We are up against a great deal in proving something that so far is not perceived well by any equipment, but only the human. We have to tackle it a whole different way. Having seen things with others who reported the same thing when interviewed separately, I have to say whatever it is, is in the environment and not all just misinterpretation or runaway minds.
It also happens that personal perceptions can be an issue with someone knowing a place is haunted, hearing something and trying to make what they heard fit what they know of the haunting (I knew a person who thought that a door opening because of an open window breeze and a rusty hinge was a woman crying out - which was the tale of the haunted location).
There is great part that is true phenomena, as I have watched objects move on their own by no means that makes any sense to physics as we know them. I have heard the voices, along with others at the same time. And, I have witnessed many apparitions over the years. (Read my books "Growing Up With Ghosts," and "Vacationing With Ghosts.")
I'm not out to prove hauntings. I'm out to find a way to follow this phenomena back to the moment of its launch into our physical world to figure out the origins and if there is intelligence behind it. I believe it is all explained by rules of science not spiritual and that is because it is launched into our physical realm and so it adheres to rules of this world. Even if we are to believe it might be caused by the souls of the head, they are affecting our world - which gives a passage for these interactions to come and go.
What the instigating force is, is still up for debate.
There is a fair deal of chicanery and shenanigans in the field of study for the mere fact someone wants to be the person who definitively proves the phenomena. You don't have to ask people who have experienced it, they know it's real. I'm not out to prove Sasquatch either. I am out to understand how they survive and who they descended from.
In ghost research, I'm out to search for patterns and repeatability. From there, if I find a consistency and predictability, I can begin to make assumptions about the force we are dealing with and, in a way, reverse-engineer a ghost.
One of the more popular teams,TAPS, did some great things for the study of phenomena by debunking and trying to look at phenomena objectively, but they also confused a lot of researchers into thinking that the purpose of what they do is to try to measure and give evidence to a client to prove or disprove a haunting. That is a different service than research. In their case, they are the mechanics, but the car designers are whole different facet of that industry.
What excites me more is the person who knows how to create the conditions for the phenomena to occur with repeatability. That is the milestone I work toward.
Anyone who tells you what a ghost is and how they work, they are no more right than anyone else. And, the minute you think you know just how the whole paranormal phenomena arena works, you stop looking for truth and work instead toward proving your belief.