The Eight Consciousnesses and the Alaya-Vijnana

Pre-Mahayana Abhidharma schools generally recognized six kinds of consciousness (vijnana): the five sense consciousnesses (visual, auditory, olfactory, gustatory, tactile) and a sixth, mano-vijnana, the mental consciousness that cognizes thoughts, memories, and mental objects and coordinates the data of the other five. Yogacara philosophy, most systematically in Vasubandhu's Trimsika and in Asanga's Mahayanasamgraha, adds two further layers beneath this sixth consciousness in order to explain phenomena the earlier sixfold scheme could not adequately account for: how karmic potential persists across the gaps of deep sleep, meditative absorption without any cognitive content, and even physical death and rebirth, and why an instinctive, pre-reflective sense of "I" persists even when no explicit conceptual thought about a self is occurring.