What lecture did J.R.R. Tolkien give in 1939 that later became the essay On Fairy-Stories?

J.R.R. Tolkien gave the Andrew Lang Lecture in 1939, and it later became the essay On Fairy-Stories.

The lecture was delivered at the University of St Andrews on 8 March 1939. Tolkien used it to examine what fairy stories are, why people value them, and what functions they can serve beyond simple entertainment.

The resulting essay is especially associated with Tolkien’s ideas of recovery, escape, and consolation. It also discusses the eucatastrophe, his term for a sudden turn from apparent disaster toward joy or deliverance.

The lecture is sometimes confused with Tolkien’s later essays or with academic lectures on Beowulf. Its significance comes from the way it presents Tolkien’s own theory of fantasy at a time when he was working on The Lord of the Rings.