Zen Buddhism is a form of mysticism, perhaps one of its highest if most puzzling forms, and not a philosophy. Therefore it is incomplete, one-sided. The evidence for this is inherent in itself for it disdains metaphysics, study, reason, and stakes everything on a flash intuition got by meditation. There is here no such check on the correctness completeness and finality of such an intuition as is provided by philosophy. A further evidence lies in the history of its own founder. Bodhidharma admittedly travelled to China to give out his teaching yet, after his arrival, he contented himself with sitting in complete solitude for nine years at Sung-Shan, waiting for a prospective disciple to approach him. Had he been a sage, however, he would surely have filled those nine years with making his knowledge readily available to whoever was ready for it, and if there existed no such elite, he would in that case have helped the masses with simpler if more indirect forms of truth.
-- Notebooks Category 15: The Orient > Chapter 3: China, Japan, Tibet > # 160
-- Perspectives > Chapter 15: The Orient > # 54