The Aitareya Upaniṣad (ऐतरेयोपनिषद्) belongs to the Rigveda, attached to the Aitareya Āraṇyaka. Brief but cosmologically expansive, it consists of three short chapters that together trace the trajectory of the self from cosmic creation through embryonic development to the climactic Vedantic recognition of consciousness as brahman. Its third chapter contains one of the four classical mahāvākyas — prajñānaṃ brahma, "consciousness is brahman" — by which the Rigveda is represented in the canonical list of great utterances.
Chapter One — The Creation
The Upanishad opens with cosmogony:
आत्मा वा इदमेक एवाग्र आसीत् । नान्यत्किञ्चन मिषत् । स ईक्षत लोकान्नु सृजा इति ।
ātmā vā idam eka evāgra āsīt, nānyat kiñcana miṣat
sa īkṣata lokān nu sṛjā iti
"In the beginning, this was ātman alone — one only — and nothing else moved. He reflected: let me create the worlds."
The opening is striking. Where the Rigvedic Nāsadīya hymn refuses to name a creator, the begins with a fully personal ātman, an "I" that is conscious, reflective, and intends creation. From this self the worlds emerge in order — the heavenly waters above, the atmosphere, the earth below, and the underworld waters.
The chapter then describes the creation of a cosmic person and the gods. The ātman summons forth a Person from the waters and then "warms him." From the Person's mouth comes speech, from speech Agni; from the nostrils comes breath, from breath Vayu; from the eyes sight, from sight the Sun; from the ears hearing, from hearing the Quarters; from the skin hair, from hair the plants; from the heart the mind, from the mind the Moon; from the navel the down-breath, from the down-breath Mṛtyu; from the procreative organ semen, from semen the Waters.
The pattern is one of nested correspondence: every cosmic deity has its origin in a faculty of the cosmic Person, and every faculty of the human being is therefore a microcosmic reflection of that primordial generation.
Chapter Two — The Three Births
The second chapter shifts dramatically from cosmogony to embryology and presents what is perhaps the earliest analytical account of birth in Indian literature.
The Upanishad asserts that a human being is born three times.
- The first birth occurs when, as semen, he is contributed by his father — already at this point he is, in essence, the father's own self.
- The second birth occurs from the mother's womb, into the world of light.
- The third birth — and the chapter is emphatic that this is the decisive one — occurs at death, when the inner self leaves the body and is reborn into the next existence.
The teaching anticipates much of the later doctrine of karma and saṃsāra and grounds it in a careful analysis: the self is not made at conception but passes through bodies. The verse explicitly cites the Rigvedic seer Vāmadeva, who is said to have realized while still in the womb that he had passed through many previous births.
Chapter Three — Brahma
The third chapter — almost a separate Upanishad — is brief and philosophically climactic. It opens with a question: Who is the self that we worship?
The text replies by enumerating cognitive capacities: sense-perception, judgment, intelligence, insight, mindfulness, vision, steadiness, thought, wisdom, courage, memory, conception, intention, breath, desire, will. All these, says the Upanishad, are aspects of one principle — and that principle is the self.
The chapter closes with the celebrated mahāvākya:
प्रज्ञानं ब्रह्म ।
prajñānaṃ brahma "Consciousness is brahman."
The phrase is the Upanishad's final declaration. Brahman is not a remote cosmic principle separate from human knowing; it is the very prajñāna, the cognitive principle, by which we know anything at all. Every act of consciousness is brahman in act. To know oneself as consciousness is to know oneself as brahman.
Significance
The Aitareya's compressed range — cosmogony, embryology, mahāvākya — has made it one of the most quoted of the short Upanishads. The opening verse on the ātman alone before creation underlies all later theistic Vedanta. The doctrine of three births undergirds the orthodox understanding of saṃskāra (the life-cycle rites) and śrāddha (the ancestor rites). The closing mahāvākya is one of the four assigned to the four Vedas in the systematic Vedanta of the Upadeshasahasri and later texts. Through these three short chapters the Rigvedic tradition reaches forward, in a single arc, from the first creative thought of the self to the realization that the seeker, knowing, is that very self.