Nichiren criticizes those who follow the two vehicles of the Śrāvakas (lit. “voice hearers” who are the Hinayāna disciples of the Buddha) and the pratyekabuddhas (lit. “privately awakened ones” who contemplate dependent origination on their own) because these kinds of Buddhists attain liberation from the sufferings of this world of birth and death, but are unable to help anyone else, including their parents. Because of this, they fail to achieve the true purpose of the Buddha Dharma. Speaking of these Hinayāna disciples, Nichiren says:

The purpose of becoming a monk by renouncing one’s family is to save one’s parents. Adherents of the two vehicles think that they can emancipate themselves from suffering. It may be true, but it is very difficult for them to benefit others. They may benefit others to some extent, but they will send their parents to the world where their parents can never become Buddhas. Therefore, I say that they do not know the favors of their parents. (Murano, p. 21. See also Hori 2002, pp. 39-40, and Gosho Translation Committee 1999, p. 228)

Nichiren’s conclusion is that only the Lotus Sūtra has the power to enable our parents to attain buddhahood. Other Buddhist teachings and sūtras may state that in principle all beings can attain buddhahood, but only in the Lotus Sūtra is the buddhahood of all men and women guaranteed and even demonstrated.