The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c8.s6.t3.4

c8.s6.t3.4

As we have already seen (above p. 314) the necessity of the assumption of the Manas is deduced by Çaṅkara from the fact that while the soul is essentially an eternal cognition, there is no reason discoverable in the organs of sense for their different behaviour at different times; from this would result that we [in a waking state which alone comes in question here] should either not perceive at all or should perceive continuously, unless there were between the soul and the organs of sense the Manas, “by whose attention (avadhânam) and non-attention apperception (upalabdhi) and non-apperception [of the soul] results” (p. 667, 6).