Killing the Undead

The undead are a favorite subject of movies, TV shows and literature. They're a special kind of threat to the heroes. Since they're already dead, it's not possible to kill them by ordinary means. They can only be killed with a ritual or a special weapon that can only be obtained after a long quest.

I believe mythical creatures, like werewolves, vampires, or the zoo of undead and spirit critters in a TV series like Supernatural are fictional representations of real world phenomenon: egregore. Egregore are entities that arise from otherwise unrelated constituent elements in the way that our consciousness seems to arise from the neurons of our brains, or in the as-yet-to-be understood relationship between our gut bacteria and our minds.

Since egregore are third things, and are ghost like, mere information and the flow of information, and not at all apparent in the matter from which they arise, the means of interacting with them are indirect and haphazard, and perhaps the effectiveness of these interactions can only be known ex post facto and through the interpretation of signs. Hence, we get rituals and hoodoo like Ouija boards and we get the fictional representations of vampires repelled by crosses and garlic, and killed with complex rituals and weapons.