The Four Loves explains four forms of human love: affection, friendship, eros, and charity. C.S. Lewis developed the book from a series of BBC radio talks, and it was published in book form in 1960.
Lewis uses Greek terms to distinguish important kinds of love. Storge describes affection, philia friendship, eros romantic or sexual love, and agape self-giving love, which Lewis also calls charity in the older Christian sense. The book considers both the goodness and the dangers of each form.
The Four Loves is not a list of four interchangeable synonyms. Lewis argues that natural loves can become distorted when treated as ultimate, while charity transforms rather than simply replaces them. Readers sometimes associate all of Lewis’s discussions of love with Mere Christianity, but The Four Loves is the work devoted specifically to this classification.