Thinking Theologically traces Aquinas's subtle grammatical and thematic engagements with the doctrine of the divine ideas throughout the Summa Theologiae. This study offers new insights into the contributions of Aquinas's doctrine to debates about eschatology, christology, providence, natural law, virtue, and creation's participation in the trinitarian life of God. It argues that Aquinas adapts the doctrine to support his pedagogical goal of guiding readers from the confession of faith to the wisdom of sacra doctrina. In turn, this demonstrates that Aquinas's reading of the divine ideas reinforces his understanding of the dynamic exchange between philosophical reasoning and theological inquiry.