In Vertigo's series iZOMBIE by Chris Roberson and Mike Allred, the existence of classic monsters in that universe is explained through the concept of the oversoul and the undersoul. From Wikipedia:
The "monsters" in iZOMBIE are explained via the concepts of over- and undersoul. The oversoul (as in Ralph Waldo Emerson's The Oversoul) is "seated in the brain, contains the thoughts, memories, and and personality", while the undersoul (as in Michael McClure's poem Dark Brown) is "seated in the heart, contains the appetites, emotions and fears". Ghosts are thus bodiless oversouls; poltergeists, bodiless undersouls; vampires bodies without undersouls (thirsting for emotions); and zombies, bodies without oversouls. Revenants, like Gwen, are unique in that they possess both oversouls and undersouls. Souls can also "infect" the living, which accounts for the possessed and werewolves and the like.
My question is, has this concept ever been applied to monsters before, or is this appropriation a unique characteristic of iZOMBIE?