Everything is satyam brahman

The next mantra presents that consciousness manifests in everything.

yataścodeti sūryo’stam yatra ca gacchati |

taṃ devāḥ sarve’rpitāstadu nātyeti kaścana |

etadvai tat ||2.1.9||

All gods are based on that from which the sun rises and in which (it) sets. Indeed,

nothing exceeds that. This is indeed that.

taṃ devāḥ sarve’rpitāḥ - all devatā are based on that (hiraṇyagarbha), and rely on it for existence. In what way each devatā rely on hiraṇyagarbha? Just take an example of sūrya devatā, yataścodeti sūryo’stam yatra ca gacchati - from which (hiraṇyagarbha) the sun rises and in which (hiraṇyagarbha) it sets.  The sūrya devatā (presiding deity of vision) appears at the beginning of creation and subsequently dissolves at pralaya into hiraṇyagarbha. There are infinite numbers of devatā because there are infinite faculties required for infinite number of functions. We could see them in the form of order. Indeed these orders include all 17 devatā / order which govern each organ of individual body. They emerge and dissolve back into hiraṇyagarbha, just like waves emerge and resolve back into ocean. This means that all orders are not different from hiraṇyagarbha itself, just as waves are not different from ocean.

tadu nātyeti kaścana - indeed, nothing exceeds that (hiraṇyagarbha). No one can exist beyond that hiraṇyagarbha just as no wave can exist outside the ocean. That hiraṇyagarbha is not different from the consciousness ātmā which is asked by naciketa - etadvai tat.

Next from mantra 5 to 9, is the conclusion, which shows the differences in all beings are only at the level of upādhi; in reality there is only one consciousness.

yadeveha tadamutra yadamutra tadanviha |

mṛtyoḥ sa mṛtyumāpnoti ya iha nāneva paśyati ||2.1.10||

That which is here alone is there. That which is there alone is here. One who sees

plurality here, as it were, goes from death to death.

yadeveha tadamutra - that which is here (the individual who endowed with micro upādhi) alone is there (Īśvara who endowed with macro upadhī). yadamutra tadanviha- that which is there (Īśvara upadhī) alone is here (appears as limited individual upādhi). There is only one consciousness manifested in the individual body (vyaṣṭi śarīram) as well as the macro universe (samaṣṭi parpañcam). Even though it appears small in the individual body and very big as the universe, smallness or bigness does not belong to the consciousness, but to the respective reflecting medium. Consciousness in Īśvara is the same as that in an ant. There is no question of higher or lower consciousness; everything is consciousness alone.

The one immerses in the name and form of a medium sees only plurality as it were - ya iha nāneva paśyati. Non-dual brahman appears many because being deluded by māyā-sakti on a total level. And on individual level, brahman is different from me because of avidyā.

Such a person goes from death to death - mṛtyoḥ sa mṛtyumāpnoti. He is not just trapped in the cycle of birth and death; his sense of insecurity and struggles will be endless. The insecurity will end only with the knowledge that I, the immortal consciousness am transacting through the mortal body. When I know that I am the consciousness, I know that everyone else is also consciousness. This is seeing one-ness in everything (advaita darśanam). There is plurality in the transactional world, but I know there is only one behind the plurality, which is consciousness - me.