Sacred scripture vs. sacred doctrine: Aquinas on metaphor

My previous post contrasting Augustine and Aquinas got me noticing how, in the preface to question one of the Summa Theologiae, Aquinas says that he will address the question of whether sacred doctrine “rightly employs metaphors and similes,” whereas the question he actually answers in article nine is whether sacred scripture “should use metaphors.” In Aquinas’s Franciscan counterpart and contemporary, St. Bonaventure, “sacred doctrine” still means something like “sacred scripture,” the study of holy writ not yet being fully distinguished from the holy writ itself. In Aquinas, by comparison, these two realities receive more of their own identity, something I think is implicit in this opening passage of the Summa Theologiae (elsewhere in question one Aquinas will formally distinguish between the two by explaining how sacred scripture provides sacred doctrine with its first principles or axioms). In this small inconsistency between Aquinas’s promise to find a place for metaphor and simile in sacred doctrine, and his actual argument defending a place for metaphor and simile in sacred scripture, we perhaps have the signs of a growing crack between the ever-new wine of Scriptural content, and the what will prove to be an increasingly brittle wine-skin of the form of Scholastic logic and its conceptual apparatus. For Aquinas, scripture may be allowed to “rightly employ metaphors and similes,” but his own practice of sacred doctrine, significantly enough, almost never will.