What does the Lotus Sutra teach? According to Nichiren Shōnin,

“Twenty important doctrines are in this Lotus Sūtra … The ‘3,000 existences in one thought’ doctrine is hidden between the lines of the sixteenth chapter on ‘The Life Span of the Buddha’ in the essential (honmon) section of the Lotus Sutra.” (Kaimoku Shö, WNS2, p. 34)

Among these doctrines, the most important one is Ichinen Sanzen. Nichiren Shōnin said,

“The doctrine of Ichinen-Sanzen, or the ‘Three Thousand Existences in One Thought,’ is the rarest and the most miraculous.” (Shōjō Daijō Funbetsu Shō, WNS2, p. 193)

In the Kaimoku-Shō, Nichiren Shōnin further stated,

“Considering these testimonies of Buddhas and Bodhisattvas in various sutras with those in the Lotus Sutra, they are like yellow rocks against gold nuggets, white clouds against white mountains, white pieces of ice against mirrors of silver, and black color against blue color.” (Kaimoku shō, WNS2, p. 44)