…when you have an interesting city you want to set a story in, you cheat your worldbuilding to support the existence of that city, you don’t just woefully hang your head and leave the city out because you forgot to draw enough farms on your map or something. I’m not at all a fan of the “begin by simulating the tectonic plate movements of your fictional planet several billion years before the story begins” style of worldbuilding; as far as I’m concerned, you write what you want to write and you shuffle things around ex post facto to support them. Or you just don’t fucking explain things at all– the mere existence of your big beautiful boondoggle should, in itself, imply that somewhere, somehow, something makes it all work, even if that background detail isn’t important to the story.
Indeed. Do we demand that the author of a fictional world pause to establish that there is enough plant biomass to produce all the oxygen the people are breathing?*
When the author needs to make sure that things are working internally consistently, it typically should be “off-stage” so the reader isn’t detained by it. An example: I have a work in which some of the people have a very low mortality rate from natural death. In order to make sure that the population dynamics wouldn’t drive them to a population of 100 billion in short order and lead to uncomfortable encounters with Dr. Malthus, I had to put limits on their reproduction rate and establish some ways that they might have non-natural deaths. My thoughts on this are archived in a file that has a differential equation and a couple of difference equations describing the population dynamics. But you never see the equations in the novel, of course. It’s in the background.
Larry Niven mentions a similar point about his novel with Jerry Pournelle, The Mote in God’s Eye. In N-Space Niven mentions that the faster-than-light drive in that novel was supported by a page of differential equations in the authors’ notes. They didn’t feel a need to include the equations in the novel.
For some reason differential equations keep popping up here. The point is not differential equations; the point is that the default setting should be to either just assume that the world functions, per Lynch above, or do the intellectual work to make sure it functions but leave that work off-screen. You must do some explaining about some things, but don’t explain unless you have some specific reason to.
*Actually, yes, when it comes to Dune, Hoth, and Tatooine. On desert or frozen worlds, where is the plant life that produces oxygen for those people? But the point is, you needn’t worry about such unless a particular feature of your fictional environment makes it necessary.