Tolkien’s 1939 lecture about the imaginative value of fantasy and fairy stories was titled On Fairy-Stories.
Tolkien delivered the lecture as the Andrew Lang lecture at the University of St Andrews. He argued that fairy stories should not be dismissed as children’s entertainment and described several functions of fantasy, including recovery, escape, and consolation.
The essay is especially important because it explains Tolkien’s idea of “sub-creation”: the making of a coherent secondary world through imaginative art. It also discusses the “eucatastrophe,” Tolkien’s term for a sudden joyful turn in a story, which he considered a defining feature of fairy-story consolation.
On Fairy-Stories was later published in expanded form. Beowulf: The Monsters and the Critics is Tolkien’s influential 1936 lecture, while A Secret Vice concerns invented languages. English and Welsh is a separate linguistic essay.