The consciousness-only theory holds that there are eight consciousnesses. These include the six consciousnesses discussed in abhidharma thought – eye, ear, nose, tongue, skin, and thinking consciousnesses – as well as the manas consciousness and the ālaya consciousness. The latter is seen as cittarājan, the basic essence of the mind. Ālaya means residence, storehouse, and container. The ālaya consciousness is also known as the “all seed consciousness,” “maturation consciousness,” “appropriating consciousness,” or “undefiled consciousness.” It dwells in and supports the body, with the results of past karma permeating it in the form of seeds. It is the basis from which the seven other consciousnesses arise, and the object of the seventh manas consciousness. Furthermore, it arises and perishes from moment to moment and is originally pure. It is certainly not a permanent self.

The manas consciousness, however, thinks that it is a self and becomes attached to the ālaya consciousness. In theory there is the possibility of āśrayaparāvṛtti, transforming the four bases of delusion into four bases of buddha-wisdom awakening. The ālaya consciousness turns into ādarśajñāna: great mirrorlike wisdom. The manas consciousness turns into samatājñāna: wisdom of equality. The thinking consciousness turns into pratyavekṣajñāna: wisdom of sublime investigation. And the first five consciousnesses turn into kṛtyānusthānajñāna: wisdom of accomplishing what is to be done.

The theory of three natures considers the existence of things from the perspective of the consciousness-only theory. The three natures are (1) parikalpitasvabhāva: the nature of existence produced by attachment to illusory discrimination, (2) paratantrasvabhāva: the nature of existence arising from causes and conditions, and (3) parinispannasvabhāva: the perfectly accomplished nature of existence. (1) refers to mistakenly understanding the objects in the discriminated world as actually existent and attaching to them as if they had an essence, despite their being illusory and originally non-existent. (2) expresses that all things exist in dependence on other things; nothing exists independently. (3) refers to the completed nature as truth. In other words, the suchness realized by awakening.

Already during the time of early Buddhism, people spoke of the dual structure of truth, namely, the mundane truth and the ultimate truth. Nāgārjuna, holding that “buddhas’ preaching relies on the two truths,” divided truth into the relative, conventional truth that comes into existence based on samvṛtisatya, the general linguistic practices of the world, and paramārthasatya, the absolute, ultimate truth that transcends these and is the object of non-discriminatory knowledge. He asserted that the former is for leading people to the latter. The ultimate truth is the Buddha’s awakened world of dependent origination which extinguishes these linguistic conceptual proliferations. In order to express it, one must rely upon worldly linguistic practices. Rather than placing weight on the ultimate truth, this two truths theory emphasizes the conventional truth: in order to express the world of awakening one must rely on the limited means of language. In other words, Nāgārjuna’s intention was to show that all existences in this conventional world are formed based on dependently arising relationships.

Tathāgatagarbha thought holds that all sentient beings have the possibility of becoming a tathāgata. It is also called “buddha-nature” thought. It began in the Tathāgatagarbha Sūtra, which teaches that “all sentient beings are the womb of the tathāgata,” and was also preached in the Śrimālādevi Sūtra, [Queen] Śrimālā Sūtra, the Anūnatvāpūrṇatvanirdeśaparivarta Sūtra, Neither Increase Nor Decrease Sūtra, and Mahāparinirvāṇa Sūtra, Great Nirvāṇa Sūtra. The tathāgatagarbha refers to the idea that sentient beings are held within the Tathāgata as fetuses and that they carry within themselves the Tathāgata as a fetus that is tathatā or suchness. This is said to be the cause of them becoming a tathāgata in the future. It is also seen as their innately pure mind, the basis of awakening that gives rise to bodhicitta, equal to the Dharma body of the Tathāgata, and unconditioned suchness.

With the evolution of Mahāyāna Buddhism, various theories about Śākyamuni Buddha’s body developed. When Śākyamuni passed away, a theory of two bodies emerged which saw the Dharma he preached as his essence. This was called the dharmakāya or Dharma-body and was distinguished from his rūpakāya or material body. After Mahāyāna Buddhism emerged, various buddhas became objects of worship, and the teaching of the three bodies appeared: (1) Dharma-body, which means the body of truth, referring to the eternal and unchanging Dharma, (2) transformation-body, nirmāṇakāya in Sanskrit, yìngshēn in Chinese, which appears in accordance with various sentient beings in order to save them, and (3) reward body, saṃbhogakāya in Sanskrit, bàoshēn in Chinese, which is endowed with perfect merit as recompense for engaging in virtuous practices that are the cause of becoming a buddha. Views of buddhas’ bodies developed even further and subsequently gave rise to many interpretations, such as the Yogācāra Consciousness-only school’s three bodies teaching: (1) Self-nature-body or svabhāvakāya in Sanskrit, (2) Enjoyment-body or saṃbhogakāya in Sanskrit and shòuyòng shen in Chinese, and (3) Transformation-body or nirmāṇakāya in Sanskrit and biànhuà shen in Chinese.

While it is believed that the Buddhism of the Mahāyāna, which means “great vehicle,” arose as a criticism of the Buddhism of the Hinayāna, which means “small vehicle,” careful judgment is needed regarding this matter. We do not clearly understand issues such as the background from which Mahāyāna Buddhism arose and whether or not an actual identifiable Hinayāna Buddhist organization existed. It is clear that Mahāyāna Buddhism criticizes those who seek practices only for self-improvement.

The term bodhisattva refers to a sentient being who seeks bodhi. It is a term that can be found in early Buddhist scriptures. There was also the notion that Śākyamuni appeared as the seventh of seven buddhas, after Vipaśyin, Śikhin, Viśvabhū, Krakucchanda, Kanakamuni, and Kāśyapa, and that there is a buddha in each buddha-land in the ten directions. This notion later developed into a view that multitudes of buddhas exist.

Along with this new view of Śākyamuni, various bodhisattvas who perform a variety of roles appeared in Mahāyāna Buddhism. They were significant as individuals who carried out practices for the benefit of others — one of Mahāyāna Buddhism’s distinguishing characteristics — rather than seeking enlightenment for themselves. In three vehicle thought, they were established as beings who reject the practices of śrāvakas and pratyekabuddhas of engaging in practices for self-improvement. Avalokiteśvara was characterized as a bodhisattva who saves sentient beings. Mañjuśrī a bodhisattva symbolizing wisdom. Maitreya is a future savior bodhisattva.

Bhaiśājyaguruvaiḍūryaprabhā is a remover of sentient beings’ illnesses. Kṣitigarbha is a bodhisattva who takes on the suffering of believers in the latter age of the Dharma. The bodhisattva ideal exerted a significant influence on sculptures and other Buddhist art.

Abhidharma thought also analyzes material units. For example, a paramāṇzu or particle is the smallest unit of matter, and a kṣaṇa, said to be 1/65th the length of a finger snap, is the smallest unit of time. A kalpa or eon is the longest unit of time. It is said to be half a day for Brahman and 4.32 billion years in the human world.

Beings … transmigrate through the four states of existence: life, death, intermediateness, and birth. The intermediate state is the time from when a being has finished one mode of existence until obtaining the next mode of existence, and it usually said to be 49 days. “Transmigration” is a translation of the Sanskrit word saṃsāra, which means “flowing” or “wandering.” Ancient Indian Upaniṣads held that after going through five processes that occur after cremation, one is either born as a human or goes to heaven. This was known as the “five fires and two paths” teaching. In contrast, Buddhism held that in these four states of existence one transmigrates between the six paths, the five destinies and the heavens.