Nichiren classifies all the Buddhas of sutras other than the Lotus and the Śākyamuni described in the first section and in the last six chapters of the second section of the Lotus scripture as temporal bodies, or “Buddhas of the Hinayāna.” Only the Śākyamuni who reveals his enlightenment in the past embodies the true Mahāyāna Buddha. To indicate the infiniteness of this Buddha, Nichiren uses the expression “without beginning and without end,” which properly belonged to a context related to Mahāvairocana Buddha and signified an existence not subject to temporal limitations. This expression suggests that Nichiren attributes an eternal nature to Śākyamuni, and at first seems to imply that he envisages a dharmakāya as the only ground of any reality. But Nichiren develops this infiniteness in a different direction.

Nichiren emphasizes that the Lotus Sutra is the only scripture where not only the dharma body, but also the recompense body, and the transformation body are presented as “infinite”: “When other Mahayana sutras speak of ‘without beginning and without end,’ they refer to the dharmakāya only, not to the three bodies.” Nichiren does not regard the distant past represented by the five hundred kalpas as a metaphorical image, but as a concrete reality identifying an active original body, a “Buddha who in the far distant past has truly manifested himself, has truly practiced, and has truly actualized his enlightenment.” Consequently, the meaning that Nichiren attributes to Śākyamuni is not symbolized either by a transcendental body whose existence is set in a world other than ours or by the recompense body of which Chih-i spoke. This “without beginning without end” of the temporal body is most difficult to believe, Nichiren repeatedly suggests, but the infiniteness of the nirmāṇakāya is the crucial evidence that the Buddha has always abided in this world and that his soteriological activity has been constant since the original time.

Thus Nichiren resolves the conflict between the mundane and the ultimate by creating an all-encompassing Śākyamuni Buddha, who maintains characteristics of the historical Śākyamuni (the activity of preaching) and at the same time is endowed with attributes of the dharmakāya (infinite existence). In this way, the dharma world itself comes to be conceived as the phenomenal reality which actualizes the ultimate truth. Borrowing from Tendai terminology, Nichiren calls this reality “a concretely accomplished ‘three thousand worlds in one single thought.’ ”
A Buddhist Kaleidoscope; Lucia Dolce, Between Duration and Eternity: Hermeneutics of the ‘Ancient Buddha’ of the Lotus Sutra in Chih-i and Nichiren, Page 231-232