I don't think I claimed the subordinating relation was one of concrete particular to abstract generality. It strikes me as odd to think that the scholastics in general thought of the divine ousia as an abstract object, let alone Augustine. Of course, you might want to look at what Aquinas has to say about the relation of the persons to the essence. One swallow does not make a spring.
I have several issues with this. 1) "The scholastics in general" and "one swallow does not make a spring" seems to indicate that Mr Robinson thinks that Scotus is in a serious minority on this issue. Unfortunately 2) having denied my representation of his view, Mr Robinson doesn't clarify what that view is, so it's unclear exactly what Scotus is in the minority on. 3) He directs me to "look at what Aquinas has to say about the relation of the persons to the essence." At what, exactly? I have to guess which text and which opinion of Aquinas' he takes issue with. I admit I don't know which he means. Presumably it has to do with his view that "the scholastics in general thought of the divine ousia as an abstract object" (I'm leaving Augustine out of this for now. Not enough time to get into that).
Of course it's pretty difficult to talk of what "the scholastics in general" thought about a difficult theological issue. When one reads a lot of them one notices that they tend to frequently disagree. What is clear, however, is that none of them "thought of the divine ousia as an abstract object". I hate to have to point this out, but they thought and wrote in Latin, and the slippery transfer between technical Greek words and technical Latin words among people who only spoke one or the other is a prime cause of misunderstanding. We shouldn't say anything about what Latin theologians thought about "the divine ousia" without being extremely careful to say just what we mean by "ousia" in Latin terms.
Thomas does so in a text in which he's discussing the relation of the persons to the essence, Summa theologiae, prima pars, Q.29 A.2, Utrum persona sit idem quod hypostasis, subsistentia et essentia. Thomas carefully distinguishes between a number of terms which might be used in place of it "ousia".
Substantia dicitur duplicter. Uno modo dicitur substantia quidditas rei, quam significat definitio, secundum quod dicimus quod definitio significat substantiam rei: quam quidem substantiam Graeci "usiam" vocant, quod nos essentiam dicere possumus. --Alio modo dicitur substantia subiectum vel suppositum quod subsistit in genere substantiae. Et hoc quidem, communiter accipiendo, nominari potest et nomine significante intentionem: et sic dicitur suppositum. Nominatur etiam tribus nominibus significantibus rem, quae quidem sunt res naturae, subsistentia et hypostasis, secundum triplicem considerationem substantiae sid dictae . . . hypostasis, apud Graecos, ex propria significatione nominis habet quod significet quodcumque individuum substantiae . . . Sed quia nomen substantiae, quod secundum proprietatem significationis respondet hypostasi, aequivocatur apud nos, cum quandoque significet essentiam, quandoque hypostasim; ne possit esse erroris occasio, maluerunt pro hypostasi transferre subsistentiam, quam substantiam.
Thomas does, therefore, conceive of "ousia" as "abstract" (I will not admit the phrase "an abstract object" unless what this means is clarified), if by "ousia" we mean the essence in the sense of quod quid erat esse, what is signified by the definition. But of course a definition is an abstraction! Is signifies what God is but not who God is, i.e. it points out what it means to be God but not any specific divine hypostasis. But this is no way implies that the divine essence or nature is conceived of as some "abstract object" somehow existing above or prior to any of the divine persons. Rather, a divine person simply is this subsistent supposit of the divine nature, the "who" (or, if you like the "this") whose "what" is defined by the essence. When we speak of the divine nature or essence we're speaking of God without speaking of any given person--but this does not imply that Thomas thinks the essence is any thing other than the persons. He certainly doesn't.