Plotinos: Complete Works, v. 1 In Chronological Order,...

10. (Some objector) might ask how one could conceive of matter without quantity? This might be answered by a retort. How then do you (as you do) manage to conceive of it without quality? Do you again object, by what conception or intelligence could it be reached? By the very indetermination of the soul. Since that which knows must be similar to that which is known (as Aristotle298 quotes from Empedocles), the indeterminate must be grasped by the indeterminate. Reason, indeed, may be determined in respect to the indeterminate; but the glance which reason directs on the indeterminate itself is indeterminate. If everything were known by reason and by intelligence, reason here tells us about matter what reason rightly should tell us about it. By wishing to conceive of matter in an intellectual manner, intelligence arrives at a state which is the absence of intelligence, or rather, reason forms of matter a "bastard" or "illegitimate" image, which is derived from the other, which is not true, and which is composed of the other (deceptive material called) reason. That is why Plato299 said that matter is perceived by a "bastard reasoning." In what does the indetermination of the soul consist? In an absolute ignorance, or in a complete absence of all knowledge? No: the indeterminate condition of the soul implies something positive (besides something negative).

As for the eye, darkness is the matter of all invisible color, so the soul, by making abstraction in sense-objects of all things that somehow are luminous, cannot determine what then remains; and likewise, as the eye, in darkness (becomes assimilated to darkness), the soul becomes assimilated to what she sees. Does she then see anything else? Doubtless, she sees something without figure, without color, without light, or even without magnitude.300 If this thing had any magnitude, the soul would lend it a form.