In Chapter 21, “Supernatural Powers of the Tathagatas,” Sakyamuni authorizes these Great Bodhisattvas from Underground to propagate the Lotus Sutra after his extinction. Besides, the Buddha teaches that the heart of the Sutra’s teachings should be manifested through four key dharmas: (1) all the teachings of the Tathagata, (2) all the unhindered, supernatural powers of the Tathagata, (3) all the treasury of the hidden core of the Tathagata, and (4) all the profound achievements of the Tathagata.

Nichiren interpreted the four key dharmas to be represented in the title, MYO-HO-REN-GE-KYO, or “Sutra of the Lotus Flower of the Wonderful Dharma.” Besides, he understood that in the Age of Degeneration, the Bodhisattvas from Underground will certainly appear in order to propagate the Name of the Dharma. As long as Sakyamuni was physically present, the essence of the Primal Mystery (Hommon) was present in the “one chapter and two halves.” In the evil world after his death, however, that key concept would be revealed in the five-character title of MYO-HO-REN-GE-KYO, or the “Sutra of the Lotus Flower of the Wonderful Dharma.

What Sakyamuni transmits [in Chapter 21, The Supernatural Powers of the Tathāgatas,] to Superb-Action and the other Great Bodhisattvas, who welled up from underground, is nothing less than (1) all the teachings of the Buddha, (2) all the unhindered supernatural powers of the Buddha, (3) all the treasury of the hidden core of the Buddha, and (4) all the profound achievements of the Buddha. These are called the Four Phrases of the Primary Mystery. Great Master Chih-i taught that the meanings that the title (Daimoku) expresses — that is, the meaning of the title itself, the purpose of the sutra, its essential teachings, the influence it has upon its readers, and the value of its teachings (which five he called the main things to be commented on in interpreting any sutra)—are expressed here in the Four Phrases of the Primary Mystery. Nichiren, on the other hand, believed that the Four Phrases of the Primary Mystery are to be found in the Sacred Title itself (Odaimoku), and what Sakyamuni now transmits to Superb-Action and the others is the Sacred Title of NAMU-MYOHO-RENGE-KYO. (“I devote myself to the Sutra of the Lotus Flower of the Wonderful Dharma.

The Buddha sings these verses to Superior-Practice Bodhisattva in Chapter 21 of the Lotus Sūtra:

Anyone who keeps this sūtra
Will be able to expound
The meanings of the teachings,
And the names and words [of this sūtra].
Their eloquence will be as boundless
And as unhindered as the wind in the sky.

Anyone who believes in and upholds the Lotus Sutra, which is transmitted from Sakyamuni, has a thorough knowledge of the meanings of its diverse teachings, words, and interpretations, and is able to expound them impartially, just as the wind sails freely through the sky. That person will be able to reach a stage of freedom, and remain there.

In Chapter 21, The Supernatural Powers of the Tathāgatas, Sakyamuni says:

Anyone who understands why the Buddhas expound [many] sūtras,
Who knows the position [of this sūtra in the series of sūtras],
And who expounds it after my extinction
According to its true meaning,
Will be able to eliminate the darkness
Of the living beings of the world where he walks about,
Just as the light of the sun and the moon
Eliminates all darkness.
He will be able to cause innumerable Bodhisattvas
To dwell finally in the One Vehicle.

Therefore, the man of wisdom
Who hears the benefits of these merits
And who keeps this sūtra after my extinction,
Will be able to attain
The enlightenment of the Buddha
Definitely and doubtlessly.

These words were especially beloved by Nichiren. Needless to say, for him all the words of the Sutra were compelling. Nevertheless, he considered this chapter, the “Supernatural Powers of the Tathagatas,” to be of singular importance. That is because it is here that Sakyamuni transmits the Four Phrases of the Primary Mystery, the essence of the Sutra, to Superb-Action and the Bodhisattvas from Underground. Nichiren believed that these Four Phrases are the Sacred Title (Odaimoku) of NAMU-MYOHO-RENGE-KYO. He maintained that in this chapter Sakyamuni calls the Bodhisattvas who had welled up from underground, headed by Superb-Action, and transmits to them the Sacred Title, the core of the Sutra manifested in its title. These Bodhisattvas, on their part, will appear in our times, the Age of Degeneration, to disseminate the Sacred Title and save all people, leading them to attain Buddhahood.

The Lotus Sutra consists of twenty-eight chapters. At the beginning, the Buddha taught from Mount Sacred Eagle (Grdhrakuta, “Vulture Peak,” in Sanskrit) near the city of Rajagriha, India, which today is called Rajgir. In Chapter Eleven, “Beholding the Stupa of Treasures,” he ascended to the sky and remained there until returning to Mt. Sacred Eagle in Chapter Twenty-three, “The Previous Life of Medicine-King Bodhisattva.” Thus he held three assemblies, which are called the First Assembly on Mt. Sacred Eagle; the Assembly in the Sky; and the Second Assembly on Mt. Sacred Eagle. We can divide the chapters of the sutra into three parts according to these three locations.

The main practice of Mahayana Buddhism, the Great Vehicle, is the Practice of a Bodhisattva: practice for helping others. The sutras in general give us many types of Bodhisattva-practices. In the Lotus Sutra, however, the principal Bodhisattva-practice is dissemination of the Sutra itself.

In Chapter Eleven, “Beholding the Stupa of Treasures,” and Chapter Eighteen, “Encouragement for Keeping the Sutra,” Sakyamuni asks Bodhisattvas to volunteer to disseminate the Sutra in the future. Answering his call, in Chapter Fifteen, “The Appearance of Bodhisattvas from Underground,” Bodhisattvas well up from beneath the earth, and in Chapter Twenty-one, “Supernatural Powers of the Tathagatas,” Sakyamuni transmits the Sutra to them. Then in Chapter Twenty-two, “Transmission,” he transmits it to all the Bodhisattvas. The mission of all of them, both the Original Bodhisattvas and the Temporal Bodhisattvas, is to disseminate the Lotus Sutra after the Buddha’s extinction.

A principal feature of the Lotus Sutra lies in showing us spiritual and practical ways by which Bodhisattvas disseminate it, overcoming all hardships in this evil world.

The studies conducted over so many centuries made possible a deeper understanding of the Lotus Sutra, and methodological standards for its interpretation were established. One example is called Kamon. It is a classification of the twenty-eight chapters into several sets for a systematic explanation of their meaning.

The major Kamon is the “Three Parts of Each of the Two Divisions of the Lotus Sutra” which was established by Great Master Chih-i. Most commentators since his time have accepted his guidelines. …

[T]he “Three Parts of Each of the Two Divisions of the Lotus Sutra” refers to the division of the Sutra into two main sections: the first half, consisting of Chapters One through Fourteen, and the second half, consisting of Chapters Fifteen through Twenty-eight. Kamon gives a detailed explanation of the reason for this division. The first half is named Shakumon, literally “imprinted gate.” Its main purpose is to teach how “hearers” and Pratyekabuddhas can attain Buddhahood in the One Vehicle. The second half is called Hommon, which means “Primal Gate” or “Primal Mystery.” This part reveals Sakyamuni to be the infinite, absolute Buddha, the Buddha who attained enlightenment in the remotest past but still leads living beings in the present. These two points are considered the fundamental ideas of the Lotus Sutra.