by Brian Tomasik
First written: 5 Sep. 2014; last update: 4 Dec. 2014

Summary

This piece discusses two of my main objections to philosophical zombies:

  1. The first directly addresses the argument: I maintain that conceiving in a first-person way of any mind that we are not is fundamentally incoherent, because we are not that other mind. While we can pretend to approximate other minds when making ethical judgments, conceiving of ourselves as other minds when making ontologically laden claims goes too far.
  2. The second addresses the way the argument looks. The zombie approach pattern-matches to an act of verbal sophistry. It's apparent that something is wrong with it -- even if we couldn't say what -- because it takes us so far from what else we know about reality.

Dialogue

Bob: Why does it feel like something to be conscious given physicalism?

Alice: When your brain reflects on itself, its thought apparatus generates that puzzle as a feeling in your mind, which you then verbalize. As Michael Graziano explains: "The brain insists that it has subjective experience because, when it accesses its inner data, it finds that information."

Bob: Ok, but that "feeling" of the brain's insisting it's conscious is still a feeling. Why does that feel like something?

Alice: You're now having another thought that you have a feeling about having a feeling.

Bob: Yes, but why does that thought feel like something? Are you going to postulate thoughts all the way down? At some point we have to explain the feeling-ness behind the thoughts.

Alice: Yes, I need to give a more satisfying account. Consider this. If you really think about all that would be happening in a supposed zombie's head, I find it hard not to see how that being would be conscious. See Dennett's "The Unimagined Preposterousness of Zombies". Zombies are like a "smoke and mirrors" trick. In order to imagine them, I have to stand on the outside and see physical processes happening and then tell myself there's no inner life. In other words, I have to adopt the physical stance. If instead I allow myself to enter their heads in a first-person way, then it seems obvious that I would have an inner mental life.

Bob: Ah, but your example is symmetric. You say I'm illegitimately stripping away consciousness by adopting a third-person mindset about zombies, but I say you're illegitimately smuggling consciousness in by plugging your own consciousness into the zombie's head.

Zombies

David Chalmers's framing of the zombie argument is superficially impressive. Chalmers is clearly one of the smartest non-reductionist philosophers I've read.

There's much discussion of the zombie argument that I won't repeat here. I find the "anti-zombie" arguments interesting, Keith Frankish's and Richard Brown's. They suggest that there must be something wrong with zombie-type reasoning.

The rest of this piece discusses two of my own reasons for rejecting the argument, although I don't claim them to be original by any means.

Problems with first-person conceivability

I don't think zombies are ideally conceivable. Yes, they seem to be naively if we take a third-person stance, but I think there's something fundamentally wrong with mixing third-person conceivability with first-person statements. All other conceivability examples concern third-person phenomena or first-person phenomena separately. There's a sort of "change of who you are" that's required to talk about other minds, and I think if we "changed who we were", we would see that functional/structural facts require that so-called zombies would have what we poetically call phenomenal experiences. That is, physical facts plus "acquaintance knowledge" logically imply qualia.

Of course, this "change of who you are" is fundamentally an incoherent notion, because if Person A becomes Person B, then Person B is not Person A, and there's no sense in which Person A is still somehow present in Person B. You can never get inside someone else's head without being that person. So we should be extremely wary of attempts to presume that we can coherently imagine anything concerning a mind that we are not -- which includes imagining that it lacks subjective experience. I might go so far as to say we can't imagine anything from another perspective than our own -- at least not in a way that has metaphysical import. Third-person imagination is legitimate because it's done from our own perspective.

Robert Kirk's article on zombies gestures along these lines: "It has been suggested that there are special factors at work in the psychophysical case which have a strong tendency to mislead us. For example it is claimed that what enables us to imagine or conceive of states of consciousness is a different cognitive faculty from what enables us to conceive of physical facts [...]".

Eric Marcus on inconceivability

In "Why zombies are inconceivable", Eric Marcus carries another challenge against conceivability involving first-person claims. He alleges that conceivability requires first-person imagining, but we can't imagine a zombie world from a first-person perspective because there are no first-person perspectives in such a world.

Casey Woodling replies that imagining whether or not a "what it's like" experience exists can be done from a third-person perspective. For instance, he says, he can know that it's like something for his brother to skydive, even if he doesn't imagine his brother's experiences from a first-person point of view (p. 114). My response is that since I think "what it's like" is not a thing that can be absent or present but is more of a poetry that we use to describe how things are, I'm not sure we can say that there's something it's like to be someone other than us in a manner that has any logical force.

Marcus also points out that failing to imagine something is not the same as ideally imagining its absence. For instance, I can imagine the arrangement of atoms in the universe without picturing mountains, but it's not ideally conceivable for the atoms of the universe to be arranged as they are without there being mountains. Likewise, I can imagine beings that are molecule-for-molecule identical with us without imagining consciousness, but this isn't the same as positively imagining an absence of consciousness (p. 484):

No one would argue that to imagine a happy family without imagining their toes is to imagine a toeless happy family. Similarly, it does not follow from the fact that we can imagine creatures third-personally like us without thereby imagining what it's like to be them, that we have imagined creatures third-personally like us whom there's nothing it's like to be.

I would add that we can imagine a toeless happy family, but it would need to be different from an ordinary happy family. For instance, the family members might need to have had medical care to prevent bleeding and might walk with abnormal movements. I can't imagine a toeless happy family with everything else held constant. (At the very least, the family members would not trim their toenails like most people do.)

Marcus's claim in the preceding paragraph is characterized by Torin Alter as a "scope confusion". I'm not sure what I think of this allegation.

Breaks too radically from everything else we know

Ultimately, my strongest reason for rejecting Chalmers's argument has to do with good rational hygiene. Jonah Sinick argues that we should doubt even a seemingly strong argument when there are many weak reasons to suspect something wrong with it. The zombie argument purports to fundamentally alter our ontology in a more radical way than any other discovery has on the basis of some armchair intuitions that may or may not hold up on closer examination. This to me is the mark that something has gone wrong, even if one can't put one's finger on exactly what.

In 2011, it was reported that the OPERA experiment had detected neutrinos moving faster than the speed of light. The Internet was abuzz with speculation about what this implied for physics. Upon hearing the news, I thought: "There must be something wrong with those results. There's too much theory behind why superluminal travel doesn't make sense. Sometimes elegance trumps empiricism." And sure enough, the observation later turned out to be flawed.

I feel the same way about the zombie argument and other anti-materialist proposals. Even if I had no idea how to attack them, I would still reject them as inconsistent with everything else we know about how the universe works. It's vastly more likely that there's some error in your reasoning or some defect in your introspection than that we should add some complicated thing to our ontology that doesn't appear to have any function other than to make us feel more intuitively satisfied. Sean Carroll and Steven Novella make similar points in an Intelligence Squared debate about near-death experiences.

History has shown us many examples in the past where people had a knock-down logical argument that was just wrong. The zombie argument shares many similarities with the ontological argument for the existence of God. I largely agree with Richard Dawkins when he says: "The very idea that such grand conclusions should follow from such logomachist trickery offends me aesthetically."

Of course, some will contend that many weak arguments also point toward anti-materialism. For instance:

  • Dualist thinking has presumably been common through a good deal of human history and is the default view of most Westerners today.
  • There are many anti-materialist arguments beyond zombies (though I feel they all amount to the same thing in different guises).
  • Dennett is widely regarded as missing something in his account of consciousness.

Sure, those are sensible weak arguments in defense of anti-materialism. But at the end of the day, it just seems obvious to me that materialism is more plausible. This was not a feeling I was born with, but rather it came to me from the cumulative rhythm I've absorbed from neuroscience and physics.

In "A Call for Modesty: A Priori Philosophy and the Mind-Body Problem", Eric Funkhouser suggests (p. 26) a kind of Moorean shift in which, rather than reasoning from Chalmers's premises to the conclusion that zombies are possible, we reason from the fact that zombies are not possible to conclusions that either conceivability does not imply possibility (at least in this case) or that zombies are not ideally conceivable.

Is possibility just conceivability?

Eliezer Yudkowsky has written (I can't find the source) that he doesn't know what philosophers mean by "possible world". Philosophers talk as if "metaphysical possibility" were a real thing. Certainly it's a helpful tool in conversation, and modal logic has its value. But does it refer to anything fundamental?

I'm not a professional philosopher and have not explored the literature on this question. But my own take is that "possibility" is a construct in human minds that we understand in a certain way. And the way we understand it seems to me best tracked by "conceivability" (specifically ideal conceivability in Chalmers's terminology). To say that a state of affairs is metaphysically possible seems to basically mean it's logically consistent.

In that case, the assumption that ideal conceivability implies 1-possibility is tautologous. This actually makes the zombie argument easier to defend, since then the only question is whether zombies are ideally conceivable, i.e., logically consistent. While this seems to deflate some of the metaphysical import of the issue, I still think the "are zombies possible?" question helps to distinguish varieties of claims about consciousness, such as between type-A and type-B physicalists. Indeed, this is arguably the most interesting distinction, and then if zombies are logically coherent, the exact details of how they would work is less dramatic. That is, the question of whether there's a hard problem of consciousness seems more important than exactly how the putative hard problem would be solved.