Thomas Cleary, one of America’s most beloved translators of Buddhist texts, brings twelfth century Chan master Dahui’s monumental compilation of teachings to life for the first time in English. Treasury of the Eye of True Teaching (Chinese Zhengfayanzang) stands as among the greatest classics of Chan (Chinese Zen) Buddhism, combining speeches, stories, dialogues, poems, and commentaries that the influential master Dahui (1089–1163) extracted from Chan lore. Compiled by Dahui’s students during Song Dynasty China, this work is replete with the enigmatic, paradoxical wisdom for which Zen Buddhism is so well known. Central to this collection is the notion of “great doubt” in matters of language, conceptual thinking, and how we conceive of our existence. By working with great doubt through koan introspection and other meditative practices, a practitioner is able to push themself to the limits of ideas and concepts until a breakthrough to enlightenment is achieved. In the words of Dahui, “Within great doubt there necessarily exists great enlightenment.” A fascinating compendium of literary and spiritual puzzles, Treasury of the Eye of True Teaching will challenge and inspire readers to work with great doubt themselves and to discover their inborn potential for enlightenment.