Thinkers in the philosophy of mind have wasted too much ink on the topic of philosophical zombies, which has been the subject of many an article and essay. The first mention of a zombies argument against materialism (using that term zombies) occurred in the paper "Zombies v. Materialism" by Robert Kirk and J. E. R Squires. Kirk made an argument that was not very clearly stated. Later in his work The Conscious Mind David Chalmers stated the argument more clearly.
On page 94 of that work we have section entitled "Argument 1: The Logical Possibility of Zombies." Here is some of the reasoning by Chalmers:
"The most obvious way (although not the only way) to investigate the logical supervenience of consciousness is to consider the logical possibility of a zombie: someone or something physically identical to me (or to any other conscious being), but lacking conscious experiences altogether. At the global level, we can consider the logical possibility of a zombie world: a world physically identical to ours, but in which there are no conscious experiences at all. In such a world, everybody is a zombie. So let us consider my zombie twin. This creature is molecule-for-molecule identical to me, and indeed identical in all the low-level properties postulated by a completed physics, but he lacks conscious experience entirely....The most obvious way (although not the only way) to investigate the logical supervenience of consciousness is to consider the logical possibility of a zombie: someone or something physically identical to me (or to any other conscious being), but lacking conscious experiences altogether. At the global level, we can consider the logical possibility of a zombie world: a world physically identical to ours, but in which there are no conscious experiences at all. In such a world, everybody is a zombie. So let us consider my zombie twin. This creature is molecule-for-molecule identical to me, and indeed identical in all the low-level properties postulated by a completed physics, but he lacks conscious experience entirely....What is going on in my zombie twin? He is physically identical to me, and we may as well suppose that he is embedded in an identical environment. He will certainly be identical to me 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. He will be psychologically identical to me, in the sense developed in Chapter 1. He will be perceiving the trees outside, in the functional sense, and tasting the chocolate, in the psychological sense. All of this follows logically from the fact that he is physically identical to me, by virtue of the functional analyses of psychological notions."
What Chalmers has said here should be enough for us to lose any confidence in what he saying. He is imagining some zombie twin of himself that is unconscious (he says " lacking conscious experiences altogether") but who he claims is "psychologically identical to me." That is nonsense. Psychology is the study of the human mind. If you had a zombie twin that was unconscious, such a being would not at all be "psychologically identical" to you.
It is clear from the above description that the "philosophical zombie" imagined by Chalmers is not simply some unmoving body with the same structure as his body, but also someone acting as he acts "reacting in a similar way to inputs." But an unconscious being would never react in a similar way to inputs as a conscious human does. So there could never be such a "philosophical zombie" that is unconscious but acting like a human and having a human body.
Chalmers then gives us some Darwin-style reasoning using the "I see no difficulties here" kind of language that Charles Darwin loved to use when suggesting the most fantastically improbable claims. Chalmers says this:
"Arguing for a logical possibility is not entirely straightforward. How, for example, would one argue that a mile-high unicycle is logically possible? It just seems obvious. Although no such thing exists in the real world, the description certainly appears to be coherent. If someone objects that it is not logically possible—it merely seems that way— there is little we can say, except to repeat the description and assert its obvious coherence. It seems quite clear that there is no hidden contradiction lurking in the description. I confess that the logical possibility of zombies seems equally obvious to me. A zombie is just something physically identical to me, but which has no conscious experience—all is dark inside. While this is probably empirically impossible, it certainly seems that a coherent situation is described; I can discern no contradiction in the description. In some ways an assertion of this logical possibility comes down to a brute intuition, but no more so than with the unicycle. Almost everybody, it seems to me, is capable of conceiving of this possibility."
This is extremely bad reasoning. There is nothing intrinsically illogical or incoherent about the idea of mile-high unicycle. It is simply an impractical thing that no one has ever built. But the philosophical zombie that Chalmers is suggesting is an impossible, incoherent idea. People act the way they do largely because they are conscious human beings who have the kind of mental experiences that humans have. If you remove human consciousness, no one would ever act in most of the more interesting ways that a human being acts. It is impossible that there could ever exist a physical being having exactly the same physical characteristics and behavior that a human has, but also no consciousness. The idea is as incoherent and impossible as a triangle that is missing one of its three sides. Take out one of the three sides of a triangle, and it is not a triangle, but merely an angle. Take away the consciousness of a human, and he would never act in any of the more complex ways that humans act.
In the paragraph above when Chalmers says "a zombie is just something physically identical to me," he is contradicting his early sketch of his philosophical zombie, in which he described such a zombie as not just someone physically identical to him, but also behaving the same as he behaves. "with indistinguishable behavior resulting." So first Chalmers has described his hypothetical zombie as someone physically identical to himself and also behaving the same; and then later he tries to make that idea sound not too unbelievable by saying "a zombie is just something physically identical to me," mentioning only half of what he had previously mentioned.
There certainly is an extremely gigantic contradiction in the philosophical zombie that Chalmers describes. I will give a simple example illustrating why. Imagine a normal human walking down the street sees a lion walking towards him, a lion that escaped from the zoo. The normal human will have a conscious experience of recognition that causes him to sense the danger; and as a result he will flee or hide. But let us imagine a philosophical zombie encountering such a lion on the path ahead of him. Not being conscious, there could occur no recognition at all for such a philosophical zombie. Nor could such a philosophical zombie ever have such a feeling as fear, for you cannot fear something when you are unconscious. And the philosophical zombie could not make a decision to hide or flee, because you can't decide something when you are unconscious. So it is obviously nonsense to imagine such a philosophical zombie behaving as a human would behave in such a situation.
I could provide endless similar examples. How could Chalmers have gone so wrong? Perhaps he made the mistake of thinking that consciousness is a kind of luxury that can occur in addition to things such as recognition, recollection, decision-making, speech, reading, writing, and so forth. Instead consciousness is a prerequisite for such things. You cannot have in human beings things such as recognition, recollection, decision-making and many other facets of human minds without the prerequisite of consciousness. So it's nonsensical to think that you could get rid of consciousness and still have all those other things, having a philosophical zombie that behaved like a human.
None of these things can occur in an unconscious human being:
- imagination
- abstract idea creation
- appreciation
- memory formation
- moral thinking and moral behavior
- instantaneous memory recall
- instantaneous creation of permanent new memories
- emotions
- desire
- speaking in a language
- understanding spoken language
- creativity
- insight
- beliefs
- pleasure
- pain
- reading
- writing
- visual perception
- recognition
- planning
- auditory perception
- attention
- fascination and interest
- the correct recall of large bodies of sequential information (such as when someone playing Hamlet recalls all his lines correctly)
- spirituality
- philosophical reasoning
- volition
Since all of these things would be excluded from an unconscious human, it is nonsensical to say that an unconscious human could behave just like a conscious human.
Now, it is quite possible that you might build a robot that could behave very much like a human. Such a robot would involve electronic functionality and transistor functionality and computer software functionality unlike anything in the human body. But that is not what Chalmers has imagined. He has claimed that there could exist something that could be physically identical to a human and behave just like a human without being conscious. There could not be any such thing.
"Supervenient" is a philosophy jargon word meaning "coming or occurring as something additional, extraneous, or unexpected." The idea of the supervenience of mind is the idea that mind is additional to matter, or something unexpected from any arrangement of matter. We do not need any appeal to philosophical zombies to establish the idea that the human mind is something unexpected to exist from the matter in a brain. The person wanting to show that the brain fails to explain the mind can discuss the facets of human experience that do not correspond to any reality in the brain. These are very many, including these:
(1) The ability of human minds to instantly form permanent new memories (such as learning of the death of a family member), an ability that does not correspond to any reality in the brain (there being nothing in the brain having any resemblance to a component capable of instantly storing new sensory information).
(2) The ability of human minds to instantly recall many detailed facts about a person after merely hearing their name or seeing an image of that person, an ability that cannot be explained by brains that lack any reading-of-brain-tissue mechanism and lack any of the things that humans put in devices they make to allow for instant retrieval (there being no sorting, indexing or addressing in the brain).
(3) The ability of humans to preserve memories for 50 years or more, something unaccountable in a brain subject to very high molecular turnover and high structural turnover, with things such as synapses and dendritic spines not lasting for years, and brain proteins having an average lifetime of only a few weeks.
(4) The ability of some humans to recall with perfect accuracy extremely long sequences such as all 6000+ verses of the Quran, an ability that cannot be explained by human brains which have no structure capable of explaining the retrieval of very long sequences of learned information.
(5) The ability of many humans to have out-of-body experiences in which they view their bodies from a position outside of it, during cardiac arrest when the brain is electrically inactive, an ability that cannot be credibly explained under any theory that the brain is the same as the mind or the source of the mind.
(6) The ability of humans to perform very high-above-chance on tests of telepathy, ESP and clairvoyance, something beyond any neural explanation.
(7) The ability of some humans (with eyes closed) to perform with blazing speed and perfect accuracy extremely hard mathematical calculations, something that should be impossible in a very noisy brain with so many signal slowing factors, in which chemical synapses (by far the most common type) do not even reliably transmit nerve signals (with the transmission reliability being only 50% or less for each transmission across a synaptic gap).
The study of these and quite a few other abilities (combined with a close study of the physical shortfalls of the brain) are enough to establish the supervenience of mind, its lack of equivalence to matter, and that human minds are unexpected from any arrangement of matter in a brain. There is no need to be appealing to "philosophical zombies" to try to establish such a thing, and such armchair reasoning appeals are not examples of sound reasoning.
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