This single practice itself may be an expression in concrete form of the very ancient belief that ultimate reality is one and only one –“only One Buddha Vehicle,” as the Lotus Sutra states. The attribute of suiting all people’s capacities similarly finds a doctrinal counterpart in the teaching that all beings are equally endowed with the Buddha nature, which can be traced back to the origins of Mahayana Buddhism and was well established in Heian Buddhism as the doctrine of original enlightenment (hongaku shisō). The attribute of eternal validity echoes the belief, equally old, that the absolute is changeless and imperishable. The idea of one practice including the merits of all practices may have its theoretical foundation in the doctrine that one truth encompasses all truths, a major theme of the Lotus Sutra and a teaching central to the Kegon, Shingon and Tendai doctrinal systems. The concept of attaining Buddhahood “quickly” probably also has connections to belief in the universality of the Buddha nature. The principle of “attaining Buddhahood in one’s present form” is integral to both Tendai and Shingon doctrine, though not until the Kamakura period was it welded to a universally feasible way of practice.

Both Dōgen and Nichiren held that, in the very act of practice, one simultaneously attains, not the stage of non-regression, but buddhahood itself. Nichiren wrote, “ ‘To attain’ [in the phrase “attain Buddhahood”] means ‘to open,’ ” reflecting his belief that Buddhahood is not something one “attains” at all, but is inherent in all sentient and non-sentient beings. At the same time, both he and Dōgen vigorously denied the view of Buddhahood as a final accomplishment rendering further practice unnecessary. Dōgen therefore urged continued exertion in zazen, and Nichiren, in chanting the daimoku, until the last moment of one’s life. In this sense, it can be argued that neither one wholly abandoned the view of enlightenment-as-process; however, both saw this process not as linear progress toward a final goal, but as “practice based on enlightenment.” For these two men, “common mortal” and “Buddha” were not the beginning and end, respectively, of a long journey. Both states, they believed, could coexist in a single individual. Their teachings thus represent a closure of the gulf that in earlier doctrines had gaped so forbiddingly between the ordinary person and ultimate truth.

Thus the supreme state of Buddhahood, previously thought to require aeons of effort to attain, comes in the Kamakura period to be viewed as obtainable “in one’s present form.” All three single practices represent attempts to allow common mortals direct access to the ultimate without the intervening process of systematically eradicating bad karma. This concept of direct attainment may be seen as illuminating yet another aspect of universality: Wherever one undertakes the Buddhist practice, the goal of his striving is immediately at hand.

[A]ll three of the single practices are said to offer direct access to the goal: That is, they enable one to attain enlightenment “quickly.” Here we have an extremely important aspect of the new Buddhism of the Kamakura period. To understand the dramatic conceptual shift that it implies, we must remember that traditional Buddhism views the attaining of enlightenment as an effort spanning a great many lifetimes. Numerous Mahayana texts inform us, for example, that the six paramitas or bodhisattva practices of almsgiving, upholding precepts, forbearance, assiduity, meditation and wisdom are to be perfected one by one, mastery of each requiring a hundred kalpas (one kalpa being generally reckoned a 15,998,000 years). Or, according to another popular explanation, one advances toward full enlightenment through fifty-two successive stages of bodhisattva practice, systematically extirpating illusions and evil karma and acquiring enlightened virtues along the way. Such views regard the attaining of Buddhahood as a linear process with a beginning and an end, commencing with one’s bodhisattva vows and concluding with the achievement of perfect liberation. The concept of attaining Buddhahood in one’s present form, though already present in Indian Mahayana Buddhism, had until this point never gained the same widespread acceptance as the notion of practice spanning countless lifetimes.

In the doctrines of the three new Kamakura schools, this vast length of time is progressively shortened until, in the teachings of Dōgen and Nichiren, it vanishes altogether, and practice and enlightenment become simultaneous.

Nichiren’s mappō thought unites two important but hitherto distinct elements of Kamakura Buddhism: a universally feasible way of practice and belief in the possibility of becoming a Buddha in this world. Honen’s nembutsu could be practiced by anyone regardless of education, ability, and so forth, but his doctrine deferred the attainment of Buddhahood until after rebirth in the Pure Land, and emphasized human limitations rather than their inherent Buddha nature. Dōgen stressed the inherent Buddha nature and held that one attains enlightenment directly in the act of seated meditation, but the practice of zazen as he taught it was not universally accessible, requiring the environment of monastic life, observance of the precepts, and, one assumes, some degree of education. Nichiren’s teaching combined both a universally practicable discipline—the daimoku of the Lotus Sutra—and the doctrine of attaining Buddhahood as a common mortal.