I am a spiritist, I believe that there are other dimensions where souls exist. I also believe that those dimensions are purely phisical, just like ours, and there is nothing mystical or holy about them unless you want them to be (the same way that a church is holy for you just because you put faith in its holiness). We can’t directly perceive those dimensions for the same reason an hypothetical 2-dimensional being can’t see us.
That said, I believe that we have subtle bodies. From now on, I am going into religious aspects from my creed, so if you are more interested in solely scientifical discussion you may skip the rest of this post.
Our body stretches in more than 4 dimensions. But, for the purpose of studying the body pieces in other dimensions, we divide the body in many other sub-bodies. The 3-dimensional body is called ‘phisical body’ for reference due to historical background. The other divisions are called subtle bodies. We go from 3-dimensional to 8-dimensional parts.
The conscience rests in the 3-dimensional body because this is the most stable stance, where it can dwell with the least effort. In cases where this phisical body is at risk, stronger minds may instinctively push the conscience to a subtle body with more dimensions. This is the primary cause for NDE’s [near death experiences].
Knowing that, I also believe that these bodies, with the exception of the 8-dimensional, may all “die”. Only the first two or three ones can be properly destroyed, though. The others simply transform into another shape, with no time between ‘death’ and ‘rebirth’. When a 4-dimensional body lacks a 3-dimensional one, it looks for one that is being generated and attaches to it, “reincarnating”. The same thing happens when a 5-dimensional body lacks a 4-dimensional one, it looks for a “soul” being generated and attaches to it.
From here on, we get into reincarnation. When the phisical body loses life, the conscience jumps to the 4-dimensional body. Here is an interesting effect. When we are in the phisical body, we are trapped in time, so we only flow in one direction in it. But the 4-dimensional body has a little mobility here, being able to go back, forward, and even to the “sides” (allowing them to see possible outcomes for an event). Those consciences which remain 4-dimensional for more than a moment become wandering souls, or as I like to call them, ‘earthbound spirits’. This is a sad form of life, in a state which is called ‘hell’ by some people. Other souls get into other bodies, and then they will go to another realms. They will eventually come back to Earth and reincarnate.
Spirits who become earthbound are those which can’t get detached of their earthly lives. The condition is very psichologically damaging, and they slowly get more and more demented untill they become sad drones. Eventually their memories decay and fade, and they undergo forced reincarnation. But even after they leave a place, a diffused reflex of what they were remains. This is a ghost. A ghost will remain in a place for a very long span of time, acting like a spiritual robot that mimicries the earthbound spirit’s actions and thoughts repeatedly. It has no conscience, and remains in one place untill other emanations, both from the “living” and from spiritual beings, slowly “overwrite” the ghost.
The ghost I described above is what Born_Loser talks about. Spirits and ghosts all emanate this thing which is called “energy”, “aura”, “soma” or whatever you name it, which carry a “signature” of its generators. That is what some sensitive people perceive.