You read it right – is it possible for Zombies to exist? Can human beings come back from the dead and feed on the flesh of the living? While all the details of the Zombie we’ve seen in the movies can be exhausted in great detail – George Romero’s Night of the Living Dead (1968), Lucio Fulci’s Zombie (1979) to Danny Boyle’s 28 Days Later (2002) – I want to examine a particular understanding of Zombie’s from a philosophical perspective. Zombie’s understood in this light simply means “[S]omeone or something physically identical to me. . . but lacking conscious experiences altogether” . In other words, zombies are an “exact physical duplicate of a human being that lacks consciousness” . To make a point clear on this,
This sort of Zombie is quite unlike the zombies found in Hollywood movies, which tend to have significant functional impairments. The sort of consciousness that Hollywood zombies most obviously lack is a psychological version: typically, they have little capacity for introspection and lack a refined ability to voluntarily control behavior. They may or may not lack phenomenal consciousness. . . it is reasonable to suppose that there is something it tastes like when they eat their victims. 
David Chalmers (1996) goes on to say, “We can call these psychological zombies; I am concerned with phenomenal zombies, which are physically and functionally identical, but which lack experience” . To have an example of what I mean, consider this comic strip of Calvin and Hobbes on zombies:
With that understood, let’s suppose that you had a twin. This twin was physically identical to you in every possible way – there’s is no dissemblance between the two of you. However, your twin is a zombie. Suppose now, that you are reading your favorite poem by Walt Whitman, enjoying the taste of the tea you are drinking with the sensation of it being sweet, and the cool breeze you feel going across the top of your head as you sit next to the open window. You feel calm. However, what if your zombie twin were to go through the same thing?
Your twin is physically identical to you in every way and is similar to you only functionally: “he will be processing the same sort of information, reacting in a similar way to inputs, with his internal configurations being modified appropriately and with indistinguishable behavior resulting” . Your zombie twin will be psychologically identical to you in the functional conscious sense (he will be awake, aware and be able to report the contents of internal states, etc.) but he will have no conscious experience to accompany his functioning.
The Question: Are Zombies Possible?
The question can be answered as yes, zombies are possible. However, it should be understood that the existence of zombies are only logically possible, at least in the sense that the expression “Beings with no conscious experience are logically possible” is not contradictory. This has gained especially notable importance from cognitive scientists who are debating the age old issue of the so-called Zombie Problem (or better known as the Problem of Other Minds). As Timothy J. Madigan (2013) writes in Problem With Zombies,
The topic of personal identity is also a perennial issue for philosophy, and zombies have been a theoretical test case for this too. If you should actually lose your mind would you still be the same individual? Moral status, too, is a longstanding issue in meta-ethics: is rationality the determining factor in whether or not one is a moral being and, if it is, are there degrees of rationality that should be taken into consideration? 
In other words, consider our twin example we discussed above. If you yourself had lost conscious experience, but we’re still able to function psychologically, would you still be you? More over, if in the sense that you can reason, think, and have the abilities to remember, reflect and etc., does that determine whether or not you are morally significant – or better put, a moral being/person? These questions and more have provoked a wide-array of discussions among philosophers for quite some time now, and while the discussion is rather extensive, there of course tend to exist disagreements among one position of philosophers opposed to another. What sort of disagreement might I be talking about?
Zombies Threat to Physicalism
To be short and to the point, physicalism (or materialism) is the view that “thinking, feeling, animals such as ourselves are constituted of nothing more than the ordinary physical stuff recognized by the natural sciences” . David Chalmers (1996) explains for us,
[M]aterialism. . . is generally taken to hold that everything in the world is physical, or that there is nothing over and above the physical, or that the physical facts in a certain sense exhaust all the facts about the world. 
Why might zombies pose a threat to this view of the world? Historically speaking, materialism has been the view that mental properties are identical (or reducible) to physical properties. As Philip Goff (2013) argues, “if philosophical zombies are possible, physicalism must be false” . In other words, mental properties cannot be distinguished from the physical properties under physicalism, yet, however, if zombies are possible, then the case that mental properties are reducible to physical properties is false. The argument goes as follows:
- Philosophical zombies are possible.
- Therefore, human brain states could possibly exist without human conscious states.
- Therefore, human brain states cannot be identical with human conscious states.
- For physical to be true, human brain states must be identical with human conscious states.
- Therefore, physicalism is false.
Now, looking at the first premise (and our argument in general), what does it matter if philosophical zombies are possible? Surely the possibility of a given thing doesn’t show some theory (a.k.a. physicalism) to be false. However, it’s important to understand that sometimes what is possible has implications for what is real. Let me explain why.
Patricia Churchland (1986) once wrote in regards to the reduction of mental states to brain states. This reduction is what is known as an explanatory unification, simply meaning that “[I]f one theory can be explained by another and thus reduced to it, then our understanding of the phenomenon described the theory is greatly enhanced” . The phenomenon in question of course being mental states. Thus, our issue is this.
If we have one given thing X and another thing Y, they can only be identical in as much as they are one and the same thing. For instance, Batman is Bruce Wayne. The two names are of course different but one cannot exist without the other – Batman is Bruce Wayne. In the same way, if, say, the feeling of pain is due to the firing of c-fibers in your brain, then they are one and the same thing and are not really two separate things – we just have two different labels of a thing. Thus, even further, physicalism and the logical possibility of zombies pose a given inconsistency with one another.
Since, if mental states and physical states are supposed to be identical with one another, and yet, philosophical zombies are possible of existing without mental states, then (3) in our argument seems to be true: “Therefore, human brain states cannot be identical with human conscious states.”
Now, although we have seen that philosophical zombies are logically possible, and that zombies pose a threat to particular [materialist] theories of the brain, we shouldn’t jump the gun and get too excited. David Chalmers (a notable popularizer of “philosophical zombies”) argues that “[w]hile this is probably empirically impossible, it certainly seems that a coherent situation is described” . Daniel Dennett (1995) argues that
[s]ometimes philosophers clutch an insupportable hypothesis to their bosoms and run headlong over the cliff edge. Then, like cartoon characters, they hang there in mid-air, until they notice what they have done and gravity takes over. 
While certainly it might seem as if this is the case where philosophers are discussing and arguing about things like philosophical zombies, the conversation I think is still nonetheless notable and interesting – even with respect to questions of materialism and consciousness.
-  David Chalmers, The Conscious Mind (Oxford University Press: 1996) p. 94
-  Philip Goff, “The Zombie Threat to a Science of Mind” in Philosophy Now (May/June 2013) p. 6
-  Ibid., p. 95
-  Ibid.
-  Ibid.
-  Timothy J. Madigan, Philosophy Now (May/June 2013) p. 4
-  Peter Jones and O.R. Smith, The Philosophy of Mind: An Introduction (Cambridge University Press: 1986) p. 180
-  David Chalmers (1996), p. 41
-  Philip Goff (2013), p. 7
-  Patricia Churchland, Neurophilosophy (MIT Press: 1986) p. 279
-  David Chalmers (1996), p. 96
-  Daniel Dennett, “The Unimagined Preposterousness of Zombies” in Journal of Consciousness Studies (vol. 2, no. 4, 1995).