Which C.S. Lewis book examines the idea of universal human affection in four categories?

The Four Loves examines universal human affection through four categories.

Published in 1960, the book develops material first presented in a BBC radio broadcast series. Lewis discusses affection, friendship, eros, and charity, using both Greek terms and ordinary examples to distinguish kinds of love that are often treated as identical. Charity, or agape, is presented as self-giving love associated with Christian theology.

Lewis does not simply rank everyday relationships as good or bad. Instead, he describes how natural loves can become distorted when they are treated as ultimate. Friendship, for example, is different from romantic love, while affection includes familiar bonds within families and households. The work is nonfiction and belongs with Lewis’s apologetic and theological writing rather than his fictional stories.