The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
25. Or on account of (its) quality (viz. intelligence), as in cases of ordinary experience.
That the soul although atomic produces effects extending over the whole body, is not contrary to reason, on account of the pervadingness of intellect which is its quality. From ordinary experience we know that luminous things, such as lamps or gems, although occupying only one spot of a chamber, produce, by means of their light which fills the chamber, an effect in every part of the chamber.--This Sûtra has the purpose of removing the doubts of those who might object that sandal-ointment, because consisting of parts, may perhaps refresh the entire body by the diffusion of imperceptible particles; that, however, the soul as a mere atom does not possess any parts by means of which it could diffuse itself through the whole body.--But how can a quality extend beyond that in which it inheres, and abide elsewhere? We certainly do not see that the whiteness which is the quality of a piece of cloth extends beyond that piece of cloth to other places. Nor must you say that the case of the soul is analogous to that of the light diffused from a lamp; for that light itself is admitted to be (not a quality but) a substance. The flame of a lamp is substantial light with its particles crowded close to one another; the light diffused from that flame is substantial light whose particles are thin and scattered.--The reply to this objection is given in the next Sûtra.