In Henry James's 1898 novella, The Turn of the Screw, filmed in 1961 by Jack Clayton as The Innocents, the main character, Miss Giddens, as played by Deborah Kerr in the movie, comes face to face with what she believes to be a scary reality--the existence of ghosts. They torment her almost to the point of a nervous breakdown; and, while reading the novella, I am very drawn in and almost ready to believe her. When the novella was first published in 1898, ghosts were very real things to many people. But today an overwhelming majority of people does not believe in ghosts. I believe, if one were to take a step back and look at the situation, there really are other explanations for what is going on.
Advances in medicine over the past 100 years, particular those dealing with mental disease should most definitely be talked about. Advances in medicine and psychology have come to show things such as schizophrenia and multiple personality disorder. The governess simply could have been unfortunate enough to suffer from one of these or a number of other conditions that would cause her to see the things she saw, to hear the things she did, and to believe the things she did. Also it could have been a result of the overwhelming pressure and stress she was feeling from her situation. An eighteen year old (in the book, but older in the movie), not a girl, not a woman, has been put in charge and responsible for the lives of two children? If that does not take a toll on someone I do not know what would.
The second problem is ghosts have become way less believable in the hundred years since the novel has been published. In the early 1900's many things that people could not find an explanation to were attributed to ghosts just as ancient civilizations attributed natural phenomena such as fire and lightning to the gods. And even more recent times, witch-hunts were an acceptable practice, and people completely believed in the existence of witches. That time has passed, and witch-hunts definitely would not go over the same way now, just as the majority of people find it hard to believe in ghosts now.
Thirdly we must take into account the governess herself. A young, very impressionable girl was given this type of responsibility. She obviously was very attracted to the children's uncle (Michael Redgrave), so it should not be ruled out that she got the idea in her subconscious that, if there were ghosts haunting the place, the uncle could come riding to her rescue like a knight in shining armor. This could cause her to actually believe that there were ghosts whether there really were or not, or whether she realized she was actually willing there to be ghosts. Maybe she broke under the stress and started hallucinating; maybe it was a cry for attention; maybe it was one or many of these or a lot of other things, all of which should be looked at and falsified before we can actually believe that it was in fact ghosts.
Luckily, whether or not there were ghosts or not does not take away from the story in the slightest. People still go see ghosts stories; people still love to read them. I believe it is our obsession with the unknown, that no matter how much we can attribute to NOT being ghosts, we shall never be able to completely rule it out, and we are fascinated and terrified by that.