Nichiren on the Buddhist principle of duality

"If you think that to proclaim the absolute superiority of the Lotus Sutra is to take too narrow a view, then one would have to conclude that no one in the world was more narrow-minded than Shakyamuni Buddha. I am afraid you are greatly mistaken in this matter. Let me quote from one of the sutras and from the commentary of one school, and see if I can resolve your confusion.

The Immeasurable Meanings Sutra says: “[Because people’s natures and desires are not alike], I preached the Law in various different ways. Preaching the Law in various different ways, I made use of the power of expedient means. But in these more than forty years, I have not yet revealed the truth.”

Hearing this pronouncement, Great Adornment and the others of the eighty thousand bodhisattvas replied in unison, voicing their understanding that “[as for those living beings who are unable to hear this sutra . . . ] though immeasurable, boundless, inconceivable asamkhya kalpas may pass, they will in the end fail to gain unsurpassed enlightenment.”

The point of this passage is to make clear that, no matter how much one may aspire to the Buddha way by calling upon the name of Amida Buddha, or by embracing the teachings of the Zen school—relying on the sutras of the Flower Garland, Agama, Correct and Equal, and Wisdom periods preached by the Buddha during the previous forty years and more—one will never succeed in attaining supreme enlightenment, even though a countless, limitless, inconceivable number of asamkhya kalpas should pass.

And this is not the only passage of this type. The “Expedient Means” chapter of the Lotus Sutra states, “The World-Honored One has long expounded his doctrines and now must reveal the truth.” It also says, “[In the Buddha lands of the ten directions] there is only the Law of the one vehicle, there are not two, there are not three.” These passages mean that only this [Lotus] sutra represents the truth.

Again, in the second volume it says, “I am the only person who can rescue and protect others.”1 And it speaks of “desiring only to accept and embrace the sutra of the great vehicle and not accepting a single verse of the other sutras.” These passages mean that only Shakyamuni Buddha can save and protect all living beings, and that one should wish to accept and uphold only the Lotus Sutra, and never even a verse from any other sutra.

It also says, “If a person fails to have faith but instead slanders this sutra, immediately he will destroy all the seeds for becoming a Buddha in this world. . . . When his life comes to an end he will enter the Avichi hell.” This passage means that, if one does not believe in the Lotus Sutra but instead turns against it, one will immediately destroy the seeds for attaining Buddhahood in this world. After death, one will fall into the hell of incessant suffering.

Examining these passages, T’ien-t’ai concluded that it was statements such as these that had prompted the words, “Is this not a devil pretending to be the Buddha?” If we merely rely upon the commentaries of various teachers and do not follow the statements of the Buddha himself, then how can we call our beliefs Buddhism? To do so would be absurd beyond description!

Therefore, the Great Teacher Chisho stated that, if one claims that there is no division of Mahayana and Hinayana among the sutras and no distinction of partial and perfect among revelations of the truth, and therefore accepts all the words of the various teachers, then the preachings of the Buddha will have been to no purpose.

T’ien-t’ai asserted, “That which has a profound doctrine and accords with the sutras is to be written down and made available. But put no faith in anything that in word or meaning fails to do so.” He also said, “All assertions that lack scriptural proof are to be branded as false.” How would you interpret such statements?" -- Questions and Answers about Embracing the Lotus Sutra

It is the Lotus Sutra, Shakyamuni Buddha, and Nichiren Daishonin that lead to emancipation, not the Kempon Hokke, SGI,  other sects, scriptures or persons.