On the hypothesis that the soul remains within herself, while making use of the light (emanated from the eye) as a rod to reach the visible object, a very sharp perception would be caused by the resistance experienced by the light in its tension and SENSE-COLOR. In so far as it is color, the light itself would possess the property of reflecting light. In this case, the contact would take place by a medium. But already before this the light has reached the object without any medium; so that the later contact operated by a medium would produce cognition by a sort of memory or reasoning — which is not the case. (Ennead IV,5 (29) 4)