Like other Buddhists of his day, Nichiren understood the six paths as actual cosmological realms into which beings are born repeatedly in accordance with their deeds, and the four holy paths of śrāvakas, pratyekabuddhas, bodhisattvas, and buddhas, as higher states achieved through cultivation. But at the same time, he understood all ten realms as lying “within ourselves.” In his major treatise “On the Contemplation of the Mind and the Object of Worship” (Kanjin honzon shō), Nichiren explains this by way of illustration. When one looks at another person’s face, they appear sometimes ecstatic, sometimes furious, and sometimes calm, or they might wear expressions of foolishness or perversity. Rage, he explains, is the hell realm; greed, the realm of hungry ghosts; foolishness, the realm of beasts; perversity, the asura realm; joy, the heavenly realm; and calm, the human realm. The four holy paths do not appear outwardly but can be known by introspection. Our understanding that all things are insubstantial and fleeting reflects the realms of the two vehicles of śrāvakas and pratyekabuddhas within our own mind. The affection that even a hardened criminal feels for his wife and children is an expression of the inner bodhisattva realm. Because the nine realms within one’s own mind can thus be demonstrated, Nichiren says, one should believe that the buddha realm is present as well.

In the above quotation, “seeing” the Buddha in one’s mind might suggest a specific cognition or insight, but for Nichiren, this meant chanting the daimoku, the expression of faith in the Lotus Sūtra. Though he encouraged study and intellectual understanding of the Buddhist teachings, the benefits of the daimoku, he said, are the same whether chanted by a wise person or a foolish one. He illustrated this by the analogies of fire that burns without intent to do so, or a newborn infant nourished unknowingly by its mother’s milk. At the beginning of [Chapter 2], when Śākyamuni Buddha first begins to speak, his opening words are: “Profound and immeasurable is the wisdom of the buddhas.” “What is this wisdom?” Nichiren asks. “It is the embodiment of the real aspect of all dharmas, the ten suchnesses realized by the Buddha. What is that embodiment? It is Namu Myōhō-renge-kyō.”