So my latest TV obsession is Paranormal State. For those who are skeptics, those of you who are non-believers, if this show doesn't change your perception then nothing will. I have always believed in ghosts, I have seen possession with my own eyes and heard stories from my friends about being haunted, these vary from regularly to sightings.
Possession is a unique circumstance and once you have seen it, it is hard to forget it. I think those who are pious and pure in vessel are the most susceptible to channel this kind of a force within themselves, willingly or unwillingly.
I think the misconception about ghosts is that they are evil and out to harm, when in fact they are just attached to the idea of being alive, or being around those who are sill alive. While evil does exist in life, it also does in death. I do think that when you die, your spirit stays within the carnation of what it was when you last lived; if you were evil, your spirit will also linger in evil. For whatever the reasons are, some spirits don't cross-over, whether they feel protective of their previous homes, or they feel connected to someone that is currently residing there.
I think it is to narrow-minded to rule out that your spirit doesn't have carnation beyond death. If you have faith and hope in change, I think it's feasible that you accept that forces that are larger than us, or that we can't see with our eyes can exist.
I also believe in demons, much like we battle our own demons on a personal level, I think that non-tangible demons are a creation of thousands of years of history and an accumulation of negative acts, thoughts, beliefs and manifestations across cultures. Demons show themselves in the manner of being aware of what you fear, much like being aware of our insecurities. More often than not, religion and religious iconography challenge these forces because they represent the faith of the living. Thus religiously sanctioned practitioners and emblems of faith challenge these demonic existences. Whether you are Christian, Hindu or Chinese, all cultures use the faith of their religious or spiritual practitioners to challenge the unseen forces of evil.
I leave you with an episode of Paranormal State that deals with demonic possession, and even leads into a full exorcism. If this catches your attention, you will be interested to know that there is a Return of Six episode that follows. Remember that believing does not always mean seeing.