So, this post has two main inspirations: last week's post on believable science in science fiction and several comments from the guys over at Writing Excuses. I know I mostly focus either on writing in general or writing for science fiction, but I also delve into fantasy from time to time. Besides, there are a lot of similarities between science fiction and fantasy (though it still bothers me that bookstores shelve them together—it makes it so much harder to browse one or the other!). For example, the technological aspects of science fiction that aren't a reality yet are not different than magic in fantasy stories.
So, on to my topic: making magic believable. The Writing Excuses guys make a really good point here (well...this is one of many): the criteria for a good magic system depend on whether or not the magic will play an integral role in the story. Brandon Sanderson puts it this way (he calls it Sanderson's First Law of Magic, which I thought was kind of clever): your ability to solve problems with magic is directly proportional to how well the character (and, therefore, the reader) understands how the magic works. So if you want magic to be an important part of the story, you really have to know how it works. Jim Butcher does this pretty well in his Dresden books.
For magic to land somewhere in the realm of believability, the reader has to feel like he or she understands it—that means knowing what it can and can't do, how one learns it, how it is used, and what it costs the user each time a spell is cast (or an ability used). Incidentally, in one of their discussions on magic, the Writing Excuses guys said that what magic can't do is often more interesting than what it can. That last thing I'm going to pull from their discussions is this: remember that if you can do something by magic easier than doing it the normal way, you've just put a whole bunch of people out of business; the point being that you have to think about the affect magic will have on your world, it's people, and it's economy.
Now on to my own thoughts. I think a good magic system has to have a process or mechanism for activating a spell (be it a ritual, a gesture, a word, or a combination thereof). I'm not a big fan of the 'just access your inner energy and it's done' kinds of magic (a la Black Magician trilogy by Trudi Canavan, which are wonderful books in spite of the anemic magic system).
I also think a good magic system has to involve some sort of risk, especially to the user. An excellent example of this is Sabriel, by Garth Nix (quite possibly my favorite fantasy book of all time); in it, Sabriel wields two powerful forms of magic, but each is perilous in its own way and there are times when you're afraid one of them is going to get her killed. I think the risk really brings magic into the realm of possibility because almost everything in life involves some sort of risk.
So, what do you all think? What makes magic come to life, in your opinion? For that matter, what do you think of my analysis? Are there wholes in it?