Simplicius (De Anima 126,1-16) – perception (aisthesis)

For perception indivisibly encompasses the beginning, middle and end of the sense-object, and it is an activity, being a perfect judgment (krisis) and standing still at once as a whole in the instant at the form (eidos) of the sensible object. This form is not imposed like a seal on wax (which is not proper to life), nor does it proceed into depth (still less does it stand still with a cognitive activity), but it is projected (proballomenon) from within by the concept of sensible objects which is preconceived (proeilemmenos logos) in the soul. (This is not the soul that gives life to the organ as an organ, but that which uses it when already alive, so that by transcending the body it may act indivisibly and have knowledge of sensible objects.) The concept is one, but not according to the contracted unity in individual things, but as fitting each of them in an appropriate way according to the formal unity which encompasses all individuals causally. For the soul perceives (aisthanesthai) all particular white things according to that one concept; for that which judges (krinein) is the soul through the appropriate contact of that which is known, and it is appropriate because the soul has in its substance a preconception (prolepsis) of the same property [that is perceived]. Therefore, the soul becomes like its sensible objects not by receiving something from them but through being active in accordance with the concept appropriate to them. Now that this has been determined generally of all sense-perception we must go on to what follows. [SorabjiPC1  :41]