A reader of the book Hay Moon and Other Stories: Sixteen Modern Tales of Horror and Suspense recently noted that my explanation for the causation of the undead/zombie phenomenon differs from that which is most common in contemporary horror films and fiction.
What did the reader mean by this? Well, today, the "naturalistic" explanation predominates.
In this version of the zombie tale, some sort of a non-supernatural cause (usually a virus) causes the zombie epidemic to spread, leading to a breakdown in social order, and the End of the World as We Know It.
Most of the George Romero films follow this formula, as does the AMC series The Walking Dead. (I highly recommend The Walking Dead, by the way. I give the Romero films mixed reviews, though Romero will always deserve credit for inventing the genre.)
The second version of the zombie tale involves supernatural causes. This notion of zombie causation goes all the way back to the New Testament, as described in the short story "Hay Moon."