In Brihadaranyaka Upanishad, Yagnavalkya tells us: ” The self-luminous being who dwells within the lotus of the heart, surrounded by the senses and the sense organs, and who is the light of the intellect, that is the Self. Becoming identified with the intellect, he moves to and fro, through birth and death, between this world and the next. Becoming identified with the intellect, the Self appears to be thinking, appears to be moving. While the mind is dreaming, the Self also appears to be dreaming, and to be beyond the next world as well as this.
When man, the individual soul is born, and assumes relationship with the body and the sense organs, he becomes associated with the evils of the world. When at death he gives up the body, he leaves all evils behind.”