The person whose name has become almost synonymous with the tradition of theological exemplarism in the Christian west is, of course, the good Bishop of Hippo, St. Augustine (354-430). Perhaps the central doctrine where a theology of the possible is concerned is Augustine’s famous and influential teaching on the divine ideas which witnessed the effective Christianization of Plato’s theory of forms, placing them within the mind of God himself. Augustine’s fullest and most direct treatment of the subject, and the one that would serve as the chief patristic source on the topic throughout the subsequent Middle Ages, occurs in the forty-sixth of his Eighty Three Different Questions (De Diversis Quaestionibus LXXXIII). His brief but formative discussion opens with Plato whom he identifies as the first to have used the name ideas, but not the first to have grasped the universal, divine reality signified by the term, something Augustine believes always and everywhere to have been understood by men deserving the title “wise.” Augustine takes inventory of the some of the other names given to the ideas—“forms” (formae), “species” (species), and “reasons” (rationes)—using the latter in particular to characterize the ideas as the “original and principal forms of things, i.e., reasons, fixed and unchangeable, which are not themselves formed and, being thus eternal and existing always in the same state, […] contained in the Divine Intelligence.” Eternal and unchanging, it is through and by the ideas that “everything which does come into being and pass away is said to be formed…. It is by participation in these that whatever is exists in whatever manner it does exist.” After summarizing how the rational soul comes to know the ideas—namely through an act of divine illumination which he describes as a “certain inner and intelligible countenance” possible only after the soul has been made “holy and pure”—Augustine gives his influential argument for both the existence and the multiplicity of the divine ideas. No devout and religious person, he says, would deny that those things existing in their own, natural order, have God as their cause, or that God is the cause not only of the things themselves but also of their order and the laws of operation. Nor, having admitted this much, would anyone say that God has created these things and their order without any kind of rational plan. Having created all things according to such a plan, moreover, it is absurd to think that God created distinct individual things, such as a man and a horse, according to the same rational plan. Everything, Augustine concludes, must therefore have been created according to a rational plan, reason, or idea unique or proper to each thing. Having thus established the existence and plurality of the ideas, Augustine returns to the question of the location of the ideas, namely the divine mind of God, asserting that it would be “sacriligious” to suggest that God had to look to something outside himself to get the pattern for what he was going to create.
 Boland, Ideas in God, 38-9, 47.
 Augustine, Eighty-Three Different Questions, trans. David L. Mosher (Washington, D.C.: Catholic University of America Press, 1982), 79-81.
 It is tempting to assume that Augustine saw himself as critiquing Plato’s Timaeus here, which, as we have seen, mythically represents the demiurge as looking to a reality apparently distinct from himself, namely the “eternal model,” for the plan of creation. It is important to realize, however, that Augustine didn’t have first-hand knowledge of the Timaeus but knew him through the textbooks of later Platonists who, like Augustine, also placed the ideas in the mind of God. As Vivian Boland suggests, Augustine probably thought that the notion of the divine ideas in the mind of God was the authentic teaching of Plato himself. Boland, Ideas in God, 45-6.