The Rules of MagicIn workshops and conferences over the past decade, I've seen groups of writers and readers come up withhundreds of ways that magic might work within a fantasy society. But the basic idea is only the beginning. Withmagic, you must be very clear about the rules. First, you don't want your readers to think that anything canhappen. Second, the more carefully you work out the rules, the more you know about the limitations on magic,the more possibilities you open up in the story.Let's take, as an example, one of the ideas that commonly crops up in the fantasy part of my thousand-ideassessions: The price of magic might be the loss of parts from the human body. It's simple, it's painful, and it'sgrotesque to imagine-sounds like a great idea to me. And there are as many variations here as there were withtime travel. Here are several different ways you might turn this idea into a useful magic system:1. When the magic user casts a spell, he loses bits off his own body, always starting with the extremities. He'snever sure quite how much he's going to lose. Inevitably, however, missing fingers or hands or feet or limbsbegin to be taken in society as a sign of great power-so that young people who wish to seem formidable pay tohave fingers and, sometimes, limbs removed, with scars artfully arranged to look like those that magicians have.It's hard to tell who really has power and who only seems to. (Your story might be about somebody who refusesto mutilate himself; he's universally regarded as a powerless coward. Which, in fact, he is-until there comes atime when a spell is needed to save his city, a spell so powerful that only a person with his entire body intact cancast it-and the spell will use up all his limbs at once. Does he do it? If so, why?)2. The magic user must actually cut off a part of his own body, or have it cut off, casting the spell while the boneis being incised. The longer he endures the pain and the larger the section of his body being removed, the morepower he obtains. A whole profession of Removers would spring up, people skilled at the excruciatingly slowremoval of limbs, using drugs that, while they don't dull the pain, do allow the magician to remain lucid enoughto perform the spell. (Here's a chance for an interesting twist on a science fiction staple: a future society devotedto "harmless" recreational drugs. Why not have a Remover who goes into the underground apothecary trade,selling the drugs to people who just want the heightened mental effects? What will the magicians do to himthen?)3. The magic user does not have to cut off his own body part; he can cut off somebody else's. Thus magicianskeep herds of human beingssocial rejects, mental defectives, and so on-to harvest their limbs for power. In mostplaces this practice would be illegal, of course, so that their victims would be concealed or masquerade assomething else. (A good horror story using this magic system might be set in our contemporary world, as wediscover people living among us who are secretly harvesting other people's limbs.)4. The magic user can only obtain power when someone else voluntarily removes a body part. Thus magic is onlyrarely used, perhaps only at times of great need. If a private person wishes to hire a spell done, he must providenot only payment to the wizard, but also a part of his body. And at a time of great public need, the hero is not thewizard,but the the volunteer who gives up part of his body so the spell can be cast to save the town. (How about apsychological study of a pair of lovers, one a magician, the other a voluntary donor, as we come to understandwhy the one is willing to give up his or her body parts for the other's use?)5. When the magician casts a spell, someone loses part of his body, but he can't predict who. It has to besomeone known to him, however, someone connected to him in some way. And, while wizards all know this darksecret of their craft, they have never told anyone, so that nobody realizes that what causes limbs to wither up andfall off is really not a disease, but rather the wizard up the street or off there in the woods or up in the castletower. (And here's the obvious variation: What if some common but nasty disease in our world is really the workof secret magicians? That's why certain diseases go in waves: twenty years ago it was bleeding ulcers; now it'scolon cancer. And the hero of our story is a wizard who is trying to stop the suffering he and others like him are causing.)When a wizard casts a spell, body parts wither and fall off the person he loves the most. The love can't befaked; if he loves himself most, it is himself who loses body parts. The greater the love, the greater the power-butalso the greater the suffering of the wizard when he sees what has happened to the person he loves. This makesthe most loving and compassionate people the ones with the most potential powerand yet they're the ones leastlikely to use it. (Here's a monstrous story idea: The child of loving parents who wakes up one morning without alimb and, seeing her devoted father getting paid, begins to suspect the connection between her maiming and hiswealth.)