Plotinos: Complete Works, v. 3 In Chronological Order,...

29. Since the Stoics speak of qualities, they must consider these as distinct from subjects; otherwise, they would not assign them to the second rank. Now, to be anything else than the subjects, qualities must be simple, and consequently, not composite; that is, they must not, in so far as they are qualities, contain any matter. In this case, the qualities must be incorporeal and active; for, according to the Stoics, matter is a passive subject. If, on the contrary, the qualities themselves be passive, the division into subjects and qualities is absurd, because it would classify separately simple and composite things, and then reunite them into one single classification. Further, it is faulty in that it locates one of the species in another (matter in the qualities), as if science were divided into two kinds, of which one would comprise grammar, and the other grammar with something additional.