When you're worldbuilding, it's easy to get caught up in the need to explain or justify the cool parts of your setting, to make it make sense. Less frequently, most often when we've tied ourselves in knots trying to do the first thing and are now attempting to get ourselves untangled, we go the other way and decide that it doesn't have to make sense. Let me be clear, both of these approaches have been used to good effect by successful authors, but the latter often leaves noticeable, distracting gaps in the fabric of the setting, and the former can easily lead to exhaustion and never finishing the book. (And sometimes to even
more glaring gaps in the logic of the setting).
Worldbuilding is like a river. Experience this metaphor with me, 'cause we're gonna be here a while. The particular place and time in which your story is set is one stretch of it, and you can put whatever you want there. Rocks, trees, a patch of waterweeds, fish...put a little island in the middle if you want. You don't need to know exactly how any of it got there. What's upstream needs to be somewhere from which what's on your stretch of river could reasonably follow, but it doesn't need to perfectly explain it. But what's downstream needs to follow much more closely from what your built on your stretch of riverbank.
Rivers are often a metaphor for time - try not to get distracted by that. Time isn't real anyway, but causality is very real, and that's what we're talking about here. For a thing to be in your story, it must first exist, and once it does, it's going to do all kinds of things, not all of which you anticipated, and all of which you will need to either deal with or take steps to prevent.
Let's take tea as an example. Like, specifically tea from the tea plant, not just herbs and spices infused into hot water. Upstream, tea plants exist somewhere in your setting. (This means plants exist). They like tropical and subtropical climates, which means those exist, or some approximation of them does. If your story isn't set in a tropical or subtropical climate, that implies the existence of trade across distances. Much of this is vague, and all of it is negotiable (except maybe "plants exist"). Often, this doesn't take a lot of additional thought. If your setting contains one or more spherical planets and like, trade at all, you're probably fine. The specifics are something you can explore, in the actual story or just in your notes, but you don't have to. If your setting just straight up doesn't have the right climate zones, or the place where the story takes place isn't there and has no interacting, you're going to need to build something farther upstream; that might be as simple as greenhouses or as complicated as magic or technology that creates the leaves ready to use.
Downstream from tea, you have less control, but that also means you have less work to do. This is also where inconsistencies or failures to think things though are going to be glaringly obvious. If tea exists, caffeine is available, at last to the people to whom tea is available. People are boiling at least some of the water they drink, et cetera. If you get into a situation where access to caffeine matters, or waterborne illness is a plot point, and you don't deal with how the established existence of tea affects that,
everyone will notice. As an aside, I've used words like "access" and "available" here, but that's not necessarily a money or privilege thing - although it's tea, so probably - if, in your setting, tea is a poor people thing, and the rich drink more fruit juice and milk, more how it is in real life right now (compare the cost of a half-gallon of milk or orange juice to the cost of the tea bags necessary to make the same volume of Lipton), or maybe everyone drinks tea, but poor people live underground, so only they boil water for tea, while rich people make son tea. As an additional aside, tea is not the unproblematic example I might have made it sound like here. The plant, and the drink that comes from it, are straightforward enough in and of themselves, which is why we're even talking about it, but it has all kinds of sociopolitical
stuff attached to it, and you
will have to deal with it one way or another, that's just not what this post is about.
Let's try a less loaded example. Cats with wings. Upstream, these actually require almost nothing. Mammals exist, and probably also birds. That's it. If you want to build further upriver and explain the cats with wing, you might in so doing create bigger upstream implications. If they're genetically engineered, that means someone somewhere knows how genetics work, or did at some point. If they're explicitly magical in origin, actually that doesn't create much complication upstream, but the downstream impact of magic that can make a flying cat is considerably greater than the downstream impact of the critter itself. If you confirm that they just evolved like that, that creatures an upstream environment that would put the appropriate selection pressures on them, but "they just evolved like that" is the unmarked case here, and explicating it doesn't saddle you with many implications that you wouldn't be taking them on and not explaining.
Downstream, though. Downstream. How fast are the songbirds in your setting? The larger insects? How are the small rodents and reptiles dealign with this? The domestic cat is an incredibly effective predator already, and you just gave it wings. And you can do that. This is by no means unmanageable, but if I see something that I know cats eat, I'm gonna be wondering how it's adapted to flying cats. Are these guys pets? Having one as like, a barn cat isn't gonna be too different, but they're gonna need slightly different accommodations as indoor cats. Cat-related figures of speech probably look a little different. If your setting doesn't have like, a postal service, or email, if sending messages by birds is a thing, these kitties are gonna be a complication. Keep in mind that while it absolutely does not have to be this way in your story, in real life, birds used to carry messages are pretty much pigeons, not hawks, owls, ravens, or anything else with natural weapons worth talking about. Unless you can use the cats themselves as messengers? I wouldn't expect them to be distance flyers, and it would raise additional questions if they were, but it's an option.
You'll notice that by and large, serious departures from reality, including and especially magic, have more downstream implications than upstream ones, while things from the real world have more upstream implications than downstream. This is not universally true, of course. While guns have more upstream implications than, say, the existence of magic does (usually magic doesn't, in and of itself, have
any), they also have more downstream implications than flying cats, and this is true whether or not your story is set in something resembling the real world. Guns
change things. Magic that can kill people
might be comparable, but only if it's something
anyone could at least theoretically access.
The stretch of river where you're putting things on purpose isn't the only place where you might need to make decisions. It's where you're putting the stuff that you want, or that's needed to make the plot go, but you may need to build further down or, less frequently (much less frequently) further up, in order to make sure the causality flows right. Consider the flying cats again. They take per-real-world homing pigeons off the table, so your options for sending mail are reduced, and you may need to make a decision about that. That's still downstream. Since your upstream just needs to be a place from which the current set of circumstances could reasonably have arisen, and that's always more flexible, you usually don't have to make decisions about it, but sometimes you want tea, but also for plants to mostly not exist, and in that kind of case, where readers are actually likes to wonder what the hell happened (and moreover, to do so before like their twelfth reread), you'll ned to make some upstream decisions about what the hell did happen.
So far, we've been looking at single worldbuilding elements in isolation, but that's almost never how that actually works. You're not just putting down on rock or willow tree, you're putting in rocks, plural,
and trees,
and fish, and they're all going to affect what downstream looks like
together. This is part of why you don't have
that many decisions to make about it, as long as you think it through properly. Whether armored pigeons, magical communication, or human messengers are the best option for sending mail that will get past the flying cats is likely to become a reasonably obvious decision once all the important bits of your worldbuilding (that is to say, all the bits that are important to
you) are in place. Consider also the situation where tea implies boiled water. You're doing waterborne illness plot among the wealthy, and either it doesn't matter whether it also affects the poor, or it's important that it doesn't. You're unlikely to decide to put the poor underground just so you can make the tea work (although you can - worldbuilding, especially prewriting and mid-draft worldbuilding, is one place where you don't necessarily need to kill your darlings. Changing a big detail you weren't invested in or counting on for plot, so you can keep a small detail that you think is cool is
absolutely valid, and in fact can sometimes help clarify plot elements, as well as leading to a more interesting setting). But if you already
have "everyone drinks tea" and "poor people live underground", then "the wealthy have a bit of a Thing about how they're up where the sun is, so they make sun tea and don't use boiled water" follows kind of naturally. It's not the only choice by any means (perhaps the pathogen resists head, but the undercity is radioactive, which
does kill it, even as it gives the poor people cancer), but it's one that requires few further additions to the setting.
Everything upstream affects everything downstream of it, whether or not it's on the part of the river where you're building. Suppose you've got magic that can put parts of different animals together into viable creatures that can even reproduce and be their own species, if enough are made to establish a breeding population. It's a plot thing, there because you want and need it, and not to facilitate or follow from some other part of the worldbuilding. And you've got the winged cats, because they're just...incredibly cool and you like them as a widespread setting detail. Both these things are in the part of the river where you're building, but since the flying cats are still, within the setting, a product of this magic, they are downstream of it, and changes to it may also affect them. (Unless there have always just been flying cats, and their apparent hybridity actually inspired the development of this kind of magic). f most hybrid animals end up more aggressive than either of the source species, but the winged cats are nice kitties, you'll need to explain, or at least acknowledge the mystery. (To be clear, when magic or science are involved, acknowledging the mystery is extremely valid). Likewise, your downstream has to do business with your upstream. If your flying cats are bioengineered instead of strictly magical (even if it's like, magic bioengineering) then as I said above, that means someone knows that genetics are a thing (upstream), which means that downstream, most people probably have a rough idea of how heredity works, even if they're a little fuzzy on the details, unless you've got some mediating factor that changed this. This is not to say that everyone's going around talking about Mendelian inheritance patterns all the time, and more than they do in real life, but they probably don't think birth defects are a curse from God either. (Although they could, if people in your setting for some reason figured out genetics and bioengineering super early, they could have developed all kinds of weird mythology about it, although they still probably don't have a changeling myth).
The thing I want to emphasize again is that you can out anything you want in your worldbuilding. as long as you're prepared to handle the implications. The upstream-downstream construction is meant to be a tool to help you do that, not to discourage you from putting messy things in your world. It's also a little bit meant to argue against the idea that you need an "explanation" or a "good reason" to put something in. The drive for explanations leads to a lot of half-justified magic systems and technology presented in just enough detail to not make any sense, and the pressure to have a "good reason" causes a lot of writers to leave out cool, distinctive details that weren't causing any harm.
I should have another Dresden files post up later this week. Until then, be gay, do crimes, and read all the things!
