On Mount Hiei, the mountain above Kyoto where the Tendai school had its headquarters, monks were taught that every being is enlightened by nature. Dōgen went up the mountain to become a monk in 1212, still a boy. The Kenzeiki, a biography compiled at Eihei-ji in the fifteenth century, tells that the teaching left him with one question: if we are enlightened already, why did the buddhas of every age still seek awakening and practise? No one on Hiei answered it, the account goes. He moved to Kennin-ji in Kyoto, the temple of Eisai, the monk who had brought Zen from China a generation earlier, and in 1223 he sailed for Song China with Myōzen, Eisai's successor at Kennin-ji.
His own writings keep the memory of what he found. In Instructions for the Cook, written in 1237, he recalls an old monk at Tiantong, the monastery where he later trained, drying mushrooms on the hot tiles of a courtyard. Dōgen asked why a man of sixty-eight did not leave the work to helpers; the cook answered that other people were not him, and asked what other time he should wait for. In 1225 Dōgen began training at Tiantong under Rujing, a master of the Caodong line of Chan, and in 1227 Rujing certified him as his successor. Later biographies tell that he awoke on hearing Rujing speak of casting off body and mind; the phrase runs through everything he wrote afterwards.
The claim he is remembered for answers the question that, by the tradition's account, he carried away from Hiei: practice and awakening are one. Sitting in meditation, zazen, is not a means that produces enlightenment later; it is enlightenment being carried out. The buddhas practised because practice is what awakening does. Among the first things he wrote after his return was Universally Recommended Instructions for Zazen, which offered seated meditation to everyone, lay people and women included; in 1231 he set the claim out in Bendōwa, "A Talk on the Endeavour of the Way".
He wrote much of that teaching in Japanese, at a time when Zen writing in Japan was done in classical Chinese. In the essays and talks of twenty-two years, later gathered as the Treasury of the True Dharma Eye (Shōbōgenzō), he pushed the classic texts until they said more than their authors had. Where the Nirvana Sutra says that all living beings have Buddha-nature, he read it as saying that all beings are Buddha-nature, impermanence included.
The Tendai establishment moved against the new Zen. Dōgen left Kyoto in 1230 for an abandoned temple at Uji, opened Kōshōji at Fukakusa south of the city in 1233, and in 1243 accepted the offer of Hatano Yoshishige, a warrior patron, to move his community to Echizen province, far to the north. The temple his followers built there was renamed Eihei-ji in 1246. In those years he attacked Dahui Zonggao, the most influential Chinese master of the previous century, and the Rinzai teachers who followed him. When Hōjō Tokiyori, the regent who governed for the shogun, called him to Kamakura in 1247, he went, and was back at Eihei-ji the next year. He fell ill in 1252 and died in Kyoto in 1253.
His school grew through his successors' successors, above all Keizan, the founder of Sōji-ji, and today Eihei-ji and Sōji-ji are the two head temples of Sōtō Zen. His essays mattered for centuries mostly inside that school, which in 1722 tried to ban their printing. In 1890 a layman, Ōuchi Seiran, and two abbots compiled a short text from them, the Shushōgi, to explain Dōgen's teaching to lay followers. In 1926 the philosopher Watsuji Tetsurō claimed him for the history of Japanese thought, and the Kyoto school of philosophy took him up after that.