Initially, the hostile spirits reside outside of the human body, but in an instant they can take possession of it, live in it, and cause significant damage, not unlike a parasite, or cancer. The demon resides inside the human body and lives off of it—but it does not belong there, it remains a foreign intruder. That means that the demon can be expelled again, or exorcised. The possessed can be freed from the intruder spirit and can be cleansed again.
