An author’s ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic.Brandon Sanderson, "Sanderson's First Law"
There are two schools of thought when it comes to magic: Does it act as part of, or separate from, its environment? I tend to veer toward the former. I’m very much a fan on understanding the technical (and metaphysical) limitations of magic inside a story.
Because any world that contains magic must also be saturated by that magic. If you’re a Tolkien fan, the argument is easy to make that understanding of magic isn’t a necessity for the use of magic. But choosing not to acknowledge that magic can lead to some speculation.
My argument isn’t that all writers become magical architects during the worldbuilding process. Some magical intricacies certainly should be siloed from the characters or the readers. But one thing is certain: magic is a tricky subject, and if the rules aren’t clearly defined, it’s an easy way to poison a story.
Soft or Hard?
If you’re looking for terminology, we’re talking about how “hard” or “soft” a magic system is. While the terms have floated around forever, Brandon Sanderson discusses the differences at length in his essay, “Sanderson’s First Law”.
In a nutshell, the hard / soft label is an easy way to judge how rigid / flexible the magic system is when it comes to rules. Is the system confined by well-defined, well understood rules, or is it veiled from the reader (and some characters) and never really explained?
How writers choose to establish the magic in their world is always something that I monitor closely, because it’s not always easily defined. Exposition inside a story often determines whether a system is hard or soft. Likewise, it’s possible to create a hard system and never explain it while making the rules clear and obvious. That’s down to the writer, and the reader’s perception of that system. In this case, my argument is neither for or against the rigidity of the system — only that a system exists in the first place.
Magic Bullets, Anyone?
By now, this might sound like a foolish argument. Magic is magic, right? So what if it’s not obvious or understood?
Then the system may come across as contrived or downright convenient, and using magic without limitation can overpower a character and destroy the the opportunity for conflict and development. Which means that magic — however powerful — must be limited. It can’t be cheap, it can’t be easy, and it can’t always be the practical or obvious solution. Otherwise, it’s the only tool the characters will ever need.
This is where the risk of overlap comes in. If a character performs a vague, magical act in one scene but doesn’t in the next, the reader’s suspension of disbelief is called into question. One awfully convenient lock-breaking spell that can break every locked door will have some explaining to do when it doesn’t work on the one door our character needs to get through.
Something for Nothing
As anyone familiar with werewolf lore will tell you: silver bullets ain’t free.
Holly Lisle wrote an article about worldbuilding magic which indicates this rather nicely. The world a writer builds needs to be authentic. Like characters, it can be exciting, unpredictable, unruly, or wild. But the one thing it has to be is real enough for the rest of the story to take place.
Several years ago, in the Dragon Page: Cover to Cover podcast, Michael A. Stackpole made a curious argument. He joked: if wizards were the only ones who could control a magic that allows communication over vast distances you know what they’d be? Rich.
Magic has consequences, and some of them can run so deep into the veins of the story that they undermine even the most basic elements of how the world is supposed to work. It’s a problem as unique to fantasy as the magic that creates it, and one easily solved with rules.
Of course, there are exceptions.
Exceptions, Detail, and Everything Else
Let’s say we have wizards or magical entities, arbiters of this power and accessible only to them.
What is the source of their power? Are they drawing this ability from the world around them? Are they accessing it through some magical void or alternate dimension? And, if so: how / why / what is it doing to them?
As a reader, maybe I don’t need to know all the answers. We can explain most of it away (and several writers do) by telling us that it’s an innate force, or it’s an issue of blood or heritage, or whatever. That’s all fine.
But what about that one character with no magic and no birthright that can do all the things that everyone else can do? We makes rules to make exceptions. A wealth of great stories come from that one rule-breaker, that one character who ignores the natural order, challenges the authority, or is blessed with a natural gift. But you know what’s interesting about him? Even he has his own set of rules.