Mindfire
Istar
I've long wondered how people of commited monotheistic persuasion could possibly accommodate fantasy/magic within their personal cosmology - not so much because two belief systems (one personally held, one personally invented) might be inconsistent - but because of what they have in common. The instant you acknowledge one form of supernature as fictional - for whatever reason - it must logically expose all forms of supernature to the same charge of potential fictionality. In other words, the age-old question of faith.
Again, I'm going to echo Foster's words on this, but I'll add the following.
The belief systems in my alternate world have quite a bit in common with Judeo-Christianity. Which is (for me) rather the point. My imagination has one limitation and one only: I cannot imagine a universe in which God does not exist. It would be dishonest to say that I am absolutely incapable of it, but I haven't tried very hard nor do I wish to. So when I create another world I ask myself, "how does the supernatural come into it?" "What are the 'rules' here?" "How would God choose to reveal himself?" I think Lewis and Tolkien asked similar questions.
Now I'm not going to turn my books into sermons. That would be neither fun to write nor read. But I believe that if a writer goes on long enough, their views about the world will inevitably show up in the work. How well they disguise it depends on the writer's level of skill. As a Christian this is more so because my faith is supposed to seep into every part of my being including my writing. The Bible says everything ought be done to the glory of God. Again, I'm not using my work as a soapbox. But in a sense, I see my writing as another way of practicing my faith.