Please read the sūtra carefully, so that you may understand that the doctrine of “mutual possession of ten realms” is clearly preached in it. For instance, we read in the second chapter that the purpose of the Buddha appearing in the world was “to cause all living beings to open their gates to the insight of the Buddha.”

Interpreting this passage in the Lotus Sūtra, T’ien-t’ai said: “If the insight of the Buddha does not exist in all living beings, how can He open the gate to it? You should know from this that the insight of the Buddha is inherent in the minds of all living beings.” And Chang-an declared: “If the insight of the Buddha is non-existent in living beings, how can anyone cause them to open the gate to or be aware of it? For instance, how can a poor woman without a treasure house show off
treasure?”

Kanjin Honzon-shō, A Treatise Revealing the Spiritual Contemplation and the Most Verable One, Writings of Nichiren Shōnin, Doctrine 2, Page 142

[In the sixth month of the 3rd year of the Kenji era (1277), Nichiren Shōnin wrote a letter of explanation in place of Inaba-bō Nichiei, a disciple of Nichiren, and submitted it to Nichiei’s father, Shimoyama Hyōgo Gorō Mitsumoto.]

I stopped reciting the Amitābha Sūtra for the following reasons. In the summer of the eleventh year of the Bun’ei Era (1274), Nichiren Shōnin, who has recently become widely known in Japan, came to live in seclusion at the foot of an isolated mountain called Mt. Minobu located in the districts of Iino, Mimaki, and Hakii in the same province of Kai, to which Shimoyama also belongs. Even those of considerably high social standing are not allowed to listen to him preach except if they have special connections.

Having heard of a certain person seeing Nichiren, I sneaked into the backyard of his hermitage and hid myself. I did not intend to become a follower but wanted just to have a glance at how things were. I could roughly hear what he preached as he answered questions.

Nichiren Shōnin compared the superiority and profundity of the Lotus Sūtra with such sūtras as the Great Sun Buddha Sūtra, the Flower Garland Sūtra, the Wisdom Sūtra, the Revealing the Profound and Secret Sūtra, the Entering Laikā Sūtra, and the Amitābha Sūtra. I could understand that the Lotus Sūtra is far superior to the Amitābha Sūtra, not just two or three times, but as much as the difference between heaven and earth. For instance, the differences among them are likened to the differences between Indra, the master, and a monkey, his retainers, a gorgeous Chinese phoenix and a small black magpie; a huge mountain and a particle of dust; or the sun and the moon and a firefly. Comparing the passages of the Lotus Sūtra with those of the other sūtras, Nichiren Shōnin enlightened ignorant people like me to understand the differences among those sūtras quite clearly. Therefore, that the superiority of the Lotus Sūtra can be perceived by many people is not surprising at all.

Shimoyama Goshōsoku, The Shimoyama Letter, Writings of Nichiren Shōnin, Volume 5, Page 66

The pre-Lotus sūtras preach that Devadatta will never be able to attain Buddhahood. If this is true, the Lotus Sūtra is a great lie. If the Lotus Sūtra that allows Devadatta to become a Buddha, is true, the various pre-Lotus sūtras are, in turn, considered committing the sin of telling a lie. The Lotus Sūtra guarantees Devadatta to be Heavenly King Buddha although he committed not only the three rebellious sins but also innumerable other serious crimes. There is, thus, no doubt that evil people who committed one or two rebellious sins can attain Buddhahood. It is just as when the earth is turned over, the vegetation growing there is also turned over, and a man who is able to break a solid stone can easily cut off the soft grass. That is why this sūtra is called “myō (wonderful).”

Hokke Daimoku Shō, Treatise on the Daimoku of the Lotus Sūtra, Writings of Nichiren Shōnin, Faith and Practice, Volume 4, Page 42-43

It is therefore impossible to know the meanings of various sūtras of Śākyamuni Buddha preached during His lifetime no matter how many times we read them without the Lotus Sūtra. Without knowing this, a practicer of the Lotus Sūtra who reads the Lotus Sūtra does not really read it. It is a mistake to insist that the pre-Lotus sūtras of the profound teaching do not reveal the meaning of those on the shallow teaching, and that the sūtras of the shallow teaching do not contain the profound teaching. The Lotus Sūtra reveals in every word the meanings of all the pre-Lotus sūtras as well as the Lotus Sūtra. Therefore, reading a word of the Lotus Sūtra is equivalent to reading all of the Buddhist scriptures. Not to read the Lotus Sūtra at all means not to read the scriptures of Buddhism. Attaining Buddhahood, therefore, is difficult in the land where there is not the Lotus Sūtra but various other sūtras. The way to read all Buddhist scriptures after the Buddha’s death such as the Flower Garland Sūtra or the Sūtra of Meditation on the Buddha of Infinite Life, then, should be to read them together with the Lotus Sūtra that reveals the meaning of each sūtra. All other sūtras should be read in the same manner.

Nijō Sabutsu Ji, Obtaining Buddhahood by the Two Vehicles, Writings of Nichiren Shōnin, Doctrine 3, Page 229

The “mutual possession of ten realms” doctrine is as difficult to maintain as it is to see fire in a rock and flowers in wood. However, it is not totally impossible because rocks spark when struck together and a tree blooms in spring. It is most difficult to believe that the realm of Buddhas is contained in the realm of men because it is just like saying that fire is in water or water is in fire. However, it is said that dragon fire comes out of water and dragon water comes out of fire. This is difficult to believe, but we cannot help but believe in it because of the evidence for this. You have come to believe that each of the eight realms is contained in the realm of men. Why can you not believe that the realm of Buddhas, too, is contained in it?

Ancient Chinese rulers, sages such as Yao and Shun, treated all people equally with compassion, proving the existence of the realm of Buddhas, at least a portion of it, within the realm of men. Never-Despising Bodhisattva, described in the 20th chapter on “Never-Despising Bodhisattva” of the Lotus Sūtra, pressed his hands together in respect and bowed to anyone he met because whenever the bodhisattva saw a man, he saw a Buddha in him. Born to the human world, Prince Siddhartha, young Śākyamuni, became the Buddha. These evidences should be enough to convince you to believe that the realm of Buddhas exists in the realm of men.

Kanjin Honzon-shō, A Treatise Revealing the Spiritual Contemplation and the Most Verable One, Writings of Nichiren Shōnin, Doctrine 2, Page 136-137

Despite being a layman and despised by everyone, you have been devoted to me though we do not see each other. Why is this? It must be due to the merit accumulated in your past lives. As the time has come for you to inevitably become a Buddha in the next life, you are inspired with the Bodhi-mind. Besides, it is preached in the Lotus Sūtra, “He whose body is taken over by evil gods does not believe in this sūtra while he whose mind is replaced by the soul of Śākyamuni Buddha has faith in it.” Therefore, I feel most confident that just as the ray of the moonlight enters a body of water and makes it clear, the soul of Lord Preacher Śākyamuni Buddha entered your mind to eliminate impurity.

Matsuno-dono Goshōsoku, Letter to Lord Matsuno, Writings of Nichiren Shōnin, Volume 7, Followers II, Page 66

QUESTION: It is not entirely clear that the six realms of illusion exist in the realms of human beings, but I am beginning to think they seem to as I listen to you. Nevertheless, I cannot see the four realms of holy ones at all. What do you say about this?

ANWSER: You doubted the existence of six realms of illusion in the realm of men, but I tried hard to explain it until you said you seemed to understand it. The same might happen with four realms of holy ones. Therefore, I shall try to explain as much as possible what the sūtras state, supplemented with reason. We see the so-called principle of impermanence everywhere in front of our eyes. We humans understand this principle, through which two groups of Hinayāna sages (Two Vehicles) called śrāvaka and pratyekabuddha try to obtain enlightenment (arhatship). How can we say then that the realms of two Hinayāna sage groups are not included in the realm of men? A man, no matter how inconsiderate he may be, loves his wife and children. It shows that he is partly in the bodhisattva realm.

The only realm contained in the realm of men and yet hard to see is that of Buddhas. However, since we see nine other realms included in the realm of human beings, we can conjecture that the realm of Buddhas, too, is contained therein. You should firmly believe this and have no doubt about it. On the existence of the realm of Buddhas contained in the human realm, the Lotus Sūtra states in the second “Expedients” chapter that the purpose of Buddhas appearing in the world was “to cause all living beings to open the gate to the insight of the Buddha.” And in the Nirvana Sūtra, we come across a passage which states: “Though having only human eye, those who study Mahāyāna Buddhism are regarded the same as having Buddha-eye because they see the truth of Buddhism.” The reason why we, ordinary people, born in the Latter Age, can put faith in the Lotus Sūtra is that the realm of Buddhas is included in the realm of human beings.

Kanjin Honzon-shō, A Treatise Revealing the Spiritual Contemplation and the Most Verable One, Writings of Nichiren Shōnin, Doctrine 2, Page 135

There are two kinds of classic works on filial piety: the Classic of Filial Piety written by a non-Buddhist sage called Confucius of China and the Buddhist work on filial piety entitled the Lotus Sūtra. Although they differ in that one is a Buddhist sūtra and another is a non-Buddhist classic, what they preach is fundamentally the same.

For what purpose did Śākyamuni Buddha strive to attain Buddhahood for an incalculably long period of time known as the dust-particle kalpa (aeons)? It was for no other reason than filial piety. However, as all the living beings in the world of delusion are the Buddha’s parents, unless they all attain Buddhahood, He cannot claim to have fulfilled His filial duties. The Buddha, therefore, did not attain Buddhahood Himself. However, the Lotus Sūtra expounds the secret dharma enabling all living beings to attain Buddhahood. That is to say, it reveals the truth of attaining Buddhahood by all living beings in the ten realms through leading one person in the realm of hell, one person in the realm of hungry spirits, or just one person in each of the nine realms to Buddhahood. It is just as when we cut a bamboo joint, other joints are cut at the same time. Or it is like the shichō strategy in the game of go, where the death of one “stone” coincides with the death of many. It is the same with the truth of the Lotus Sūtra. As metal can cut trees and grass, and water has the virtue of extinguishing all fires, the Lotus Sūtra is equipped with the virtue of enabling all living beings to become Buddhas.

Hōren-shō, Letter to Hōren, Writings of Nichiren Shōnin, Volume 6, Followers I, Page 51