Thanks for the quick response! I think I get it now....
My mistake was in assuming that if a character solves a problem using a magic ability, and the reader didn't know and couldn't figure out beforehand that the character has that ability, then it's automatically deus ex machina. This is wrong; there's another common possibility:
- 2.5) If the reader doesn't know and can't figure out that the character has that ability, but can reasonably guess, then the author might or might not have committed deus ex machina.
For example, if Gandalf Jr. levitated an dog in chapter one, and then in chapter ten gets away from a rampaging elephant by levitating it, this might or might not be deus ex machina, because the reader only knew he could levitate dogs, but some readers might assume that that meant he could levitate elephants as well, while others might assume that elephants would be too heavy for him to levitate.
In this case, Sanderson’s First Law of Magics applies and can be restated as: The more completely the reader understands what a character is capable of doing, the less likely the author is to commit deus ex machina when that character uses his abilities to get out of trouble.
I initially assumed (as Matt apparently did) that Brandon was saying we should be creating natural sciences of imaginary worlds if we wanted to use magic a lot. But this completely misses the point. If Q hands James Bond a watch and says that pushing the button on the watch will let Bond becomes invisible for up to thirty seconds, then in terms of this discussion, we would say that the reader now
completely understands the magic, even though there's no explanation of
how the watch makes Bond invisible.
By the way, regarding whether it matters how minor the conflict is, we're looking at this from different viewpoints again. I agree that if you use deus ex machina to save the dog, you're likely to end up with a
better book than if you used deus ex machina to save the child. What I meant was, the fact that the dog isn't very important doesn't by itself somehow make it
not deus ex machina to invent a new ability in order for your character to save it.