Fifteen Upanishads 11 Brihadaranyaka

The Aitareya Upanishad (Sanskrit: ऐतरेय उपनिषद् IAST Aitareyopaniṣad) is a Mukhya Upanishad, associated with the Rigveda. It comprises the fourth, fifth and sixth chapters of the second book of Aitareya Aranyaka, which is one of the four layers of Rig vedic text.
Aitareya Upanishad discusses three philosophical themes: first, that the world and man is the creation of the Atman (Universal Self); second, the theory that the Atman undergoes threefold birth; third, that Consciousness is the essence of Atman.