I'm the author. Here's my original response:
Damned if I know. I seem to recall something about "coherence of the fluxions," so that would be the research path to go down. Since I'm not entirely sure what fluxions are, other than the "cords that tie together the universe," I can't really comment. You're welcome to speculate.
Here's my answer to the response to that answer.
How does it answer your question?
In the only way possible. I'm writing lightweight entertainments, not creating a detailed cosmos. If you want these imaginings to have any more foundation than the froth that I base them on, you'll have to provide it yourself.
And now I'll add this: the universe in which these stories take place does not exist. They're meant to be taken as light entertainments, picaresque adventures of a skilled but largely unlucky thief named Raffalon.
I have a vague notion that magic works, in this unreal universe, because there are hard-to-see integuments that connect parts of phenomenality together. Adepts who have trained in the thaumaturgical arts can identify these connections and influence them by a combination of focused will and particular sounds and gestures called magic.
And that's about as far as I've taken the rationale, and as far as I'm likely to. It's just for fun, not for real.