Ts'ao-tung school 

One of the major schools of Ch'an Buddhism in China that arose during the late T'ang dynasty (618-907). The name derives from the first character in the names of the two founding figures, Ts'ao-shan Pen-chi (840-901) and Tung-shan Liang-chieh (807-69), the former being the student of the latter. Although the school takes its name from these two figures, the line of disciples emanating from Ts'ao-shan actually died out after four generations; it was the line of Tung-shan's other distinguished student, Yün-chü Tao-ying (d. 902), that thrived and carried on. Perhaps because of this, others say that the ‘Ts'ao’ actually derives from the Ts'ao-hsi Temple where the sixth patriarch of Ch'an, Hui-neng (638-713), made his home; this might also account for the fact that the ‘Ts'ao’ comes first in the name.

The main achievement of Tung-shan and Ts'ao-shan was to systematize the teaching of the Five Ranks, a scheme which mapped out five stages of ever-deeper realization of the interrelationship between absolute and phenomenal reality (in Chinese, li, principle, and shih, phenomena). While the generations immediately following Tung-shan and Ts'ao-shan showed little interest in this teaching, it became the basis for a revival of the school during the Sung dynasty (960-1279). At this time, a controversy broke out between two monks that helped define the Ts'ao-tung vision of practice and attainment over against that of the other dominant school of Ch'an, Lin-chi. A Lin-chi monk named Ta-hui Tsung-kao (1089-1163) wrote letters and tracts asserting that the practice of meditation ought to be energetic and goal-oriented. He stressed kōan (Chinese, kung-an) practice as a quick and efficient way to overcome ignorance and attain the goal of enlightenment. Hung-chih Cheng-chüeh (1091-1157) of the Ts'ao-tung school argued that practice was not to be so goal-directed, as this implied an artificial distinction between ignorance and enlightenment, ordinary beings and Buddhas, and practice and attainment. Instead, he articulated the view that came to be known as ‘silent illumination Ch'an’ (Chinese, mo-chao Ch'an), in which no such dualities are propounded, and, consequently, meditation becomes a self-fulfilling rather than a goal-directed activity. One sits just to sit, and the sitting itself manifests the Buddha-nature that is already inherent in every being. Ironically, the term ‘silent illumination Ch'an’ began as a term of disparagement given by the Lin-chi side, but it stuck. In the 13th century, the Japanese monk Dōgen (1200-53) came to China to study Ch'an, and brought the philosophy and practice of the Ts'ao-tung school back to Japan, where he established it under the Japanese pronunciation of the two Chinese characters: Sōtō (see Sōtō-shū).

A Dictionary of Buddhism, Oxford University Press, 2003, 2004 (which is available in electronic version from answer.com)