I kind of have to agree with that (I do believe in the supernatural, though).

One of my favorite quotations is by the nihilist Friedrich Nietzsche and it goes:

"The 'kingdom of Heaven' is a condition of the heart - not something that comes 'upon the earth' or 'after death.'"

And it means that we make our own heavens or hells. We are our own demons or angels. Metaphorically speaking, though. Not for real. Nietzsche believed, as he put forth in his book The Antichrist, that the kingdom of God is within us.

Remember that mental illness really was only starting to truly be understood in the late 19th-early 20th Century with Sigmund Freud paving the way.

Many people used to believe that mental illnesses were cases of possession -- and I'm sure that if you read about cases of possession from 200 or so years ago, they'll bear resemblance to a variety of mental illnesses.

I think sometimes the lack of control we can experience over our own brains, our own thoughts, perceptions, and feelings, can feel very much like a possession. And it can be very scary because there is that duality, of "something else" taking over while you are hidden away somewhere as events play out and all you can do, if anything, is watch yourself set the world on fire, so-to-speak.

But you are not possessed. You will not be forever lost, or damned, and demons have nothing to with it.

Now, if you start spitting out fluent Latin or Aramaic one day, without ever having learned it, that might be a different story.