Brahma Sutras – According to Shankara 3-3 33-34
Topic 33 - Various Vidyās like the Śāndilya Vidyā, Dahara Vidyā, and so on are to be kept separate and not combined into one entire Upāsanā
Sutra 3,3.58
नाना, शब्दादिभेदात् ॥ ५८ ॥
nānā, śabdādibhedāt || 58 ||
nānā—Different; śabdādi-bhedāt—owing to difference of words etc.
58. (Various Vidyās like the Śāndilya, Dahara, etc. are) different owing to difference of words etc.
In the last Sutra it was shown that though the Śruti mentions meditations on parts of the cosmic form, yet the meditation on the entire form is what is intended by the Śruti.
Following this argument the opponent says that as the object of meditation is the one Lord, we are to combine all the different Vidyās like the Śāndilya Vidyā, Dahara Vidyā, Satya Vidyā, and so on into one composite meditation on the Lord.
This Sutra refutes that view and says that these different Vidyās are separate, because the Śruti prescribes them using different words, ‘He knows’, ‘Let him meditate’, ‘Let him form the idea’, etc. and this difference of terms is acknowledged to be a test of the difference of acts by Pūrva Mīmāṃsā.
‘Etc.’ refers to other reasons like the difference in qualities.
Though the object of meditation is the one Lord, yet owing to the difference in qualities that are imagined in different Upāsanās He is different. Moreover, it is an impossibility to combine all the various Vidyās into one.
So the different Vidyās are to be kept separate, and not combined into one general meditation.
Topic 34 - Among Vidyās relating to Brahman any one alone should be selected according to one’s choice
Sutra 3,3.59
विकल्पः, अविशिष्ट-फलत्वात् ॥ ५९ ॥
vikalpaḥ, aviśiṣṭa-phalatvāt || 59 ||
vikalpaḥ—Option; aviśiṣṭa-phalatvāt—on account of (all Vidyās) having the same result.
59. There is option (with respect to the several Vidyās), because the result (of all the Vidyās) is the same.
As the result of all the Vidyās is the realization of Brahman, it is enough if one takes up any one of them according to his liking and sticks to it till he reaches the goal. And once Brahman is realized through one of these Vidyās, resorting to another is useless.
Besides, to practise more than one meditation at a time would only distract one’s mind and thereby retard one’s progress. Therefore one must restrict oneself to one particular Vidyā.