First and Second Philosophy

I raised the question in an earlier post: If Aristotle, in Met. Z, appeals to the form/matter distinction in order to reply to Platonist-type philosophers with a taste for the abstract, wouldn't we expect him to be using that distinction to draw attention to the importance of matter, not form? After all, form is what Platonists truck in.

Perhaps you gathered that, underlying my question, was a concern that a usual way of setting up Z --Aristotle is trying to figure out what substance is, and his answer is that it is form--was off the mark; that Aristotle isn't asking this question or answering it in that way; that we were missing what he was truly interested in.

Someone might say in response: "If his point in introducing the form/matter distinction was to draw attention to the matter, then his discussion in Z would be no more 'second philosophy', that is, physics. But it is supposed to be 'first philosophy'. And it's by drawing attention to the form that his discussion counts as first philosophy."

But I don't see how. If discussions appealing to matter count as second philosophy, why not also discussions appealing to form-in-matter? Or, if you say that it's the fact that a discussion of form-in-matter leads up to a discussion of separate substance, form on its own, which makes it 'first philosophy', then I can say, just as well, that it's the fact that a discussion of matter leads up to a consideration of form on its own which makes that 'first philosophy'.

In fact, this whole question of the distinction between 'first' and 'second' philosophy seems confused to me, as I'll explain in my next post.