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

5. If, we were to conclude that there were no matter in intelligible entities, because they were immutable, and because, in them, matter is always combined with (shape), we would be logically compelled to deny the existence of matter in bodies; for the matter of bodies always has a form, and every body is always complete (containing a form and a matter). Each body, however, is none the less composite, and intelligence observes its doubleness; for it splits until it arrives to simplicity, namely, to that which can no longer be decomposed; it does not stop until it reaches the bottom things. Now the bottom of each thing is matter. Every matter is dark, because the reason (the form) is the light, and because intelligence is the reason.284 When, in an object, intelligence considers the reason, it considers as dark that which is below reason, or light. Likewise, the eye, being luminous, and directing its gaze on light and on the colors which are kinds of light, considers what is beneath, and hidden by the colors, as dark and material.