Arthur C. Clarke’s Third Law states that any sufficiently advanced technology is indistinguishable from magic. In fiction, that law calls to mind the way a 12th century human would feel if transported to modern day. People speaking to voices in their heads, metal vehicles moving by themselves, people trading important resources by waving a card, never before seen colors, light available by touching the wall, moving illusions everywhere.
Often, when I’m dissecting someone’s world building, I talk about technology and magic as if they were the same thing. Of course, in terms of what they are from within the story context, they’re very different. But in so many ways, they’re alike.
Some fiction involves technology, perhaps just a little in advance of our own. Say, microwave power beams down from satellites, and has done so for much of the technologically advanced nations of the planet for around 25 years. Now, if you want a believable world, you must consider what effects this new power has – and it will be starting to have many effects. Power plants might shrink or disappear, vehicles and public transport will look very different, every home might have a receiver that powers it, there might be a greater emphasis on controlling the weather and on sunspot shielding.
In addition, you must think of interlocking effects this may have on other technologies. What if power receivers were miniaturized and formed into a substance that could be painted right onto transport systems, buildings, clothing? Many other technologies would shift and change around that one paradigm. And that would be far from the only advance made in the time frame. Each of them will have their implications, impacting on existing systems and on one another. And there will be long-term cultural effects from new technology, as there have always been, which must also be considered by the author.
For a world where magic exists, the complexity and structure is no less important. Magical systems cannot simply serve the story. They must have internal consistency, and they will also have their impact. If you have wizards who can, for a low cost in terms of resources or personal power, light up a certain type of crystal, will it be in every home? Only that of the rich? Will there be lighted pathways? Will it impact exploration speeds, crop growth, theft?
Much like technology, magic is most believable when new advances rest upon turbulent changes to old, established systems. When new ideas or new discoveries shift the nature of resource management, usage, wealth distribution, religions, interpersonal relations. When the innovators who went before are recognized, at least by the author, and the impact of change and interlocking systems is considered.
Both technology and magic involve forces that impact the world around your characters. A magic system’s or a technology system’s far-reaching past, current changes, cultural impacts, and expansive consequences, all must be considered and consistent. In that way, for the writer, magic and technology are indeed indistinguishable.