I finished watching season 1 of "The Haunting of Hill House" last night. It's a very interesting series, and it looks like there's a season 2 coming! Throughout the series it really makes you wonder whether the house was actually haunted or whether the whole family had Schizophrenia or some other mental illness that made hallucinations of the various people and ghosts manifest. It would make sense if it was an illness, considering the house keepers went through trauma too, and they were seeing things.
But it doesn't necessarily explain some of the other scenes and why they saw ghosts other than the people they lost; so perhaps it could be a bit of both. Maybe the family did see ghosts of previous residents, and that image merged with mental illness; so as a result, they saw a combination of both ghosts and hallucinations and were unable to figure out the difference. It's a plausible theory for the intentions of the series, anyway. What do you think?