Ghosts?

I've been researching just for fun different stories of ghosts and ive come across the "real" reasons we (or some) may see them. It can all be traced to electromagnetic fields, sleep paralysis(when your body feels frozen, awake but cant move or speak, feeling of doom, etc.), carbon monoxide, and lack of oxygen. There's a few more but this is the main ones ive found. I'm curious if people agree with the concrete reasons, or if those who have seen them KNOW what they saw and it cannot be explained by these few reasons. If you have any stories, id love to hear.