The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
7. Thus also, on account of the existence of the former (qualities), (admitted) owing to reference and so on, there is absence of contradiction, (as) Bâdarâyana (thinks).
Thus also, i.e. although it be admitted that intelligence only constitutes the true nature of the Self, also the former nature, i.e. lordly power like that of Brahman, which is intimated by reference and the rest, is--with a view to the world of appearances--not rejected; and hence there is no contradiction. This is the opinion of the teacher Bâdarâyana.
8. But by mere will (the released effect their purposes); because scripture states that.
In the meditation on Brahman within the heart we read as follows: 'If he desires the world of the fathers, by his mere will the fathers rise,' &c. (Kh. Up. VIII, 2, 1).--A doubt here presents itself whether the will alone is the cause of the rising of the fathers, or the will joined with some other operative cause.--The pûrvapakshin maintains that although scripture says 'by his mere will,' some other cause must be supposed to co-operate, as in ordinary life. For as in our ordinary experience the meeting with one's father is caused by one's will, and, in addition, by the act of going and so on, so it will be in the case of the released soul also; and
thus we do not assume something contrary to observation. When the text says 'by his mere will,' it implies, as in the case of a king, the whole apparatus of other easily procurable instrumental causes by which the desired object is obtained. Besides, if the fathers and so on rose owing to a mere wish, they would be of unstable nature, like the imaginary representation of some desired object, and thus not be able to procure any solid enjoyment.--To this we reply that the rising of the fathers and so on is due to the will only.--Why so?--Because scripture declares this. If any other cause were required, the direct scriptural statement 'by his will only' would thereby be contradicted. And even if we admit some other cause accompanying the act of will, it cannot be a cause to be realised by an effort; for therefrom it would follow that before the realisation of that cause the will would be barren. Nor can the analogies of ordinary experience be applied to something to be learned from scripture. For as the will of the released differs in nature from the will of ordinary men, it may have the power of effecting something that possesses as much stability as the special purpose requires.