Originally Posted by tagutcow
But there clearly ARE supernatural forces afoot in The Shining. How did Jack manage to escape from the storage room if not for something
opening the door from the other side?
There's an ambiguity throughout the film of what is garden-variety delirium, what is some supernaturally-provoked hallucination, and what is a genuinely supernatural occurrence. Arguably, this is part of what makes it unsatisfactory as a horror movie.
The way the Shining its filmed it makes you sure the supernatural is real which is why it's frightening. Disbelief is suspended which makes it a successful horror in my opinion. The delirium acts as another device to maintain suspension of disbelief.
In the Exorcist, even if the supernatural was real, the girl would have died with her neck broken after that scene, spoiling the film as realistic horror for me. Up until that point the Exorcist is genuinely terrifying, the parents act exactly as you would expect real parents to, trying medical help first and only turning to the Church in desperation.