Before I get into this I'd just like to say that it's all just fun stuff to think about, and I can't say that I'll actually take this approach to spiritual beings in my fiction.
Are ghosts real? To some that answer is obvious, while others shuffle their feet and admit that they don't know. All responses are fine. I am personally a believer in beings which we do not yet understand and which we may interpret to be demons or ghosts or other such creatures of ethereal spirit. I can't say whether they are the disturbed souls of the once living, the malevolent monsters of an eternal volcano, the gatherers of the damned, or the granters of wishes. Perhaps some of them are, and I'll get into the once-living aspect of all that in just a short while.
But first let me propose to you that alongside us more material creatures evolved another biological form which had for its building blocks energy. Instead of being made up of cells this entire spectrum (perhaps referred to as a "Plane"?) of life is made up of photons or other such energy particles, probably many of which we have yet to discover. The majority of this energy probably cannot interact with the material world directly, and the same is true of the reverse, so both biological spectrums could continue a peaceful coexistence without ever discovering the other is there (until one invents and applies the proper technology, of course).
However, maybe among both forms of life are individuals who are capable of breaking these spectral barriers. We all know that the living creatures of the material world are surrounded by an electric field of sorts. It could be possible that individuals with more potent electric fields could use them, perhaps even by accident, to interact with energy beings. And it might also be possible that beings from the energy spectrum with frequencies (sorry, I skipped a step! Energy vibrates at specific frequencies and those frequencies determine what and how it is interpreted! That's real science by the way, it's why you can see colors.) similar enough to specific humans or perhaps similar enough to an average electromagnetic frequency could interact with us, here on our spectrum of matter and physical stuff.
If that were the case, we might call these creatures "Demons", "Ghosts", "Genies", and what have you, and an argument could be made for the accuracy of those claims (I was going to go into that here, but it seems like a topic worthy of its own discussion). Of course reaching this theory of energy creatures requires going about the scientific method all backwards, which is unfortunate. That doesn't make it any less fun to think about.
See, what are some common things in ghost lore and ghost hunting? Well, typically people are aware of the presence of a spirit before they even see it, often they describe sensations of numbness or tingling. This isn't too different from how you can feel a storm coming by sensing the static in the air. Energy beings would have a similar effect on us. Also, most ghost hunters swear by some kind of electromagnetic device to pick up on "Spikes" in a given hunt or room. Why would these sensors detect something which was not made of electricity? (Again, assuming they occasionally detect any real ghosts at all.) Why is it that ghosts and demons seem to mess with electronic equipment like cameras when they are around? Well, for the same reason an EMP would. When you get these colliding energy fields, things happen. Just like how you can hear the tingle of a television turned on from the other room.
Could beings made of energy pass through solid objects the way ghosts pass through walls? Yeah, absolutely. And it might even be possible that creatures born of and into energy could in some ways manipulate the vibrations of their bodies to appear visible or invisible to us simple human folk. This might also be why poltergeists tend to simply whip things around a room as opposed to handling them with any care. All they can do is charge it with static or magnetism and pull, and hope it goes where they want it to.
But dead people couldn't possibly be among these energy creatures, right? Wrong.
As I mentioned earlier, we all have an electromagnetic field surrounding us, possibly even manipulating us. A slight derail to give another fun thought: many people believe that we are "Spiritual beings having a physical experience". Maybe there's a little truth to that. Maybe instead of the electrofield responding to the thoughts of our brain, our brain responds to the thoughts of the electrofield. Imagine that the electromagnetic field is a series of strings connecting into the brain. We already know that applying shocks to specific parts of the nervous system can make the body perform certain tasks. Isn't it possible that our electrofield shocks our brain to make the body perform what we need it to? In effect, making us a being driving some kind of shell?
That thought alone brings all sorts of new possibilities to the realms of, say, telepathy. If you have two electromagnetic fields crossing into each other, the way you would if two humans stood close enough together, it should be theoretically possible for the "Switchboards" (brains) to interpret the frequencies of both fields, or if it's the fields themselves which do the thinking well, then the thoughts are all mingled and such.
And remember what I mentioned earlier about poltergeists maybe only being able to charge objects with static and whip them across a room? Sounds kind of like telekinesis, doesn't it?
Back to ghosts. If our electric field does hold some portion of our personality and memory within it (which it could), then what happens to the us when our body dies? Logically, that field should simply disperse (and if you aren't keeping up with how I'm tying this into a billion religions, this dispersal would lead our electricity to join the atmosphere and contribute to the collective energy of our world, being a sort of unified pool of all electric souls. This would be the collective "Life stream" or "Ether" talked about in some religious theory), but perhaps there are individuals, as I mentioned earlier, with abnormally powerful fields. It might be possible for those individuals to hold their energy together in some way, thus becoming a ghost.
Maybe those ghosts can then inhabit new bodies (resurrection) or simply remain on the planet as a ghost, doin' ghost things. That ghosts do.
The other fun thing about this, is that it would effectively make the electromagnetic field of each individual their soul, or their aura.
Whether all this is true or not, who knows? I don't. I like to think so, it's what makes sense to me. Just something fun to think about. I hope you have fun with it, too.
AFTERTHOUGHT: I meant to include this in the main body, but I completely forgot about it. If there are beings made of energy, this might explain why the light can protect us from them, particularly now that we use electronic lighting. It might be that our lights disturb the frequencies of energy creatures in ways that make them unable to manifest a visual form and possibly prevent them from charging a cling to physical objects. It could also be that the photons from all light sources disturb them in some ways. I do think, within the context of this thought exercise, that the rise in electronic appliances has directly contributed to the decrease in ghost sightings.
