The age old question: Do ghosts exist?
For many, it's like religion; you either believe or you don't, or you take an agnostic point of view and say "I'll believe it when I see it."
If ghosts are defined as souls from departed humans that remain on the earthly plane - ghosts may exist, but they are not proven yet.
If ghosts are defined by unexplained phenomena often attributed to the spirits of the dead, but whose actual origin is not known for certain, then ghosts do exist. If we use "ghosts" interchangeably with "phenomena," then they most certainly exist because phenomena does.
This is kind of like using the term"UFOs" when we see unexplained things in the sky, but whether they are alien or ours, we do not know and have not yet proven. Still, we use "UFO" as a term to explain it.
In the ghost hunting field, we use "ghost" as a term to cover any unexplained paranormal activity.
I believe in "ghosts" when I use that term to mean "phenomena." I have not, however, come to the conclusion all the phenomena is related to the dead. There could be a component that is in some situations, and then other situations could be explained by forces we do not detect, memories recorded into a location, shifts in time/space so we view something not actually in our realm, aspects of physics that are not yet discovered, earthly influences like seismic and geomagnetic storms affecting our brain chemistry, and then there is the human brain and the glitches it can get in perceptions.
The interesting thing, when you think about it, is that ghosts are ghosts. What a ghost is, is still a specter in the field of science.