Bhashya
अथ अवतिष्ठेत, क्षणिकवादहानिः; अथ अदृष्टवतो व्यप-देशः सादृश्यप्रत्ययश्च, तदानीं जात्यन्धस्येव रूपविशेषव्यप-देशः तत्सादृश्यप्रत्ययश्च सर्वमन्धपरम्परेति प्रसज्येत सर्व-ज्ञशास्त्रप्रणयनादि; न चैतदिष्यते ।अकृताभ्यागमकृतविप्र-णाशदोषौ तु प्रसिद्धतरौ क्षणवादे ।दृष्टव्यपदेशहेतुः पूर्वो-त्तरसहित एक एव हि शृङ्खलावत् प्रत्ययो जायत इति चेत्,तेनेदं सदृशमिति च- न, वर्तमानातीतयोः भिन्नकालत्वा-त्-तत्र वर्तमानप्रत्यय एकः शृङ्खलावयवस्थानीयः, अतीत-श्चापरः, तौ प्रत्ययौ भिन्नकालौ; तदुभयप्रत्ययविषयस्पृक्चेत् शृङ्खलाप्रत्ययः, ततः क्षणद्वयव्यापित्वादेकस्य विज्ञानस्यपुनः क्षणवादहानिः ।ममतवतादिविशेषानुपपत्तेश्च सर्वसं-व्यवहारलोपप्रसङ्गः ॥सर्वस्य च स्वसंवेद्यविज्ञानमात्रत्वे, विज्ञानस्य च स्वच्छा-वबोधावभासमात्रस्वाभाव्याभ्युपगमात्, तद्दर्शिनश्चान्यस्या-भावे, अनित्यदुःखशून्यानात्मत्वाद्यने ककल्पनानुपपत्तिः ।नच दाडिमादेरिव विरुद्धानेकांशवत्त्वं विज्ञानस्य, स्वच्छा-वभासस्वाभाव्याद्विज्ञानस्य ।अनित्यदुःखादीनां विज्ञानांशत्वेच सति अनुभूयमानत्वात् व्यतिरिक्तविषयत्वप्रसङ्गः ।अथअनित्यदुःखाद्यात्मकमेकत्वमेव विज्ञानस्य, तदा तद्वियोगात् वि-शुद्धिकल्पनानुपपत्तिः; संयोगिमलवियोगाद्धि विशुद्धिर्भवति,
In plain words
Suppose that earlier moment of awareness lingered on into this one -- then the whole doctrine that everything lasts only an instant falls apart on the spot. Suppose instead it doesn't linger -- then whoever is aware right now never actually witnessed the earlier thing, and yet turns around and calls it familiar, calls it similar. That is exactly the position of a man born blind, describing a color he has never once seen: pure hearsay, passed down an endless relay of blind men with nothing behind it -- which would turn even the scriptures of an omniscient teacher into just another rumor nobody ever verified. No one who holds this view actually accepts that consequence. And momentariness carries defects far more notorious than this one: it makes someone reap the fruit of a deed he never performed, and it makes the doer's own deed vanish without ever bearing fruit. Someone may object: what gives you the sense of 'seen before' is that a single cognition arises bound to what came just before and just after, like the links of a chain -- that is why you feel 'this matches that.' It doesn't work. The present cognition and the past cognition happen at different times; the present one is only one link, the past one another, and two cognitions occupying two different moments remain two different moments. And if you now say a further, chain-like cognition reaches across and touches the content of both, then one single awareness is spanning two separate moments -- and momentariness has collapsed all over again. Since something as basic as the felt sense 'this is mine' can never be explained this way either, the whole of ordinary life falls apart along with it. There is a second failure, in the claim that everything is only consciousness, known solely to itself. If consciousness is nothing but clear, self-luminous awareness, with no one else ever watching it from outside, you cannot honestly say of it: this part is impermanent, this part is suffering, this part is empty, this part is not the self. That would make consciousness lumpy, built of clashing pieces, like the sections of a pomegranate -- yet you have already said its very nature is clear luminosity straight through, nothing else. And if impermanence and suffering really were pieces of it, then the instant you experience them, they stand apart from it as objects -- which is exactly what your own position denies. Say instead that impermanence and suffering are not pieces but consciousness's own single identity. Then freedom can never truly be called 'getting free of them' -- because you only earn the word purification when what falls away was a stain that arrived from outside. Nothing is purified by losing the very self it always was.
Close to the Sanskrit
Now, if the earlier cognition were to persist, the doctrine of momentariness would have to be abandoned; or, if it does not persist, there would be a designation of something not seen and a cognition of similarity made [by the one who never saw it] — in which case, exactly as with a man blind from birth, there would be a designation of a particular color and a cognition of similarity regarding it, so that it would follow that the whole thing is a succession of blind men, [and] the very composing of scripture by the omniscient one and the like [would likewise be groundless]; and this is not accepted. But the two defects — the arrival of a result upon one who did not act, and the utter loss of what was done — are far better known in the doctrine of momentariness. If it is argued that the cause of the designation 'seen' is that a single cognition alone arises together with the prior and the subsequent, like a chain, and hence 'this is similar to that' — no. Because the present and the past cognitions occur at different times: there the present cognition is one, standing in the place of a link of the chain, and the past one is another; those two cognitions belong to different times. If the chain-cognition touches the object of both those cognitions, then, because a single consciousness would thereby pervade two moments, the doctrine of momentariness collapses once again. And because a particular such as the sense of 'mine' cannot be accounted for, it follows that all worldly dealing would be lost. And when everything is held to be nothing but self-cognized consciousness, and it is admitted that consciousness has as its nature nothing but clear awareness and appearance, there being no other seer of it apart from itself, the positing of the many [predicates] such as impermanence, suffering, emptiness, selflessness, and so on becomes untenable. Nor does consciousness have a multiplicity of mutually opposed parts, like a pomegranate and the like, since consciousness has as its nature only clear appearance. And if impermanence, suffering, and the rest were parts of consciousness, then, since they are in fact experienced, it would follow that they are objects distinct from it. Or if the very oneness of consciousness itself consisted in impermanence, suffering, and the rest, then it would become impossible to conceive of purification as separation from that nature; for purification comes about only from separation from an adventitious stain.