" 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 swift water. If it could do the one, it could do the other; it inevitably did both. 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. It does not follow that we shall use that power well on any plane. We may put a deadly green upon a man's face and produce a horror; we may make the rare and terrible blue moon to shine; or we may make woods to spring with silver leaves and rams to wear fleeces of gold, and put hot fire into the belly of the cold worm. "

― J.R.R. Tolkien , On Fairy-Stories