"On the subject of perception in its totality, we must understand it as what receives the forms of things sensed in isolation from their matter, the way wax receives the device [sēmeîon] of a signet-ring in isolation from its iron or silver: the iron or silver device is taken in, but not the iron or silver as such. Similarly, the senses are in every case affected by a thing's color, taste or noise -- not that which a thing is said to be, but qualities which it has and are accounted for."
"If thinking is indeed comparable to perception, it is either an affection caused by what is thinkable or something of the kind. Though thought itself is unaffected, it must be receptive of its object's form, and able to be like it while remaining something else. As the sensory faculty is to the object of sense, so must mind be to the thinkable. Now since the mind thinks all things, in order to exercise its force -- that is, to know -- it must as Anaxagoras says be 'unmixed' (59B12 DK), for any foreign object that comes in from outside hinders and obstructs it. Thus the mind can have no nature but a potential one. So that part of the soul called 'mind' (with which the soul does its thinking and conceiving) has no actual existence until it thinks. For this reason it cannot rightly be said to mix with the body either. For then it would take on qualities like hot or cold, or it would reside in an organ as do the senses. But it has none. It is not wrong to call the soul a place of forms, as long as this is restricted to its thinking capacity, and the forms are understood to be potential and not actual.
"The senses and the mind are dissimilar in their imperviousness to affection. On considering the sensory organs and sensation this is easy to see, for after an intense sensation the sense is rendered inoperative -- as with the sense of hearing after a loud sound, or the inability to see or smell in the wake of strong colors and aromas. But the mind that thinks an intense thought finds that lesser thoughts are heightened, not diminished."
On the Soul II.12, III.4
"If thinking is indeed comparable to perception, it is either an affection caused by what is thinkable or something of the kind. Though thought itself is unaffected, it must be receptive of its object's form, and able to be like it while remaining something else. As the sensory faculty is to the object of sense, so must mind be to the thinkable. Now since the mind thinks all things, in order to exercise its force -- that is, to know -- it must as Anaxagoras says be 'unmixed' (59B12 DK), for any foreign object that comes in from outside hinders and obstructs it. Thus the mind can have no nature but a potential one. So that part of the soul called 'mind' (with which the soul does its thinking and conceiving) has no actual existence until it thinks. For this reason it cannot rightly be said to mix with the body either. For then it would take on qualities like hot or cold, or it would reside in an organ as do the senses. But it has none. It is not wrong to call the soul a place of forms, as long as this is restricted to its thinking capacity, and the forms are understood to be potential and not actual.
"The senses and the mind are dissimilar in their imperviousness to affection. On considering the sensory organs and sensation this is easy to see, for after an intense sensation the sense is rendered inoperative -- as with the sense of hearing after a loud sound, or the inability to see or smell in the wake of strong colors and aromas. But the mind that thinks an intense thought finds that lesser thoughts are heightened, not diminished."
On the Soul II.12, III.4
