The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
58. (The vidyâs are) separate, on account of the difference of words and the like.
In the preceding adhikarana we have arrived at the conclusion that a meditation on Vaisvânara as a whole is the pre-eminent meaning of the text, although special results are stated for meditations on Sutegas and so on. On the ground of this it may be presumed that other meditations also which are enjoined by separate scriptural texts have to be combined into more general meditations. Moreover, we cannot acknowledge a separation of vidyâs (acts of cognition; meditations) as long as the object of cognition is the same; for the object constitutes the character of a cognition in the same way as the material offered and the divinity to which the offering is made constitute the character of a sacrifice. Now we understand that the Lord forms the only object of cognition in a number of scriptural passages, although the latter are separate in enunciation; cp. e.g. 'He consisting of mind, whose body is prâna' (Kh. Up. III, 14, 2); 'Brahman is Ka, Brahman is Kha' (Kh. Up. IV, 10, 5); 'He whose wishes are true, whose purposes are true' (Kh. Up. VIII, 7, 3). Analogously one and the same Prâna is referred to in different texts; cp. 'Prâna indeed is the end of all' (Kh. Up. IV, 3, 3); 'Prâna indeed is the oldest and the best' (Kh. Up. V, 1, 1); 'Prâna is father, Prâna is mother' (Kh. Up. VII, 15, 1). And from the unity of the object of cognition there follows unity of cognition. Nor
can it be said that, on this view, the separateness of the different scriptural statements would be purposeless, since each text serves to set forth other qualities (of the one pradhâna which is their common subject). Hence the different qualities which are enjoined in one's own and in other Sâkhâs, and which all belong to one object of knowledge, must be combined so that a totality of cognition may be effected.
To this conclusion we reply, 'Separate,' &c. Although the object of cognition is one, such cognitions must be considered as separate 'on account of the difference of words and the like.'--For the text exhibits a difference of words such as 'he knows,' 'let him meditate,' 'let him form the idea' (cp. Kh. Up. III, 14, 1). And difference of terms is acknowledged as a reason of difference of acts, according to Pûrva Mîmâmsâ-sûtras II, 2, 1.--The clause 'and the like' in the Sûtra intimates that also qualities and so on may be employed, according to circumstances, as reasons for the separateness of acts.--But, an objection is raised, from passages such as 'he knows' and so on we indeed apprehend a difference of words, but not a difference of sense such as we apprehend when meeting with such clauses as 'he sacrifices' and the like (yagate, guhoti, dadâti). For all these words (viz. veda, upâsîta, &c.) denote one thing only, viz. a certain activity of the mind, and another meaning is not possible in their case 1. How then does difference of vidyâ follow from difference of words?--This objection is without force, we reply; for although all those words equally denote a certain activity of the mind only, yet a difference of vidyâ may result from a difference of connexion. The Lord indeed is the only object of meditation in the passages quoted, but according to its general purport each passage teaches different qualities of the Lord; and similarly, although one and the same Prâna is the object of meditation in the other series
of passages, yet one of his qualities has to be meditated upon in one place and another in another place. From difference of connexion there thus follows difference of injunction, and from the latter we apprehend the separateness of the vidyâs. Nor can it be maintained (as the pûrvapakshin did) that one of those injunctions is the injunction of the vidyâ itself, while the others enjoin mere qualities; for there is no determining reason (as to which is the vidyâvidhi and which the gunavidhis), and as in each passage more than one quality are mentioned it is impossible that those passages should enjoin qualities with reference to a vidyâ established elsewhere 1. Nor should, in the case of the pûrvapakshin's view being the true one, the qualities which are common to several passages, such as 'having true wishes,' be repeated more than once. Nor can the different sections be combined into one syntactical whole, because in each one a certain kind of meditation is enjoined on those who have a certain wish, whence we understand that the passage is complete in itself 2. Nor is there in the present case an additional injunction of a meditation on something whole--such as there is in the case of the cognition of the Vaisvânara--owing to the force of which the meditations on the single parts which are contained in each section would combine themselves into a whole. And if on the ground of the object of cognition being one we should admit unity of vidyâ without any restriction, we should thereby admit an altogether impossible combination of all qualities (mentioned anywhere in the Upanishads). The Sûtra therefore rightly declares the separateness of the vidyâs.--The present adhikarana being thus settled, the first Sûtra of the pâda has now to be considered 3.
278:1 Vedopâsîtetyâdisabdânam kvakig gñânam kvakid dhyânam ity arthabhedam âsaṅkya gñânasyâvidheyatvâd vidhîyamânam upâsanam evety âha arthântareti. Ân. Gi.
279:1 For to enjoin in one passage several qualities--none of which is established already--would involve an objectionable vâkyabheda.
279:2 A sentence is to be combined with another one into a larger whole only if the sentences are not complete in themselves but evince an âkaṅkshâ, a desire of complementation.
279:3 I.e. the present adhikarana ought in reality to head the entire pâda.