Tastes Great/Less Filling?

Dr. Bob Rich begins his review of The Last Protector by saying:

This is the best fantasy book I have ever edited. Or is it science fiction?

OK, debating fantasy vs. science fiction is kind of like debating tastes great vs. less filling*

But let me propose this simple test, based on the idea that in fantasy the supernatural intrudes into the natural world (gods, demons, spirits, magic and such are part of the story), while science fiction takes place entirely in the natural world:

If something gets destroyed by a lightning bolt from heaven, it's fantasy.

If the same thing gets destroyed by high explosives, it's science fiction.

Case closed. For now, at least...

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*Tastes great vs. less filling: Of course, if we're talking about "light" beers, the answer is "neither"--most "light" beers are pretty devoid of flavor, and so over-carbonated that you inflate like a balloon after a couple.