Luminous mind (also, "brightly shining mind," "brightly shining citta") (Sanskrit prakṛti-prabhāsvara-citta,Pali pabhassara citta) is a term attributed to the Buddha in the Nikayas. The mind (Citta) is said to be "luminous" whether or not it is tainted by mental defilements.
The statement is given no direct doctrinal explanation in the Pali discourses, but later Buddhist schools explained it using various concepts developed by them. The Theravada school identifies the "luminous mind" with the bhavanga, a concept first proposed in the Theravada Abhidhamma. The later schools of the Mahayana identify it with both the Mahayana concepts of bodhicitta and tathagatagarbha. The idea is also connected with features of Dzogchen thought.
In the Anguttara Nikaya (A.I.8-10) the Buddha states: "Luminous, monks, is the mind. And it is defiled by incoming defilements." The discourses indicate that the mind's natural radiance can be made manifest by meditation.
Ajahn Mun, the leading figure behind the modern Thai Forest Tradition, comments on this verse:
The mind is something more radiant than anything else can be, but because counterfeits – passing defilements – come and obscure it, it loses its radiance, like the sun when obscured by clouds. Don’t go thinking that the sun goes after the clouds. Instead, the clouds come drifting along and obscure the sun. So meditators, when they know in this manner, should do away with these counterfeits by analyzing them shrewdly... When they develop the mind to the stage of the primal mind, this will mean that all counterfeits are destroyed, or rather, counterfeit things won’t be able to reach into the primal mind, because the bridge making the connection will have been destroyed. Even though the mind may then still have to come into contact with the preoccupations of the world, its contact will be like that of a bead of water rolling over a lotus leaf.