Ātmā enlivens the body

The indicator of that ātmā - the principle of life presents in the body is being told in the next mantra.

ūrdhvam prāṇamunnayatyapānam pratyagasyati |

madhye vāmanamāsīnam viśve devā upāsate ||2.2.3||

(Ātmā) lifts prāṇa upwards (and) draws apāna downwards. All presiding deities (of sense organs) worship (this) adorable one who resides in the middle (of the heart).

The body-mind-sense-complex is inert in nature. It is made up of five elements that

have no life-force of their own. Ātmā in the form of reflected consciousness lends sentiency to the gross body through the subtle body (reflected medium). What happens at the time of death? The subtle body, as the reflected medium, left the gross body; thus there is no more reflected consciousness in the body. But ātmā, the original consciousness, is very much there as the existence of the gross body.

What is the indicator that reflected consciousness is present in the body? Our breathing is the proof. The reflected consciousness draws prāṇan out of your lungs and throws it outside (exhalation) - ūrdhvam prāṇam unnayati. Then it draws apāna inward that goes downward into the lungs (inhalation) - apānam pratyag asyati. All the presiding deities of sense organs worship this ātmā who resides in the sanctum (the mind) - madhye vāmanam āsīnam viśve devā upāsate. Each sense organ offers different sense objects (sound, touch, form, taste and smell) to this reflected consciousness that resides in the mind. Ātmā doesn’t reside in the mind physically; it is recognised in the mind as “I”. It is like saying that Īśvara is in the temple, although Īśvara is all-pervading. All-pervading Īśvara is available for worship in the temple.

On the other hand, what is the indicator that ātmā is absent in the body?

asya visramsamānasya śarīrasthasya dehinaḥ |

dehād vimucyamānasya kimatra pariśiṣyate | etadvai tat ||2.2.4||

When this ātmā, which resides in the body, gets detached as it is freed from the

body, what remains in this (body)? This is indeed that.

When reflected consciousness departs from the body along with the subtle body, which is the reflected medium, what remains in the body? Only the gross insentient body remains. This consciousness that blesses the body is what naciketa wanted to know - etadvai tat.