Chandogya Upanishad Ch-8.7

and the Bhagavadgita. Among the ten major Upanishads, the Chandogya and the Brihadaranyaka stand above the rest in their grand stature and majesty, these two texts being viewed by scholars as representing the cosmic and the a-cosmic aspect of Reality. The Chandogya, tries to be more realistic in its rather matter-of-fact consideration of the issues of life.The sections of the Chandogya Upanishad, is a study of a gradational ascent of knowledge for the purpose of meditations which lift us above the phenomena of ordinary experience, such as birth and death and bondage of every kind, and point to the methods of transcending all sorrow, whatever be its nature, and regaining the originality of being. The various sections that follow are a systematic teaching on what we may call Adhyatma-Vidya, or Atma-Vidya, a knowledge of the ultimate Self, which is the only remedy for the malady of empirical existence. The sections 8.7 through 8.12 of the Chandogya Upanishad return to the question, "what is true Self, and what is not"? The opening passage declares Self as the one that is eternally free of grief, suffering and death; it is happy, serene being that desires, feels and thinks what it ought to. Thereafter, the text structures its analysis of true and false Atman as four answers. The three Self, which are false Self, asserts the text are the material body corporeal self in dreams, individual self in deep sleep, while the fourth is the true Self – the self in beyond deep sleep state that is one with others and the entire universe. This theory is also known as the "four states of consciousness", explained as the awake state, dream-filled sleep state, deep sleep state, and beyond deep sleep state