“For my present purpose I require a word which shall embrace both the Sub-Creative Art in itself, and a quality of strangeness and wonder in the Expression, derived from the Image: a quality essential to fairy-story. I propose, therefore, to arrogate to myself the powers of Humpty-Dumpty, and to use Fantasy for this purpose: in a sense, that is, which combines with its older and higher use as an equivalent of Imagination the derived notions of 'unreality' (that is, of unlikeness to the Primary World), of freedom from the dominion of 'observed fact,' in short of the fantastic. I am thus not only aware but glad of the etymological and semantic connexions of fantasy with fantastic: with images of things that are not only 'not actually present,' but which are indeed not to be found in our primary world at all, or are generally believed not to be found there. But while admitting that, I do not assent to the depreciative tone. That the images are of things not in the primary world (if that indeed is possible) is, I think, not a lower but a higher form of Art, indeed the most nearly pure form, and so (when achieved) the most Potent.
Fantasy, of course, starts out with an advantage: arresting strangeness. But that advantage has been turned against it, and has contributed to its disrepute. Many people dislike being 'arrested.' They dislike any meddling with the Primary World, or such small glimpses of it as are familiar to them. They, therefore, stupidly and even maliciously confound Fantasy with Dreaming, in which there is no Art; and with mental disorders, in which there is not even control; with delusion and hallucination.
But the error or malice, engendered by disquiet and consequent dislike, is not the only cause of this confusion. Fantasy has also an essential drawback: it is difficult to achieve. . . . Anyone inheriting the fantastic device of human language can say the green sun. Many can then imagine or picture it. But that is not enough -- though it may already be a more potent thing than many a 'thumbnail sketch' or 'transcript of life' that receives literary praise.
To make a Secondary World inside which the green sun will be credible, commanding Secondary Belief, will probably require labour and thought, and will certainly demand a special skill, a kind of elvish craft. Few attempt such difficult tasks. But when they are attempted and in any degree accomplished then we have a rare achievement of Art: indeed narrative art, story-making in its primary and most potent mode.”
― J.R.R. Tolkien