Bhashya
यद्वै सुषुप्ते तत् न पश्यति, पश्यन्वै तत् तत्र पश्यन्नेवन पश्यति ।यत् तत्र सुषुप्ते न पश्यतीति जानीषे, तत् नतथा गृह्णीयाः ; कस्मात् ? पश्यन्वै भवति तत्र ।ननु एवंन पश्यतीति सुषुप्ते जानीमः, यतः न चक्षुर्वा मनो वादर्शने करणं व्यापृतमस्ति ; व्यापृतेषु हि दर्शनश्रवणादिषु,पश्यतीति व्यवहारो भवति, शृणोतीति वा ; न चव्यापृतानि करणानि पश्यामः ; तस्मात् न पश्यत्येवअयम् ।न हि ; किं तर्हि पश्यन्नेव भवति ; कथम् ? न-हि यस्मात् द्रष्टुः दृष्टिकर्तुः या दृष्टिः, तस्या दृष्टेः विपरि-लोपः विनाशः, सः न विद्यते ।यथा अग्नेरौष्ण्यंयावदग्निभावि, तथा अयं च आत्मा द्रष्टा अविनाशी, अतःअविनाशित्वात् आत्मनो दृष्टिरपि अविनाशिनी, यावद्द्रष्टृ-भाविनी हि सा ।ननु विप्रतिषिद्धमिदमभिधीयते- द्रष्टुःसा दृष्टिः न विपरिलुप्यते इति च ; दृष्टिश्च द्रष्ट्रा क्रियते;दृष्टिकर्तृत्वात् हि द्रष्टेत्युच्यते ; क्रियमाणा च द्रष्ट्रा दृष्टिः नविपरिलुप्यत इति च अशक्यं वक्तुम् ; ननु न विपरिलु-प्यते इति वचनात् अविनाशिनी स्यात्, न, वचनस्य ज्ञाप-कत्वात् ; न हि न्यायप्राप्तो विनाशः कृतकस्य वचनशते-नापि वारयितुं शक्यते, वचनस्य यथाप्राप्तार्थज्ञापकत्वात् ।नैष दोषः, आदित्यादिप्रकाशकत्ववत् दर्शनोपपत्तेः ; यथाआदित्यादयः नित्यप्रकाशस्वभावा एव सन्तः स्वाभाविकेननित्येनैव प्रकाशेन प्रकाशयन्ति ; न हि अप्रकाशात्मानःसन्तः प्रकाशं कुर्वन्तः प्रकाशयन्तीत्युच्यन्ते, किं तर्हि स्व-भावेनैव नित्येन प्रकाशेन- तथा अयमपि आत्मा अविप-रिलुप्तस्वभावया दृष्ट्या नित्यया द्रष्टेत्युच्यते ।गौणं तर्हिद्रष्टृत्वम्, न, एवमेव मुख्यत्वोपपत्तेः ; यदि हि अन्यथापिआत्मनो द्रष्टृत्वं दृष्टम्, तदा अस्य द्रष्टृत्वस्य गौणत्वम् ; नतु आत्मनः अन्यो दर्शनप्रकारोऽस्ति ; तत् एवमेव मुख्यंद्रष्टृत्वमुपपद्यते, नान्यथा- यथा आदित्यादीनां प्रकाशयि-तृत्वं नित्येनैव स्वाभाविकेन अक्रियमाणेन प्रकाशेन, तदेव चप्रकाशयितृत्वं मुख्यम्, प्रकाशयितृत्वान्तरानुपपत्तेः ।तस्मात्न द्रष्टुः दृष्टिः विपरिलुप्यते इति न विप्रतिषेधगन्धोऽप्यस्ति ।
In plain words
When it says he doesn't see anything in deep sleep, here is what that actually means: he is still seeing the whole time — he simply isn't seeing any object. Don't read it the way it first sounds. Someone might object: we know he doesn't see in sleep, because neither the eye nor the mind is doing anything — we only say "he sees" or "he hears" when an organ is actually at work, and no organ is at work in sleep. But that's not right. He is seeing, always. Why? Because the seer's power to see cannot be lost — it can no more stop than fire's heat can stop while fire exists. The Self is the seer, and the Self cannot die; and because it cannot die, its seeing cannot die either — the two last exactly as long as each other. But wait, comes the objection: isn't that contradictory? You say vision is never lost, yet you also say the seer produces it — and how can something a person actively produces also be something that's never destroyed? And even if you just declare "it isn't lost," does saying so make it true? No — because words only reveal what's already the case, they don't create it, and no amount of insisting can save something genuinely made from its fate of ending. Here is the real answer: think of the sun. The sun doesn't first sit in darkness and then switch on a light — it simply is luminous, eternally, by its own nature. In exactly the same way, the Self isn't a blank that starts producing vision — seeing is simply what it eternally is, a nature that can never be lost. Someone might still object: doesn't that make "seer" a mere figure of speech? No — it's exactly the opposite. It's the primary meaning, because there is no other kind of seeing that could belong to the Self and make this one figurative by comparison. Just as the sun has no other, better way of shining that its everyday light merely imitates, the Self has no other, truer way of seeing behind this one. This is what seeing most fundamentally is. So there is no contradiction here — not even a trace of one.
Close to the Sanskrit
That which he does not see there in deep sleep—seeing, indeed, he then, even while seeing, does not see there. What you understand as "he does not see there in deep sleep", you should not take it that way; why? Because he is indeed seeing, there. Objection: We know in this way that he does not see in deep sleep, because neither the eye nor the mind is engaged as an instrument in seeing; for it is only when instruments such as sight and hearing are engaged that the usage "he sees" or "he hears" arises; and we do not observe any engaged instruments; therefore this one does not see at all. Not so; then what is the case? He is indeed [always] seeing. How? Because, of the seer, the producer of vision, whatever vision there is—of that vision there is no loss, no destruction; that does not exist. Just as the heat of fire lasts exactly as long as fire itself, so too this Self, the seer, is imperishable; therefore, because of that imperishability, the Self's vision too is imperishable, for it lasts exactly as long as the seer exists. Objection: This statement is self-contradictory—that the seer's vision is not lost, and yet vision is produced by the seer; for he is called "the seer" precisely because he produces vision; and it is impossible to say that a vision being produced by the seer is, at the same time, not lost. Well then, from the mere statement "it is not lost" would it become imperishable? No—because a statement only makes known [a fact], it does not produce it; for the destruction proper to anything produced cannot be averted even by a hundred statements, since a statement's function is only to reveal a fact exactly as it stands. This is no flaw, because seeing is established on the very footing of the sun's and similar bodies' power of illumination; just as the sun and the rest, having eternal light as their very nature, illumine by means of their own natural, ever-existing light—for they are not said to illumine by first being without light and then producing light, but rather by their very nature, through eternal light—so too this Self is called "the seer" by means of an eternal vision whose nature is never lost. Then would seer-hood be merely figurative? No—because it is on precisely this footing that its primary sense is established; for if the Self's seer-hood had been observed in some other way as well, then this seer-hood would be figurative; but there is no other mode of seeing belonging to the Self; therefore it is only in this way that seer-hood is established in its primary sense, not otherwise—just as the sun's and similar bodies' power of illumination consists in an eternal, natural light that is never produced, and that alone is the primary sense of "illuminator", since no other kind of illuminator-hood is ever established for them. Therefore, in saying that the seer's vision is not lost, there is not even the faintest whiff of contradiction.