In Opus Maius: Moral Philosophy, Roger Bacon attempts to justify the teaching of pagans to Christian contemporaries, who were skeptical of having to be subjected to anything predating Christ. Bacon restates Horace’s “teach and delight” dictum, and emphasizes poetry’s didactic function. He cites Aristotle’s Poetics despite having never seen it, as neither Latin nor English translations were available at the time. Instead, he knows Aristotle only through the 12th-century Arab scholar Averroes. Yet despite not having direct access to Aristotle, he insists that such indirect access is still valuable: “Still, a studious person can catch a faint scent of his views, even though he cannot taste them; for a wine that is decanted from a third vase retains little of its vigor.”
In this essay he outlines the three "species" of rhetorical argument: faith (“proof of the true religion,” rhetorical), justice (e.g., Cicero’s rhetorical works), and the persuasive (arguments that sway us into action and direct us regarding divine worship, laws, and virtues). Poetry, Bacon asserts, belongs to this third "species," which is both rhetorical and poetic.