Well one thing I'll say upfront is that I don't think anyone will be able to fully explain WHY a spirit does the things they do. Keep in mind that these are ALL intelligent and willful entities... meaning they are like you and I... they have different personalities and a will of their own. Most of what they do is simply to let us know they are there... they do things to install fear... they do things to irritate us... and I would most of all they do things to confuse us.
If something goes contrary to the Bible, especially in spiritual matters, I will go with the Bible every time. It's just been proven to me over and over again and I stake my life on what it says.
So in considering whether a spirit is a ghost or a demon... I will go with what the Bible says. First of all there is only one reference in scripture to an actual human spirit manifesting and that is when King Saul consulted the Witch of Endor. Personally I believe this is a one time event God allowed to happen to pronounce judgement on the wayward King of Israel. I do not AT ALL believe this one piece of scripture describes what modern day mediums believe they are doing in calling up spirits. I do not believe that ghosts, as human spirits, remain on earth. I believe that 99% of all spirit manifestations are demonic... and the remaining few are acually misunerstood angelic visitations. Here's what the Bible does say about the situation...
Luke 16 Jesus tells the story of a rich man and a poor man that had died. The rich man begged for relief in that the poor man who he mistreated in life could come and give him a drop of water. He also asked that he could return to life to warn his family of his torment in Hell. His wishes were denied in that there is a chasm between this life and eternity. There is a serparation also between Heaven and Hell.
2 Corinthians 5:8 also describes (for believers) that to be away from out body (in death) is to be present eternally with Christ.
The Bible never mentions people being able to return or wander the earth as spirits. In fact it implies quite the contrary. Now does the word of God say out right that human spirits don't exist on earth ourside of the body? No, but if the previous scripture weren't a strong enough hint we are (thankfully) told in 1 John 4:1 to NOT BELIEVE every spirit... but rather to put them to the test. That means, fine.. maybe a spirit will appear and say it is dead Aunt Sally... in that instance we are to apply a test to that spirit. That is that if the spirit can attest to Jesus Christ come to earth, dying for mankind and being raised from the dead.
I know of many ghostly situations that when the above test was applied they were shown to be deceptive spirits. Rarely is this biblical action ever applied to a haunting situation and therefor the truth is never separated from the myth.
