Which C.S. Lewis book examines affection through four categories of love?

The Four Loves examines affection through four categories of love: storge, philia, eros, and agape.

C.S. Lewis developed the book from a 1958 BBC radio series, and the book was published in 1960. He discusses familiar forms of human attachment, including family affection, friendship, romantic love, and charitable or self-giving love.

The categories are drawn partly from Greek vocabulary, but Lewis does not present them as completely sealed compartments. He explains how different kinds of love can overlap, become distorted, or depend on one another. His argument also considers the danger of treating a natural affection as self-sufficient.

The title can lead readers to expect a simple list of four emotions. Instead, Lewis combines literary examples, philosophical reflection, and Christian theology. The book is distinct from The Allegory of Love, his scholarly study of medieval literature, and from The Problem of Pain, which addresses suffering and belief.