Bhashya
अथाध्यात्मम्— यः प्राणे प्राणवायुसहिते घ्राणे, योवाचि, चक्षुषि, श्रोत्रे, मनसि, त्वचि, विज्ञाने, बुद्धौ,रेतसि प्रजनने ।कस्मात्पुनः कारणात् पृथिव्यादिदेवतामहाभागाः सत्यः मनुष्यादिवत् आत्मनि तिष्ठन्तम् आत्मनोनियन्तारमन्तर्यामिणं न विदुरित्यत आह— अदृष्टः नदृष्टो न विषयीभूतश्चक्षुर्दर्शनस्य कस्यचित्, स्वयं तु चक्षु-षि संनिहितत्वात् दृशिस्वरूप इति द्रष्टा ।तथा अश्रुतःश्रोत्रगोचरत्वमनापन्नः कस्यचित्, स्वयं तु अलुप्तश्रवणशक्तिःसर्वश्रोत्रेषु संनिहितत्वात् श्रोता ।तथा अमतः मनःसंक-ल्पविषयतामनापन्नः; दृष्टश्रुते एव हि सर्वः संकल्पयति;अदृष्टत्वात् अश्रुतत्वादेव अमतः; अलुप्तमननशक्तित्वात् सर्व-मनःसु संनिहितत्वाच्च मन्ता ।तथा अविज्ञातः निश्चयगो-चरतामनापन्नः रूपादिवत् सुखादिवद्वा, स्वयं तु अलुप्तवि-ज्ञानशक्तित्वात् तत्संनिधानाच्च विज्ञाता ।तत्र यं पृथिवीन वेद यं सर्वाणि भूतानि न विदुरिति च अन्ये नियन्त-व्या विज्ञातारः अन्यो नियन्ता अन्तर्यामीति प्राप्तम्;तदन्यत्वाशङ्कानिवृत्त्यर्थमुच्यते- नान्योऽतः- नान्यः-अतः अस्मात् अन्तर्यामिणः नान्योऽस्ति द्रष्टा; तथानान्योऽतोऽस्ति श्रोता; नान्योऽतोऽस्ति मन्ता; नान्योऽतोऽस्ति विज्ञाता ।यस्मात्परो नास्ति द्रष्टा श्रोता मन्ताविज्ञाता, यः अदृष्टो द्रष्टा, अश्रुतं श्रोता, अमतो मन्ता,अविज्ञातो विज्ञाता, अमृतः सर्वसंसारधर्मवर्जितः सर्वसंसा-रिणां कर्मफलविभागकर्ता- एष ते आत्मा अन्तर्याम्यमृतः;अस्मादीश्वरादात्मनोऽन्यत् आर्तम् ।ततो होद्दालक आ-रुणिरुपरराम ॥
In plain words
Now the same teaching, told through your own body. What was called 'the breath' is really the breath behind your sense of smell, in your nose. The same one is in your speech, your eye, your ear, your mind, your skin, your understanding -- your intellect -- and in the seed that makes new life. So why don't even the great powers, earth among them, real as they are, know the one who lives inside them and rules them from within, any more than an ordinary person knows him? Here is the answer. Unseen: no eye has ever caught him as its object. And yet he sits right behind every eye, and is the very act of seeing -- so he is the seer. Unheard: no ear has ever caught him. And yet his hearing never runs dry, and he sits inside every ear -- so he is the hearer. Unthought: you only ever think about what you've seen or heard, and since he is neither, he never becomes a thought. And yet his power to think never runs dry, and he is inside every mind -- so he is the thinker. Ununderstood: he is never pinned down the way a shape is, or a feeling is. And yet his understanding never fails, and it sits right beside him -- so he is the understander. Now, since the earth doesn't know him, and no being knows him, you might guess that the ones who perceive are one thing and the ruler within is something else entirely, a stranger. That guess is answered directly: there is no other. No other seer than this one. No other hearer. No other thinker. No other understander than this very ruler within. Since nothing anywhere sees, hears, thinks, or understands beyond him -- he who sees without being seen, hears without being heard, thinks without being thought, understands without being understood, who never dies, who carries none of the marks of this wandering existence, and who hands every being caught in it the exact fruit of its own actions -- this is your self, the ruler within, deathless. Everything except this Lord, this self, wears out and suffers. At that, Uddalaka, son of Aruna, fell silent.
Close to the Sanskrit
Now, as regards the individual self: he who [dwells] in the breath, that is, in the nose together with its vital air; who [dwells] in speech, in the eye, in the ear, in the mind, in the skin, in understanding, that is, in the intellect, in the seed, that is, in the organ of generation. For what reason, then, do the great and real deities beginning with the earth fail to know, just as a human being and the like fail to know, the one who dwells in the self and is the controller of the self, the inner ruler? To this it is said: unseen -- he is not seen, he does not become an object of anyone's sight; yet he himself, because he is present in the eye, is of the very nature of seeing -- thus he is the seer. Likewise, unheard -- he has not come within the range of anyone's hearing; yet he himself, whose power of hearing never fails, being present in every ear, is the hearer. Likewise, unthought -- he has not come within the range of the mind's conceiving; for everyone conceives only of what has been seen or heard; precisely because he is unseen and unheard, he is unthought; yet because his power of thinking never fails, and because he is present in every mind, he is the thinker. Likewise, ununderstood -- he has not come within the range of definite ascertainment, as form and the like are, or as pleasure and the like are; yet he himself, because his power of understanding never fails, and because of its nearness to him, is the understander. Here, since it is said 'whom the earth does not know' and 'whom all beings do not know', it might follow that the knowers to be controlled are one set of beings and the controller, the inner ruler, another. To remove this apprehension of his being a different being, it is said: no other than this -- that is, there is no other seer than this, than this inner ruler; likewise there is no other hearer than this; no other thinker than this; no other understander than this. Since there exists no seer, hearer, thinker, or understander beyond him -- he who, unseen, is the seer; unheard, is the hearer; unthought, is the thinker; ununderstood, is the understander; who is immortal, free of every characteristic of transmigratory existence, the apportioner of the fruits of action for all who transmigrate -- this is your self, the inner controller, the immortal. Other than this Lord, this self, everything is subject to affliction. Thereupon Uddalaka, son of Aruna, fell silent.