Eihei Dōgen’s role as founder of Sōtō Zen in Japan rests first on his spiritual search and training. Born into the milieu of established Japanese Buddhism, he entered the Tendai tradition but became dissatisfied with its emphasis on doctrine and ritual. A deep question about how innate Buddha-nature relates to the need for practice drove him to seek a more direct realization of the Dharma. This inner questioning led him to turn away from prevailing forms of Buddhism in Japan and to look beyond them for a living expression of awakening grounded in actual practice.

That search took him to China, where he encountered the Caodong tradition, the Chinese antecedent of Sōtō Zen. Under the guidance of Tiantong Rujing, he immersed himself in the discipline of shikantaza, “just sitting,” a form of zazen that does not rely on objects of meditation or kōan study. In this training, he came to embody the insight that practice and enlightenment are not two separate stages but a single, unified reality. Rujing acknowledged this realization and conferred Dharma transmission upon him, authorizing him as a legitimate heir in the Caodong lineage and giving him the formal basis to carry that tradition back to Japan.

Returning to Japan with this transmission, Dōgen began to teach a way of Zen centered on zazen and rigorous monastic conduct. He first taught in the Kyoto area and then established Kōshō-ji as a dedicated Sōtō training monastery, introducing Caodong practices in a systematic manner. Later, he founded Eihei-ji in Echizen province, which became a principal monastery of the emerging Sōtō school. Through these institutions, he distinguished his teaching from other Zen currents in Japan, especially by emphasizing seated meditation and the thorough integration of practice into every aspect of daily monastic life.

Alongside institutional work, Dōgen articulated the vision of Sōtō Zen in a rich body of writings. Texts such as the Shōbōgenzō and Eihei Shingi set forth a distinctive understanding of the unity of practice and realization, and of everyday activity as the field of awakening. His teaching presented zazen not as a mere technique but as the complete expression of the Buddha Way. By transmitting the Caodong lineage, founding enduring monasteries, and formulating a coherent doctrinal and practical framework, he established a tradition that later generations recognized as Sōtō Zen, and for which he came to be honored as its founding ancestor in Japan.