QUOTE
But if ghost are dead. And aura shows on all living things or things able to be killed or destoryed. Does that mean there is a phyical way of killing a ghost?
Are you talking about a ghost or a spirit?
A ghost is nothing more than a residual energy imprint/replay from the past. That's not to say that it can't be sensed or felt all the same. Residual energy can contain a wealth of information to an empath or medium. Often it's connected to a highly emotive or traumatic event before death, somehow it becomes recorded in the atmosphere. So yes the energy can go on regardless or in the right conditions become apparant to us.
If your talking about spirits, then spirit energy is the essence and sig of someone, like our aura or energy field. Physically we can be killed, but spiritually? that is a tough question. I don't think it's possible to destroy a spirit as it's energy. But it's possible for mediums to move spirits on or back to the spirit world if need be ( spirit rescue/cleansing )
Exorcisms only really matter I guess if you believe in possession. I don't but lots of people do, so I will respect that. Personally I think exorcisms work on an intense psychological level. I guess it could then be called a cleansing/healing of somesort.
I think it does have it's place though as it's so tied up with belief and culture. But the cynical side of me sees it as laststraw 'counteractive therpy' to deal the ugly side of the bible

Religion/belief afterall can be the most powerful thing or part of a person.