Turning the Tables on Dualism

Richard Brown

Two of the more popular arguments against physicalism are The Knowledge argument and The Zombie argument. They both aim to show that physicalism cannot capture qualitative properties –the What It’s Likeness of experience– Though in slightly different ways. In this presentation I will argue that both fail to present any real problem for physicalism. Each of these arguments begs the question against physicalism. In the sense that the argument will only seem compelling if one is already assuming that qualitative properties are non-physical. To show this I will present the Reverse-Zombie and Reverse-Knowledge arguments.

I. The Reverse-Zombie Argument

As developed by David Chalmers the zombie argument against physicalism in its simplest form goes as follows. Where ‘P’ here stands for the description of the world given by a completed microphysics and ‘Q’ is the complete qualitative facts about us.

1. P and ~Q is conceivable

2. If (P & ~ Q) is conceivable, then (P & ~ Q) is possible

3. If (P & ~Q) is possible then materialism is false

4. Therefore materialism is false

The basic idea then is that it is conceivable that we could have a world that was microphysically identical to the world that we live in and which lacked qualitative consciousness. Since this is conceivable in the right way it follows that it is possible. And from this possibility it follows that materialism is false. This is because the materialist is committed to the strong claim that the mind-brain identities are (metaphysically) necessary.

A lot of the debate about this argument has centered on premise (2) and whether or not conceivability entails possibility. The typical argument that conceivability doesn’t entail possibility is the standard Kripkean line about a posteriori necessities. So, it is suggested, I can conceive that water is not H2O but as Kripke argued, it is not metaphysically possible that water not be H2O. Chalmers argues that there is clearly a sense in which ‘water is not H2O’ is ideally conceivable and so metaphysically possible. It is conceivable in the sense that if Twin Earth had turned out to be actual it would have been the case that water was not H2O. If Twin Earth were actual, as opposed to counter-factual, then water would have been XYZ. Whether we call the watery-stuff in Twin Earth –that is, the stuff which would have been water if twin Earth were actual— ‘water’ or not is irrelevant. When we are imagining Twin Earth we really do have access to some possible situation and if that possible situation had been actual then it would have been true that water was not H2O.

Chalmers then argues that when we conceive of the zombie world we really have access to something which is metaphysically possible and since it is metaphysically possible that there be a zombie world materialism is false. Therefore physicalists who endorse a posteriori identities between qualitative states and brain states cannot avoid the zombie argument by invoking Kripke. The dualist is in some sense conceiving a real possibility when they imagine the zombie world (just like the person conceiving Twin Earth is conceiving something which is metaphysically possible). Whether we apply our word ‘consciousness’ to it is irrelevant. The realm of possibilities has not shrunk and ideal conceivability is still a good guide to what is metaphysically possible.

But are zombies really conceivable? There are those who deny that they are. These are what Chalmers calls a type-A physicalists. This is an elimitivistic position usually associated with Dennett or Churchland. These kinds of physicalists hold that when we have a completed microphysics we will be able to deduce the qualitative facts from the physical facts and we will see that the way that we describe the qualitative now is drastically misguided. The people who adopt the Kripkean strategy are what Chalmers calls type-B materialists. But there is a way to be a type-B materialist that denies that zombies are conceivable. Consider the classical Twin Earth thought experiment. An alternative way of describing what happens here is that it seems to us as though we are imagining a world where water is not H2O but we actually fail at that since it is impossible. It seems to us that we can imagine this situation but we cannot. What we actually succeed in imagining is something which looks like water but isn’t.

This is closer to the spirit of Kripke’s remarks. The whole point about Hesperus and Phosphorus is that once we know they are the same object we realize that we weren’t really imagining a case where the they were separate. We cannot imagine that one thing is really two things. Similarly we cannot really conceive that water is other than H2O, since that is to conceive of H2O as other than H2O which is absurd. What we can conceive of is a different substance which presents the same contingent appearance properties as H2O does. This is, I believe, the correct way to respond to the zombie argument. How can we tell whether or not we are really conceiving of zombies in the relevant sense or whether we are merely conceiving of creatures which very closely resemble us but which are not conscious? The case of water and H2O shows us that our seeming to be able to conceive of something does not guarantee that we can really conceive of the thing in question. It certainly seems to us as though we can conceive of water that isn’t H2O but we can’t. So too it seems to us as though we can conceive of zombies but we cannot.

The zombie argument begs the question against this kind of Kripkean response. If physicalism is true then it will --of course-- be the case that qualitative states are just physical states. That is simply because if physicalism is true then everything is physical and since it is undeniably true that consciousness exists it will be undeniably true that consciousness is physical (if physicalism is true). So if this turns out to be true of our world then we cannot really conceive of zombies in the way that the zombie argument requires. Therefore the zombie argument cannot be an argument against materialism of this type unless we have already shown that dualism is true. The problem is that the proponents of the zombie argument, and some of those against it, just assert that zombies are conceivable. But we need some evidence that this is actually the case. You’re telling me that you seem to be able to do it is not evidence that you are really doing it. I, for instance, find that I can’t do it.

To illustrate this I will present the Reverse-Zombie argument against dualism. There are two kinds of reverse-zombies that I call ‘zoombies’ and ‘shombies’. Each of these corresponds to a way of being ‘the opposite’ of the traditional philosophical zombie. A zoombie is a creature which is identical to me in every non-physical respect but which lacks any (non-physical) conscious experience. I don’t merely mean that the zoombie exists in a world where there are different bridge laws and the link between the physical and the mental is severed. I am conceiving of the zoombie world as having any appropriate laws. If there were non-physical properties that resulted from the microphysics of the zoombie world they would be linked in the right way. Thus a zoombie is the dualist equivalent of a zombie: a creature just like me in the right respect that lacks (non-physical) qualitative consciousness. Zoombies are conceivable and so dualism is false.

One may object to the zoombie argument in the following way.

Look, the question here is one of whether or not the qualitative facts can be deduced from the complete micro-physical facts or not (like, say, table facts can). Let’s say that answering ‘yes’ means that the mental is reduced to the physical. The original zombie argument then shows that the mental cannot be reduced to the physical. What the zoombie argument shows is that neither can qualia be reduced to any non-physical facts that are not themselves qualitative; but no dualist has ever thought that! Therefore the zoombie argument doesn’t truly parody the original zombie argument and so doesn’t show that there is anything wrong with the original argument.[1]

But there are actually two separate questions here. One question is whether our mental concept words, like ‘pain’ or ‘belief’, can be linked to the brain and its states. This is a question of inter-theoretic reduction. This is a separate question from the ontological question of whether there is anything more to the world than the physical. There are some physicalists who think that mental concepts cannot be reduced to physical concepts even though ontologically speaking all there is that exists is the physical state.[2] One famous version of this kind of theory is Davidson’s anomalous monism. Davidson held that the mind and the brain were identical but that we could not reduce one set of concepts to the other in the sense that we could not deduce mental facts from physical facts.[3] If this is all that one takes the original zombie argument to be showing then one has admitted that you haven’t shown that physicalism is false. What you have shown is that a certain kind of physicalism is counter-intuitive. Namely, the kind which holds that you can deduce the mental facts from the physical facts, but one may admit that while still holding that all there is in the world are physical things.

One may try one more time.

Look, the issue is whether we need to add anything to a completed microphysics or not. The dualists says ‘yes’ we need to add non-physical properties. The classical zombie argument is what shows this. The dualist says the same in the zoombie case. In such a world we still need to add non-physical qualitative properties explicitly. So the issue of reduction is beside the point; the zoombie argument still doesn’t parody the zombie argument.

But this just begs the question again. I say that I can conceive of a creature just like me in all relevant respects (the non-physical ones) which lacks non-physical qualitative properties and doesn’t need any additional non-physical qualitative properties added. It is a complete non-physical duplicate of me. This is the zoombie and its conceivability shows that qualitative consciousness is not a non-physical property or that the original zombie argument makes the same mistake as the zoombie argument. What we need is some reason to think that we are really conceiving of a zombie world as opposed to a world that is very similar to ours but not micro-physically identical.

But still this issue of reduction can get in the way. It is better to avoid it altogether. To do so consider the other kind of reverse-zombie: the shombie.[4] A shombie is a creature that is micro-physically identical to me, has conscious experience, and is completely physical.[5] Shombie pain is just as painful as my pain is and shombie orgasms are every bit as pleasurable as mine are. My shombie twin and I have all of the same experiences. The only difference, if it is a difference, is that shombie pain is completely physical. That doesn’t make it any different from the inside. What it is like for me to have a pain and what it is like for my shombie twin to have a pain are identical in all respects. We have stipulated that shombie pain is just like my pain in every respect (qualitatively) and that my shombie twin is a complete micro-physical duplicate of me and that this is all there is to the shombie. The shombie is NOT a zombie. A zombie lacks qualitative consciousness; a shombie doesn’t, though both are micro-physical duplicates of me. So am I my own shombie twin?[6] I do not want to beg that question here so I will take no stand on whether I am a shombie or not. The point is that shombies are conceivable. The qualitative does, therefore, logically supervene on the physical and dualism is false. Zombies are metaphysically impossible.

We can now formulate the reverse-zombie argument with shombies. Let ‘P’ be a complete micro-physical description of the world and ‘MQ’ be a complete description of the qualitative facts that either follows from P, ‘(Q(d))’ for ‘deductive’, or doesn’t, ‘(Q(a))’ ‘for anomalous’, but is still just a different way of describing P (i.e. both ways of construing Q are purely in keeping with physicalism. To keep things simple I will just say that,

MQ= (Q(d) or (Q(a)).

Given this we can formulate an exactly analogous argument against dualism as follows.

1’. P and MQ is conceivable

2’. If (P & MQ) is conceivable, then (P & MQ) is possible

3’. If (P & MQ) is possible then dualism is false

4’. Therefore dualism is false

Premise (1’) says that the Shombie world is conceivable, premise (2’) concludes from that fact that the shombie world is possible and from that we conclude that dualism is false. This argument is in every way parallel to the original zombie argument.

In closing let us briefly consider how a dualist might respond to this argument. Well, Chalmers is committed to accepting premise (2’). Conceivability entails possibility for him so if shombies are conceivable then they are possible. How about premise (3’)? Might a dualist allow that shombies are possible but dualism was still true? Such a position would hold that it might be true at some possible world that there are non-physical properties but that there were also possible worlds where consciousness was a physical property. But if this is the case then we loose all of our motivation for being dualists in the first place. Why should we posit mysterious non-physical properties if we could have a completely physical account of consciousness? And if such a physical account of consciousness is possible shouldn’t we primarily be focused on seeing if it is true of the world we live in? So, it seems to me that Chalmers should accept premise (3’). Besides this to reject premise (3’) would require an argument that identity was not metaphysically necessary which is a completely different story.

This brings us to the first premise. Is (1’) really conceivable? Can we really imagine a world where consciousness is a completely non-mysterious physical property? It seems to me that I can. Since it seems like I can do this I cannot really imagine the traditional zombie scenario anymore. It no longer seems to me that I can coherently conceive of a creature that is physically identical to me but which lacks qualitative states. It seems to me that I must be overlooking some small subtle difference in my imagined physical world. If you find yourself thinking “hey, but the shombie argument just assumes that consciousness is physical!” or “yeah, but the zoombie argument just assumes that a non-physical duplicate of me can lack (non-physical) qualitative consciousness even with the same laws of physics!” then you are starting to see my point. The way you think the world is shapes what seems conceivable to you. It cannot be the case that intuitions about zombies are evidence for or against any theory of consciousness. All it can do is to let us know where our sympathies lie, or to draw out some implicit commitment that we did not know that we had. But what it cannot do is show that physicalism is false.

Dualism is therefore false or the original zombie argument is question begging. It will only have any pull on you at all if you think that zombies are conceivable. But to concede that is already to concede that physicalism is false. Type-B materialists should then adopt the present strategy. The question is begged right when Chalmers says that whether we call the zombie world one which lacks consciousness or not we clearly have conceived something and that is enough to show that physicalism is false. He has only succeeded in imagining a zombie world if our world is not a shombie world. Chalmers must hold that the shombie world is not really conceivable. I hold that this is an empirical question that we do not yet know the answer to. But even so there is a lot of evidence which suggest that the world we live in is in fact the shombie world. That is, there is a lot of evidence that we are shombies. But strictly speaking we really are not in a position to say which world we are imagining when we try to imagine the zombie world. We may be succeeding in imagining a world that is truly physically identical to ours, in which case we are really imagining the shombie world, or we do not in which case we imagine a world that looks as though it is physically identical to ours but is not.

Either way the zombie argument does not threaten physicalism unless one has already assumed that qualitative properties are not physical.

II. The Reverse-Knowledge Argument

The knowledge argument against physicalism is well know, and much discussed. We are asked to consider Mary, a super-scientist who is confined to a black and white room. From within this room she learns all of the physical facts about color perception but she is never allowed to see any colors. She is then let out of the room and sees a ripe tomato. We are expected to have the intuition that Mary learns something new when she sees the tomato. In particular she learns what it is like for her to see red. But since she was supposed to know all of the physical facts when she was in her room this must mean that there is a fact about color perception that isn’t physical.

Chalmers puts the knowledge argument as follows

(1) 'P ⊃ Q' is a posteriori. (The knowledge intuition)

(2) If 'P ⊃ Q' is a posteriori, 'P ⊃ Q' is contingent.

(3) If 'P ⊃ Q' is contingent, physicalism is false.

—

(4) Physicalism is false.

There have been numerous responses to this argument from physicalists ranging from the claim that what she gets is a new ability rather than new knowledge, or that she learns a new way of identifying an old fact. But I do not want to dwell on these.

My goal in this paper is to show that the knowledge argument simply begs the question against physicalism. It will only seem convincing to you if you antecedently think that physicalism is false. I will do this by presenting the Reverse-Knowledge argument against dualism. The problem here is the same as before If qualitative facts are physical facts, As physicalism claims, Then Mary knows about these qualitative facts inside her room. To assume otherwise is to assume that the qualitative facts are not physical, Which is to beg the question at hand.

To show this we can, as before, construct two kinds of reverse-knowledge arguments against dualism. One of them, the one that parallels the zoombie argument, was first given by Paul Chruchland. The other, the one that parallels the shombie argument, will be introduced by me afterwards. Paul Churchland, in his paper “Knowing Qualia: A Reply to Jackson,” briefly tried to formulate a parity of reasoning objection to the knowledge argument. He first formalizes the knowledge argument as follows,

(1) (x) (Hx & Px) à Kmx

(2) (Ex) (Hx & ~Kmx) (viz., “what it is like to see red”)

Therefore

(3) (Ex) (Hx & ~Px)

Here m=Mary; Kyx= y knows about x; Hx=x is about persons; Px= x is about something physical in character (p 571)

Thus, premise (1) reads ‘for all things knowable x, if x is about persons and x is about something physical then Mary knows x’, premise (2) says ‘there exists an x such that x is about persons and Mary does not know about x,’ and the conclusion ‘is there exists an x such that x is about persons and x is not about something physical in character’. He then goes on to formulate the parity of reasoning argument as follows.

If valid Jackson’s argument, or one formally parallel, would also serve to refute the possibility of substance dualism….the basic point is that the canonical presentation of the knowledge argument, as outline above, would be just as valid if the predicate terms “P” was everywhere replaced by “E.” and the resulting premise would be just as plausibly true if

(1) “E” stood for “is about something ectoplasmic in nature” (where ectoplasm is an arbitrary name for the dualist’s non-physical substance, and

(2) the story is altered so that Mary becomes an exhaustive expert on a completed ectoplasmic science of human nature (p 574)

The basic idea behind Churchland’s knowledge argument against dualism is that if Mary, in her black and white room, were taught all of the principles of ectoplasmic science, being the complete non-physical theory of qualitative properties, she still would learn something new when she was let out of her room. She would, according to Churchland, learn the very same fact; viz, what it is like to see red. To put it in the way that Chalmers does. Churchland’s argument shows that ‘NP ⊃ Q’ is a posteriori and so contingent, and from this we can conclude that dualism is false. Therefore the knowledge argument, if it works against physicalism, also works against substance dualism.

Also as before, a dualist is likely to object that what Churchland’s argument shows is only that Qualitative properties cannot be reduced to any kind of property that is not itself a qualitative property. This objection has been worked out in more detail by Yujin Nagasawa in his 2002 paper, “The Knowledge Argument Against Dualism” (Theoria LXVIII, pp. 205-223). Nagasawa there argues that this argument is successful against any kind of reductive dualism, whether property or substance. A reductive dualism holds that qualitative facts can be reduced to, or deduced from, a set of non-physical facts, like the protophenomenal facts that Chalmers postulated in his panprotopsychism. The argument, however, is not successful against a non-reductive version of dualism. The non-reductive dualist claims that qualitative properties cannot be reduced to any other kind of property whether protophenomenal or not. The knowledge argument against dualism, accordning to Nagasawa, shows that non-reductive dualism is the only viable option for someone who wants to use the knowledge argument against physicalism.

But also as before, we need to be careful with the issue of reduction Since it is arguably besides the ontological point And is merely an explanatory/epistemic point. And again, as before, we can simply insist that Mark (Nagasawa’s name for the Mary-like non-physical scientist) knows all of the non-physical facts he should be able to deduce the qualitative facts. Now let us move on to the second kind of reverse-knowledge argument. Even so, does the knowledge argument show that physicalism is in trouble? No. To show this let us introduce the Reverse-Knowledge argument. Consider Maria. Unlike Mary, Maria is not a super-scientist. She is a super-phenomenologist. Maria knows all of the qualitative facts about colors. She knows what it is like for her to see red in such a way that she can discriminate between very fine shades, and is able to make very fine comparisons as to complementary colors, she is able to discriminate very accurately as between hue, shade, intensity, etc. Maria achieves a mastery of introspective phenomenology that would make Hegel jealous. But like Mary, Maria was raised in a special room. This is not a black and white room; it is a science-free room. So, though Maria knows all of the qualitative facts about red she knows none of the physical facts about color perception. She is kept in total ignorance about physical color theory. She has a masterful grasp of the qualitative facts but no grasp of the physical facts. In this sense Maria has the exact opposite kind of knowledge that Mary had. Now let us suppose that Maria is let out of her room and taught color science. In particular let us suppose that Maria gets out of her room after we have a completed physical theory. She then learns all of the (complete) physical theory about the brain, the way it works, wavelengths, light receptors at the eyes, the transduction of signals, etc, etc. Won’t she have learned something new about color? The answer is yes; she will learn that her color experience is a physical event in her brain. Maria will learn something that she would express by saying ‘oh, so that what my color experience is!’ In short she will learn that qualitative facts simply are physical facts.

We can formulate the Reverse-Knowledge argument as follows

(1) 'P ⊃ Q' is a priori (the reverse-knowledge intuition)

(2) If 'P ⊃ Q' is a priori, 'P ⊃ Q' is necessary.

(3) If 'P ⊃ Q' is necessary, dualism is false.

—

(4) Dualism is false.

Now the dualist is likely to object that the reverse-knowledge argument just assumes that qualitative facts are deducible from physical facts. Or that they do not have the intuition that Maria will learn anything that is threatening to dualism when she is let out of her room And this is exactly how the physicalist feels about the classical knowledge argument. As before, what theory you accept shapes your intuition

So, the Reverse-Knowledge argument shows that qualitative facts are deducible from a completed physics. That is, Maria having only phenomenal concepts and then introduced to the completed physical theory will be able to tell a priori when phenomenal concepts apply in other cases. One may also object to the notion that Maria’s deduction is a priori. After all, she is able to do so only because she has had the relevant phenomenal experience. But this is no objection, for as Chalmers and Jackson have argued Empirical knowledge that plays a causal role (e.g. that needed for concept acquisition) is no bar to a priori knowledge.

Chalmers briefly mentions a strategy like this in his ‘Phenomenal Concepts and the Knowledge Argument’ Calling it “one of the more powerful replies available to the materialist”. He lists several prima facie objections to this strategy. His first objection is to fall back on the zombie intuition. But as we have seen this doesn’t help. Secondly he wonders whether someone like Maria will be able to deduce that other creatures, like bats and Martians, have phenomenal experience. But there is no non-question begging reason to think that Maria will not be able to do this. The same is true for his third response along the lines that Mary might have a concept like phenomenally indistinguishable and yet be unable to tell if two people were having the same qualitative experience.

Finally he objects that someone like Maria will have to crucially rely on introspection in order to complete the deduction. And since introspection yields a posteriori knowledge the deduction will not be a priori. First it is not clear why she would need to rely on introspection in this way. The reverse-knowledge intuition suggests that she wouldn’t. But even if she did have to rely on introspection to complete the deduction It is not immediately clear that this is a bar to the deduction being a priori. This is because, as before, introspection may be playing only a causal role. Or it may be playing only a mediating role. And the reverse-knowledge intuition strongly suggests that it is one of these

III. Conclusion

So as we have seen the use of a priori methods to determine whether physicalism is false simply fail to do anything except to tell us where our sympathies lie. What we need to know is whether physicalism is true or false. Only then will a priori methods yield anything useful; But of course by then we won’t need them!

[1] I am grateful to Richard Chappell for pressing this objection, if not for the manner in which he did it.

[2] Jose Luis Bermudez’s recent book Philosophy of Psychology: a Contemporary Introduction provides a nice discussion of this point.

[3] Because, Davidson famously argued, one set of concepts was essentially normative and the other essentially descriptive.

[4] I have just discovered that shombies were anticipated by Keith Franklish in “The Anti-Zombie Argument” The Philosophical Quarterly Vol. 57,No. 229. What he calls anti-zombies are what I call shombies. Also Gualtierro Piccinni, in an unpublished manuscript, advances a similar argument.

[5] Shombies are not zimboes. According to Dennett a zimbo is a zombie that is able to monitor its internal states. For Dennett a zombie is a creature that is behaviorally indistinguishable from a a creature that has conscious states but it itself doesn’t. A zimbo is a zombie that has a certain functional organization. According to Dennett we are zimboes. People object to this because they feel as though Dennett is leaving something out. This is where shombies come in. Whatever is thought to be left out on Dennet’s account is included in the shombie world. Shombies are not zombies of any kid with or without anything added or subtracted. Shombies are creatures that are completely physical and have qualitative consciousness of the very same kind as I do. This seems very different from a zimbo. A zimbo is the human being as the elimativist imagines them. So a zimbo is a type of shombie (or could be if I am getting this right). But a shombie need not be an elimativist model. There is still the issue of reduction or not and one kind of shombie is the anomalous monist kind that has distinct mental and physical concepts that cannot be reduced to each other.