There are, however, many theories to explain the thousands of experiences that people around the world have had. I think ghosts and spirits are a common part of the so called human experience. It also appears to be several types of ghosts or hauntings, and more than one theory might be needed to explain them all. The traditional view of a ghost is that it is the spirit of a dead person that for some reason is "stuck" between this world and the next, often as a result of some tragedy or trauma. I believe that some of these earth-bound spirits don't know they are dead, and others know they are dead but remain because they are attached to someone or something, or some place. These ghost/spirits are what I believe to be an "intelligent haunt." These ghosts exist in a kind of limbo state in which they haunt the scenes of their deaths or locations that were pleasant to them in life. I think that often, these types of ghosts are able to interact with the living, and on occasions they can even materialize. I know as an investigator I try to communicate with them, with hope of a response. If we get a response though do we know what to do with it.
On the other hand some ghosts appear to be mere recordings on the environment in which they once existed. A soldier is seen on repeated occasions staring out a window where he once stood watch. A child's laughter is heard in a hallway where the child once played. There are even cases of ghost trains that can still be heard and sometimes seen, even though they are long gone. These types of ghosts, I think, do not interact with or seem to be aware of the living as much as intelligent ghost. Their appearance and actions seem to be always the same, to me it's like a spirit-level recording - residual energies - that replay over and over again. One of my theories concerning a residual haunt is that these entities are actually what has been called a "thought form." I think that some of the most famous ghosts are commonly referred to as residual hauntings and are suspected to be thought form ghost. These ghost were created by some sort of emotional disturbance such as a suicide, war, even a natural death and grew through the energy of people believing in and adding their thought energy which in turn provides an ongoing source of power for this ghost. In this occasion is there a way to find out if this ghost is a thought form? I think one way of finding out is to do some research. While researching the location and you find out that nothing has been documented to support the claims but the story of this ghost has been passed down through generations then you may have a thought form entity. As an Paranormal Investigator these are the things I try to conclude.
Are there such things as ghosts? The phenomena of ghosts and hauntings are very real experiences. It is their true cause and nature that is the ongoing mystery. These are just my thoughts and ideas ~Tracy.