The question that was put by Gārgi Vācaknavī pertained to the various realms of existence, the different worlds which succeed, one after another, in different degrees of density, the succeeding ones pervading the preceding ones and being larger in extent than them; ultimately, the highest pervading principle being regarded as Prajāpati Hiraṇyagarbha, beyond which there can be nothing conceivably more pervasive. Now this question of immanence of Reality is pursued further in a very important section of this Upaniṣhad which is called the Antāryamin Brāhmaṇa. This Brāhmana deals with the great subject 'Antāryamin', or the Supreme Immanent Principle. When Gārgi got down and occupied her seat and did not put any further questions, another sage, Uddālka of renown, Aruna's son, (Aruni), got up from his seat and picked up the discussion with Yājñavalkya.

1. atha hainam uddᾱlaka ᾱruṇiḥ papraccha: yᾱjñavalkya, iti hovᾱca madreṣv avasᾱma, patañcalasya kᾱpyasya gṛheṣu, yajñam adhīyᾱnᾱḥ. tasyᾱsīd bhᾱryᾱ gandharva-gṛhītᾱ, tam apṛcchᾱma, ko'sīti: so'bravīt, kabandha ᾱtharvaṇa iti. so'bravīt patañcalaṁ kᾱpyaṁ yᾱjñikᾱṁś ca; vettha nu tvam, kᾱpya, tat sῡtram yasminn (v: yena) ayaṁ ca lokaḥ, paraś ca lokaḥ, sarvᾱṇi ca bhῡtᾱni saṁdṛbdhᾱni, bhavantīti. so'bravīt patañcalaḥ kᾱpyam yᾱjñikᾱṁś ca. vettha nu tvam, kᾱpya, tam antaryᾱmiṇam, ya imaṁ ca lokam paraṁ ca lokam sarvᾱṇi ca bhῡtᾱni yo'ntaro yamayatīti. so'bravīt patañcalaḥ kᾱpyaḥ nᾱhaṁ tam, bhagavan, vedeti. so'bravīt patañcalaṁ kᾱpyaṁ yᾱjñikᾱṁś ca, yo vai tat, kᾱpya, sῡtraṁ vidyᾱt, taṁ cᾱntaryᾱmiṇam iti, sa brahma-vit, sa loka-vit, sa deva-vit, sa veda-vit, sa bhῡta-vit, sa ᾱtma-vit, sa sarva-vit, iti tebhyo'bravīt tad aham veda; tac cet tvam, yᾱjñavalkya, sῡtram avidvᾱms taṁ cᾱntaryᾱmiṇam brahmagavīr udajase, mῡrdhᾱ te vipatiṣyatīti. veda vᾱ aham, gautama, tat sῡtram taṁ cᾱntaryᾱmiṇam iti. yo vᾱ idaṁ kaś cid brῡyᾱt, veda vedeti: yathᾱ vettha, tathᾱ brῡhīti.

Atha hainam uddᾱlaka ᾱruṇiḥ papraccha: yᾱjñavalkya, iti hovᾱca: First Uddalaka tells the very same story that was mentioned earlier, in connection with a few disciples of Patañcala Kāpya, who went into the land of Madra and found the daughter of the owner of the house possessed by the Gandharva. Then he says: "We went to that place at night. Having moved to that place, for the purpose of study and performance of our rites, we found that the wife of Patañcala also was possessed by a Gandharva and was speaking something very strange." Madreṣv avasᾱma, patañcalasya kᾱpyasya gṛheṣu, yajñam adhīyᾱnᾱḥ. tasyᾱsīd bhᾱryᾱ gandharva-gṛhītᾱ, tam apṛcchᾱma, ko'sīti: "We asked that spirit, 'Who are you?' The spirit that was speaking through the personality of the wife of Patañcala Kāpya answered. So'bravīt, kabandha ᾱtharvaṇa iti: 'My name is Kabandha, coming as a descendant in the line of Ātharvaṇa.' So'bravīt patañcalaṁ kᾱpyaṁ yᾱjñikᾱṁś ca: It further continued speaking of its own accord without being queried by us. That Gandharva, the spirit, spoke to the owner of the house, the master of the house, Patañcala and to us. We were all present there. And while he spoke, he put a question to us. That Gandharva himself put a question. He asked our master, Vettha nu tvam, kᾱpya, tat sῡtram: 'O great one who comes as a seer in the line of the sage Kāpya;' Yasminn (v: yena) ayaṁ ca lokaḥ, paraś ca lokaḥ, sarvᾱṇi ca bhῡtᾱni saṁdṛbdhᾱni, bhavantīti: 'Do you know the thread in which are strung, as if they are beads, all these worlds, and this world as well as the other worlds, and everything that is created?' All the worlds, all beings, are strung in a thread. 'What is this thread? Do you know this thread?' was the question. How can there be a thread which can contain, or hold together, all the worlds and all the beings? So'bravīt patañcalaḥ kᾱpyaḥ nᾱhaṁ tam, bhagavan, vedeti: Then that Master Patañcala said: 'I do not know this Sūtra. This thread that you are speaking of, I am not aware of what it is about.' So'bravīt patañcalaḥ kᾱpyam yᾱjñikᾱṁś ca. vettha nu tvam, kᾱpya, tam antaryᾱmiṇam: 'Well, you do not know the thread. But do you know that Immanent Principle, the Antāryamin?' 'What sort of immanent principle you are speaking of?' Ya imaṁ ca lokam paraṁ ca lokam sarvᾱṇi ca bhῡtᾱni yo'ntaro yamayatīti: 'I am speaking of that immanent Being, which controls internally, without being known to anyone, everything that is outside.' This world and other worlds and all beings are regulated, restrained and controlled by something, internally, which is not known to anyone. Its existence is not known to anyone, and yet it controls everyone. 'Do you know that Immanent Principle?' That was another question which that Gandharva put to us when we were in that house. So'bravīt patañcalaḥ kᾱpyaḥ nᾱhaṁ tam, bhagavan, vedeti: The same reply was given by us. "We cannot understand what this Immanent Principle means. We have never seen such a thing nor heard about it.' So'bravīt patañcalaṁ kᾱpyaṁ yᾱjñikᾱṁś ca: Then he told us: 'You people do not know either of these things. You do not know that thread in which everything is strung, nor do you know this Immanent Principle which controls everything from within. But the one who has this knowledge (of this Sūtra, or the thread, and that Immanent Principle), he alone can be regarded as a knower of Truth, and nobody else.' 'Who is the knower of Reality?' 'That person who has comprehended this Immanent Principle and knows this thread in which everything is strung, that person can be regarded as a knower of Reality. He is a knower of Brahman - sa brahma-vit. And he is a knower of all the worlds at one stroke - sa loka-vit. He is a knower of all the gods, the celestials, at the same time - sa deva-vit. He is the knower of the content of every Veda. He is a real knower of the Veda - sa veda-vit. He is the knower of the inner structure of every created being at the same time - sa bhūta-vit. And he is the knower of the Self of everything - sa ātmā-vit. Well; in short, he is the knower of everything - sa sarva-vit. sa brahma-vit, sa loka-vit, sa deva-vit, sa veda-vit, sa bhūta-vit, sa ātmā-vit, sa sarva-vit: Such a person, alone, can be regarded as all-knowing.' 'What person?' 'The one who knows the Immanent Principle and the thread in which all the worlds are strung together.'"

Tebhyo'bravīt tad aham veda; tac cet tvam, yᾱjñavalkya, sῡtram avidvᾱms taṁ cᾱntaryᾱmiṇam brahmagavīr udajase, mῡrdhᾱ te vipatiṣyatīti: Now Uddālaka tells Yājñavalkya: "Yājñavalkya! We were told by this Gandharva what this thread was because we did not know about it. He explained it all. We also learnt the nature of the Immanent Principle from this very Gandharva. That is how I know both these things. I know the thread; I know the Immanent Principle. Now, do you know also? Yājñavalkya, I put this question. Without knowing the answer to this question that I put to you, if you drive these cows home, your head will fall." This, he tells Yājñavalkya himself.

Yājñavalkya replies: "Why do you speak like this? I know what you are speaking about. Veda vᾱ aham, gautama, tat sῡtram taṁ cᾱntaryᾱmiṇam iti: Gautama (that is Uddālaka), I know this thread and the Immanent Principle."

Then Uddālaka says: "What is the use of merely saying 'I know'? Anybody can say 'I know, I know'. Tell me what you know. What is it that you know? Yo vᾱ idaṁ kaś cid brῡyᾱt, veda vedeti yathᾱ vettha, tathᾱ brῡhīti: As you know, you let me know what it is that you know."

Yājñavalkya's reply to this question is the famous Antāryamin Brāhmaṇa.

2. sa hovᾱca vᾱyur vai, gautama, tat sῡtram; vᾱyunᾱ vai, gautama, sῡtreṇᾱyaṁ ca lokaḥ paraś ca lokaḥ sarvᾱṇi ca bhῡtᾱni saṁdṛbdhᾱni bhavanti, tasmᾱd vai, gautama, puruṣam pretam ᾱhuḥ vyasraṁsiṣatᾱsyᾱṅgᾱnīti; vᾱyunᾱ hi, gautama, sῡtreṇa  saṁdṛbdhᾱni bhavantīti. evam etat, yᾱjñavalkya, antaryᾱmiṇaṁ brῡhīti.

Sa hovᾱca vᾱyur vai, gautama, tat sῡtram; vᾱyunᾱ vai, gautama, sῡtreṇᾱyaṁ ca lokaḥ paraś ca lokaḥ sarvᾱṇi ca bhῡtᾱni saṁdṛbdhᾱni bhavanti: "O Gautama (Āruni Uddālaka); the Supreme Vital Force of the cosmos can be regarded as the thread on which everything is strung, because all bodies, whatever be their structure, are formed in the mould of this Vital Energy. It is this Vital Force of the cosmos that has taken the shape of all these forms, whether they are the forms of the world or are the forms of individual beings. Outside, the very same Energy looks like the world, and inside, as a content thereof, it looks like individuals. It is the subtle constitutive Essence of the whole universe. It cannot be designated by any other name than an ethereal Being, like 'Vāyu', wind, air." And these days, you may say, it is something like electricity, something subtler than that, Prāṇa, Vital Energy. What other word can you use to designate it, or call it? That universal Vital Force is the thread. It is a thread in the sense that it is the power which holds all bodies in proper positions. And every body, individual or otherwise, is strung on this thread in the sense that everything is a form taken by it, and therefore, controlled by it. So, you will not find a place where this is not, and you will not find anything operating unless it Wills. It is His Will and His Action that appears outside as the action of people.

Tasmᾱd vai, gautama, puruṣam pretam ᾱhuḥ vyasraṁsiṣatᾱsyᾱṅgᾱnīti; vᾱyunᾱ hi, gautama, sῡtreṇa  saṁdṛbdhᾱni bhavantīti. evam etat, yᾱjñavalkya, antaryᾱmiṇaṁ brῡhīti: When a person is alive, why does that person look whole and complete and integrated? And why is it that when something happens at the time we call death, there is dismemberment of the body and parts of the body get dislocated and hang loosely without being held firmly? What is the cause? The cause is that this Vital Force was holding the limbs of the body in unison and harmony when the body was alive. What we call life is nothing but the operation of this universal Energy through a particular body. When the particular function through this individual body does not take place, the Energy withdraws itself. There is then no sustaining power left in the building-bricks of the body. So the bricks collapse. There is, therefore, the return of the constituents of the physical body to their sources. They cannot be held in the form which they were assuming when the body was alive. So the body of an individual is nothing but a form assumed, or taken by certain elements. And it begins to function by the action of this Vital Energy. When this action of the Vital Energy is withdrawn, it is called death, or demise of the individual. So, we say that the parts of the body of a dead person get loosened and they are not able to perform the functions that they were doing earlier, merely because this principle is absent.

That, is the thread which controls everything, individual or cosmic. "Well," Uddālaka says, "yes! I have to admit that it is very right. This is the thread in which the worlds and the individuals are strung together. This answer is very correct. I appreciate your reply to my query, but now, what about the Immanent Principle? What is that Immanent Principle? Answer that. Let me hear from you, what it is."

The Immanent Principle is the Antaryāmin, the one that controls everything from within. It is a very peculiar something, whose existence cannot be known for reasons which will be obvious, as we go further. Yet, nothing can be more powerful than that. That which is most powerful and capable of controlling everything is that which cannot be observed by anything, or seen or known. What is that? That is what we call the internal Reality of the cosmos. That we call the Antaryāmin, the Immanent Reality.

3. yaḥ prthivyᾱṁ tiṣṭhan pṛthivyᾱ antaraḥ, yam pṛthivī na veda, yasya pṛthivī śarīram, yaḥ pṛthivīm antaro yamayati, eṣa ta ᾱtmᾱntaryᾱmy amṛtaḥ.

Yaḥ prthivyᾱṁ tiṣṭhan pṛthivyᾱ antaraḥ: That principle is inside this very earth, internal to the earth. Outside is the body of the earth, but inside is this principle which holds the earth in unison as a compact completeness. But the earth does not know its existence - yam pṛthivī na veda. The earth and anyone on it cannot know that the principle exists even though it is the cause of the very existence of the earth. Yasya pṛthivī śarīram: The whole earth is the body of this principle, as it were. The principle is embodied in the form of this earth. Yaḥ pṛthivīm antaro yamayati: Internally seated in the very heart of the earth is this principle working. Eṣa ta ᾱtmᾱntaryᾱmy amṛtaḥ: This is your own Self. It is the immortal Being. This Ātman, which is your own Ātman, which is your own Self, is the internal Ruler, the principle that controls all things. And it is the only thing that can be called immortal. Everything else is mortal. Everything moves around it, as a wheel moves round the hub. The hub does not revolve with the wheel. Even so, everything resolves as if mounted on a machine, but this does not revolve. When everything is active, this is not active. When everything is restless, this is full of rest. When everything is visible as an object, this is not seen by anybody. When everything is transient, this is permanent. While everything has a goal to reach, this itself is the goal of everyone. Such is the Immanent Being. This is the Antaryāmin, or the internal ruler of everyone - earth, water, fire, air, ether; everything that is external everything that is internal also, like the physical organs, etc.