Caodong school
During the 12th century, a rivalry emerged between the Linji and the Caodong schools for the support of the scholar-official class. Hongzhi Zhengjue (1091–1157) of the Caodong school emphasized silent illumination or serene reflection ("mòzhào") as a means for solitary practice, which could be undertaken by lay-followers. The Linji school's Dahui Zonggao (1089–1163) meanwhile, introduced "k'an-hua" "chan" ("observing the word-head" chan), which involved meditation on the crucial phrase or "punch line" ("hua-tou") of a gong'an.