The phrase, “the willing suspension of disbelieve” was first coined in 1817 by Samuel Coleridge. He was trying to revive the older tales of drama and fantastic that had fallen out of favor with the “age of reason.” He believed that if you could have “human interest and a semblance of truth” in a fantastic tale, it would be possible for the audience to enjoy the story and put aside their disbelieve for the duration of the tale. I believe he was correct, and will go so far as to say it is a necessary part of enjoying any good work of fiction.
In a good work of literature, if the characters support a good story then it is an easy thing to go along for the ride. Whether it is fantastical, mythical, or even a modern day crime drama, with good characters you can buy into the less realistic aspects of the story. This s not as easy when watching movies however.
During a classroom discussion about this topic, the teacher pointed out a scenario that makes the point nicely. If you are watching the second movie in the Lord of the Rings series, The Two Towers, and just before the big battle starts and the two armies are facing off… then the Starship Enterprise flies down and blows up the orcs, saving the day, would you buy it.? Probably not, you would be yelling with everyone else that is not realistic, there is no starship. Except, the whole story of wizards, orcs, dwarves and elves, isn’t exactly realistic now is it? None of those things exist either.
Movies are harder to pull off the wiling suspense of disbelieve, and that is why the fantastical has a harder time selling in the theaters than books, and mixing the scientific and magical, as was done in the example, is almost unheard of in movies. Mixing genres seems to be something people have a hard time with. (See, Cowboys and Aliens.)
Yet in books it is easier to mix genres, or get into the fantastic and magical, because it is our own imagination that is fueling what we see. As I said, as long as the characters are engaging and the story is good, bring it on.
As a footnote if you are interested in mixing genres, Roger Zelazny did it like no one else in his Amber series. Or Jack L. Cha
lker was excellent mixing magic and sci-fi.