Plutarch, De communibus notitiis adversus Stoicos
Goodwin, Ed.

Moreover, they say that subsistence and matter are subject to qualities, and do so in a manner define them; and again, they make the qualities to be also bodies. But these things have much perplexity. For if qualities have a peculiar substance, for which they both are and are called bodies, they need no other substance; for they have one of their own. But if they have under them in common only that which the Stoics call essence and matter, it is manifest they do but participate of the body; for they are not bodies. But the subject and recipient must of necessity differ from those things which it receives and to which it is subject. But these men see by halves; for they say indeed that matter is void of quality, but they will not call qualities immaterial. Now how can they make a body without quality, who understand no quality without a body? For the reason which joins a body to all quality [p. 427] suffers not the understanding to comprehend any body without some quality. Either, therefore, he who oppugns incorporeal quality seems also to oppugn unqualified matter; or separating the one from the other, he mutually parts them both. As for the reason which some pretend, that matter is called unqualified not because it is void of all quality, but because it has all qualities, it is most of all against sense. For no man calls that unqualified which is capable of every quality, nor that impassible which is by nature always apt to suffer all things, nor that immovable which is moved every way. And this doubt is not solved, that, however matter is always understood with quality, yet it is understood to be another thing and differing from quality.