The word ösalwa, often translated as luminous, is related to the word light in that it expresses some kind of brightness or clarity. However, the real meaning of this is not a light that is visible to the eye. Luminosity refers more to the capacity to know.… Hearing that mind is emptiness may lead us to believe that there is no mind. It sounds like we are a mindless piece of matter, which we are not. We are able to experience. Our natural cognizance is available at any moment. That is luminosity, which is not made out of anything whatsoever.
– Thrangu Rinpoche
from the book “Songs of Naropa: Commentaries on Songs of Realization”