Although there are various Buddhist teachings, none allows the attainment of Buddhahood by the Two Vehicles. As a result, when the attainment of Buddhahood by the Vehicles is not allowed, bodhisattvas, too, are not allowed to attain Buddhahood. This is because the attainment of Buddhahood by the Two Vehicles is inevitable for bodhisattvas to fulfill their Four Great Vows. They made a vow to save all the people however numerous they are. Therefore, even the bodhisattvas of the Perfect Teachings preached in such sūtras as the Flower Garland Sūtra, Hōdō sūtras and the Wisdom Sūtra cannot reach the shojū stage of enlightenment though they are considered to become Buddhas according to the scriptural statement cited above. It is needless to say that ordinary people and those of the Two Vehicles cannot become Buddhas by those sūtras. Therefore, it is stated in the chapter on “Expedients” of the Lotus Sūtra that the Buddha made a vow to teach all the people and cause them to enter the way leading to Buddhahood, that is to say, they can attain Buddhahood only in the Lotus Sūtra.

Nijō Sabutsu Ji, Obtaining Buddhahood by the Two Vehicles, Writings of Nichiren Shōnin, Doctrine 3, Page 226