On Quantum Mechanics and the Art of Observation.

"In some basic way, according to quantum mechanics, it's not possible for us to be impartial observers. We are participants in reality because we create it as we watch it. In quantum mechanics, this is on a very literal level, and it has to do with wave particle duality and what an object of matter is made up of. Sometimes it's one thing, and sometimes it's another.  

The more you get into physics, the more bizarre it gets. I did a lot of studying after Big Trouble in Little China; I got into physics pretty heavily, especially quantum mechanics, and read a lot of books on it, and felt that there was something in the philosophy of quantum mechanics that would work in a horror film like Prince of Darkness—Prince of Darkness being a culmination for me of all the work I'd done in horror movies and of all the horror movies that I've seen, relating them also to science fiction. And I think it finally comes out to Five Million Years to Earth, which was the first movie that I know of that dealt with this kind of science fiction horror—this explanation for the occult. I did it on a little bit different basis, the devil coming alive in a church, bringing his father, the anti-God, back from the mirror world, which relates again to quantum mechanics and particle physics in terms of antimatter, reverse world. 

But I could only dress up the story of Prince of Darkness with particle physics. I really couldn't show what it would be like. I'd love to do that someday, and have a character in a movie who has all the characteristics of the wave in particle physics. It would be really interesting to do. On the other hand, I realize that the audience and most of the public out there has no idea about the Uncertainty Principle. And if they do have an idea about it, they reject it because it's too complicated. You always run into a problem when you're dealing with something like this. It reminds me a lot of the beginning of Casablanca when you show a map and have a narrator tell you what's going on in this particular section of the world. You don't necessarily have to do that in a Vietnam story—you know you're in Vietnam, and here comes the story. 

It's an old-fashioned way of dealing with the lowest common denominator, which is people who don't know anything about where Casablanca is, or what particle physics is, or what the Ark of the Covenant is. And you always run into that if you're going to deal with something that's not common knowledge among the audience like Love Story. I have run into those scenes myself, and it's very difficult. I think Nigel Kneale did exposition pretty well in his Quatermass movies. His characters would talk, but they wouldn't insult each other by saying things that the other already knew. And they would come to a conclusion by piecing together evidence. Those movies were always to me a scientific, Sherlock Holmes kind of situation where you had a Watson character who was a little less educated than Holmes: "I don't get it, what are you getting at, Holmes?" ... "I'm getting at this." And that seems to be what Quatermass did pretty well."

John Carpenter, in Order in the Universe - The Films of John Carpenter, de Robert C. Cunbow, pp. 180-81