Ta-hui Tsung-kao (1089-1163)

One of a pair of Chinese Ch'an monks of the Sung dynasty period who defined the difference in the practices of the Ts'ao-tung and Lin-chi schools. The other, Hung-chih Cheng-chüeh (1091-1157), argued that meditation was a self-fulfilling activity rather than a goal-oriented one, and counseled students to just sit and in so doing to manifest their innate Buddha-nature. Ta-hui, in contrast, belittled this as ‘silent illumination Ch'an’ (Chinese, ‘mo chao Ch'an’, a term that ironically came to be used as a proper designation rather than a derogatory term), and promoted a more active style of Ch'an wherein the practitioner strove after enlightenment with all his energy, primarily through the use of riddles (Chinese, kung-an; Jap., kōan). He used the kōan to generate a great doubt in the student's mind so as to induce a crisis that could only be overcome through awakening. His teachings, and his controversy with Hung-chih, helped to identify the Lin-chi school as the more active and goal-oriented, and the Ts'ao-tung as the more passive and philosophical.

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