Cao-Dong School.
The Five Ranks of Dongshan are a set of five modes in which apparent or phenomenal reality interacts with ultimate or absolute reality. In traditional Buddhist terms, the teaching demonstrates five possibilities for the construction of form and emptiness. In traditional Chinese terms, the Five Ranks show the interactive relations of li (principle) and shi (phenomena). The recorded teachings of Caoshan Benji likewise indicate the importance of the Five Ranks in the early years of Cao-Dong School. They contain extensive elaboration, through the systematic use of metaphor and symbol, of Dongshan's original theory.