One who can see the truth of the self through the eye of wisdom - jñānacakṣusaḥ is being explained next.
yatanto yoginaścainaṁ paśyantyātmanyavasthitam | yatanto’pyakṛtātmāno nainaṁ paśyantyacetasaḥ ||15.11||
The yogis, who are making effort, see this self obtaining in the buddhi. Those whose minds are not mature and who do not have viveka, do not see this (ātman) even if they are making effort.
Lord Krsna is using the word yogī here implies that people who can see one’s true nature is the one whose mind has been made tranquil by proper efforts - yatantaḥ, like eight limps of raja-yoga, karma-yoga or other values which have been talked about. These yogī with qualified mind, having done śravana, manana and nididhyāsana, recognise ātmā obtaining in the intellect - paśyantyātmanyavasthitam. It is not that they see ātmā in the intellect as an object, but they recognise directly without any interference of sense organs or thought. Every cognition is recognised directly as me. In the seventh chapter, we saw jñāna which is the knowledge of jagad-karana-brahman where the duality is still there. And vijñāna where I recognise I am that brahman alone, and that recognition doesn’t happened somewhere else, but in my intellect.
On the other hand, even some people make effort, they do not see - nainaṁ paśyanti. Because they are akṛtātmānah - not gaining proper antaḥ-karana-śuddhi - purity of the mind because being coloured by likes and dislikes, and acetasaḥ - lacking of viveka - discrimination power and enquiry. They can be gained by life of karma-yoga and cultivation of values. Since the nature of oneself is the same and śāstra as pramana is given yet some can see but not others. It is because prerequisite is needed, as in seeing, mere eyes are not enough but eyes that are free from defects are required.
The next four verses show that ātmā is the self of all - sarvātmā.
yadādityagataṁ tejo jagad bhāsayate’khilam | yaccandramasi yaccāgnau tattejo viddhi māmakam ||15.12||
May you know that the brilliance that obtains in the sun and illumines the entire world, that which is in the moon, and which is in the fire, belongs to me.
māmakam - that which belongs to me, any glory is Īśvara’s glory. A few of them, the basics of the creations, are shortly presented here. The brilliance that is in the sun and other luminaries like moon and fire which lights up the entire creation, is belong to Bhagavān. We can see the meaning in two ways. The light that you see in the sun is the light of Īśvara, because the sun etc are manifestation of Īśvara alone. Each one, according to its upādhi, manifests the glory of Parameśvara.
These words, āditya, candramas, and agni, can also be taken as referring to the presiding deities of the sun, moon and fire. The consciousness manifests in the form of deities called āditya, candramas and agni, because of which each one is capable of its own unique function, is not separate from Bhagavān. Īśvara from the standpoint of these phenomena is given these names.
Here we can see how un-objectified brahman manifested into objectified names and forms where the words illumine is used. That same light makes everything becomes evident, sustains the manifested world in the form of energy.
gāmāviśya ca bhūtāni dhārayāmyahamojasā | puṣṇāmi cauṣadhīssarvāḥ somo bhūtvā rasātmakaḥ ||15.13||
Having entered the earth, I sustain the beings with strength, and I nourish all the vegetation, having become soma in the form of (their) essence.
gāmāviśya - having entered the earth, means manifesting himself into the entire universe. Bhagavān sustains all beings by himself in the form of strength - dhārayāmyahamojasā by giving the sun light for vegetation, and the essence of those plants nourishing us. If Bhagavān is the food, are we not eating him? No, the eater is also Bhagavān.
ahaṁ vaiśvānaro bhūtvā prāṇināṁ dehamāśritaḥ | prāṇāpānasamāyuktaḥ pacāmyannaṁ caturvidham ||15.14||
Having become the digestive fire obtaining in the bodies of living beings, endowed with prāṇa and apāna, I digest the four-fold food.
Bhagavān in the form of vaiśvānaraḥ - digestive fire, that which obtaining in the physical body of the living beings - prāṇināṁ dehamāśritaḥ, and by which the food is digested, convert to energy to sustain life. To see it in the different angle, we can divide vital energy into five forms according to their function:
ENERGY RESPONSIBLE FOR
1. Prāna respiratory system
2. Apāna excretory system
3. Vyāna circulatory system
4. Samāna digestive system
5. Udāna evacuatory system
This fire digests four types of food - pacāmyannaṁ caturvidham consisting of what is drunk - bhojya; masticated - bhaksya; licked - lehya; and sucked - cosya. Since both the eater and the eaten are brahman himself, there is no different entity called doer and enjoyer who eat the food and to be eaten. It is only the food chain which is in the order of Bhagavān himself.