Skinner’s explanation, I’ll suggest, captures the agonistic connotations of “ornatus” very well, and I do remember hearing (from Peter Marston, one of my rhetoric professors) that the “cosmitor” would have been the person charged with making sure the troops were properly outfitted for battle. But the operative concepts here – propriety, fittingness – also refer to part-whole relations, with the implication that stylistic devices are to gain their power contextually. In short, the metaphors (or whatever) need to fit – or outfit – the argument, just as the argument itself needs to fit the concrete situation.

Not that I’m an expert on these matters, but the ancients do seem to have had an extremely rich approach to signification. Still, (unlike unto more than a few late 20th. century thinkers) they tended to focus on the promise of coherence, rather than to dwell on the prospects for multiplicity. In any case, a particularly illuminating passage comes from Ernesto Grassi’s Rhetoric as Philosophy: The Humanistic Tradition (1980/2001). The explanation appears, tellingly enough, in a chapter titled “Rhetoric as the Ground of Society,” and I'll quote the whole paragraph:

As far as the meaning and importance of the term ornatus is concerned, which we usually think of as "outer decoration," we should recall that ornatus originally came from the Greek term Kosmos, which refers in an ontological perspective to the "relationship" between particular parts and a whole and names the particular order that holds among them. The ornatus, therefore, is never something that belongs to particulars in isolation; only in relation to something else, a whole, does the particular receive its essential meaning and become part of an interconnected arrangement. Cicero uses ornatus in this original sense in reference to the reality of the world when he says: "Since in this one world the order of the relationships [ornatus] is so wonderful. . . ." Similarly he says in De natura deorum, "In this world there is great beauty and every order [eximia pulchritudo sit atque omnis ornatus]." Cicero uses this term in a political context as well, by remarking that "because the Athenians did not possess different grades of dignity, citizenship [civitas] did not retain its own order [ornatum]." (91)

per fjelstad first brought this connection to my attention in an ancient rhetoric seminar with jerry hauser. there's also a connection between "ornatus" and "kosmos" ...; per has published this somewhere (maybe P&R), but i've got garden all over my hands and so can't check it right now. and my laptop is now a mess. ah bartleby.