A critical overview examines the main chronological stages and philosophical discussions that characterize the unfolding of the koan tradition extending from the earliest days of Zen Buddhism through the classical, medieval, and modern phases of development. Also shown are the ways that diverse cultural influences, including imagery borrowed from legalism, the fine arts, folklore, and military strategies, infiltrated and helped shape the construction of koan writings. In addition, the analysis considers the role of schismatic debates, forceful at times, involving rhetorical strategies in relation to meditative training with koan cases. Koans were originally oral teachings that were not supposed to be written down, but without transcribed documents their meaning would be lost. From the onset of the koan tradition, a fundamental source of tension or conflict eventually led to harsh sectarian discord about the role of speech and silence in forming and practicing this discourse.