It is not allowed to explain the true meaning of the doctrine of “3,000 existences contained in one thought” even in the theoretical section of the Lotus Sūtra. Needless to say, it is not mentioned at all in the pre-Lotus sūtras. The doctrine stems from the passage describing the ten aspects of existence in the paragraph on the “brief replacement of the three vehicles with the one true vehicle” (ryaku kaisan-ken’ichi) in the second chapter in the theoretical section of the Lotus Sūtra. Nevertheless, the true meaning of the doctrine is based solely on the essential section of the sūtra. The pre-Lotus sūtras should be judged according to the meaning of the theoretical section, which in turn should be judged by the meaning of the essential section. Only the essential section of the Lotus Sūtra can define its meaning as it preaches.

Jisshō-shō, A Treatise on the Ten Chapters of the Great Concentration and Insight, Writings of Nichiren Shōnin, Doctrine 2, Page 4