An explanation, which is as good as any, is that demons surround a person from the time they are born until the time they die, knowing every little secret of that person. After you die, the demons split and attach themselves to another baby. When a person tries to connect to the dead, either through themselves (dreams, etc.) or though a medium (a sance, etc.), the demons re-unite and answer any questions to make you believe in ghosts and therefore turn you back on God.