Thanks to Zizka from Vanitysite for recommending I look up the writing of Steven Toulmin in re my arguments about rhetoric.
Here's the beginning of whatever it is I'm going to write next

The debate with Scalia et al. comes down to whether a philosophy of justice should be posited as a question or a statement. The philosophy of free speech extends from the assumption that justice should be based on a question, therefore requiring -political- debate. What is freedom? What is obligation, and to whom is it owed? To be seen as consistent, Scalia's philosophy, in its opposition to the act of interpretation, must not recognize the logical and 'moral' validity of free speech (or of democracy itself).
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A philosophy of open debate is a defense of art...
Art is the world filtered through a sensibility. In a democracy, what is law? Not the sensibility of the individual but of the group. How is the law made to change?
Since law in a democracy must be seen as a questioning and literature is nothing but questioing at the level of mimesis and abstraction, art (literature) has the legal status of a hypothetical case.

If artmaking is to be considered an important activity rather than a 'spandrel' -the result of necessity but not itself necessary- can this be argued without recourse to metaphysics?
Easily, in literature and theater.
What about the rest?