Which C.S. Lewis book argues that Christianity makes a trilemma about Jesus's identity?

C.S. Lewis's Mere Christianity presents the famous trilemma about Jesus's identity.

Lewis argues that Jesus cannot be treated merely as a great moral teacher if the Gospel claims about his identity are accepted. He frames the alternatives as “Lord,” “liar,” or “lunatic,” a compact argument often called the trilemma. The wording is a rhetorical part of Lewis’s apologetic case, not a complete historical analysis of every possible interpretation.

Mere Christianity grew from radio broadcasts Lewis gave during the Second World War and later from published talks. The book presents shared Christian doctrines rather than focusing on differences between denominations, which explains its title.

The argument is often mistakenly attributed to a single standalone essay. Lewis developed it within the book’s discussion of Christian belief, alongside sections on morality, theology, and the virtues. The work was published in book form in 1952.