Even if the “perfect teaching” expounded in the pre-Lotus sūtras is put in the “perfect teaching” expounded in the Lotus Sūtra, they cannot be the same teaching. The “perfect teaching” of the pre-Lotus sūtras included in the Lotus Sūtra is called not the True Dharma but just “an expedient teaching within the Lotus Sūtra.” When an expedient teaching is taken out of the Lotus Sūtra, and the “One Buddha-Vehicle is divided into three” (the second chapter of the Lotus Sūtra), it is called “the perfect teaching within the Three Vehicles.” (It can be said that because an expedient teaching is expounded based on the “perfect teaching” of the Lotus Sūtra, the expedient should be called the “perfect teaching,” but strictly speaking the “perfect teaching” of the Lotus Sūtra is different from that of other sūtras. That is why the “perfect teaching” as an expedient is called “the perfect teaching within the Three Vehicles.”)

Shoshū Mondō-shō, Questions and Answers Regarding Other Schools, Writings of Nichiren Shōnin, Doctrine 3, Page 181