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

Of the people who put faith in the Lotus Sūtra today, some have faith like fire while others have it like water. Those who have faith like fire refer to those who become enthusiastic upon listening to the preaching but their passion cools down as times goes by, and eventually forget the teaching. On the other hand, those whose faith is like water mean those whose faith is like a ceaselessly flowing water, namely those who retain their faith without retreating.

Ueno-dono Gohenji, A Reply to Lord Ueno, Writings of Nichiren Shōnin, Faith and Practice, Volume 4, Page 126

In order to study and propagate the dharma of Buddhism, it is indispensable to know the difference between Mahāyāna and Hinayāna teachings, provisional and true teachings, and exoteric and esoteric teachings among the various sūtras. In addition, it is also necessary to know the proper time for propagating the teaching, and the capacity for learning of those who are to receive the teaching. Nevertheless, most people in Japan automatically recite the Amitābha Sūtra, chanting “Namu Amida-butsu” devoutly, but thinking little of the Lotus Sūtra.

Many, who are respected for being wise, seem to think that they know the proper time for propagation and the capacity of the people, but actually they believe in the insignificant rather than the significant, believing in the provisional sūtras, while casting aside the true sūtras. Just as the insignificant may become a great evil, a medicine changes to poison, and close relatives become sworn enemies, it is impossible to save such people.

Even those who excel in understanding Buddhism, if they don’t grasp the social conditions of the time, the capacity of the people to receive the teaching, the conditions of the country, and the order of the teachings to be spread, they will not obtain the expected results no matter how hard they work to propagate the teachings. For example, it may be permissible to propagate Mahāyāna teachings in an absolute Hinayāna country, but to propagate Hinayāna teachings in the absolute Mahāyāna country must definitely be avoided. If Hinayāna teachings are forcibly propagated in the country of Mahāyāna Buddhism, disasters will befall the country and the people fall into evil realms.

Shimoyama Goshōsoku, The Shimoyama Letter, Writings of Nichiren Shōnin, Volume 5, Page 66-67

Generally speaking, there are 4 kinds of people who cannot attain Buddhahood or enter the Buddha land. The first is the Two Vehicles with fixed natures namely pratyekabuddha and śrāvaka. Next is the icchantika, who did not listen to the teaching of the Buddha and spoiled the seed of Buddhahood. The third is those with empty mind who do not believe in the doctrine of cause and effect expounded by the Buddha. And finally those who slander the True Dharma. These people, who have long been denied the attainment of Buddhahood in the various pre-Lotus sūtras, were allowed to become Buddhas for the first time in the Lotus Sūtra. This is the reason why the Lotus Sūtra is called “myō.”

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

[I]t is against the will of the Buddha to interpret the pre-Lotus sūtras according to the words of those sūtras. This is so because, as stated in the third fascicle of the Annotations on the Words and Phrases of the Lotus Sūtra, the whole truth is not revealed in the pre-Lotus sūtras. It is further said in the tenth fascicle of the Commentary on the Profound Meaning of the Lotus Sūtra that only the Lotus Sūtra reveals the true meaning of the pre-Lotus as well as the meaning of the Lotus Sūtra, the sole purpose of the Buddha appearing in this world.

Nijō Sabutsu Ji, Obtaining Buddhahood by the Two Vehicles, Writings of Nichiren Shōnin, Doctrine 3, Page 228

QUESTION: I do not dare question what the Lotus Sūtra says and how T’ien-t’ai and his disciple Chang-an interpreted it regarding the “mutual possession of ten realms.” However, they sound as though they are calling fire, “water,” and black, “white.” It is hard to understand although I believe this is what the Buddha preached. Now, no matter how many times we look at each other’s faces, we see only a human being, not anything of other realms. It is the same with our own face. How is it possible to believe in the “mutual possession of the ten realms” doctrine?

ANSWER: As we often look at each other’s faces, we notice our facial expression changes from time to time. It is full of delight, anger, or calm sometimes; but other times it changes to greed, ignorance, or flattery. Anger represents hells; greed—hungry spirits; ignorance—beasts; flattery—asura demons; delight—gods; and calm—men. Thus, we see in the countenance of people six realms of illusion, from hells to the realm of gods. We cannot see four realms of holy ones (śrāvaka, pratyekabuddha, bodhisattvas, and Buddhas), which are hidden from our eyes. Nevertheless, we must be able to see them, too, if we look for them carefully.

Kanjin Honzon-shō, A Treatise Revealing the Spiritual Contemplation and the Most Verable One, Writings of Nichiren Shōnin, Doctrine 2, Page 134-135