[I]n order to understand Nichiren’s theory of the substance of morality thoroughly, we must consider the evolution of this concept through the whole history of Buddhism, especially its formulation by the Tendai philosophy.

The Abhidharmakośa of Hinayāna, on which the Sarvāstivā School is based, declares the substance of morality of non-action (mu sa no kai tai) to be a “material thing” (Shiki hō). The Jōjitsu ron (Satyasiddhi), on which the Jōjitsu or Satyasiddhi School stands, which is part Hinayāna and part Mahāyāna, judges the substance of morality of non-action to be “neither matter nor mind” (hi shiki hi shin). The Hossō School of Mahāyāna, the Chinese form of the Indian Yogācāra School, holds the substance of morality of non-action to be the “seed of the good mind” (zenshin no shuji).

Tendai Daishi, who stands on the principle of the “one thought being the three thousand,” considers the substance of morality to be a quasi-matter of non-action possessed originally within the nature of the mind. By declaring the substance of morality to be “temporal matter of nonaction,” Tendai Daishi acknowledges it as a “material thing,” as the Sarvāstivā held. By declaring the substance of morality to be “possessed originally within the nature of the mind,” he acknowledges it as “mental,” as the Yogācāra school held. In short, Tendai Daishi harmonizes the Hinayāna theory of kaitai and the Temporal Mahāyāna theory of kaitai from the standpoint of the theory “that all things have real form” (i.e. “that all things are absolute” as stated in the shakumon of the Hoke-kyō). The substance of morality in Hinayāna is “single matter”; that of Temporal Mahāyāna is the “single mind,” while that of the shakumon of the Hoke-kyō is the “plural mind.”

Nichiren’s conception of the formula “one thought being the three thousand” takes its stand on the hommon of the Hoke-kyō and therefore differs from Tendai Daishi’s conception which, according to Nichiren, stands on the shakumon. While shakumon makes clear that the “three thousand” (i.e. all psychical and physical phenomena) are possessed completely within the nature of the mind of the living beings; hommon elucidates that the substance and form of the Original Buddha is omnipresent within the “three thousand” dharma worlds. Whereas in shakumon, and thus to Tendai Daishi, the substance of morality is “the temporal matter of non-action of the nature,” in hommon and to Nichiren the substance of morality is “the wonderful matter of nonaction of the substance.” Thus, to Tendai’s “temporal,” Nichiren opposes “wonderful”; to “nature,” “substance”—the distinction here being that nature is understood to be the Absolute Reality considered as mind, i.e. abstract; while substance is the Absolute Reality as matter, i.e. concrete and tangible.

To Nichiren the substance of morality is not obtainable by “the good mind” or by “reason meditation,” but solely by the deep and fundamental “believing mind” (shin jin), that receives the vow and keeps it. This “believing mind” originates with the Original Buddha, and ultimately its effect harmonizes the man with the omnipresent substance of the Original Buddha. This highest effect is a result of the co-operation between self-power (ji riki) and other-power (ta riki).