Apologetics is a genre concerned with explicating and defending a given religious belief system. Apologetic literature exists within most contemporary religious traditions, but in the Western world, Christian apologetics is the best-known genre, dating back almost as long as the religion itself. Saint Augustine, Thomas Aquinas, Blaise Pascal, and C. S. Lewis are among the most famous Christian apologists.

Because it concerns the often-nuanced claims of a given faith, much apologetics takes the form of outright argumentation: treatises, thought experiments, and other forms of persuasive text. The Screwtape Letters, however, combines a relatively in-depth elaboration of Christian theology with a fictional narrative: the saga of Wormwood’s attempted corruption of his “patient.” This distinguishes it not only from more traditional Christian apologetics but also from much Christian fiction, even by Lewis himself. For instance, while The Chronicles of Narnia employs many elements of Christian allegory, it does not contain the extended defense of Christian faith, including rebuttals of critiques of Christianity, that typify apologetics.