According to the Zen tradition, enlightenment is a cosmic experience of universal unity. Here, Heinrich Dumoulin traces the development of Zen and the concept of enlightenment from its origins in India through its development in China to its fruition in Japan. Delineating the Buddhist origins, as well as the Taoist and yogic influences, he traces the historical path Zen has followed, with special emphasis given to the development of the koan and the writings of the great Japanese Zen master Dogen (1200-1253). He then presents, in his own words, the enlightenment experiences of a number of contemporary practitioners of Zen.