Belief sloshes around in the firmament like lumps of clay spiralling into a potter's wheel. That's how gods get created, for example. They clearly must be created by their own believers, because a brief resume of the lives of most gods suggests that their origins certainly couldn't be divine. They tend to do exactly the things people would do if only they could, especially when it comes to nymphs, golden showers, and the smiting of your enemies.
Terry PratchettAnd it came to pass that in time the Great God Om spake unto Brutha, the Chosen One: "Psst!
Terry PratchettThe dwarfs can turn lead into gold... It reached the pointy ears of the dwarfs. -Can we? -Damned if I know. I can't. -Yeah, but if you could, you wouldn't say. I wouldn't say, if I could. -Can you? -No! -Ah-ha!
Terry PratchettWriting, for me, is a little like wood carving. You find the lump of tree (the big central theme that gets you started), and you start cutting the shape that you think you want it to be. But you find, if you do it right, that the wood has a grain of its own (characters develop and present new insights, concentrated thinking about the story opens new avenues). If you're sensible, you work with the grain and, if you come across a knot hole, you incorporate that into the design. This is not the same as 'making it up as you go along'; it's a very careful process of control.
Terry Pratchett