The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
7. (The pradhâna cannot be designated by the term 'Self') because release is taught of him who takes his stand on that (the Sat).
The non-intelligent pradhâna cannot be the object of the term 'Self' because in the passage Kh. Up. VI, 2 ff., where the subtle Sat which is under discussion is at first referred to in the sentence, 'That is the Self,' and where the subsequent clause, 'That art thou, O Svetaketu,' declares the intelligent Svetaketu to have his abode in the Self, a passage subsequent to the two quoted (viz. 'a man who has a teacher obtains true knowledge; for him there is only delay as long as he is not delivered, then he will be perfect') declares final release. For if the non-intelligent pradhâna were denoted by the term 'Sat' and did comprehend--by means of the phrase 'That art thou'--persons desirous of final release who as such are intelligent, the meaning could only be 'Thou art non-intelligent;' so that Scripture would virtually make contradictory statements to the disadvantage of man, and would thus cease to be a means of right knowledge. But to assume that the faultless sâstra is not a means of right knowledge, would be contrary to reason. And if the sâstra, considered as a means of right knowledge, should point out to a man desirous of release, but ignorant of the way to it, a non-intelligent Self as the real Self, he would--comparable to the blind man who had caught hold of the ox's tail 1--cling to the view of that being the Self,
and thus never be able to reach the real Self different from the false Self pointed out to him; hence he would be debarred from what constitutes man's good, and would incur evil. We must therefore conclude that, just as the sâstra teaches the agnihotra and similar performances in their true nature as means for those who are desirous of the heavenly world, so the passage 'that is the Self, that art thou, O Svetaketu,' teaches the Self in its true nature also. Only on that condition release for him whose thoughts are true can be taught by means of the simile in which the person to be released is compared to the man grasping the heated axe (Kh. Up. VI, 16). For in the other case, if the doctrine of the Sat constituting the Self had a secondary meaning only, the cognition founded on the passage 'that art thou' would be of the nature of a fanciful combination only 1, like the knowledge derived from the passage, 'I am the hymn' (Ait. Âr. II, 1, 2, 6), and would lead to a mere transitory reward; so that the simile quoted could not convey the doctrine of release. Therefore the word 'Self is applied to the subtle Sat not in a merely figurative sense. In the case of the faithful servant, on the other hand, the word 'Self' can--in such phrases as 'Bhadrasena is my Self'--be taken in a figurative sense, because the difference between master and servant is well established by perception. Moreover, to assume that, because words are sometimes seen to be used in figurative senses, a figurative sense may be resorted to in the case of those things also for which words (i.e. Vedic words) are the only means of knowledge, is altogether indefensible; for an assumption of that nature would lead to a general want of confidence. The assertion that the word 'Self' may (primarily) signify what is non-intelligent as well as what is intelligent, just as the word 'gyotis' signifies a certain sacrifice as well as light, is inadmissible, because we have no right to attribute to words a plurality of meanings. Hence (we rather assume that) the word 'Self' in its primary meaning refers to what is intelligent only and is then, by a figurative
attribution of intelligence, applied to the elements and the like also; whence such phrases as 'the Self of the elements,' 'the Self of the senses.' And even if we assume that the word 'Self' primarily signifies both classes of beings, we are unable to settle in any special case which of the two meanings the word has, unless we are aided either by the general heading under which it stands, or some determinative attributive word. But in the passage under discussion there is nothing to determine that the word refers to something non-intelligent, while, on the other hand, the Sat distinguished by thought forms the general heading, and Svetaketu, i.e. a being endowed with intelligence, is mentioned in close proximity. That a non-intelligent Self does not agree with Svetaketu, who possesses intelligence, we have already shown. All these circumstances determine the object of the word 'Self' here to be something intelligent. The word 'gyotis' does moreover not furnish an appropriate example; for according to common use it has the settled meaning of 'light' only, and is used in the sense of sacrifice only on account of the arthavâda assuming a similarity (of the sacrifice) to light.
A different explanation of the Sûtra is also possible. The preceding Sûtra may be taken completely to refute all doubts as to the word 'Self' having a figurative or double sense, and then the present Sûtra is to be explained as containing an independent reason, proving that the doctrine of the pradhâna being the general cause is untenable.
Hence the non-intelligent pradhâna is not denoted by the word 'Self.' This the teacher now proceeds to prove by an additional reason.
55:1 A wicked man meets in a forest a blind person who has lost his way, and implores him to lead him to his village; instead of doing so the wicked man persuades the blind one to catch hold of the tail of an ox, which he promises would lead him to his place. The consequence is that the blind man is, owing to his trustfulness, led even farther astray, and injured by the bushes, &c., through which the ox drags him.
56:1 Cp. above, p. 30.