There is a spiritual consciousness, the Manasic mind illumined by the light of Buddhi, that which subjectively perceives abstractions; and the sentient consciousness (the lower Manasic light), inseparable from our physical brain and senses. This latter consciousness is held in subjection by the brain and physical senses, and, being in its turn equally dependent on them, must of course fade out and finally die with the disappearance of the brain and physical senses. It is only the former kind of consciousness, whose root lies in eternity, which survives and lives for ever, and may, therefore, be regarded as immortal. Everything else belongs to passing illusions.
The Key to Theosophy p. 179 H.P. Blavatsky