The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
6. But it is seen.
The word 'but' discards the pûrvapaksha.
Your assertion that this world cannot have originated from Brahman on account of the difference of its character is not founded on an absolutely true tenet. For we see that from man, who is acknowledged to be intelligent, non-intelligent things such as hair and nails originate, and that, on the other hand, from avowedly non-intelligent matter, such as cow-dung, scorpions and similar animals are produced.--But--to state an objection--the real cause of the non-intelligent hair and nails is the human body which is itself non-intelligent, and the non-intelligent bodies only of scorpions are the effects of non-intelligent dung.--Even thus, we reply, there remains a difference in character (between the cause, for instance, the dung, and the effect, for instance, the body of the scorpion), in so far as some non-intelligent matter (the body) is the abode of an intelligent principle (the scorpion's soul), while other non-intelligent matter (the dung) is not. Moreover, the difference of nature--due to the cause passing over into the effect--between the bodies of men on the one side and hair and nails on the other side, is, on account of the divergence of colour, form, &c., very considerable after all. The same remark holds good with regard to cow-dung and the bodies of scorpions, &c. If absolute equality were insisted on (in the case of one thing being the effect of another), the relation of material cause and effect (which after all requires a distinction of the two) would be annihilated. If, again, it be remarked that in the case of men and hair as well as in that of scorpions and
cow-dung there is one characteristic feature, at least, which is found in the effect as well as in the cause, viz. the quality of being of an earthy nature; we reply that in the case of Brahman and the world also one characteristic feature, viz. that of existence (sattâ), is found in ether, &c. (which are the effects) as well as in Brahman (which is the cause).--He, moreover, who on the ground of the difference of the attributes tries to invalidate the doctrine of Brahman being the cause of the world, must assert that he understands by difference of attributes either the non-occurrence (in the world) of the entire complex of the characteristics of Brahman, or the non-occurrence of any (some or other) characteristic, or the non-occurrence of the characteristic of intelligence. The first assertion would lead to the negation of the relation of cause and effect in general, which relation is based on the fact of there being in the effect something over and above the cause (for if the two were absolutely identical they could not be distinguished). The second assertion is open to the charge of running counter to what is well known; for, as we have already remarked, the characteristic quality of existence which belongs to Brahman is found likewise in ether and so on. For the third assertion the requisite proving instances are wanting; for what instances could be brought forward against the upholder of Brahman, in order to prove the general assertion that whatever is devoid of intelligence is seen not to be an effect of Brahman? (The upholder of Brahman would simply not admit any such instances) because he maintains that this entire complex of things has Brahman for its material cause. And that all such assertions are contrary to Scripture, is clear, as we have already shown it to be the purport of Scripture that Brahman is the cause and substance of the world. It has indeed been maintained by the pûrvapakshin that the other means of proof also (and not merely sacred tradition) apply to Brahman, on account of its being an accomplished entity (not something to be accomplished as religious duties are); but such an assertion is entirely gratuitous. For Brahman, as being devoid of form and so on, cannot become an object of
perception; and as there are in its case no characteristic marks (on which conclusions, &c. might be based), inference also and the other means of proof do not apply to it; but, like religious duty, it is to be known solely on the ground of holy tradition. Thus Scripture also declares, 'That doctrine is not to be obtained by argument, but when it is declared by another then, O dearest! it is easy to understand' (Ka. Up. I, 2, 9). And again, 'Who in truth knows it? Who could here proclaim it, whence this creation sprang?' (Rig-v. Samh. X, 129, 6). These two mantras show that the cause of this world is not to be known even by divine beings (îsvara) 1 of extraordinary power and wisdom.
There are also the following Smriti passages to the same effect: 'Do not apply reasoning to those things which are uncognisable 2;' 'Unevolved he is called, uncognisable, unchangeable;' 'Not the legions of the gods know my origin, not the great rishis. For I myself am in every way the origin of the gods and great rishis' (Bha. Gî. X, 2).--And if it has been maintained above that the scriptural passage enjoining thought (on Brahman) in addition to mere hearing (of the sacred texts treating of Brahman) shows that reasoning also is to be allowed its place, we reply that the passage must not deceitfully be taken as enjoining bare independent ratiocination, but must be understood to represent reasoning as a subordinate auxiliary of intuitional knowledge. By reasoning of the latter type we may, for instance, arrive at the following conclusions; that because the state of dream and the waking state exclude each other the Self is not connected with those states; that, as the soul in the state of deep sleep leaves the phenomenal world behind and becomes one with that whose Self is pure Being, it has for its Self pure Being apart from the phenomenal world; that as the world springs from Brahman it cannot be separate from Brahman,
according to the principle of the non-difference of cause and effect, &c. 1 The fallaciousness of mere reasoning will moreover be demonstrated later on (II, 1, 11).--He 2, moreover, who merely on the ground of the sacred tradition about an intelligent cause of the world would assume this entire world to be of an intellectual nature would find room for the other scriptural passage quoted above ('He became knowledge and what is devoid of knowledge') which teaches a distinction of intellect and non-intellect; for he could avail himself of the doctrine of intellect being sometimes manifested and sometimes non-manifested. His antagonist, on the other hand (i. e. the Sânkhya), would not be able to make anything of the passage, for it distinctly teaches that the highest cause constitutes the Self of the entire world.
If, then, on account of difference of character that which is intelligent cannot pass over into what is non-intelligent, that also which is non-intelligent (i.e. in our case, the non-intelligent pradhâna of the Sânkhyas) cannot pass over into what is intelligent.--(So much for argument's sake,) but apart from that, as the argument resting on difference of character has already been refuted, we must assume an intelligent cause of the world in agreement with Scripture.
307:1 On îsvara in the above meaning, compare Deussen, p. 69, note 41.
307:2 The line 'prakritibhyah param,' &c. is wanting in all MSS. I have consulted.
308:1 Ânanda Giri on the above passage: srutyâkânkshitam tarkam eva mananavidhivishayam udâharati svapnânteti. Svapnagâgaritayor mithovyabhikârâd âtmanah svabhâvatas tadvattvâbhâvâd avasthâdvayena tasya svato#sampriktatvam ato gîvasyâvasthâvatvena nâbrahmatvam ity arthah. Tathâpi dehâditâdâtmyenâtmano bhâvân na nihprapañkabrahmatety âsankyâha samprasâde keti. Satâ somya tadâ sampanno bhavatîti sruteh sushupte nihprapañkasadâtmatvâvagamâd âtmanas tathâvidhabrahmatvasiddhir ity arthah. Dvaitagrâhipratyakshâdivirodhât katham âtmano#dvitîyabrahmatvam ity âsankya taggatvâdihetunâ brahmâtiriktavastvabhâvasiddher adhyakshâdînâm atatvâvedakaprâmânyâd avirodhâd yuktam âtmano#dvitîyabrahmatvam ity âha prapañkasyeti.
308:2 Let us finally assume, merely for argument's sake, that a vailakshanya of cause and effect is not admissible, and enquire whether that assumption can be reconciled more easily with an intelligent or a non-intelligent cause of the world.