It's all about balance, do you see? Balance is the trick. Keep the balance and - " she stopped. "You've ridden on a seesaw? One end goes up, one end goes down. But the bit in the middle, that stays where it is. Upness and downness go right through it. Don't matter how high or low the ends go, it keeps the balance." She sniffed. "Magic is mostly movin' stuff around.
Terry Pratchett, Wintersmith
balance