The Inconceivability of the Zombie Argument


In The Conscious Mind, Chalmers [1996] uses the conceivability argument (also known as the zombie argument) to argue that materialism is false. He furthermore argues for what he terms ‘naturalistic dualism’ (1996 : 128), a type of dualism where mental states are caused by physical states, but not reduced to them. He supports his natural dualism by explaining how the zombie argument refutes materialism, as it proves “consciousness is a feature over and above the physical features of the world” (1996 : 125),  which materialism denies. I however disagree with Chalmers, as the zombie argument rests on the conceivability of the zombie world he describes, and if you find reason to not buy into the conceivability, you do not need to buy into his argument. In this paper, I discuss Chalmers’s argument and its premises, attempt to weaken the intuition he relies upon, and conclude that if one denies the conceivability of a zombie world as Chalmers describes it, one can also deny Chalmers’s naturalistic dualism and its refutation of materialism.

Chalmers approaches the argument by attempting to demonstrate that any endeavor to reduce consciousness to a solely physical explanation will be insufficient. He differentiates between physical theories, which could presumably advance cognitive science but not explain consciousness, from  non-reductionist theories, which he believes would be a better approach to developing a theory of consciousness: if phenomenal states are not entailed by the physical, phenomenal states will not be reducible to physical states. With this idea of disproving entailment in mind, Chalmers presents his version of the zombie argument, as follows:

(1) Zombie worlds are conceivable.

(2) If zombie worlds are conceivable, they are metaphysically possible.

(3) Therefore, zombie worlds are metaphysically possible.

(4) If zombie worlds are metaphysically possible, physicalism– the view that the mental supervenes on the physical –is false (1996).

Chalmers defines a zombie as “someone or something physically identical to me (or any other conscious being), but lacking conscious experience altogether” (1996: 94). The zombie argument envisions a conceivable (and thus, according to him, possible) world in which these zombies exist. They  talk and behave as normal humans and are physically identical to humans down to every atom, but they do not have any conscious, phenomenal, or qualic experiences.

Conscious, phenomenal, and qualic experiences all refer to the idea of ‘what is it like’ to have these experiences; i.e., seeing the color red has a conscious, phenomenal or qualic attribute that encapsulates what it is like to see red. It is “impossible to define except that in terms that are unintelligible without a grasp of what consciousness means.” (Sutherland, 1995). The three terms themselves, however, are used interchangeably (at least in this paper) to refer to the same thing.

Chalmers’s argument posits that one can conceive of a world where these ‘phenomenal zombies’ exist, mimicking human behavior but lacking phenomenal human experience.   Following the reasoning of Chalmers’s argument, he asserts that if (2) is true, then we must admit that (3) is true, and therefore have no choice but to also agree with (4). If a zombie world is metaphysically possible, then consciousness is not entailed by the physical; if it is not entailed by the physical, then it cannot be reduced to the physical, as there must be something separate from the physical that elicits consciousness.

In this manner, Chalmers believes he disproves materialism, which he defines as “the doctrine that the physical facts about the world exhaust all the facts, in that every positive fact is entailed by the physical facts” (1996 : 110). If the zombie argument is true, then there are facts “over and above the physical facts” (1996 : 126), meaning that they cannot be reduced to physical features, and thus materialism is false. If a zombie world is conceivable, then the physical facts cannot exhaust all the facts about the world. If Chalmers’s argument is correct, then something  beyond the physical is at play in consciousness, establishing a dualism argument. Chalmers explicitly states that he is not arguing for Descartes’s brand of dualism, but instead what Chalmers refers to as naturalistic dualism.

Chalmers’s definition of naturalistic dualism “posits that everything is a consequence of a network of basic properties and laws, and… is compatible with all the results of contemporary science” (1996 : 113). It grants that mental states, including phenomenal ones, can be caused by physical states, but that they aren’t reducible to them; phenomenal states cannot be explained purely by something physical. Under this soft dualism, Chalmers is able to argue for both the importance of physical states within the brain and the separate inclusion of conscious experience.

Inconceivability of Zombies

Chalmers’s argument, irrespective of its logical construction, holds only minor weight if one does not take his first premise to be true: the conceivability of a zombie world and the zombies that inhabit it. If one does not accept this premise, then one does not need to accept the rest of the argument, nor have any reason to accept naturalistic dualism, as there is little reason to accept a dualistic theory if a physical one can suffice. Chalmers’s recognizes the heavy appeal to intuition he is making, but as he states, “I have tried to make clear just how natural and plain these intuitions are, and how forced it is to deny them” (1996 : 97). To do this, he fleshes out his zombie argument with additional examples that do not use zombies.

In an example where Chalmers attempts to make his point without using a zombie, he introduces a new possible world: one which is physically identical to ours and in which conscious experience still exists, but experience for colors is inverted (i.e., whereas we experience red when we see a fire truck, someone in this new world would experience a blue fire truck). Chalmers, again, claims this world is conceivable, and since there are no physical facts to differentiate why we see red when someone in this other world sees blue, materialism is again refuted.

The intuition for this possible world builds from the idea that there does not seem to be any physical explanation for why experiences feel the way they do; i.e., in regards to color, “nothing in the neurophysiology dictates that one sort of processing should be accompanied by red experiences rather than by yellow experiences” (1996 : 88). Following this intuition, Chalmers believes the answer to this explanatory gap lies outside the physical. But this seems too large of a leap. Not currently having a physical explanation for why experiences feel the way they do does not logically exclude a physical explanation. Similarly, not currently having a physical explanation for consciousness does not logically exclude a physical explanation. No one claims to have a complete understanding of the brain at present; it therefore seems premature to renounce materialism, based on intuition, for a theory that does not explain consciousness or phenomenal experience any better.

In another non-zombie scenario, Chalmers addresses the conceivability of his zombie argument by utilizing an example of a synthetic isomorph. The isomorph is a physical copy of Chalmers, with the one caveat that it is recreated with silicon chips in place of neurons. Another appeal to tuition: if it is conceivable that the isomorph lacks consciousness, then similarly it is conceivable that the zombies lack consciousness as well. But I do not think there is a possibility of the isomorph lacking consciousness; if the brain is recreated entirely synthetically, with every function remaining exactly the same down to the last neuron, then the isomorph would possess consciousness. Similarly, it is impossible for the zombie world, as Chalmers describes it, to exist: if a world was exactly physically identical to our own world, then there could not be zombies; the inhabitants would be conscious.

The origin of the zombie argument comes from Kirk [1974]. In his example, a zombie (named Dan) begins as a normal human, whom gradually loses phenomenal experience until he is a zombie. But Kirk’s original example of a deteriorating consciousness seems to hinder the intuition of Chalmers’s argument. The first experience Dan loses is pain; in an example scenario, Dan’s hand is cut, and he exhibits the normal behavior of one experiencing pain: “he winced, exclaimed ‘Ouch!’, nursed his hand, answered ‘Yes’ to questions about whether it hurt, and so on” (1974 : 4). But additionally, Dan also has odd behavior: “He appeared to be astonished by two things: first, by the fact (as he seemed to regard it) that he really felt no pain at all in spite of a fairly serious injury; and second, by the fact that he was nevertheless wincing, groaning, and uttering such sentences as ‘It hurts like hell’” (1974 : 4).

In Chalmers’s zombie world, the zombies exhibit normal behavior (such as saying ouch when cut) even though they do not have any qualitative experiences (such as feeling the pain of the cut). The strangeness of this premise is lost, however, until one looks at Kirk’s similar zombie scenario. Though the two arguments differ, under both scenarios, a zombie Dan could cut his hand and behave as if he was in pain, even though he was not. It is only in Kirk’s scenario– where Dan still possesses some consciousness –that it becomes clear how strange this is. Why would one behave as if they were in pain if they did not feel any? In Kirk’s example, Dan is surprised that he reacts as if he’s in pain, when he doesn’t feel any. Dan’s incredulousness seems to point to an intuition that our behaviors (such as saying ouch) are products of our phenomenal experiences (such as pain); we only say ouch because we feel pain. It then seems even stranger, even less intuitive, that a zombie world could exist where the behaviors are present without the phenomenal experiences that drive them.


Chalmers’s zombie argument, regardless of its validity, is ineffective if one does not agree to his first premise that a zombie world is conceivable, a premise that is based on intuition. Though Chalmers attempts to solidify this intuition by using examples such as the inverted world and isomorph twin, these do not seem to help, particularly when one also considers the overall strangeness of the intuition Chalmers asks us to accept. Without his first premise– if zombie worlds, as Chalmers describes them, are not conceivable –then the rest of his argument does not stand on its own. Chalmers’s intuition is no guarantee that his theory is correct, and without this intuition, the argument does not refute materialism; without refuting materialism, the naturalistic dualism Chalmers argues for holds less weight.

Works Referenced

Chalmers, David John. The Conscious Mind: In Search of a Fundamental Theory. New York: Oxford UP, 1996.

Sutherland, N. S. The International Dictionary of Psychology. New York: Continuum, 1995.

Majeed, Raamy. “Pleading Ignorance in Response to Experiential Primitivism.” Philosophical Studies (2011).

Kirk, Robert. “Sentience and Behavior.” Mind (1974).

Loar, Brian. “David Chalmers’s The Conscious Mind.” Philosophy and Phenomenological Research (1974).


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