Are zombies really dead? How do we know? People are often reported “clinically dead” only to be revived later. If it is moving, if it reacts to stimuli like a food source or sounds, and if metabolic processes are in play, how can we call a zombie dead?
The most basic definition of life is the ability to have “signaling and self-sustaining processes” as the all-knowing Wikipedia
Zombies do indeed undergo a qualified form of metabolism, sort of maintain homeostasis, and definitely respond to stimuli. Alternately, zombies do not grow, reproduce, or go through natural selection. So much for a clear answer there.
Consider the following: When we “kill” something, we are implying that our action has made an “alive” thing “dead.” We commonly refer to “killing” zombies. Therefore, a zombie is alive until it is killed. Not quite, some might argue, a zombie is undead. Undead is a special word that describes an entity which was once alive in the full meaning of that word, then died, and was then re-animated (e.g. a zombie). The zombie was not re-vivified, that is, brought back to life, but its bare biological systems were re-started.
For example, dismembered frog legs that are given electrical shocks are not “alive” they are merely re-animated. But the frog leg example is insufficient, because the electrical shocks are external, and not part of an organism. In the case of a zombie, the electrical shocks that trigger muscle movement are, as with a living being, generated internally by metabolic processes and neural pathways. The frog legs are not “re-animated,” just artificially stimulated.
At the other end of the spectrum, how about a person who has a heart attack and, due to a delay in resuscitation, temporarily experiences cardio-pulmonary-death and brain-death: a total cessation in life functions. The person is, for a moment, clinically dead. That person is then successfully revived. The heart and lungs begin functioning again and the re-oxygenated brain “comes back to life” with no harm done. This person who is “back from the grave” is revivified. Though their biological functions ceased, for a variety of reasons the destructive postmortem processes were delayed long enough to allow total system restoration.
A zombie isn’t a shocked frog leg nor is it a revived person. Instead, we want to understand whether or not a moving, metabolizing, stimulus-responding corpse is alive. I submit that various parts of a zombie may resemble life, but in reality, it has less “life” than the bacterium eating its eyeball. It is more accurate to say that the pathogen inside the zombie is alive, while the corpse itself is dead. The corpse, as noted in my description of a zombie, is in a constant state of decomposition. While decomposition may be slowed by the pathogen, the process is not stopped.
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