Oh, yes! I do believe in what others call "ghosts" , "shades", "specters", or "phantoms".
Myself, I would prefer "visitors", seeing as they never stay too long and, like any proper guest, they don't leave messes... with some exceptions.
These past-human life forms are not all like "Casper"; smiling and gracious and non-threatening. Many unfortunate mortals, have encountered some fairly nasty visitors. They seem hell-bent on wreaking havoc while still connected to this plane of existence. I blame this on a gnawing envy they feel toward the quickened.
The entertainment industry has thrived off the innate fears and fascination most people have with the possibility of having a paranormal experience. Movies try to delve into the deep rooted desire to know and understand what awaits us in the after life...if there is an after life!
Most religions believe in a reward and punishment system that will be applied by the supernatural being that created all life and the universe itself.
This certainly fits into my theory of visitors, bringing some kind of messages back to the living; messages that might help those in this special audience, to live a better life.
But then, there is another theory I believe deserves examination.
What if these visitors, these spirits of souls that have departed this plane, have joined together to frighten, confuse and mislead their living brethren? What if they conspire to infiltrate our lives with their negative energies; drawn to us like lightning to a high point?
Can they insert themselves into our plane of existence by using our human curiosity to snare us in their traps? If so, do they feed off our terror of the unknown and drink in our fears, when we feel the touch of their cold, dead hand upon our face.
If the ghosts do conspire to be a constant presence in our lives, perhaps it would be prudent of us to leave the night light on. It works for me!