Over on Whatever, John Scalzi pokes a little fun at the folks who (are? profess to be?) thrown out of the Lord of the Rings by the viscosity of the lava in Mount Doom. He makes an excellent point that the suspension of disbelief is a highly personal thing, subject to much head-scratching by observers (and especially by writers, who may veer into hair-pulling and sobbing). My comment there started to get overlong, so I’m posting it here.
First, I take his point that the fires of Mount Doom are set up as being magical and important, and are presented in a context where trees walk and orcs are born from mud. He is perfectly correct that it would have been reasonable to have magical or otherwise nonstandard lava in Mt. Doom. And if Jackson had made the lava blue or sparkly or put little morphing orc faces in it or otherwise made it obviously magical, I would have bought that without blinking. But a difference of viscosity is a useless, thoughtless difference, especially in comparison to the more overt differences he mentions, like the shrubbery being alive or the landscape giving birth to orcs, that border on the metaphorical. Subtle differences aren’t always a bad thing — not at all! But subtle differences are more likely to be mistaken for errors.
Those changes he mentions don’t come out of nowhere, either: there are plenty of hints given that we’re about to see something weird: spooky forests where orcs disappear, enough cobwebbing to put a Halloween house to shame, the presence of Christopher Lee, etc. When something comes as a surprise, the work is more vulnerable to booting the viewer/reader out of their suspension of disbelief than at other times, and it takes skill and preparation to avoid that, plus the knowledge of the degree to which disbelief needs to be suspended. If Peter Jackson knew how viscous lava really was but still wanted this particular visual effect, surely he is savvy enough to know how to clue in his geologist viewers that this is what he was doing? Because he can do it well, when he fails we suspect a deeper failure.
Anything that can be done well can be done badly, of course: surely you can envision a version of the Lord of the Rings in which the Ents are presented in such a way as to guarantee that the audience bursts out laughing at the sudden appearance of talking trees?
Perhaps a better comparison would be, not to Ents, but to horses. Writers are always getting horses wrong, treating them like hairy motorcycles. Add hay, drive all day, add more hay, drive all night! Most readers will never know the difference, but people who know horses get thrown out of stories by that sort of thing. If a fantasy writer *needs* to treat a horse like a motorcycle, then that writer needs to prep the reader — by, for example, praising this particular breed of horse, or having a set of magic horseshoes, or… well, that’s getting a little silly, isn’t it? In order to know when it’s actually necessary to treat a horse like a motorcycle, the writer needs to know an awful lot about horses, I should think.
Besides, we as readers and viewers can generally tell the difference between “someone thought this through and decided it should be this way” and “someone was lazy or thoughtless.” Let’s say that I set a fantasy story in rural Ohio and, in among the unicorns and magic wands, describe all the people there as having Southern accents. If all the wonderful folks who know the region then complained that this threw them out of the story, it would be ridiculous of me to counter with, “What, but the unicorns and orange Congressmen were OK?” I could argue until my face turned blue that this was actually a deep philosophical statement about the realignment of culture in a magical world, but would you ever really shake the feeling that I’d just never been to Ohio?