Tuesday, April 08, 2008

How To Imagine Zombies

Some of the recent discussion on other blogs has assumed a sloppy version of the zombie argument, whereby we are to imagine a world just like ours but subtract consciousness. Hence Eliezer complains:
The epiphenomenalist imagines eliminating an effectless phenomenon, and that separately, a distinct phenomenon makes Chalmers go on writing philosophy papers. A substance dualist, or reductionist, imagines eliminating the very phenomenon that causes Chalmers to write philosophy papers.

Right, so that's a bad way to present the argument. The better way to imagine the zombie world is not by subtraction, but by building it up. Give a complete microphysical description of the world, and specify "that's all". A Laplacean demon can infer that the world contains tables, brain states, and a book entitled 'The Conscious Mind'. That is, the world contains particles arranged table-wise, brain-wise, book-wise, etc.

The Laplacean demon knows all that there is to know about this world. Does he know that it contains phenomenal consciousness, that there is something it is like to be the particles-arranged-humanwise in this world? Seems not. There's nothing in the microphysics that entails the presence of such subjectivity. So we've successfully imagined the zombie world. Not by subtracting, but by building up from the physics alone and noting that more needs to be added in order to obtain our (consciousness-containing) world.

Richard Brown makes a similar mistake in his attempted parody:
I am conceiving of a world that is just like this one in all non-physical respects except that it lacks consciousness. Therefore dualism is false.

The zombie argument begins by providing an undisputed specification of the "physical respects" of the world. It then asks whether phenomenal consciousness logically follows from the specification. Our answer is 'no'. That's why physicalism is false.

A proper analogy, then, would require building up the "non-physical zombie" world from an undisputed non-physical specification, just as we earlier built up a physical zombie world from an undisputed physical specification. But of course RB cannot do this. So that's why the zombie argument cannot be turned against dualism in this way.


  1. Reading this, plus some more thought generally, has resurrected (brought back from the dead, zombie-like, even) my earlier worry. Why would a complete microphysical description of the world not include these "bridging laws" that give rise to consciousness?

    Generally, laws would be included in a complete microphysical description of the world. For example, if the speed of light in this world isn't c, then it's not an otherwise identical world.

    So there has to be some kind of distinction between the law "the speed of light is c" and the law "brain cells arranged in manner X give rise to consciousness" that supports including one of them in the microphysical description of the universe and not the other.

    And it can't be that the second law describes something nonphysical, because that's question-begging: the argument is supposed to establish the non-physicalness of consciousness.

    What is it?

  2. Terminological. Scrap the word 'physical'. The substantive question is whether matters of structure and function (as discovered via third-personal scientific inquiry) entail anything about phenomenology.

  3. I'm not sure that works, because the classification of (somethings -- I'm not sure how the ontology works here) into "structure and function (as discovered via third-personal scientific inquiry)" and "phenomenology" is itself at issue.

    Why shouldn't Laplace's demon be able to know my phenomenology? (And, for that matter, a bat's?)

  4. As a fundamental datum, you mean? I'd be fine with that. Reductionists want to claim that we don't need to include any mention of mental properties in our fundamental description of the world. They're meant to be an ontological "free lunch" just like tables and brain states. Since you grant that we need something more in this case (i.e. psycho-physical bridging laws, even if you insist on classifying them as 'physical'), I think you're granting me everything I want here. (I don't care about the classification.)

  5. I think I just find it hard to think that the notion of some kind of bridging law is inconsistent with reduction.

    One way to understand reductionism is as saying that all there is is composed of a) particles, and b) laws. So we have photons, and we have laws describing how fast they move, and those two things together reduce "light."

    Likewise, we have atoms (themselves reducible to subatomic particles and their own laws, etc.), and laws describing how they arrange themselves into molecules and stick together, and those two things together give us tables.

    Why do we not also have brain cells (themselves reducible, to atoms and then to the things atoms are reducible to) and laws describing how they give rise to consciousness, and those two things together give us first-person experience?

    In that sense, we don't need to mention mental properties, just like we don't need to mention tables. We do, however, need to mention the laws that give rise to tableness and the laws that give rise to mentalness.

  6. I think that if we buy my last comment, the issue becomes whether we can describe the brain cells --> consciousness laws in terms of more fundamental laws of microphysics. If so, then we've definitely accomplished a reduction. If not, I'm not sure..

  7. Richard, I don't really see how you reach any new insights here, by "building up" the alternate world instead of "subtracting." Both parties would be talking about the same example, only perhaps without a negative connotation of "subtracting consciousness." I do realize that the "does subjectivity follow from the physical details" argument becomes somewhat clearer, but the end result is the same world.

    Again, I also don't see how you address some of the core arguments with the zombie hypothesis. Such as: we do not possess enough understanding of the nature of all the microphysical details to justify a belief that subjective experience wouldn't necessarily follow from them. ~Complete (or merely better) knowledge is often requisite to ~complete (or merely better) understanding: so many unexpected "surprising" facts don't appear to follow from a more limited set of knowledge.

    If I say that I don't see how the zombie argument makes verifiable, testable claims it is called scientism, but I see it as a good measuring stick for verisimilitude.

  8. What I'm saying is:

    You say:

    "The zombie argument begins by providing an undisputed specification of the "physical respects" of the world. It then asks whether phenomenal consciousness logically follows from the specification. Our answer is 'no'. That's why physicalism is false."

    And yet I and no other human will be capable of offering this undisputed specification of the physical respects of the world. We do not possess that knowledge. Furthermore, there is some evidence to indicate that we may never possess this knowledge to a high degree of certainty at our current level of intelligence. Without this specification of microphysical facts how can we answer the question you present? Certainly the Laplacean demon could present an answer, but we can only conceive of an answer if we sufficiently cloud our understanding of the model.

    You too easily jump from requesting a specification to saying "and from this we would say 'no'" when it isn't at all clear what we would say had we that information. If we answer using what information we have now, we can't answer absolutely in any direction. We would have to make a betting guess. Why should that guess not be informed by previous guesses we have made in previous similar situations? Chalmers says "but this time, it's different!" but in no way that seems convincing...

  9. "Again, I also don't see how you address some of the core arguments with the zombie hypothesis."

    I wasn't trying to address every possible objection. I was addressing the specific objection Eliezer raised that epiphenomenalists and reductionists are going to imagine different things if they try subtracting (their model of) consciousness from the world. We avoid this problem by building up from a shared understanding of physics.

    Now, you're right that in fact our (shared) understanding of physics is incomplete. So some other objections may be raised in virtue of this. But I'm not talking about those other objections in this post. For now, I'm merely addressing the worry that we need a shared recipe to ensure that everyone is actually engaging in the same thought experiment to begin with.

  10. Brandon, I think it clear they are both equivalent (subtraction vs. addition) but I think that in terms of trying to explain what the problem is that the addition method works a lot better. (At least in my experience)

    Ultimately though as others have mentioned the problem is how something purely in 3rd person description can become something in 1st person description. I can't see how laws could even in theory do that.

    Obviously if the first person is irreducible that needn't entail dualism. But that's more complex.

  11. Dear Richard: keep fighting the good fight (although maybe someday I'll try to convert you to the Type F church!)
    Best regards, - Steve Esser

  12. Hey Richard,

    I'm not sure the 'building it up' version of the argument is any better because it seems there's a difference between (a) the possibility of deducing/inferring Y-facts from X-facts and (b) the possibility of worlds indiscernible with respect to the X-facts while being discernible with respect to the Y-facts. Think about the moral case. We cannot derive the ought from the is, but there cannot be two worlds that are indiscernible with respect to their non-moral features but discernible with respect to their moral features.

  13. Clayton - you're right about "deducing", but I think there's an important difference when it comes to the broader notion of "inferring". By this latter I mean a priori implication, which includes all our a priori knowledge (incl. the fundamental moral principles). Given a complete natural description of the world, an ideally rational agent had better be in a position to infer the moral facts.

    One might try to push a similar line in the case of qualia. It's true that nothing I've said here precludes such a position. But it doesn't seem so plausible on the face of it. Intuitively: qualia are in the world -- concrete constituents -- in a way that moral or mathematical facts are not. So by 'building up' the physical world I've described, it's not just that the qualia facts are non-deducible from this base; it seems that they are not present at all in the scenario as specified. The moral case is clearly not like this: given a complete natural description (physics + qualia), we can tell that the moral facts are settled, it's just not obvious what they are until we do some moral philosophy.

  14. Richard,

    Well said.

    Casual observation suggests that most of this criticism of Chalmers is coming from people who haven't read the book. Eliezer's admitted he hasn't.

    I don't have a strong opinion on materialism vs. dualism, but I do strongly opine that Overcoming Bias is a materialist echo chamber that fails to squarely face its dualist opponents. It's much to the good that you hang around.

  15. Yeah. I haven't read all the discussion, but the debate is hampered by unfamiliarity with the actual conceivability argument.
    1. Many jump in thinking the zombie argument is a positive argument for the plausibility of epiphenomenalism instead of an argument for the falsity of physicalism.
    2. The modal aspect of the argument is new to people.
    3. Many have never grappled with the hard problem of consciousness which motivates the argument in the first place.

    Also, differing terminology makes it difficult and people wander away from the hard problem: I think a good way to phrase things is to say that physicalism is the thesis that the facts of first-person experience are entailed by fixing the non-experiential facts of the world.

  16. Hey Richard,

    Suppose we change things in the way you suggest. I remember that the way Chalmers does it, you are supposed to be equipped with a description of the physical plus the relevant concepts for thinking of things in terms of chemistry, biology, psychology, morality, etc... I think it's pretty clear that the mere fact that you have these concepts, it won't follow that you'll have apriori knowledge of conditionals linking the physical to the higher-up, as it were, but let's not worry about that.

    You said:
    you're right about "deducing", but I think there's an important difference when it comes to the broader notion of "inferring". By this latter I mean a priori implication, which includes all our a priori knowledge (incl. the fundamental moral principles). Given a complete natural description of the world, an ideally rational agent had better be in a position to infer the moral facts.

    I just don't see that at all. _Our_ apriori knowledge of morality does not include knowledge of any conditionals with antecedents that can be stated in purely non-moral terms and consequents that state what we have reason to do, what we ought to do, what has value, etc... You might imagine ideally reflective versions of ourselves, but if idealizing us is a matter of idealizing our _capacities_, that won't help. If you ask us to imagine a morally omniscient being, even that might not help. It won't help unless we assume a kind of reductivist view about morality is right. Nevertheless, we oughtn't deny supervenience of a sort that precludes the possibility of worlds physically just like this one without any moral properties (i.e., moral zombie worlds).

    [There's also the entertaining but cheap response. You say that it should in principle be possible to combine what we know apriori about morality with complete knowledge of the physical world to arrive at complete moral knowledge of this world. But, if we lacked knowledge of qualia, you've just shown that qualia are strongly irrelevant to morality. So, there's no reason to refrain from inflicting pain, preferring kicking a zombie to a normal person if forced to kick one, no reason to refrain from asserting that a particular zombie feels pain, etc...]

    Minor quibble. Qualia are _not_ concrete constituents. They are properties or qualities.

    Here's a story that a physicalist can tell to explain why there is no 'apriori passage' from the physical description of the world to the description of qualia that is similar to the story we can tell about morality. The problem with the view that there is apriori passage from the physical way things are to the moral way things are is that there are no strict principles with non-moral antecedents and moral consequents. Explaining this might require settling some substantive moral issues, but it's a respectable view.

    As for the bridge from the material to the mental, what if someone says that it is necessary to grasp certain mental concepts (e.g., concepts of qualia) that we use certain indexical and demonstratives in order to grasp them? [Someone might have a non-indexical or non-demonstrative way of conceptualizing what we conceptualize as qualia, but that won't be _our_ concept. Concepts are not individuated solely by that which it is a concept of.] As we know, indexical and demonstrative knowledge cannot be understood in terms of knowledge by description. So, there's no way to infer from what can be known by description what is true of qualia.

  17. Hi Clayton, see Jackson and Chalmers' 'Conceptual Analysis and Reductive Explanation' [pdf] for the argument that macrophysical truths are a priori entailed by microphysical ones.

    [Also, your 'cheap response' rests on a misreading. I said moral truths are a priori entailed by the natural truths (i.e. physical + phenomenal), not the physical alone.]

    I'm not sure what you mean by suggesting that idealized capacities "won't help". I'm basically working from the assumption that empirical data is required to discern which possible world is actual, but that's all. Everything all is a priori knowable, at least in principle. (See my post 'Limited Omniscience' for more background.)

    But I agree that there obviously couldn't be "moral zombies". In fact, the obviousness of this is precisely what indicates a disanalogy between moral and phenomenal properties here. It's just clearly incoherent to have a natural duplicate of our world that somehow differed in its moral properties. Phenomenal zombies, on the other hand, do not seem to be incoherent in this way.

    "Here's a story that a physicalist can tell to explain why there is no 'apriori passage' from the physical description of the world to the description of qualia..."

    Of course, every non-reductionist will agree there's some story to be told about why zombies are conceivable. That's no help at all to the physicalist unless they can further show why this conceivability claim is an unreliable guide to possibility. Cf. Chalmers: "After all, one can also give a psychological explanation of why we can conceive of red squares, in terms of the distinct cognitive processes and epistemic constraints involved in conceiving of color and shape. One can give a psychological explanation of why we can conceive of five-horned animals, or of silicon-based life. But no-one would infer that there are strong necessities denying the metaphysical possibility of red squares or five-horned animals or silicon-based life."

  18. hmm... just for fun Ill have a go at making a moral zombie.

    here is a couple of hypotheticals

    1) Lets cheat a little and throw qualia into the mix - say a qualia bridging law gets changed so that harm becomes benefit and benefit becomes harm. Now, lets say, any person taking any act that is bad is good and anyone taking any action that is good is bad and that this difference is in terms of a view of the rest of the world - indiscernible.
    I suppose the disanalogy here is that a morally reversed person might be able to tell something is different if they were to compare (although that is hypothetical because they can't compare) where as a normal zombie cant 'tell' anything at all

    2) Lets say there is a quality called 'morality' that exists in a parallel 'world'. this is collected or not collected based on one's morality. now I want to infuse it with some value you might relate to it - so let's say it is in some sense sentient (or to be simpler lets say it has a trait that fulfills the desires of the people in the real world - a monument to their morality maybe?)- unable to effect the world, and not existing in some senses, but of value in itself.

    Now let's say we switch this morality around so that now doing the opposite builds this unknowable monument/spirit creature.

  19. Richard,

    I've read the Jackson and Chalmers. I don't find it convincing.

    We've already agreed (I hope) that there's no guarantee that morality could be 'read off' from non-normative facts. That seems to depend on whether it is possible for even an idealized intelligence to know conditionals that state non-normative sufficient conditions for normative truths. I see no reason to think that the thought that this cannot be done is due to our ignorance or due to the fact that we are less than ideal cognizers.

    As for the phenomenal and the physical, I'm not really sure what your response is. If what we need to know to grasp concepts of phenomenal properties is in part indexical or demonstrative knowledge and there is no apriori connection between descriptive (non-indexical and non-demonstrative) knowledge and indexical/demonstrative knowledge, the inability to deduce, infer, or whatever the phenomenal from the rest is just no more reason to assert that the phenomenal properties can possibly come apart from the physical. I can't tell if you disagree about the relationship between descriptive knowledge and indexical/demonstrative knowledge or if you think we can have knowledge of the phenomenal and grasp of the relevant concepts without needing such indexical/demonstrative knowledge. So far as I can tell, this _is_ the story the physicalist will tell about the reliability of these modal intuitions. Non-indexical descriptive knowledge does not give us a reliable guide to determining what indexical or demonstrative knowledge there is or could be. The inability to describe the world's phenomenal profile given a complete description of the physical profile is no more surprising than, say, the inability to connect the 'here' and 'now' facts with facts stated in non-indexical terms.


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