If you're asking 'why do people believe ghosts are in this world' in terms of why they believe they exist, its simply because people can believe whatever they want, and some experiences or strong religious beliefs or other reasons give them that belief. If you're asking 'Why do ghosts and spirits get stuck in this world', then there are MANY different beliefs as to why ghosts and spirits exist. One of the most common beliefs is that ghosts who are here on Earth are usually people who died suddenly and unexpectedly...they either do not realize that they have died, or simply do not understand yet that they are dead. This may lead to the spirit wandering desperately seeking to make contact with people. Others may be vengeance...most old ghost stories had a ghost that comes back with the intention of wreaking vengeance upon those that may have done them wrong. People who have been murdered are usually suspected to be ghosts...the soul of the person left wandering, trying to find their killer and exact revenge, or try to help people bring the killer to justice. Some may simply be malevolent, wanting to do harm to the living because they are jealous, and angry to be dead. Perhaps it is a type of 'limbo' or 'purgatory', where these poor souls are forced to be among the living in an ethereal form, unable to interact directly with people and go about their life. Maybe these ghosts cannot pass because they have something yet to do, or a message to be passed on. It is said that ghosts often appear to people in their dreams, and often their nightmares as well. Ghosts tend to 'haunt' certain places. These may be areas where they have died or met with foul play. They may also be areas that had a special significance for the ghost when it was living, such as houses or hotels or other such areas. The bottom line is that there are SO MANY theories as to why ghosts get 'stuck' on this world. An alternate dimension or plane of existence, a flaw in their soul, a divine reason...there are so many ideas for the explanation of ghosts that there is no one single answer, right or wrong. Hopefully others will contribute their own ideas and information for your question!

Each person has their own conception based on what is real to that individual. The truth of the matter is that each individual is a spirit. The individual is a spirit (or soul or ghost or whatever you want to call it). The spirit or individual has a body or doesn't have a body. It is easy for human beings to identify a spirit with a body. There is some mass there with a body. A spirit itself has no mass or wavelength or energy or innately even time or space, but is capable of creating or trying to 'possess' these things. The spirit is aware and aware of being aware. In other words, the spirit is "you". So, "you" are not a physical type thing and can not be measured except for those things (like energy) which you create. One could say that a ghost is someone without a body. Many spirits or individuals upon losing their body want to get back into the game and eventually pick one up around birth, but typically now-a-days there is a lot of amnesia associated with the previous lifetimes and most people don't recall too well. But not every individual has a body or goes to get one right away. It is nothing to worry about. You are a spirit too. You have a body and they don't. There can be benefits either way. Here is a little demonstration: Close your eyes and get the picture of what you had for breakfast or lunch. Get a good recall of your food in front of you, chewing, smells, etc. So, you see the picture(s)? Now, who is looking at those pictures? It is "you". Not your mind, it is "you" who looks, who views, who is aware of being aware. It is you who observes and knows that you are observing. You, as a spirit, "know". The spirit can make a thought and observe it. A thing that an individual or spirit has is a mind. An individual often confuses himself with his mind, (i.e. all the clutter he carries around with him), which is different from the individual himself. The mind is made up of those mental images and you can view them. You can (and do) take those images with you. Just because you may not be able to easily recall all the images or mental pictures of your past lives or early childhood this lifetime, doesn't mean your past is not there. I could go on, but this kind of stuff is best if it is real to the individual himself. I am not trying to convince anyone. I do know what I recall and things that I have experienced personally, and I'll pass it on. If you ran across an individual without a body (a ghost) that was having a hard time; try telling them to move on, get a life (ha!), get a body or something appropriate for that individual. The reverse could also help...if an individual's body is okay, but they just won't get back into it (looks like they might die) -- tell them that the body is okay, that different people need them right now, touch their body and tell them to feel your hand, and just generally coax them back into the body. These latter actions can help bring someone out of a coma or "back to life".

Ghosts do not get stuck in our world,...some do. According to Einstein and his theory of relativivety, the Fourth Dimension, is an existance of time and light happening alltogther at a simultaneous instance. Uncomprehensible, and inconcievable at it may seem? But no one else seems to know whats on the otherside. Albert took a really good educated guess, and one with the most common sense as Ive discovered through all my metaphysical research. If this is the case, when you die, you experience your life simultaneously. Your life flashes before your eyes.Ghosts are nothing but that residual energy experiencing the quality of their lives to discover if they are worthy to be pulled beyond the Fourth Dimension (judgement, purgatory), into the Fifth Dimension (heaven, zen?). Or if they were unworthy and must be reincarnated again until they get it right. However, if one soul stole the life of another, or the soul took its own life. It could be trapped in the Fourth Dimension for all time, or sent back to the Second Dimension (hell) which is the realm of shadows. Its an interesting theory.

Unfinished business... but that goes for those who still believe they're alive as well...

People believe in ghosts or spirits because it's a common human trait to create ideas or familiarites about what they don't or can't understand. Believing in ghosts may help them to give reason to something that has not (yet) been explained by logic. Often, when a person experiences something out of the ordinary, or unexplained, the easy decision is to believe that it could have been a ghost. Our culture has also popularised this concept through films and television. It should be noted, for the record, that ghosts are not proven to exist. This is despite the availability of new technology (such as camera phones) which would make it easy to film and record events which were claimed to have occurred. Most 'believers' would respond to this assertion that the camera cannot pick up such images, however, this fundamentally contradicts the design of our universe - anything that exists within it must have 3 dimensions to be seen (human, ghost or otherwise). I have met someone who claims they can see ghosts, while others with her at the same time could not. Her belief is that she has a connection with the 'other side' and that perhaps she has contact with another dimension. While there may be some merit to this, the argument fails when you take into account that anything that can be seen in our universe must take up three dimensions. If a 4th or 5th dimension exists, it is not visible to the human eye in this universe. This is not to say this person had not seen any 'images', but I'm afraid to say that any such thing would have appeared in her own head only, and did not take existance in our three-dimensional world. On a personal note, I actually wish I was a believer, but I'm too much of a reallist to make this possible. I tend to think of 'believers' as selfish to think that we can die, then turn into a ghost and somehow keep our personality functioning in order to suffer from jealousy or anger (i.e. live brainwave activities). Many infants meet a sudden or untimely death - so to believe that they could exist as ghosts would mean that they would have to do so with an undeveloped brain or personality, possibly for an eternity. We are all afraid of the unknown to some degree. If we can admit that, and remove our fear of losing our individualality when we pass away, we might just take a giant step forward...

And then, some of us believe that there is not such a thing as "souls" and that all talk about ghost and "spirits" is really a load of bored imagination..

I think that the mind can be a very lonely place. Some people may feel they need to connect what they do not know or what they do not understand to 'ghosts.' One's mind can create a form when there is a lot of nervous tension or anxiety pent-up and they fail to communicate what they truly feel bringing the mind to a state of psychosis which then can project images, ghostlike. Isn't it odd that ghosts only seem to become present in dark, hidden, lonely places or if a person is disconnected from what is happening in the everyday world around them? What would a ghost have to hide from if it was real? Why can only certain individuals claim they have had experiences with ghosts? It is all a state of mind people. We should stop focusing on what is out of our control and get in touch with what we can control.