On Fairy-Stories is an essay written by J. R. R. Tolkien, first published within Essays Presented to Charles Williams in 1947. It was subsequently published with Leaf by Niggle in Tree and Leaf as well as in The Tolkien Reader around 1966.
The essay is important because it contains Tolkien's explanation of his philosophy on fantasy and thoughts on the crafting of the mythos.
Tolkien named the genre Fairy Stories, which he carefully distinguishes from actual "Fairy Tales". This distinction seems to be twofold. First, he defines fairy stories as not stories about fairies or other supernatural beings, but stories about the interaction between humans and those beings. Second, he emphasizes that through the use of fantasy, which he equates with fancy and imagination, the author can bring the reader to experience a world which is consistent and rational, yet utterly strange as well. He calls this "a rare achievement of Art", and notes that it was important to him as a reader: "It was in fairy-stories that I first divined the potency of the words, and the wonder of things, such as stone, and wood, and iron; tree and grass; house and fire; bread and wine."
Having defined the genre, Tolkien goes on to defend its utility on three grounds. First, suggesting that fairy stories allow the reader to review his or her own world from the "perspective" of a different world. This concept, which shares much in common with cultural relativism]], Tolkien calls "recovery", in the sense that one's unquestioned assumptions might be recovered and changed by an outside perspective. Second, he defends fairy stories as offering escapist pleasure to the reader. And third, Tolkien suggests that fairy stories (can) provide moral or emotional consolation, through their happy ending, which he terms a "eucatastrophe".