Luminous mind

Luminous mind is a Buddhist term that appears only rarely in the Pali Canon, but is common in the Mahayana sūtras and central to the Buddhist tantras. It is variously translated as "brightly shining mind" or "mind of clear light", while the related term luminosity is also translated as "clear light" or "luminosity" in Tibetan Buddhist contexts or "purity" in East Asian contexts.
The Theravada school identifies the "luminous mind" with the bhavanga, a concept first proposed in the Theravāda Abhidhamma. The later schools of the Mahayana identify it with bodhicitta and tathagatagarbha. The luminosity of mind is of central importance in the philosophy and practice of the Buddhist tantras, Mahamudra, and Dzogchen.

Early Buddhist texts

The Early Buddhist Texts contain mentions of luminosity or radiance that refer to the development of the mind in meditation. In the Saṅgīti-sutta, for example, it relates to the attainment of samadhi, where the perception of light leads to a mind endowed with luminescence.
According to Anālayo, the Upakkilesa-sutta and its parallels mention that the presence of defilements "results in a loss of whatever inner light or luminescence had been experienced during meditation". The Pali Dhātuvibhaṅga-sutta uses the metaphor of refining gold to describe equanimity reached through meditation, which is said to be "pure, bright, soft, workable, and luminous". The Chinese parallel to this text does not describe equanimity as luminous. Anālayo sees this difference as due to the propensity of the reciters of the Theravada canon to prefer fire and light imagery.
The Pali Anguttara Nikaya states:

Luminous, monks, is the mind. And it is freed from incoming defilements. The well-instructed disciple of the noble ones discerns that as it actually is present, which is why I tell you that—for the well-instructed disciple of the noble ones—there is development of the mind.

A parallel passage can be found in the Śāriputrābhidharma, an Abhidharma treatise possibly of the Dharmaguptaka tradition.
Another mention of a similar term in the Pali discourses occurs in the Brahmanimantaṇika-sutta of the Majjhima-nikāya, and in the Kevaḍḍha-sutta of the Dīgha-nikāya, the latter has a parallel in a Dharmaguptaka collection surviving in Chinese translation.
The Brahmanimantaṇika-sutta describes an "invisible consciousness" that is "infinite" and "luminous in every way". There is disagreement among the various editions of the Pāli Canon as to whom the statement is spoken by, and in some editions it seems as if it is spoken not by the Buddha but by the deva Baka Brahmā in a debate with the Buddha. The Chinese parallel to the Brahmanimantaṇika-sutta has the term used by Baka Brahma.
The Kevaḍḍha-sutta and its parallel in the Dharmaguptaka Dīrgha-āgama, meanwhile, does have a statement spoken by the Buddha that mentions luminous consciousness. The Dīrgha-āgama sutra states:

Consciousness that is invisible, Infinite, and luminous of its own: This ceasing, the four elements cease, Coarse and subtle, pretty and ugly cease. Herein name-and-form cease. Consciousness ceasing, the remainder also ceases.

Analayo mentions that parallel recensions of this sutra in other languages such as Sanskrit and Tibetan do not mention luminosity and even the various Pali editions do not agree that this verse mentions luminosity, sometimes using pahaṃ instead of pabhaṃ. Whatever the case, according to Analayo, the passage refers to "the cessation mode of dependent arising, according to which name-and-form cease with the cessation of consciousness".
According to Bhikkhu Brahmāli, the references to luminosity in the Brahmanimantaṇika-sutta refer to states of samadhi known only to ariyas, while the pabhassaracitta of Anguttara Nikaya is a reference to the mind in jhana. He cites a common passage that notes that the mind with the five hindrances is not considered radiant and thus it makes sense to say that a mind in jhana, which does not have the five hindrances, can be said to be radiant:

So too, bhikkhus, there are these five corruptions of the mind, corrupted by which the mind is neither malleable nor wieldy nor radiant but brittle and not rightly concentrated for the destruction of the taints. What five? Sensual desire... ill will... sloth and torpor... restlessness and remorse... doubt is a corruption of the mind, corrupted by which the mind is neither malleable nor wieldy nor radiant but brittle and not rightly concentrated for the destruction of the taints..

Theravada

The Theravadin Anguttara Nikaya ''Atthakatha commentary identifies the luminous mind as the bhavanga, the "ground of becoming" or "latent dynamic continuum", the most fundamental level of mental functioning in the Theravada Abhidhammic scheme. The Kathavatthu also explains the luminous mind sutra passage as the bhavanga, which is the mind in its nature state and is described as luminous. This interpretation is also used by Buddhaghosa in his commentary on the Dhammasangani. Buddhaghosa also mentions that the mind is made luminous by the fourth jhana in his Visuddhimagga.
Thanissaro Bhikkhu holds that the commentaries' identification of the luminous mind with the bhavanga'' is problematic, but Peter Harvey finds it to be a plausible interpretation.
Ajahn Mun, the leading figure behind the modern Thai Forest Tradition, comments on this verse:
Thanissaro Bhikkhu sees the luminous mind as "the mind that the meditator is trying to develop. To perceive its luminosity means understanding that defilements such as greed, aversion, or delusion are not intrinsic to its nature, are not a necessary part of awareness." He associates the term with the simile used to describe the fourth jhana, which states:

Just as if a man were sitting covered from head to foot with a white cloth so that there would be no part of his body to which the white cloth did not extend; even so, the monk sits, permeating the body with a pure, bright awareness. There is nothing of his entire body unpervaded by pure, bright awareness.

Mahāsāṃghika

The Mahāsāṃghikas also held that the mind’s nature is fundamentally pure, but can be contaminated by adventitious defilements. Vasumitra's Nikayabheda-dharmamati-chakra-sastra discusses this theory, and cites the sutra passage the Mahāsāṃghikas drew on to defend it. This passage is quoted by Vasumitra as:

The self-nature of the mind is luminous. It is the adventitious impurities that defile it. The self substance of the mind is eternally pure.

K’ouei-ki's commentary on Vasumitra adds: "It is because afflictions are produced which soil it that it is said to be defiled. But these defilements, not being of the original nature of the mind, are called adventitious."
The Kathāvatthu'' also cites this idea as a thesis of the Andhakas.

Vaibhāṣika

In contrast, the Sarvāstivāda-Vaibhāṣika school held that the mind was not naturally luminous. According to Skorupski for Vaibhāṣika, the mind:

is initially or originally contaminated by defilements, and must be purified by abandoning defilements. For them a primordially luminous mind cannot be contaminated by adventitious defilements. If such a mind were contaminated by adventitious defilements, then these naturally impure defilements would become pure once they become associated with the naturally luminous mind. On the other hand, if adventitious defilements remained to be impure, then a naturally luminous mind would not become defiled by their presence. For them the constantly evolving mind is in possession of defilements.

Mahayana

In Sanskrit Mahayana texts and their translations, the term is a compound of the intensifying prefix pra-; the verbal root bhāsa, which means light, radiance or luminosity; and the modifier vara, which means "clear" or "the best of, the highest type". Jeffrey Hopkins's Tibetan-Sanskrit dictionary glosses the term compound as:

clear light; clearly luminous; transparently luminous; translucent; brightly shining; transparent lucidity; splendor; radiance; illumination; spread the light; lustre; come to hear; effulgence; brilliance.

Mahayana texts

generally affirm the mind's pure and luminous nature, adding that this is its natural condition. In the Pañcavimsati Prajñaparamita sutra, the prabhsvara-citta is interpreted thus:

This mind is no-mind, because its natural character is luminous. What is this state of the mind’s luminosity ? When the mind is neither associated with nor dissociated from greed, hatred, delusion, proclivities, fetters, or false views, then this constitutes its luminosity. Does the mind exist as no-mind? In the state of no-mind, the states of existence or non-existence can be neither found nor established... What is this state of no-mind? The state of no-mind, which is immutable and undifferentiated, constitutes the ultimate reality of all dharmas. Such is the state of no-mind.

A similar teaching appears in some recensions of the Aṣṭasāhasrikā ''Prajñāpāramitā Sūtra. Edward Conze considered the teaching on the "essential purity of the nature of mind" a central Mahayana teaching. According to Shi Huifeng, this term is not present in the earliest textual witness of the Aṣṭasāhasrikā, the Daoxing Banruo Jing, attributed to Lokaksema.
Mahayana texts like the Ratnagotravibhanga also associate prabhsvara with awakening and another term, natural or original purity of mind.
In some Mahayana treatises, natural purity is another term for Emptiness, Suchness and Dharmadhatu. Asanga's Mahayanasamgraha, for example, states:
The essential purity, i.e., the true nature, emptiness, the utmost point of reality, the signless, the absolute, the fundamental element.
The Bhadrapala-sutra'' states that the element of consciousness is pure and penetrates all things while not being affected by them, like the rays of the sun, even though it may appear defiled. This sutra states:

Furthermore, Bhadrapāla, the element of consciousness is completely purified; it encompasses everything, yet it is not tainted by anything.