I have a few thoughts on this subject.
First of all, no, I don’t believe in ghosts.
Secondly, like Pingnak, I do believe in “hallucinations, sensory deprivation, sleep deprivation, drugs, food poisoning, fever and psychoses, and all manner of other things that cause hallucinations.”
That said, three times in my life I “felt the presence” of a loved one who had recently died. The first was my grandmother, in her home surrounded by family. The second time was my sweet father, after his death. But I pushed that away really hard. My father was a rabid atheist, and would have been really pissed if I was having any “supernatural” responses to his death.
The third time, was my beloved mom. As I cleaned out her home, and packed up her possessions to keep or give away or throw out, I frequently felt her presence. I am pretty sure that I understand that the context, of being in her home, touching the things that she loved and worked for, just created some set of chemical reactions in my brain. I wasn’t ready to lose her. I was in shock. Distraught. Overwhelmed with decisions I was not prepared to make. And I felt completely unprepared to go forward in my life without her.
I know that my experience was not unique, and that many people have similar feelings after losing a loved on. Perhaps it is part of the process of letting go.
Finally, I remember as a young girl, maybe 12 or so, being certain that I saw “ghosts” of non-specific people on various occasions. I understand that this is also common among young girls that age. It is a time of great hormonal upheaval, and a time of great transition, and who knows what is happening inside of those changing brains.
So I guess I understand WHY people believe in ghosts.
Freakygin, I do not know exactly how to explain what you saw. I do not pretend to be a scientist who understands the nature of the universe or could speculate about how we might interact with dark matter or dark energy or if remnants of parallel universes could be visible from our own. I do not have enough knowledge to completely dismiss this sort of possibility. But I really suspect that most of what we see or imagine we see comes from inside or our own brains, and not from external sources.