As a young man in the early 1940s, Nishijima became a student of the Zen teacherKōdō Sawaki. Shortly after the end of the Second World War, Nishijima received a law degree from Tokyo University and began a career in finance. It was not until 1973, when he was in his mid-fifties, that Nishijima was ordained as a Buddhist priest. His preceptor for this occasion was Rempo Niwa, a former head of the Soto Zen sect. Four years later, Niwa gave him shiho, formally accepting him as one of his successors. Nishijima continued his professional career until 1979. During the 1960s, Nishijima began giving regular public lectures on Buddhism and Zen meditation. From the 1980s, he lectured in English and had several foreign students. Nishijima was the author of several books in Japanese and English. He was also a notable translator of Buddhist texts: working with student and Dharma heir Mike Chodo Cross, Nishijima compiled one of three complete English versions of Dōgen's ninety-five-fascicle Kana Shobogenzo; he also translated Dogen's Shinji Shōbōgenzō. He also published an English translation of Nagarjuna's Fundamental Verses of the Middle Way. In 2007, Nishijima and a group of his students organized as the Dogen Sangha International. In April 2012, the president of the organization, Brad Warner, dissolved it subsequent to Nishijima's death.
While studying the Shōbōgenzō, Nishijima developed a theory he called "three philosophies and one reality," which presents his distinctive interpretation of the Four Noble Truths as well as explaining the structure of Dogen's writing. According to Nishijima, Dōgen carefully constructed the Shōbōgenzō according to a fourfold structure, in which he described each issue from four different perspectives. The first perspective is "idealist," "abstract," "spiritual," and "subjective"; Nishijima says this is the correct interpretation of the first Noble Truth. The second perspective is "concrete," "materialistic," "scientific," and "objective". The third perspective is described as an integration of the first two, producing a "realistic" synthesis. The fourth perspective is reality itself, which Nishijima argues cannot be contained in philosophy or stated in words, but which Dōgen attempts to suggest through poetry and symbolism. In mainstream Buddhism, the fourth Noble Truth is the Eightfold Path. Nishijima stated that "Buddhism is just Humanism" and he explains Dogen's teaching on zazen in terms of balancing the autonomic nervous system.
