[N]ichiren rejects the Hinayāna and Mahāyāna kai, and maintains that purity can be gained only through a pure teaching. And as the teaching was preached by Buddha, the purity of Buddha himself becomes a thing of fundamental importance. Nichiren says in this respect that by manifesting the fundamental truth of the enlightenment of the very substance of Myō Hō Ren Ge Kyō all living beings inherited also the purity of the Wonderful Teaching. Since they were unaware of it themselves, they lost the purity of it. If one believes that the wonderful substance of the Original Buddha Śākyamuni is the very essence of one’s own substance, and if one trusts in and practices Namu Myō Hō Ren Ge Kyō, then the kaitai of incomparable purity becomes active naturally. Textually, Nichiren says in the Kanjin Honzon: “The Venerable Śākyamuni of wonderful enlightenment is our blood and flesh. His merits of cause and effect are our bones and marrow.” “Śākyamuni’s two dharmas of cause and practice and effect-virtue are possessed completely in the five characters of Myō Hō Ren Ge Kyō. If we accept and keep these five characters, then he naturally gives us his merits of cause and effect.” Nichiren says, thus, that the wonderful substance of ourselves is manifested openly and truly only by the Myō Hō Ren Ge Kyō. Whoever believes in this sutra obeys the precepts.

It is clear, then, that belief in the Hoke-kyō, implying its acceptance and keeping, facilitates the rise of the substance of morality. In simple terms, Nichiren has reduced the various śīlas [morality] into an acceptance of the teachings of the Hoke-kyō. The verbal expression of this is the recitation of Namu Myōhōrengekyō. Dogmatic justification of his conviction is the aim of his Kaitai sokushin jóbutsugi, which itself is the theoretical foundation of his practice of Daimoku.

p73-74