In the Hinayāna teachings the attainment of buddhahood is not presented as the goal of Buddhist practice, so the bodhisattva vehicle is also not presented as something that can be taken up by ordinary people. The Hinayāna teachings state that there can only be one buddha on any given world at a time. Furthermore, the time between the appearances of a buddha is vast. Each time a buddha appears they set in motion the Wheel of the Dharma (i.e. they expound the Buddha Dharma), and after a buddha’s final nirvāṇa the teachings may last for a period of time known as the Age of the True Dharma, linger on in a corrupted form during a period of time known as the Age of the Semblance of the Dharma, and finally they begin to disappear during a Latter Age of Degeneration that can last for ten thousand years or more until the Dharma is completely forgotten. There may then be a period of millions of years before another buddha rolls the Wheel of Dharma again. The Hinayāna teachings do not speak of buddhas in other regions of the universe. The only two bodhisattvas who are recognized are the bodhisattva who became Śākyamuni Buddha, and Maitreya Bodhisattva who resides in the Tushita Heaven awaiting his time to become the next buddha in the distant future after Śākyamuni Buddha’s Dharma has completely disappeared. Bodhisattvas are therefore rare and extraordinary beings. What all of this means is that the attainment of buddhahood is not presented as an even remotely realistic goal. The Hinayāna teaches that the only feasible way to attain cessation from suffering and escape saṃsāra is to take up one the two vehicles of the śrāvaka or pratyekabuddha, with the former being the easier as the śrāvakas can rely upon the four noble truths and the Middle Way taught by Śākyamuni Buddha.

Once one sees the true nature of life and the futility of craving, the next step is to realize that if craving were given up then one would be free from suffering. This is the true meaning of nirvāṇa, the extinguishing of the flames of passionate greed or craving. Zhiyi spoke of this as the elimination of deluded views and attitudes that puts an end to transmigration within the six lower realms. From the perspective of the Hinayāna teachings, the arhats, pratyekabuddhas and even the buddhas who accomplish this are not reborn anywhere after death, not even in a pure land. They are simply gone, beyond the reach of conditioned existence and suffering. In life they attain nirvāṇa, the extinction of the greed, hatred, and delusion, and upon death they are said to attain parinirvāṇa or “final nirvana” whereby they are no longer even subject to physical pain and infirmity. While there may be śrāvakas, pratyekabuddhas, bodhisattvas, and buddhas as individuals, they have no lands or worlds of their own, but simply live in the human world (or some of the others in the case of bodhisattvas) until they attain final nirvāṇa. Then they are gone forever. This is why the attainment of final nirvāṇa is referred to as reducing the body to ashes and annihilating consciousness and also why the Hinayāna teachings are only said to expound the six lower realms and not the realms of the four noble states.

The second noble truth teaches that the true root of suffering is the craving for happiness itself. This craving is the result of the unrealistic expectation that life should be a source of unchangeable happiness as discussed under the first noble truth. Craving is what transforms the occasionally painful process of life into an ongoing cycle of agony and unbearable suffering at worst or a life of subtle agitation and anxiety at best. Thus, while external circumstances can indeed bring about uncomfortable or tragic experiences, it is the internal craving that turns mere pain into suffering. Indeed, craving can even spoil pleasant circumstances with its incessant demands and impoverished outlook on life. All of this is not to deny or denigrate the experiences of those who have or are experiencing affliction, exploitation, or tragedy. The point is that when one lets craving compound painful circumstances with emotional suffering or lets craving spoil even pleasant circumstances, then one has truly given up one’s power and is destined for a life determined by the forces of greed, anger and ignorance which are naturally generated in reaction to suffering.

The Middle Way as taught here by Śākyamuni Buddha is the Middle Way between self-indulgence and self-denial, both of which perpetuate the self-absorption that generates craving for worldly and otherworldly gain and is reinforced by deluded views. The Middle Way is in fact none other than the eightfold path that is the fourth of the four noble truths that the Buddha then proceeds to expound. Here is the first of the four:

“Now this, monks, is the noble truth of suffering: birth is suffering, aging is suffering, illness is suffering, death is suffering; union with what is displeasing is suffering; separation from what is pleasing is suffering; not to get what one wants is suffering; in brief, the five aggregates subject to clinging are suffering.”

The first noble truth of suffering means that conditioned phenomena are incapable of providing real lasting happiness. This does not mean that there is no happiness at all, but it does mean that even when we do get what we hoped for the happiness never lasts. In terms of the six lower realms, the worlds of the hell-dwellers, hungry ghosts, animals, and fighting demons are full of pain, ceaseless torment, and strife. Human life is naturally subject to old age, sickness, and death as well as the other sufferings enumerated. Even those who make wholesome causes and find themselves in heavenly circumstances will find that eventually the causes and conditions that put them there will change and they will find themselves forced to take birth into a new situation. In the six lower realms happiness is rare and fleeting whereas painful circumstances are abundant and insecurity is pervasive.

I would like to clarify here what is meant by the term “Hinayāna.” The term means “Small Vehicle” whereas Mahāyāna means “Great Vehicle.” The Mahāyānists referred to those Buddhists who rejected the Mahāyāna sūtras as Hinayāna Buddhists. The so-called Hinayāna Buddhists believed that the Buddha’s teachings could only be found in a closed canonical collection called the Three Baskets (S. tripiṭaka) composed of the sūtras that are the Buddha’s discourses, the monastic rules and procedures (S. vinaya), and the “Higher Dharma” (S. abhidharma) treatises that systematized the teachings in the discourses. The southern recension of these discourses is called the Pāli canon, since it was recorded in the Pāli language. It is composed of five Nikāyas or “Collections.” The northern recension of these discourses was in Sanskrit. They were called the Āgamas or “Sources” and exist now in Chinese translation. Today the Theravādin schools of Southeast Asia and Sri Lanka continue to uphold the Pāli canon as the only authoritative canonical collection of the Buddha’s teachings. The Sarvāstivādin and other northern schools that upheld the Āgama sūtras have long since disappeared in India. Because the term Hinayāna is a disparaging epithet and not the proper name of a school, it is best to use the term Theravāda and not Hinayāna when referring to the Buddhism of Southeast Asia. Calling the Āgama sūtras, their teachings, and the schools that rely upon them Hinayāna, as they are by East Asian Buddhists to this day, is problematic for a couple of reasons. The first is that, as Nichiren points out, those who study these teachings or who belong to these schools may have actually adopted Mahāyāna views. The second problem is that, according to Zhiyi, the teachings introduced in the Āgama sūtras can themselves express the perspective of the Mahāyāna if understood more deeply. Nevertheless, the term Hinayāna can be understood to refer to those teachings and schools that confine themselves to pre-Mahāyāna teachings, perspectives, and motivations, for that is how Nichiren uses the term in Kaimoku-shō.

When each of the ten realms is multiplied by the ten realms again due to the mutual possession of the ten realms one arrives at a hundred realms. Since each of the hundred realms has ten suchnesses there are said to be one thousand realms. In addition to all this, Zhiyi taught that there are three categories of existence that must be taken into account. These categories are the five aggregates (form, feeling, perception, mental formations, and consciousness); the sentient beings of the ten realms; and the environments in which they live. These three categories show that the one thousand realms are present in and manifest themselves in terms of the components of each beings, the sentient beings themselves as a whole, and the environments inhabited by them. The one thousand realms multiplied by the three categories brings the final total up to three thousand realms that are operative in every single thought-moment.

The single thought-moment is nothing other than each singular moment of conscious awareness that comprises the here and now of our life. Each moment of awareness contains all three thousand realms. The single thought-moment and the three thousand realms arise simultaneously. There is never a single moment of awareness without all the realms present within and all the realms are always united in a single moment of awareness. In support of this

1. The realm of the hell-dwellers is the lowest of the realms. Those who willfully commit the ten evil acts are reborn as hell-dwellers as the fruition of their deeds. Likewise, those who commit one of the five grave offences (killing one’s father, killing one’s mother, killing an arhat, injuring the Buddha, causing a schism in the Sangha) will immediately be reborn in the lowest hell in their next life. The hot hells and cold hells (perhaps for the passionately unrestrained and the cold-hearted respectively) are the abode of those so consumed with hatred, bitterness, and despair that their only wish is to destroy themselves and others out of spite and the desire to end their miserable existence.
2. The realm of the hungry ghosts is only slightly better. Those who commit the ten evil acts primarily motivated by selfish craving are reborn as hungry ghosts as the fruition of their deeds. Hungry ghosts are said to have large mouths and bellies, but only tiny throats. Hungry ghosts can never be satisfied and are consumed by craving. This is the state of those who suffer from addictions that control and dominate their lives. These addictions can be to drugs, alcohol, sex, gambling, power, work, entertainment, or even religion.
3. The realm of animals is the state of cunning, primitive aggression, and instinctive desires. Those who unthinkingly commit the ten evil acts are reborn as animals. It is a state of mind that does not look beyond immediate gratification and pays no heed to consequences or long-term benefit. Here, pleasure and pain reign supreme over reason amid the brute struggle for survival as the strong prey upon the weak. Though not as inherently painful as the two previous worlds, those who are in this state will inevitably meet with frustration and confusion, if not outright pain and suffering.
4. The realm of the fighting demons is the realm of arrogant demons who are obsessed with issues of status and power and whose ambition is to overthrow the gods of heaven. Those who follow the five precepts or even the five constant virtues (of Confucianism) but with ulterior motives and in a spirit of hypocrisy and self-righteousness are reborn as fighting demons. Those in this state are full of pride and arrogance and are extremely competitive and envious. They can never rest or feel secure because they must constantly strive to maintain and improve their position and prestige, no matter how well off they may actually be.
5. The realm of humanity is, of course, the realm we are most familiar with. Those who follow the five constant virtues or who take refuge in the Three Treasures (Buddha, Dharma, and Sangha) and follow the five precepts are able to be reborn as humans. In the human world, suffering is recognized for what it is, and morality and reason are called upon to improve the human condition. At this point, civilized life can truly begin. The human state is considered a very fortunate one, because the suffering and striving of the previous four realms does not overcome reason, nor is there the complacency brought about by the pleasures of the heavens. From this realm of humanity, one can find the opportunity to encounter the Three Treasures, take up the teachings, put them into practice, and attain liberation.
6. The realm of the heavenly beings is where the gods make their abode. Those who take refuge in the Three Treasures, follow the ten good acts, and give generously to worthy people and causes are able to be reborn in the heavens of desire. Those who follow the ten good acts and also go on to cultivate states of meditative absorption to overcome all inner disturbance and negativity are able to be reborn in the more refined heavens of form or formlessness, which correspond to the states of concentration they attained. The heavens are temporary (though long lasting) realms of spiritual bliss of increasing subtlety and refinement.
7. The realm of the śrāvakas is the first of the four noble states. Śrāvakas are those who hear the teachings of the Buddha, specifically the four noble truths, and put them into practice by becoming monks or nuns and taking up a life of strict discipline and rigorous contemplative practices in order to awaken to the fact that all conditioned things are ultimately unsatisfactory, impermanent, selfless, and empty of any fixed unchanging essence. This awakening is their attainment of nirvärpa. Nirväna, for them, is the elimination of the fetters of greed, hatred, and false views that bind them to rebirth among the six lower realms. Upon attaining nirvāṇa, śrāvakas are known as arhats (lit. worthy ones), who are worthy to receive offerings. Though this is called a realm, arhats do not exist in a separate realm apart from the world of humanity. Arhats are invariably human beings who attain nirvāṇa and upon their deaths (which is called final nirvāṇa) they are no longer to be found anywhere, much like a fire that has been extinguished.
8. The realm of the pratyekabuddhas is the second of the four noble states. Pratyekabuddhas are the ascetics and hermits who live in a time and place where Buddhism is unknown but attain liberation by contemplating causes and conditions and awakening to the unsatisfactory, impermanent, selfless, and empty nature of all conditioned phenomena. Unlike buddhas, they do not afterwards try to teach others how to awaken. Like the arhats they are invariably human beings who have eliminated greed, hatred, and false views. They too have realized nirvāṇa and are no longer bound to be reborn among the six lower realms. Sometimes pratyekabuddhas are not viewed as hermits who awaken on their own apart from Buddhism. Sometimes they are thought to be those Buddhist practitioners who live as forest-hermits and attain nirvāṇa by contemplating the twelve-fold chain of dependent origination taught by the Buddha to provide a deeper understanding of causes and conditions. In this case they are known as “cause-knowers” (J. engaku).
9. The realm of the bodhisattvas is the third of the four noble states. Bodhisattvas are those who aspire to attain buddhahood so that they too can lead all sentient beings to liberation. To do this they make vows, for instance the four great vows of the bodhisattva (to save all being, quench all defilements, know all the teachings, and attain the path to buddhahood), and take up the practice of the six perfections (of generosity, morality, patience, energy, meditative absorption, and wisdom). Bodhisattvas sometimes reside in the pure lands of the buddhas of the ten directions but can just as often be found taking rebirth among those in the six worlds in accordance with their vows so that they can help sentient beings, cultivate wisdom, and accrue the merit needed to attain buddhahood.
10. The realm of the buddhas is the fourth of the four noble states. Buddhahood is the state characterized by purity, bliss, eternity, and self (or authenticity). With perfect wisdom and great compassion, the buddhas spontaneously and unselfconsciously respond to the spiritual needs of all sentient beings. They reside in the pure lands but also appear in the world of humanity as a person who attains buddhahood, teaches the Dharma, and establishes the Sangha.

Each of these ten realms contains the causes and conditions of all ten within themselves. This means that any of the ten contains the potential to manifest any of the others. This is the mutual possession of the ten realms. One might say that the lower realms contain the higher realms as seeds of their future growth and maturity, while the higher realms embrace the lower realms insofar as they are perspectives that have been outgrown and yet assimilated. These are not ten separate realms lined up alongside each other, but rather ten different subjective modes of the interplay of causes and conditions. This means that if you change the causes and conditions you can also change the kind of realm that is or will be experienced. This also means that the realm of buddhahood is accessible to all the other realms and conversely the realm of buddhahood is able to compassionately interact with the lower realms.

As for the ten wonders of the Original Gate they involve the causes and effects of buddhahood from the perspective of the Eternal Buddha and are as follows:

1. The Wonder of Original Cause: The Eternal Buddha’s practice of the bodhisattva path occurred in the incalculably remote past and thereby puts the previous wonders of knowledges, practices, and stages of the Trace Gate in a timeless perspective.
2. The Wonder of Original Effect: Likewise the Eternal Buddha’s attainment of buddhahood occurred in the remote past, and thus the wonder of the threefold Dharma is put into this timeless perspective.
3. The Wonder of the Original Land: Since the time of the Eternal Buddha’s attainment of buddhahood in the remote past he has remained in this world of Endurance (Skt. sahā) teaching sentient beings. This world is, therefore, the true Pure Land of Eternally Tranquil Light of the Eternal Buddha.
4. The Wonder of Original Receptivity and Response: The wonder of receptivity and response is now shown to have begun in the remote past.
5. The Wonder of Original Supernatural Powers: The wonder of the Eternal Buddha’s use of supernatural powers is now shown to have begun in the remote past.
6. The Wonder of the Original Expounding of the Dharma: The wonder of the Eternal Buddha’s expounding of the Dharma is now shown to have begun in the remote past.
7. The Wonder of Original Attendants: The wonder of the Eternal Buddha’s relationship with sentient beings and fostering of bodhisattvas is now shown to have begun in the remote past.
8. The Wonder of the Original Nirvāṇa: This is the wonder of the Eternal Buddha’s actual abiding in nirvāṇa since the remote past, though he repeatedly displays the attainment of nirvāṇa with remainder (the extinction of greed, hatred, and delusion in life) and final nirvāṇa or nirvāṇa without remainder (physical extinction) in order to inspire sentient beings.
9. The Wonder of the Original Lifespan: This is the wonder of the Eternal Buddha’s unborn and deathless lifespan, though he takes on various transient lives in the world in order to teach, guide, and inspire sentient beings.
10. The Wonder of Original Benefits: The wonder of the Eternal Buddha’s merit and beneficial influence on sentient beings is now shown to have begun in the remote past.