Brown (whose name is quite difficult to misspell, though I tried) certainly outdoes me by a country mile in posting to his blog, an admirable quality that is underrated in the philosophical community. Blogging is I think more in the spirit of philosophy in the Socratic tradition than the institutional control exercised by professional journals and presses. (Anybody who has received the typically biased and ignorant comments on a rejected article from journal reviewers will probably agree wholheartedly with the title of Brown's blog, Philosophy Sucks!) In the future, I will try to do better than the, hmmmm,,, 10 month gap between this and my last post. (Which is a bit less than the gap in my arts blog. Yikes.) In any case, kudos to Dr. Brown for his blogging efforts - not to mention his Cel-ray tonic. (Jeez, names really do get confusing, don't they? Maybe someone should do some philosophical work on this topic.)
What follows is the complete text of my comments on Brown's paper, delivered yesterday (10/18/08) at the conference of the Long Island Philosophical Society. The papers and replies will eventually be published in Calipso, the LIPS online journal, at which point I may remove it from here and put in a link. In the next post I will reply to Brown's replies to my reply to his paper. (And perhaps to some of the replies to his replies to my reply to his reply to Chalmers - which can be found on his blog.)
Most opponents of the materialist view rely heavily on one or more intuition pumps that allegedly bring out a gap between the knowledge and understanding of physical facts and an explanation of consciousness. The "zombie" argument is one such effort. Imagine a creature that has all the physical properties that we would expect a human being to have, and behaves in the ordinary way that human beings would in similar situations, but lacks any hint of consciousness. If this is conceivable (so the argument goes) then physical facts cannot be the logical, or conceptual, foundation of consciousness.
In "The Reverse-Zombie Argument Against Dualism" Richard Brown suggests that the zombie thought experiment provides no compelling evidence that physicalism is wrong. There appear to be at least three tracks to his argument, which I will try to bring out.
The first idea is the contention that zombies, as described by David Chalmers and others, may not actually be conceivable at all. It is easy to miss the logic of Brown's argument here, because at the end he leads us somewhat astray, in my opinion, with suggestions that point in a different direction. One is that proponents of zombieism ought to offer some "evidence" for the conceivability of zombies. A second, related one occurs when Brown says that he himself cannot conceive of a zombie; and again, when he demands "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 microphysically identical". These points all seem a bit odd, to say the least. Conceptual arguments involve the logic of concepts; any "evidence" for them would surely not be of the empirical sort, and plenty of support has been offered on the conceptual side. The arguments do not depend on the strength of any one person's imagination, but on whether anyone can find a logical contradiction in their use of concepts. And though gross imaginative errors may be to some degree corrigible (I might say I'm imagining a duck but in fact be imagining a chicken), it makes no sense to say that someone who claims to be imagining a microphysical duplicate of me might "really" be imagining something that differs in some small way. (What does "really" really mean here?) But let me try to respond with a defense of the zombie imaginer before we move on to Brown's main argument. My "evidence" will consist in conceptual support for the point that conceiving of a zombie requires nothing more than adding and subtracting properties, something any normal person can do. So first, I can imagine someone physically identical to myself who is in the same room but is not aware of the slightly bluish tint of the late afternoon light, or the background humming of the air conditioning, while I am aware of all that. For I can imagine myself not having been aware of any them, and yet being physically identical to my actual self; just as when I see the duck and then see the rabbit in the same drawing, I have no reason to believe that a microphysical change took place, and even less reason to think that a determinate, repeatable microphysical change took place. Similar arguments could be brought for memory, imagination, and other components of consciousness. Therefore I can imagine a being that is physically identical to myself but lacks consciousness. Second, we can arrive at the concept of a zombie by expanding on concepts like blindsight or sleepwalking. These documented empirical states involve acting and behaving in certain situations like a normal human being but completely lacking awareness of one's behavior or surroundings. A being who is always in such states would be a zombie.
This should suffice for evidence of the conceivability of zombies. It is always possible to submerge one's conceptual abilities by becoming enmeshed in a theory. If one believes that all properties are directly reducible to underlying physical characteristics, it becomes difficult to conceive of anything that is not so reducible. In this way, entities that lacked the Aristotelian notion of substance were inconceivable prior to 18th century empiricism. If someone finds it impossible in theory to separate physical structure from any higher-order property whatsoever, then they might react to the notion of a zombie as "inconceivable" in the sense of "beyond the capabilities of imagination". But imagination tied down by theory is not the relevant power for assessing the viability of zombie conceptions.
The more important aspect of Brown's position does not rely on imaginative prowess. His point is that we ought to grant the physicalist at least the possibility that consciousness is nothing more than a high-level effect of the biophysics of the brain. If we do that, then we grant the possibility that consciousness is a natural kind term for some complex configuration of physical parts and processes. On a Kripkean theory of reference, a natural kind terms refer to a natural kind by means of some property that constitutes its identity. "Water" refers to all and only substances that are actually H2O . Once we know that that is the case, we realize that it is necessarily the case, and that the statement "it's water, alright, but it's not H2O" contains a conceptual confusion. "Consciousness" may similarly refer to whatever the underlying physical basis of consciousness turns out to be. We may not know that identity now, but when we do we will realize that zombies - physical duplicates of ourselves but without consciousness - never really were conceivable in the first place. According to Brown, if we insist that zombies are conceivable, we simply beg the question against this argument.
The question I have about this argument is, who is really begging the question? The logic of Brown's argument is that dualists cannot force the issue against materialism by stating a priori that zombies are conceivable, since it may turn out a posteriori that the connection between brains and consciousness is a necessary one. By the same token, one could have argued in the 19th century that a thought experiment designed to show that light is not a substance but a wave begs the question against the a posteriori necessary truth that light is the propagation of photons. The form of the objection seems wrong, because we cannot say in advance that discovering a physical basis for consciousness will make zombies inconceivable. Consciousness could be more like the terms "evolution" or "radiation" than like "water" or "heat". The former are natural kind terms, but neither has an essence that can be expressed in an identity statement. I fail to see any reason why thought experiments should be constrained by the combined demands of a controversial theory of reference for natural kind terms and the empirical possibility that reductionist programs will be successful. To focus on the latter for a moment, after two centuries of psychophysical experiments we still have no reason to believe that consciousness can be reduced to biophysical properties. As Chalmers carefully explains, none of the popular reduction programs have brought us any closer to bridging consciousness with the physical world. Take our current, fairly sophisticated understanding of color vision; how does it even come close to explaining why red objects appear red and not green? No physicalist story even gets off the ground on this kind of question. The same holds for consciousness in general: in spite of having mapped and experimented with dozens of brain areas, having sophisticated biochemical analyses of brain activity, and even manipulating some basic motor functions with digitally simulated brain signals, we don't have so much as a program for explaining conscious experience, or even the function of consciousness, as an outcome of any of this biophysical research. I think it is quite a leap to say that dualists beg the question by ignoring the possibility that the holy grail of materialism will someday be found.
A second point Brown makes is that conceivability does not entail possibility. The zombie argument depends on the following kind of reasoning. Suppose it were the case that the mental logically supervenes on the physical. Then it would be a metaphysical fact about the universe that whenever you have mind, you have a material foundation. But logical supervenience is an identity relation, so whenever you have the appropriate physical foundation, you must also have mind. Then the concept of a physical foundation without mind ought to be a contradiction of some sort, like the concept of space without distance or consciousness without thought. But the zombie argument is designed to show that this is not the case. Let it be granted, then, that the zombie argument demonstrates the conceivability of zombies. We can conceive of life without death, too, and many other things that may not in fact be physically possible. In the end, then, the zombie argument demonstrates nothing of interest to anyone except philosophers, and the search for a materialist explanation of consciousness can proceed.
I think Brown can reasonably object that while zombies may be metaphysically possible, this kind of conclusion may not establish anything very useful in the debate on consciousness. It establishes that one can be a dualist without violating any rules of metaphysics. But that is an achievement of very limited scope. For no modern dualist wants to be a dualist about substances; we all begin from essentially the same scientific conception of the universe. We believe there is nothing added to biological substrate of consciousness in the sense in which some god or unknown force disperses some ethereal quasi-matter which, combining with our brains, creates consciousness. On the contrary, we all agree that there is no substrate except matter, and the question is how, from matter, you get the qualitative view that is awkwardly expressed by the phrase "what it is like to be" a human, raptor, etc.
But the logical possibility may, on the other hand, be sufficient for what the modern dualist really wants to establish. The point is to argue against the program in which, by assembling enough information about the mechanics of brain processes, and relating that through tomography and other techniques to certain mental phenomena, we will eventually be able to reduce consciousness to brain processes. Someone who believes that there is no matter or force except the ones described by modern physics does not have to purchase that program. They can hold that it is the wrong level of explanation for mental processes. They can believe that mental predicates collect the phenomena that physically supervene on biological entities at too high a level to ever be reduced. They can hold that enormous differences in the underlying structures can accommodate the same mental phenomena, described by the same psychological terms and following the same psychological laws. On this view, the correct kinds of programs for understanding consciousness could be those of William James, Husserl, and Wittgenstein, and not those of Smart, Churchland and Dennett.
I turn finally to the "zoombie" and "shombie" examples Brown offers. As he describes them, a "zoombie" is "a creature which is identical to me in every non-physical respect but which lacks any (non-physical) conscious experience". The idea seems to be that just as my zombie twin is identical to me in every physical respect but lacks qualitative consciousness, my "zoombie" twin is identical to me in every non-physical respect but lacks qualitative consciousness. If the former suggests that consciousness is not a physical property, the latter suggests that it is not a non-physical property.
A "shombie" is "a creature that is microphysically identical to me, has conscious experience, and is completely physical". If shombies are conceivable, then dualists are at best guilty of rejecting the principle of inference to the simplest explanation that accounts for all the known facts. For why should we go about imagining exotic explanations for consciousness when it is perfectly conceivable that physics can explain it all?
According to Brown, these two thought experiments constitute something like a parity of reasoning argument against the zombie argument, and therefore against this particular kind of objection to physicalism. The zombie argument says that it is conceptually possible to disassociate the human body and behavior from conscious experience, and that therefore it is not incumbent on those who hold a naturalistic view of the universe to believe that consciousness is identical to some set of physical processes in the brain. The zoombie argument says that it is conceptually possible to dissociate all non-physical human qualities from conscious experience, and the shombie argument says that it is possible to associate all conscious experience with physical systems like the one in which our minds are embodied. Both thought experiments attempt to show that the zombie argument does not produce any conclusion against physicalism that cannot be produced against dualism by parity of reasoning. So either the zombie argument fails against physicalism, or the zoombie and shombie arguments are equally conclusive against dualism.
I agree that the zombie argument is not a conclusive argument against physicalism; but what it purports to show, at least, is that we are not forced to choose between a materialist theory of consciousness and a spooky view of the universe. If we can conceptually dissociate consciousness from the particular forms in which it is embodied, we can imagine a universe in which it is realized in other ways; and if we can do that, we can give up the idea that there must be a reductive, biophysical explanation of consciousness. I fail to see what parallel objective is achieved by positing "zoombies", since no one is claiming that there is a necessary link between our "non-physical" qualities and consciousness. Brown gives no indication of what he means by such qualities, but it cannot be things like mental or emotional states, because to assume those are non-physical would surely beg the question about consciousness. Perhaps we are talking about relational properties, value-bearing predicates, multiplicity and the like. But we can agree that there is no conceptual link between those properties and consciousness without inventing any new creatures. Since the basis for the sort of property dualism that people like Chalmers propose is not parallel to the metaphysical claims of the materialists, I don't see that this argument has a target.
"Shombies" allegedly show that we can imagine a creature that is "completely physical" having conscious experience. Brown again avoids unpacking the notion of "completely physical", but one thing we cannot say here is that no predicates other than physical ones apply to such creatures, since there is no such thing as an entity to which relational predicates, for instance, do not apply. It appears, then, that the idea of a "shombie" must be roughly that of a machine that has conscious experience. This sort of thought experiment has been tried many times, and I'm not sure what is added by calling it a "shombie". But it does bring out the foolishness of depending on either zombies or robots to prove anything about consciousness. One side says "I can imagine a conscious machine, so consciousness must be reducible to physics"; the other side says "I can imagine a non-conscious twin, so consciousness must not be reducible to physics". Personally I can imagine a talking cloud; am I entitled to the conclusion that we are in cloud-cuckoo land?
Thought experiments, as Wittgenstein pointed out, are not analogous to real experiments, only with thought-materials. They are devices to make us think about what we would say in a very unusual situation; and this can give us insights into how our concepts are organized and how our language works. If we conceive of the mind-body problem along these lines, thought experiments might help us solve it. The zombie idea is therefore somewhat effective in refuting the idea of a conceptual link between matter and mental phenomena; not a small accomplishment in light of the very strong pull that our basic scientific convictions have on our thinking as a whole. But they cannot answer any naturalistic questions, such as whether the notion of conscious experience will eventually fall out of a detailed description of the operation of brain cells. This is a matter for scientific research, and the only reasonable answer we can give right now is that it is far from doing so at this stage of the game. The materialists want to press on because they are convinced there is no other way. The zombie argument suggests that they are wrong about that, but it does not prove that success is conceptually impossible. Brown's thought experiments are helpful is suggesting this corrective to anyone who uses a zombie to scare the materialists away from their research projects.
LIPS Conference, St. John's University, Queens, New York, October 18, 2008