This complete translation of Masao Abe's essays on Dogen probes the core of the Zen master's philosophy and religion. This work analyzes Dogen's formative doubt concerning the notion of original awakening as the basis for his unique approach to nonduality in the doctrines of the oneness of practice and attainment, the unity of beings and Buddha-nature, the simultaneity of time and eternity, and the identity of life and death. Abe also offers insightful, critical comparisons of Dogen and various Buddhist and Western thinkers, especially Shinran and Heidegger.