That short phrase represents the essence of HBS.

Undoubtedly, we recite by habitual practice. Shakyamuni Buddha's aim was to provide the true teachings for attainment of enlightenment to his disciples. But he also intended to provide the teachings to the world of the Mappo Period (The Period of the Last Dharma).

The Theoretical Section of the Lotus Sutra consisted of the following 14 Chapters:

Chapter 01: Introduction Introduction
Chapter 02: Expedient Means
Chapter 03: Simile and Parable
Chapter 04: Belief and Understanding
Chapter 05: Medicinal Herbs
Chapter 06: Bestowal of Prophecy
Chapter 07: Parable of the Conjured City
Chapter 08: Receipt of Prophecy by Five Hundred Disciples
Chapter 09: Prophecies Conferred on Learners and Adepts
Chapter 10: Preachers of Dharma
Chapter 11: Apparition of the Jeweled Stupa
Chapter 12: Devadatta
Chapter 13: Fortitude
Chapter 14: Comfortable Conduct

The following 14 Chapters are the Essential Section of the Lotus Sutra:

Chapter 15: Welling Up out of the Earth
Chapter 16: The Life-span of the Tathagata
Chapter 17: Discrimination of Merits
Chapter 18: The Merits of Appropriate Joy
Chapter 19: The Merits of the Dharma-Preacher
Chapter 20: The Bodhisattva Never Disparaging
Chapter 21: The Supernatural Powers of the Tathagata
Chapter 22: Entrustment
Chapter 23: The Former Affairs of the Bodhisattva Medicine King
Chapter 24: The Bodhisattva Fine Sound
Chapter 25: The Universal Gateway of the Bodhisattva of the World Sounds
Chapter 26: Dharma
Chapter 27: Former Affairs of King Wonderful Adornment
Chapter 28: Encouragements of the Bodhisattva Universal Worthy

Among the 28 Chapters, Chapters 15 to 22 are considered the most important teachings for us. The reason HBS places emphasis and esteem on the eight chapters is because they expound how the religion should be practiced and upheld by the people born in the Mappo Period.

A brief summary of what was elucidated in those eight Essential Section chapters is as follows: Chapter 15 illustrated dramatically the burden placed on Jyogyo Bodhisattva and other Bodhisattvas to circulate and spread its teachings to the people of the Mappo Period.

Chapter 16 revealed Shakyamuni Buddha to be the Eternal Buddha, and the Odaimoku he preached to contain the merits of enlightenment of the Eternal Buddha.

Chapters, 17, 18 and 19 elucidated that practitioners should place faith in the religion and abide by the methods of practices to gain virtuous deeds and good fortunes.

Chapter 20 elucidated that Never Disparaging Bodhisattva (Fukyo Bosatsu) should be a model for Lotus Sutra practitioners in the Mappo Period.

Chapter 21 and 22 elucidated that the Eternal Buddha entrusted Jyogyo Bodhisattva and other Boddhisattvas to circulate the Odaimoku and spread its teachings to the minds of the people of the Mappo Period.

The aforementioned are a synopsis of the circumstances and developments of the eight essential chapters.

Yes. After the death of Great Master Nichiren, some priests began to equally emphasize the importance of the Theoretical and Essential Sections of the Lotus Sutra.

Great Master Nichren's doctrine is basically based on Great Master Tendai's ideas. And because the priests of Nichiren related sects were required to have some knowledge of Great Master Tendai's doctrines, they visited Tendai Shu's Temple and studied his teachings. Through this influence, some priests considered the Theoretical and Essential Sections equally important.

Yes. Since the Tendai Shu Sect was extremely influential, the priests may have just wanted to flatter themselves. In any case, Great Master Nichiren stated:
"The difference of the Essential Section compared to the Theoretical Section is like water from fire and heaven from earth"
There is a great difference between the Theoretical Section and the Essential Section. To advocate that those two sections are equal is a hindrance to the Essential Section. Nissen Shonin stated:
"Tendai Shu spreads its teachings based on the Theoretical Section. On the other hand, Great Master Nichiren emphasized the Essential Section".
The Tendai Shu Sects teachings are based on the Theoretical Section of the Lotus Sutra. Why, because the teachings of the Theoretical Section were spread to the people in the Zobo Period. During that period, only that section was necessary. There are some related sects of Nichiren Shu that only expound the teachings of the latter half of Chapter 15, the entire Chapter 16, and on the first half of Chapter 17.

They stress Chapter 16 especialy. It is true that Chapter 16 contains the Eternal Buddha's practices to gain religious merits and to attain the state of enlightenment in the remote past. There is no doubt that Chapter 16 is important within the 28 chapters of the Lotus Sutra, but to advocate Chapter 16 only is a teaching for the people of the remote past.

That is correct. Chapter 16 elucidated the Eternal Buddha's law of the AgThree Thousand Realms Contained in One Thought (Ichinen Sanzen)". (Ichinen means a life for one instant or a life of exceedingly short period of time, and Sanzen means all phenomena in this world are included in both our thought for one instant and even in a minute grain of sand). Thus, if it were not included among the eight essential chapters, it would not be a beneficial teaching for the Mappo Period.

Mm. Let me give you and example. Chapter 16 is similar to an excellent ingredient for hourishing food. However, common people of the Mappo Period are unable to grasp even a small portion of enlightenment on their own. In other words, we are infants from the standpoint of religion unable to take nourishment by ourselves. Therefore, the Buddha, like an excellent cook, prepared the food that even a child could digest, and entrusted it to Jyogyo Bodhisattva to deliver it to the children of the Mappo Period.

Yes. To draw a line between the relationship of Chapter 16 and the eight chapters, Nichiryu Shonin logically and accurately deployed the true intention of the Buddha. Let's examine Nissen Shonin's nstructive Poem.
"Chapter 16 is the teaching for the people of The Buddha Shakyamuni's Period To harvest the seeds of enlightenment. The Mappo Period is the period to sow seed Of the Odaimoku for the genuine cause of Buddhahood".

A Gokyoka that elucidated the three stages of planting Buddhahood seeds are as follows:
"The Essential Section's eight chapters are teachings for the people of the Mappo Period to sow the seeds of Buddhahood. The latter half of Chapter 16 and th first half of Chapter 17 were teachings of harvesting the seed of enlightenment during Shakymuni Buddha's lifetime. And, for the benefit of the common people in the Mappo Period, the Eternal Buddha wrapped the Law of AgIchinen Sanzen" and the merits of enlightenment into the Odaimoku and entrusted it to Jyogyo Bodhisattva to spread it among the people of the Mappo Period".
Due to Buddha's entrustment of the Odaimoku and the true teachings of the Dharma to Jyogyo Bodhisattva, we, the juvenile people in the Mappo Period, are able to attain the merits of the Odaimoku by just chanting it.

The Buddha did not even entrust the sacred (seven syllables, Namumyo]horengekyo), the quintessence of the primordial teachings part of the Lotus Sutra to such great Bodhisattvas as Majjussri or Bhaisajyaraja, not to mention the lesser Bodhisattvas until after he had summoned Bodhisattvas of a thousand worlds welling up out the earth and revealed to them the primordial eight chapters of the Lotus Sutra. So, Nichiren Shonin stated

"Such a sublime Sacred Object, Namumyohorengekyo, was never revealed by Buddha Shakymuni during the forty plus years of his life as a preacher, and even during the eight years that, his techings only the primordial eight chapters." (Kanjin Honzon Sho)