This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Aitareya Upanishad tells an unusual creation story, and it is worth reading closely because its odd details are doing philosophical work. The self alone exists at first, and out of a wish for worlds it brings forth the sky, the waters, death and the further regions, along with deities to preside over each. Those deities, however, once created, find themselves with nowhere to act: they are offered a body, the human form, but cannot find their proper places in it until each enters through one of its openings, fire becoming speech through the mouth, wind becoming breath through the nostrils, the sun becoming sight through the eyes, and so on through the whole array of the senses.
That image, deities settling into a body through its sense organs, sets up the text's real interest, which is not cosmology for its own sake but the question of what actually does the seeing, hearing and thinking once those deities are in place. The second chapter briefly turns to a person's three births, as a child conceived, as a child born and as the self's persistence through offspring after death, before the text arrives at the passage it is really building toward.
In the third and final chapter, the sage Vamadeva teaches that the self a person knows through eating, seeing, speaking and thinking is not one more inhabitant of the body among the deities already listed, it is Brahman itself, the same undivided reality that underlies the whole created world. The text names this consciousness the eye of all things, its firm foundation, and closes with the declaration prajnanam brahma, "consciousness is Brahman," a formula the later Vedanta tradition singled out as one of its four great sayings, the moment several of the darkest Upanishads converge on the same claim from different directions.