" In dreams you should focus on flying, because you can’t fly in this world, but you can in the dream world. And when you fly in the dream world, that gives you practice for when you fly in the spirit world. The spirit world and the dream world aren’t the same, but they come together in the sky. The dream world is inside this world, the spirit world is outside it, but you can fly in both. And they meet, too, out beyond the sky. So you can fly back and forth. The spirit world is where all the worlds meet, that’s why shamans go there. So when you’re there you can be in all of them at once. "
― Kim Stanley Robinson , Shaman