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Zombies are Inconceivable

A philosophical zombie looks and acts exactly like a person, but has no consciousness and no subjective experience of anything. This conceptual prop is used in many discussion of consciousness, but it is deeply flawed. What I show here is that the concept of a zombie is not conceivable according to normally accepted rules of conceivability.  Any theory that depends on zombies for support should be argued again without zombies.

Zombies are used to justify certain theories about consciousness by many people including David Chalmers along with too many to mention. Nobody is suggesting that zombies actually exist. The arguments revolve around whether zombies are conceivable. This is important, because if zombies are not conceivable, then many arguments for theories of consciousness do not stand.

I am going show here that zombies are not conceivable.  Additionally anyone who thinks that zombies are conceivable is showing a bias in their thinking that will lead to the wrong conclusion. Thus any argument that relies on a zombie is probably a expression of that bias.  Many such arguments actually only conclude the bias itself, and the arguments can be shown to be circular. I won’t do all this, just show that zombies fail the conceivability test.

What is Conceivable?​

Like any philosophical topic, the definition of what is and is not conceivable is subject to great discussion and disagreement. Still, there I believe all philosophers agree that something that is conceivable is something that can not be shown to be impossible by apriori knowledge/logic.

For example, the expression “1 == 2” is false. But is it conceivable? No. Because the numbers 1 and 2 are well defined, and 2 is one more than one, and so it can not be equal. Numbers and mathematics fall into the realm of apriori knowledge (you don’t need any experience to know them) and we can prove in mathematics that 1 can never equal 2, and therefor the expression is not conceivable.

Another example, “the world is flat” is false as well. However, in this case we can’t point to any apriori knowledge that could show it to be inconceivable. One might be able to construct a universe where the various field strengths are adjusted in such a way that flat worlds might exist and be stable. We need aposteriori knowledge about our own universe in order to show the flat world false (here).

Another example, is the idea of a “married bachelor” conceivable? No, because the definition of bachelor is an unmarried man, and thus a married man would never be a bachelor. So it is impossible for there to be a married bachelor, and we don’t need any knowledge of the state of the universe to say this.

So anything that can be ruled out by definition, is not conceivable.

What is a Zombie?​

We are not talking about “Hollywood Zombies” so this is not about Zombie Apocolypse or World War Z. Philosophical zombies do not wander around trying to find brains to eat. Philosophical zombies look and act EXACTLY like real humans, the only difference is that they have no consciousness which means they have no subjective experience of anything. They are exactly the same as normal humans, but the lights are out. No internal experience, they just go about their day as robots that behave exactly like humans.

By definition, a “Zombie-Dave” acts EXACTLY like a Dave (a regular human). They do all the same things including sex, drugs, and rock’n’roll. If you ask a zombie if they are conscious, they will say “Yes I am” but only because they have no awareness that they have no awareness. Zombies cry at weddings, and rejoice when their favorite hockey team wins, but inside they feel nothing. They just act the part.

The zombie is missing all subjective experience. None of us have access to anyone else’s internal subjective experience. I can never know how you experience the taste of apple pie, and you can not know my experience. We can talk about it, but we can only compare to other experiences which we can never be sure are experienced the same. So, the zombie is missing something that we outside the zombie can never detect.

The argument relies on zombies being identical in behavior to normal humans. What is being removed is the undetectable part of subjective experience.  Zombie-Dave can not be distinguished from the real Dave.

The only difference is that Dave has conscious experience (undetectable to us) while Zombie-Dave does not.

An Assumption is Required​

The problem with this logic is that you must assume that there is nothing about consciousness that makes Dave like Dave. You assume that consciousness makes no causal difference. When you postulate that Zombie-Dave (without consciousness) acts exactly like Dave (with consciousness), you imply that consciousness must have no effect on the behavior of Dave.   Zombie-Dave has all the same skills, can recognize all the same things, remembers all the same things, can do all the same things, likes all the same things to the same degree as Dave. You assume that Dave’s consciousness has absolutely no effect on his behavior.

Things with no effect are exactly the same as not existing. I might insist that I have an invisible flying dragon in my garage who is not detectable by any means. XRays, gamma rays, fingerprint powers, blood hounds, random groping, none of these will ever detect this dragon. It never talks, it never eats anything, it never bumps into things, it never leaves any trace. I just know it exists. Something that has no effect on the universe is exactly the same as something that does not exist.

How can we say that Dave’s consciousness has no effect on him?   We know that we experience pain, and we respond to pain. Pain is part of the causal loop for behavior. We smell the apple pie, and get the desire to eat because of anticipation of the pleasant experience of eating apple pie.  Zombie-Dave does not experience pain, and yet jumps in exactly the same way. Why?  Zombie-Dave salivates before eating the apple pie exactly like Dave. Why?  But for now, assume that there is some reason that Zombie-Dave acts exactly like Dave — it is just not consciousness that does this.

Zombie-Dave can conceivably act exactly like Dave, only if conscious experience has no effect on Dave’s behavior.  If Dave’s conscious experience makes any difference in Dave’s behavior, then Dave would act different from the Zombie-Dave who does not have conscious experience.  If the lack of consciousness changes the behavior of the zombie, then it is not a zombie according to the definition.

Does Consciousness Matter?​

I think consciousness does matter to my behavior. Whatever you think consciousness is, surely it has some effect on your behavior.

Pain: If I stomp on your foot, you will feel that pain an jump. It is not the case that you jump and swear, but the pain is just felt on the side. Pain is not an epiphenomenon that just occurs without mattering. We can apply an anesthetic, and then when I stomp on your foot you won’t jump. Because you don’t feel the pain. The pain itself is part of the causal loop for the action.

Taste: You try an apple-pie and you try a moose-turd-pie. Clearly the pleasant experience of the apple pie will lead you to seek out more opportunities to eat apple pie. Not so with the moose-turd. The taste and smell drive future behavior.

Pleasure: A similar argument can be made about pleasure. Clearly the enjoyment of sex drive one to look for future opportunities. Otherwise, why do it?  One might imagine Zombie-Dave going through the motions of sex without feeling any ecstasy, but it is impossible to imagine Zombie-Dave having the same enthusiasm for the act that Dave has.

This might not convince you that consciousness matters, but I just want to convince you that we can’t say that consciousness never matters.   The zombie argument requires that consciousness never matters one little bit. Never ever. Because you must never see a difference between Dave and Zombie-Dave in any situation.

Zombies are Inconceivable​

P1: Zombies are conceivable only if consciousness has no effect (by definition of zombie)
P2: Consciousness has an effect (otherwise there is no point in discussing consciousness)

QED: Zombies are not conceivable

See any problems with this logic?  Please, please, please let me know. Because there is nothing convoluted here.

P1 is clear I think: Zombie-Dave can act exactly like Dave only if consciousness does not matter and makes no difference.

One might disagree with P2, and claim that consciousness has no effect on anything (epiphenominalism), but you shoot yourself in the foot. Any conclusion you make is only for something that has no effect on the world, and therefor is indistinguishable from not existing.  If it simply does not matter that you feel pain, then you obviously have a very different subjective experience than I do.

Conclusion​

The typical zombie argument assumes from the beginning that consciousness is not physical, so that it can be removed from Dave without changing Dave’s behavior.  Based on the assumption removing consciousness does not remove anything physical, any conclusion that consciousness is not physical (not part of the material world) is just a consequence of the original assumption.

I stand firmly convinced that consciousness is a real thing that plays a causal role in the world. It is somehow manifest in the material world. I can’t prove that, so I am certainly willing to entertain other possibilities as long as they don’t assume from the beginning that consciousness has no effect on the world.

I don’t give any credence to any argument that involves philosophical zombies.  Zombies are not conceivable if consciousness matters, and so any conclusion is unfounded.  Zombie arguments prove only that the part of consciousness that has no effect is not part of the material world.  We already know that things that that have no effect are not part of the physical world.  Any conclusion about the physicality of consciousness is simply a restatement of the assumption made at the beginning.

Appendix — Discussion​

You don’t need to read this, but I try to answer anticipated questions here

Partial Zombies​

Maybe I am being too strict. They said that Zombie-Dave is exactly like Dave, but what if they really meant “mostly” like Dave. like maybe 99.999% like Dave, but sometimes just a little different.

As soon as there is any behavior that indicates consciousness, then the arguments built on zombies fall apart.

One argument is “Consciousness is not physical, because it is conceivable that a physical world could exist exactly like this one without consciousness.” As soon as you admit, no actually the world won’t be exactly the same, and that the world will be a little bit different, then we have to conclude that consciousness is at least a little bit physical.

For example, let’s propose that Zombie-Dave can feel pain, but that is the only subjective experience. So when I stomp on Zombie-Dave’s toes, he feels pain and jumps. Well, then, pain would then be recognized as a physical phenomenon. If pain is physical, then why not pleasure? Or taste? or smell?

I don’t want to go down this path too far. I only want to show that the concept of a philosophical zombie identical to a human is inconceivable. Arguing whether a “partial-zombie” would work to support theories is left as an exercise to the reader.

Zombie Surgery​

Lets say a zombie needs the appendix removed (they act indistinguishable from humans, so they certainly get appendicitis).  Before the surgery the Zombie-Dave is given an anesthetic in order to enter an unconscious state.   Does this have any effect on the zombie?  Well certainly Zombie-Dave would act indistinguishably from Dave.  Clearly, whatever we call consciousness has now been blotted out for both Dave and Zombie-Dave.  This means that whatever we call consciousness has to be in both, but that is incoherent.

Because all behaviors between Dave and Zombie-Dave are the same, no matter what chemicals they are given, we can conclude that whatever Dave has, that the zombie is missing, can not in any way be effected by any chemicals.  Any effect on consciousness by chemicals is more evidence that zombies are inconceivable.

Daniel Dennett​

Daniel Dennett thinks those who accept the conceivability of zombies have failed to imagine them thoroughly enough: ‘they invariably underestimate the task of conception (or imagination), and end up imagining something that violates their own definition.’

“Philosophers ought to have dropped the zombie like a hot potato, but since they persist in their embrace, this gives me a golden opportunity to focus attention on the most seductive error in current thinking.”

Nigel Thomas argues that the zombie concept is inherently self-contradictory: Because zombies, ex hypothesis, behave just like regular humans, they will claim to be conscious. Thomas argues that any construal of this claim (that is, whether it is taken to be true, false, or neither true nor false) inevitably entails either a contradiction or a manifest absurdity.

Zombie Utterances​

Suppose Dave smells roasting coffee beans and says, ‘Mm! I love that smell!’. Everyone would rightly assume Dave was talking about his experience. But now suppose Zombie-Dave produces the same utterance. He too seems to be talking about an experience, but in fact he isn’t because he’s just a zombie. Is he mistaken? Is he lying? Could his utterance somehow be interpreted as true, or is it totally without truth value? Nigel Thomas (1996) argues that ‘any line that zombiphiles take on these questions will get them into serious trouble’.

Zombie Qualia​

Zombies can do wine tasting (but in their case it is “wine not-tasting”).  Even though there is no experience of taste, Zombie-Dave can distinguish a Syrah from a Pino Noir just as well as Dave.  In fact zombies can train and be able to discern any wine variety.  What is the difference between what the zombie is doing and actually tasting?

Sean Carroll​

Sean Carroll wrote a paper on the topic of Consciousness and the Laws of Physics. He argues that consciousness is emergent from the known laws of physics, and he is particularly eloquent on how we can’t just suppose that there are new laws to support consciousness when we have never seen any effect of those laws to date.

In his November 2021 Ask Me Anything Podcast, he says about zombies:  “What you’re imagining is a person who acts exactly like me but doesn’t have that inner conscious experience, okay, but I think that they’re not really taking seriously enough the idea of exactly the same as me behaving in exactly the same way, okay. Because what that means is that a zombie would say they were conscious, a zombie… If David… If there was a zombie David Chalmers, that zombie David Chalmers would invent the zombie argument in favour of non-physicalism of consciousness. If there were a zombie Philip Goff, zombie Philip Goff would write a book in favour of panpsychism because that’s a behaviour. If someone says, “I am experiencing the redness of red,” or “I am in love,” or “I am sad,” that statement they are making is a behaviour. So what that means is, if you can conceive of zombies, the zombies are reporting what they take to be their innermost experiences. Right? I mean the zombies aren’t lying to you any more than a regular person is lying to you. When a zombie says “I am experiencing the redness of red,” they think they’re experiencing the redness of red.”

“But the zombie thought experiment provides excellent evidence that if zombies are conceivable, then introspection is entirely unreliable, because the zombies are reporting their results of introspection also, and they’re completely wrong, ’cause they’re saying that they’re conscious and they’re not. ”

” the kind of consciousness that is purportedly being explained by panpsychism, if you don’t change the laws of physics, is the kind of consciousness that has no effect on behaviour, a kind of consciousness that is completely unrelated to what we talk about when we talk about consciousness, because our talking is a behaviour. Our talking obeys the laws of physics, right? And if that’s what you’re explaining, if you’re explaining something that literally cannot be reported on, talked about, or had any influence on how we behave, then I don’t think you’re explaining consciousness at all. What kind of conscience is it that has no effect on my behaviour at all? That’s not what I think of when I think of consciousness anyway.”

Problem of Epiphenominalism and Epistemology​

My argument above finds zombies conceivable only if epiphenominalism is true, that is consciousness can have no effect.

Stanford Encyclopedia of Philosophy says: ” In that case the friends of zombies must explain how the epiphenomenal qualia in such worlds could possibly be objects of acquaintance, or indeed make any sort of intimate contribution to people’s lives; and here Kirk (2005; 2008) suggests the zombie idea faces a further difficulty. This emerges when we consider such things as attending to, thinking about, remembering, and comparing our experiences: activities that bring us into ‘epistemic contact’ with them. Such activities involve cognitive processing, which in turn involves changes causing other changes. Since epiphenomenal qualia are causally inert, they themselves could not do that processing; so if they actually constitute our experiences (as epiphenomenalism and parallelism imply) then the necessary processing must be done by the body. The trouble is that the zombie story makes it impossible for such processing to put us into epistemic contact with epiphenomenal qualia. This is because the only resources it can appeal to for that purpose are the assumed causation of qualia by neural processes and their isomorphism with them: factors which (Kirk argues) cannot do the necessary cognitive work. If that is right, the notions of epiphenomenal qualia and zombies lead to a contradiction. They imply a conception of consciousness which requires people to be in epistemic contact with their qualia, while at the same time ruling out the possibility of such contact”

All “imagine if” arguments fall into the same trap​

A silly comparison: assume it is conceivable that you have something that is exactly like a car, but it has no wheels. Since it is conceivable that there is a world where none of the cars have wheels, I then conclude that wheels are not part of the material world. I can imagine a car without wheels (e.g. a hovercraft), but it would be a lie to say it is “exactly like a car”. A car without wheels would be very very different from a car.

All arguments of “imagine something that is exactly like X but is missing Y”

  • In most cases, removal of Y does not leave you with something exactly like X, because in most cases things effect each other.  Y is there usually for a reason, and so you can’t say it has no effect.
  • But maybe Y has really no effect (e.g. a small pebble stuck to the undercarriage of a car in an innocuous place).  You can imagine something exactly like the car, except with the pebble removed.  The pebble makes almost no difference, but even that might be detectable.   If Y really makes no difference, it is the same as if it did not exist.
  • Any argument is going to be based on intuition: some conclusions you have made about how the world works, and whether Y matters to X and in what ways.   This is particularly problematic when nobody has ever experienced an X without a Y.  Imagine something just like a human, except it could breath in outer space.  Nobody has any experience with such a thing, and all our intuition might be different.  I am a fan of Star Trek so I might have one idea what such a space-human would be.   But a fundamentalist Christian might have a very different idea.  All this is limited but our imagination which is limited by our experience which is unique to all of us.

Blog Post Reinforcing this Position​

  • https://johnguru.wordpress.com/2008/08/02/philosophical-zombies/
  • Brian Tomasik, https://reducing-suffering.org/objections-to-the-zombie-argument/
  • Frankish, Keith (2007). The anti-zombie argument. Philosophical Quarterly, 57(229) pp. 650–666 (http://oro.open.ac.uk/2191/1/Antizombie_eprint_rev.pdf)
    • “In recent years the ‘zombie argument’ has come to occupy a central role in the case against physicalist views of consciousness, in large part because of the powerful advocacy it has received from David Chalmers.1 In this paper I seek to neutralize it by showing that a parallel argument can be run for physicalism, an argument turning on the conceivability of what I shall call anti-zombies. I shall argue that the result is a stand-off, and that the zombie argument offers no independent reason to reject physicalism.”
    • “My anti-zombie twin is just something which is physically identical with me, and has no non-physical properties, but which has conscious experience.
      1. Anti-zombies are conceivable
      2. If anti-zombies are conceivable, then anti-zombies are possible
      3. If anti-zombies are possible, then consciousness is physical
      4. So consciousness is physical.”
  • Richard Brown (https://philpapers.org/archive/BRODTA.pdf)
    • “Zombies are creatures that are nonphysically identical to me in every respect, and which lack any nonphysical phenomenal consciousness.  Put more formally we can say that where NP is the totality of the nonphysical facts about me now and Q is some qualitative fact about me, say that I am now seeing green.  It is conceivable that NP & ~Q obtain.That is to say  that I can conceive of all the actual nonphysical properties being instantiated in just the way they are now, and yet not including qualitative properties.  There is no obvious contradiction that emerges from conceiving of all actual nonphysical properties being instantiated and yet not including phenomenal properties.  Thus dualism is false.”
  • Eric Marcus, WHY ZOMBIES ARE INCONCEIVABLE, Australasian Journal of Philosophy
    Vol. 82, No. 3, pp. 477±490; September 2004 (http://webhome.auburn.edu/~marcuea/zombies.pdf)
    • ” argue that zombies are inconceivable. More precisely, I argue that the conceivability-intuition that is used to demonstrate their possibility has been misconstrued. Thought experiments alleged to feature zombies founder on the fact that, on the one hand, they must involve Ærst-person imagining, and yet, on the other hand, cannot. “
    • “What is it like to be a zombie? Well, zombies are beings without consciousness. There is nothing that it’s like to be a zombie.“
    • “To `imagine’ creatures that are objectively identical
      to us with all subjectivity removed is neither an act of third-person imagining, nor an act of First-person imagining. No, to `imagine’ a zombie is not really to imagine at all.“
  • Artificial intelligence researcher Marvin Minsky claims that the argument is simply circular. By proposing the possibility of something which is physically identical to a human but has no subjective experiences, the argument is implicitly assuming that the physical characteristics of humans are not what produces those experiences. But that is exactly what the argument was claiming to prove
  • Nigel Thomas, Zombie Killer, ( https://philpapers.org/rec/THOZK)
    • This brief article shows that any way of understanding the behavior of zombies that does in fact support the suggested entailment, leads to contradictions and absurdities. Zombies are _not_ conceptually possible
    • Zombie says it is conscious, but it is lying.  Lying is a different mental activity than telling the truth, thus Zombie-Dave is NOT acting exactly like Dave.
  • Eric Schwitzgebel – https://schwitzsplinters.blogspot.com/2007/08/zombies-and-anti-zombies-by-guest.html
  • Trick Slattery says “Philosophical Zombies? Inconceivable!”
    • the topic of consciousness and the “hard problem” is a very large topic, with many different ideas swirling around many different minds. And though I think there is no evidence for mind-body dualism (the mind being something that is in some way separate from the body) and much evidence pointing to mind being an aspect of the physical body’s configuration, and though I think consciousness, at least for various biological creatures, plays an important causally functional role, I still seek more conclusive evidence in either direction. In the meantime I’m swayed over to the side that physically identical p-zombies are not conceivable.