J. R. R. Tolkien was a profoundly metaphysical thinker, and one of the most formative influences on his imagination, according to this new study of his works, was the great thirteenth-century theologian, St. Thomas Aquinas. Structured around Tolkien’s Middle-earth creation myth, the Ainulindale, The Flame Imperishable follows the thought of Aquinas as a guide in laying bare the deeper foundations of many of the more familiar themes from Tolkien’s legendarium, including such notions as sub-creation, free will, evil, and eucatastrophe. More than merely using Aquinas to illuminate Tolkien, however, this study concludes that, through its appropriation of many of the philosophical and theological insights of Aquinas, what Tolkien’s literary opus achieves is an important and unique landmark in the history of Thomism itself, offering an imaginative and powerful contemporary retrieval, interpretation, and application of Thomistic metaphysics for the twentieth and twenty-first centuries.