The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
6. The non-abandonment of the promissory statements (results only) from the non-difference (of the entire world from Brahman), according to the words of the Veda.
In all the Vedânta-texts we meet with promissory statements of the following nature:--'That by which we hear what is not heard, perceive what is not perceived, know what is not known' (Kh. Up. VI, 1, 3); 'When the Self has been seen, heard, perceived, and known, then all this is known' (Bri. Up. IV, 5, 6); 'Sir, what is that through which if it is known everything else becomes known?' (Mu. Up. I, 1, 3); 'Outside that which is there is no knowledge.' These promissory statements are not abandoned, i.e. not stultified, only if the entire aggregate of things is non-different from Brahman, the object of knowledge; for if there were any difference, the affirmation that by the knowledge of one thing everything is known, would be contradicted thereby. Non-difference again of the two is possible only if the whole aggregate of things originates from the one Brahman. And we understand from the words of the Veda that that affirmation can be established only through the theory of the non-difference of the material cause and its effects. For the affirmation contained in the clause 'That by which we hear what is not heard,' &c., is proved by the analogous instances of clay, &c., which all aim at showing the identity of effect and cause. In order to establish this, the subsequent clauses also ('Being only, my dear, this was in the beginning, one only, without a second; it thought; it sent forth fire,' &c.) at first state that the aggregate of effects belongs to Brahman, and then declare its identity with Brahman, viz. from the passage 'In it all that exists has its Self' (VI, 8, 7), up to the end of the prapâthaka.--If, now, the ether were not one of the effects of Brahman, it could not be known by Brahman being known, and that would involve an abandonment of a (previous) affirmation; an
alternative which, as invalidating the authoritativeness of the Veda, is of course altogether unacceptable.--Similarly in all the Vedânta-texts certain passages are to be found which, by means of various instances, make the same affirmation, so e.g. 'This everything, all is that Self' (Bri. Up. II, 4, 6); 'Brahman alone is that Immortal before' (Mu. Up. II, 2, 11).--Hence, like fire and the other substances, the ether also is a product.--The averment made by the pûrvapakshin that on account of the absence of scriptural statements the ether is not a product is unfounded, since a scriptural passage referring to the origin of ether has already been pointed out, viz. 'from that Self sprang ether.'--True,--the pûrvapakshin may reply,--such a statement has indeed been pointed out, but it is contradicted by another statement, viz. 'It sent forth fire,' &c. Should it be alleged that there can be no contradiction, because all scriptural passages form one whole, the reply is that all non-contradictory passages form a whole; in the present case, however, a contradiction has been shown to exist, because the creator, who is mentioned only once, cannot be connected with two things created; because two things cannot both be created first; and because an option is, in that case, inadmissible 1.--This reply, we rejoin, is without force. It is indeed true that it is impossible to explain the passage of the Taittirîyaka in any modified sense; for it distinctly declares that fire was produced in the third place, 'From that Self sprang the ether, from ether air, from air fire.' But, on the other hand, it is possible to give a different turn to the passage from the Khândogya, which may be explained to mean that 'Brahman, after having created ether and air, created fire.' For as the purport of this passage is to relate the origin of fire, it cannot at the same time impugn the account of the origin of ether given in another passage; according to the principle that to one and the same sentence a double purport must not be ascribed. As, on the
other hand, one creator may successively create more than one thing, and as on that ground the combination of the two passages into one syntactical whole is possible, we are not obliged to disregard any scriptural statement on account of its meaning being contradicted (by other scriptural passages). Nor do we mean to say that a creator mentioned only once is to be connected with two created things; for the other (second) created thing is supplied from another scriptural passage. And, in the same way as the fact of the whole aggregate of things being produced from Brahman--which is stated directly in the passage 'Let a man meditate with calm mind on that as beginning, ending and breathing in it' (Kh. Up. III, 14, 1)--does not impugn the order of creation stated elsewhere to begin with fire; so also the statement as to fire being produced from Brahman has no force to impugn the order of creation which, in another scriptural passage, is said to begin with ether.
But, it may be objected, the passage 'Let a man meditate with calm mind,' &c. has the purpose of enjoining calmness, and does not state anything with regard to creation; it need not therefore adapt itself to the order (of creation) established by another passage 1. On the other hand, the passage 'It sent forth fire' refers to the creation, and we must therefore accept the order exactly as stated there.--This objection we refute by the remark that it is not legitimate to abandon, from deference to the circumstance of fire occupying the first place (in the Kh. Up.), the thing, viz. the ether which is known (to have been created) from another passage; for order of succession is a mere attribute of things (and therefore subordinate to the latter). Moreover, in the passage 'It sent forth fire' we meet with no word directly indicating the order of succession; but we merely infer the latter from the sense, and this (merely inferred) order is impugned by the order established by another direct scriptural statement,
viz. 'From air there sprang fire.' Now with regard to the question whether ether or fire were created first, neither option nor addition are permissible, because the former is impossible in itself, and the latter non-admitted by the texts 1. Hence the two scriptural passages are not contradictory.--Moreover, in order to justify the promise made in the Khândogya in the beginning of the chapter ('That instruction by which we hear what is not heard'), we have to count the ether, although 'not heard' (i.e. not mentioned in the text) among the things produced; how much more impossible then is it for us not to accept the statement actually made about the ether in the Taittirîyaka!--To the assertion, made above by the pûrvapakshin, that the ether as occupying the same space with everything is known together with Brahman and its effects, and that thus the assertion (of everything being known through Brahman) is not contradicted; and that moreover the scriptural passage 'one only, without a second' is not contradicted, because Brahman and the ether may be considered as non-separate, like milk and water, we make the following reply. That knowledge of everything through the knowledge of one thing (of which scripture speaks) cannot be explained through the analogy of milk mixed with water, because we understand from the parallel instance of a piece of clay being brought forward (Kh. Up. VI, 1, 4) that the knowledge of everything has to be explained through the relation of the material cause and the material effect (the knowledge of the cause implying the knowledge of the effect). Moreover, the knowledge of everything, if assumed to be analogous to the case of the knowledge of milk and water, could not be called a perfect knowledge (samyag-vigñâna), because the water which is
apprehended only through the knowledge of the milk (with which it is mixed) is not grasped by perfect knowledge 1. Nor can Vedic affirmations about things be viewed, like ordinary human statements, as mixed up with error, untruth, and deceit 2. And we should do violence to the emphatic assertion made in the passage 'one only, without a second,' if we explained it according to the analogy of milk mixed with water.--Nor must we explain the cognition of everything (through one thing), and the assertion as to the one without a second, as referring only to a part of existing things, viz. the avowed effects of Brahman (to the exclusion of ether), on the ground that such is the case in the parallel instances of clay and the like. For what is said about clay and the like is not something altogether new and independent; but has to be understood in connexion with the previous passage 'Svetaketu, as you are so conceited,' &c. We therefore must conclude that the 'knowledge of everything' has all things whatever for its objects, and is here introduced with a view to showing that everything is the effect of Brahman.
The next Sûtra replies to the assertion, made by the pûrvapakshin, that the passage which speaks of the origin of ether is to be understood in a secondary sense, on account of the impossibility (of ether having an origin).
10:1 For we cannot maintain that optionally either the one or the other was created first.
11:1 Yatparah sabdah sabdârtho na kâyam sabdah srishtiparoऽto na prasiddham kramam bâdhitum alam iti. Ân. Gi.
12:1 An optional proceeding, i.e. the doctrine that either ether or fire was the first product is impossible because only actions to be done, not existing things, fall within the sphere of option; addition, i.e. the fact of fire and ether together being the first creation is not admitted by scripture, which teaches a successive creation of the elements.
13:1 For the water, although mixed with the milk, yet is different from it.
13:2 But the promise that through the knowledge of one thing everything becomes known is to be taken in its full literal meaning.