That state of mind has been called “willing suspension of disbelief.” But this does not seem to me a good description of what happens. What really happens is that the story-maker proves a successful “sub-creator.” He makes a Secondary World which your mind can enter. Inside it, what he relates is “true”: it accords with the laws of that world. You therefore believe it, while you are, as it were, inside. The moment disbelief arises, the spell is broken; the magic, or rather art, has failed. You are then out in the Primary World again, looking at the little abortive Secondary World from outside.

—J. R. R. Tolkien, “On Fairy-Stories”

The mind that thought of light, heavy, grey, yellow, still, swift, also conceived of magic that would make heavy things light and able to fly, turn grey lead into yellow gold, and the still rock into a swift water…

When we can take green from grass, blue from heaven, and red from blood, we have already an enchanter’s power—upon one plane; and the desire to wield that power in the world external to our minds awakes.

—J. R. R. Tolkien, “On Fairy-Stories”

I desired dragons with a profound desire. Of course, I in my timid body did not wish to have them in the neighborhood, intruding into my relatively safe world, in which it was, for instance, possible to read stories in peace of mind, free from fear. But the world that contained even the imagination of Fáfnir was richer and more beautiful, at whatever cost of peril. The dweller in the quiet and fertile plains may hear of the tormented hills and the unharvested sea and long for them in his heart. For the heart is hard though the body be soft.

—J. R. R. Tolkien, “On Fairy-Stories”