Brahman as the Inner Self — Antaryamin
Brahman as Antaryamin (the inner controller) is the teaching of the Brihadaranyaka Upanishad that the ultimate reality dwells as the innermost self of all beings, controlling all from within.
The Brihadaranyaka Upanishad's Antaryamin Brahmana (3.7) describes Brahman as the Antaryamin — the inner ruler, the one who controls all things from within without being seen, known, or comprehended by those it controls. Brahman dwells within the earth controlling it; within water controlling it; within fire, air, sky, space, sun, directions, moon, stars, space, darkness, light, mind, intellect, ego, and the individual soul — controlling all from within. The teaching is that the same reality that is the transcendent ground of all existence is simultaneously the immanent presence within every being and every phenomenon. Nothing exists independently of Brahman's sustaining presence; everything is continuously dependent on Brahman as a wave is dependent on the ocean. This dual aspect — transcendent and immanent — is captured in the Isha Upanishad's teaching: 'That moves, and That moves not; That is far, and That is near; That is within all this, and That is outside all this.'
He who dwells in the earth, yet is within the earth, whom the earth does not know, whose body is the earth, who controls the earth from within — He is the Antaryamin, the immortal Self.
Philosopher Michael Polanyi's concept of 'tacit knowledge' — the dimension of all knowledge that is not explicit or articulable but that makes all explicit knowledge possible — provides a parallel to Antaryamin: the inner controller that is never directly known but without which nothing could be known.
Brihadaranyaka Upanishad