Which C.S. Lewis book presents a debate about Christianity between the characters Mark and Jane Studdock?

That Hideous Strength presents a debate about Christianity through the marriage of Mark and Jane Studdock.

That Hideous Strength was published in 1945 as the third novel of C.S. Lewis’s Space Trilogy. Mark Studdock is a sociologist drawn toward the powerful National Institute of Coordinated Experiments, while his wife, Jane, becomes connected with a community resisting the institute’s ambitions. Their strained marriage provides an important human perspective on the novel’s larger conflict.

The book combines science fiction, Arthurian themes, social criticism, and Christian philosophy. Its title comes from a line associated with the sixteenth-century English writer David Lyndsay. The novel’s imagined institution seeks to reshape humanity through technocratic power, making the story concerned with both political control and the limits of purely material accounts of human life.

Unlike the first two trilogy novels, much of the action takes place on Earth. Mark and Jane are not simply protagonists in a conventional romantic story; their separate encounters with competing visions of humanity drive the book’s central debate.