Got a new one. Zombies work on basic human instincts, which is why they eat, because finding food is one of the oldest and simplest urges.
If that were true, Zombies would be absolutely terrified of fire, kill each other for dominance, and fuck anything they could convince themselve was a female.
Actually... the Japanese have a few Visual Games of that...
Zombies are a mixed bag. Before the newer Dawn of the Dead movies, zombies had several immutable laws of existence, which are now... mutable. Before NewDotD, they were slow, craved brains, and simply overwhelmed dumbasses who didnt move faster than a brisk walk or who tripped over *EVERYTHING*.
If you look at the recent popular literature and entertainment:
Books: "Zombie survival Guide", "WW:Z", "Feed", etc.
RPGs: "Outbreak:Undead", and "All Flesh Must Be Eaten"
Games: "Left 4 Dead" and "Dead Rising", tenuous other games
Movies: "Dawn of the Dead" (new and old), 28 Days/Weeks Later, Shawn of the Dead, Pandora, and much much more.
Given the very divergent forms and abilities of zombies in their own seperate universes, its a grab bag what is possible and not.
Lately the trend is what would happen in our world, right now, July 2011. How would/could a zombie be possible?
Most likely, a virus or bacterium that is rabies-like that causes severe degenerative brain damage. You will have zombies that are still technically alive, and very mobile. Congnitive abilities will be low, it can traverse terrain, but maybe a door knob will stump it, maybe not. I have no idea what it would do. Its like a dog with rabies, no idea what will set it off. The "good" news is that it is alive... double tap to the chest and it will bleed out and I've not heard of rabies inflicted dogs choosing healthy over other inflicted. I'd also assume that the majority of the infected would die out from dehydration/starvation/cannibalism rather soon. It would be a hellacious few months thats for sure.
The only tenuous immutable laws I can think of that pertains to every zombie type (save the voodoo kind) at the moment is:
(and given the vast multitude of zombies, even this may be wrong)
-A zombie must have an over-riding desire to harm the non-zombie
-A zombie completely lacks empathy
-A zombie lacks the ability to recognize or acknowledge any previous connections it had pre-affliction (i.e. emotional ties to husband/wife/bf/gf/son/daughter no longer exist in zombie's mind)
-There is no cure for the afflicted (cure is different from vaccine)