[T]he most important thing for non-Buddhist teachings is, like Confucianism, to prepare the way to Buddhism. This is why some non-Buddhists maintain that the Buddha will be born 1,000 years later, while others insist on 100 years later. It is said, therefore, in the Nirvana Sūtra that what is written in all the non-Buddhist scriptures is nothing but the teaching of the Buddha. Again, it is said in the Lotus Sūtra, chapter eight, “Assurance of Future Buddhahood,” that disciples of the Buddha sometimes pretend to be contaminated with the Three Poisons of greed, anger, and ignorance or show the heretic view denying the law of cause and effect as an expedient means to save the people.

Kaimoku-shō, Open Your Eyes to the Lotus Teaching, Writings of Nichiren Shōnin, Doctrine 2, Page 33