Bennett on Non-Reductive Physicalism

I just re-read Karen Bennett’s paper Exclusion, Again. In this paper she argues that causal exclusion arguments provide a nice overall argument for physicalism but do not cut against non-reductive physicalism as usually thought.

Here is how she defines non-reductive physicalism.

Let us begin with the ‘physicalism’ part. It is notoriously hard to define it adequately, but I can at least offer up the same slogans as everyone else. Physicalists not only endorse the completeness of physics, but also think that all the facts are physical facts—that there is nothing ‘over and above’ the physical. Physicalists believe that everything globally supervenes6 on the physical as a matter of metaphysical necessity (see Lewis 1983, Chalmers 1996, and Jackson 1998; see Hawthorne 2002 for interesting challenges to their definitions). That is, physicalists deny that it is merely nomologically impossible for there to be a world physically just like this one but mentally different. There are no special psychophysical laws that link or tether the mental to the physical, and that can be broken.

She is officially neutral on the issue of the a priori entailment of the mental by the physical but she clearly rejects the metaphysical possibility of zombie worlds. So, what, then, is non-reductive about her view?

Nonreductive physicalists do not think—or, at any rate, should not think—that mental events and properties really are not identical to any physical ones. All we think is that they are not identical to any standard physical ones. We have no reason to deny that they are identical to physical events and properties reachable by extension or analogy with standard ones. Let me try to put this marginally more carefully, by loosely distinguishing between a narrow and a broad sense of ‘physical’.

What she means by this seems to be the following. On the one hand we have ‘narrow’ physical properties, events, or objects, which means that they figure in the laws of a ‘clearly physical’ science. So she will count neurons as narrow physical objects because they figure in neuroscience. She will also count electrons and elements, etc. On the other hand there are what she calls ‘broad’ physical properties, events, or objects, which means that we can construct the thing in question out of the narrow properties in some ‘clearly articulated’ way. So,

Broadly physical properties are those constructed from narrowly physical ones by means of property-forming operations like disjunction, conjunction, and quantification (though presumably not negation!). Broadly physical events are those constructed from narrowly physical ones by means of various forms of spatio-temporal, mereological, and modal gerrymandering. And so on. This list is merely supposed to give the general idea, and presumably needs to be expanded and tweaked in various ways.

Given these two notions she formulates non-reductive physicalism as the view that mental states are broadly physical but not narrowly physical. She thus finds it to be a mistake on the part of the non-reductive physicalist to claim that mental properties are not physical at all. They are physical, just not in the narrow sense. There is no neurological state that she will want to say is identical to the mental state, though the mental state is constructed out of those narrow states. So on her view the functional characterization of mental states picks out some narrow physical property as its realizer. When thought of in this way, she continues, non-reductive physicalism has no worries with casual exclusion but dualists do.

The crux of the argument is that if one really wants to maintain a role for the mental in causation you must endorse some kind of over-determination and if that is the case then the following two counterfactuals must be non-vacuously true (which I take to mean; true because the antecedent is true):

(O1) if m had happened without p, e would still have happened and
(O2) if p had happened without m, e would still have happened.

These are supposed to capture our ordinary understanding of overdetermination. Had there been only one of the causes the effect would have been produced by the other cause, and vice versa. The real action is over (O2). She argues that only a physicalist can interpret it in the required way. That is, only the physicalist can say that it is either vacuous or false. A physicalist will think it is vacuously true just in case she thinks that it is impossible that p happen without m. If that is false then (O2) is vacuously true. The dualist has to deny this (zombie worlds are worlds where p happens without m and e happens) and so the dualist cannot say that (O2) can ever be vacuously true. The physicalist can also say that it is false. How? Bennett argues that (O2) is false when we have p ‘out of context’. So, if we replicate the brain state that is pain in the normal brain in some petri dish or if that state were hooked up in some strange/unusual fashion it will be false that e would still come about. The effect depends on the state being in a normally functioning brain in an environment, etc. So in those cases (O2) is false. Bennett then goes on to argue that the dualist cannot take this option. This is because,

doing so would abandoning standard ways of evaluating counterfactuals. For the dualist, the closest world in which the C-fibers fire without pain is not a world in which various surrounding physical facts go differently. It is not a world in which the C-fiber firing takes place in a petri dish, or otherwise without crucial background conditions that actually obtain. It is instead a world in which the psychophysical law linking firing C-fibers in such and such circumstances to pains is violated. It is not a full-blown zombie world, mind you—that would clearly involve the kinds of “big, widespread, diverse violations of law” that Lewis says it is of the first importance to avoid (1979, 47). It is instead simply a world in which just that particular physical occurrence fails to give rise to the sort of mental one that usually accompanies it. That is merely a “small, localized, simple violation of law,” that allows us to “maximize the spatio- temporal region throughout which perfect match of particular fact prevails” (47-48). This one tiny little violation of psychophysical law is a lot easier to accomplish—if it can be accomplished at all—than a big sweeping change in circumstances.

If all of this is right, she concludes, then only the non-reductive physicalist (or the reductive physicist) can avoid the exclusion problem.

But this doesn’t seem right to me. It is wrong to say that the closest possible world where we have p without m is one where there is a small violation of the bridging laws. At least not if one is thinking in terms of the kind of dualism that Dave Chalmers advocates. Since he thinks that consciousness and mental activity are functionally invariant, under normal conditions, he can happily accept that in the cases that Bennett cites (O2) will be false. Sure they do in fact think that there are worlds like the ones that Bennett talks about where the is a local violation of a law and sure Bennett does not really think that there are any such worlds (I tend to agree) but the point is that the worlds that Bennett thinks falsify (O2) are closer to the actual world on both accounts. In those worlds no laws are violated. So the property dualist can say that (O2) is false when you have p without m in the way that Bennett talks about (i.e. p without the general background conditions that let p function normally) but that it is true when you have p without m in the law-violating way. Thus the property dualist can think that (O2) is false in the usual cases, just like the non-reductive physicalist.

Thus if the causal exclusion argument is an argument for physicalism it is an argument for reductive physicalism.

[cross posted at Brains]

cfp: SSPP

Pete Mandik is the program chair for the 104th annual meeting of the Southern Society for Philosophy and Psychology, to be held March 22-24, 2012 in Savannah, GA. SSPP meetings feature concurrent programs in philosophy and psychology, as well as plenary sessions jointly sponsored by the philosophy and psychology program committees. The deadline for all submissions is November 1, 2011.

Invited Speakers:

David Rosenthal (CUNY Graduate Center)

William Bechtel (UC San Diego)

Jesse Prinz (CUNY Graduate Center)

Invited Symposia:

Cognition and the Social: Carrie Figdor, Bryce Huebner, Anthony Chemero

Perplexities of Perception: Brian Keeley, Robert Briscoe, Berit Brogaard

Fictionalism, Falsehood and the Epistemic Value of Truth: Anthony Dardis, Chase Wrenn, Tad Zawidzki

Explaining Consciousness: Richard Brown, Josh Weisberg, Kenneth Williford

The Philosophy Program Committee encourages the submission of papers and symposium proposals. Their selection will be based on quality and relevance to philosophy, psychology, and other sciences of the mind. The aim of the committee is to present as balanced a program as the quality of submissions in each area permits.

Papers: Submissions exceeding 3,000 words will not be considered. Submissions should include a word count and an abstract of no more than 150 words. Self-reference should be deleted to permit blind reviewing; authors should indicate their identity only on the cover letter that accompanies their submission. All papers submitted and presented should employ gender-neutral language. Please submit file as lastname.firstname.doc or lastname.firstname.rtf or lastname.firstname.pdf.

Papers, along with the Abstract Submission Form on the website, should be submitted electronically to:

Dr. Pete Mandik

Certain papers may be selected for commentary depending on overall programmatic considerations. People who wish to comment on a paper or to chair a session may volunteer by sending a short version of their curriculum vitae directly to the program chairperson at the above address.

Please specify ‘SSPP Submission’ in the subject line. If the paper is being submitted in consideration of a Graduate Student Travel Award, please specify ‘SSPP Submisson– GSTA.’ If the paper should be considered for the Griffith prize, please specify ‘SSPP submission – Griffith.’

Further info can be found at the SSPP website and especially in the SSPP August Newsletter.

Cohen & Dennett’s Perfect Experiment

I was re-reading Dennett and Cohen’s recent paper in Trends in Cognitive Science, “Consciousness Cannot be Separated from Function” and I am now puzzled by their view (before I go on, I would like to note that this issue of TICS also has Joe LeDoux’s paper where he mentions the Qualia Fest, and Lau & Rosenthal’s paper…all in all a great issue!).

Cohen and Dennett want to argue against phenomenological overflow, which is a debate I am currently in the middle of myself, by showing that it is essentially an unscientific view. To do this they introduce what they call the ‘perfect experiment’. They imagine that the area of the brain that is responsible for processing color is somehow allowed to function but is isolated in such a way that it cannot be accessed. The subject in this experiment is shown a blue cup, say, and will deny that they see the color even though the isolated brain area is doing what it normally does. They say,

In spite of this frank denial by subjects, theories that posit dissociation between consciousness and function would necessarily assume that participants of the ‘perfect experiment’ are conscious of the apple’s color but simply cannot access that experience. After all, the conditions these theories stipulate for phenomenal consciousness of color are all met, so this experiment does not disprove the existence of isolated consciousness; it merely provides another particularly crisp example of consciousness with- out access.

However, there is a crucial problem with this logic. If this ‘perfect experiment’ could not definitively disprove [overflow theories] theories, then what could? The subject man- ifests all the functional criteria for not being conscious of color so what would ground the claim that the subject nevertheless enjoys a special kind of consciousness: phenomenal consciousness without access consciousness

I think it is interesting to note that this kind of argument against overflow has been around for a long time. Here is a passage from Huxley’s On the Hypothesis that Animals are Automata, and Its History (from 1874),

If the spinal cord is divided in the middle of the back, for example, the skin of the feet may be cut, or pinched, or burned, or wetted with vitrol, without any sensation of touch, or of pain, arising in consciousness. So far as the man is concerned, therefore, the part of the central nervous system which lies beyond the injury is cut off from consciousness. It must be admitted, that, if any one think fit to maintain that the spinal cord below the injury is conscious, but that it is cut off from any means of making its consciousness known to the other consciousness in the brain, there is no means of driving him from his position by logic. But assuredly there is no way of proving it, and in the matter of consciousness, if anything, we may hold the rule, “De non apparentibus et de non existentibus eadem est ratio.”

The latin phrase there means something like “things that can’t be detected don’t exist.” As Huxley himself points out in the matter of consciousness, if anything, this seems correct. What sense can we make of a phenomenally conscious state that one is in no way aware of?

But it seems to me that these kinds of arguments need to deal with the mesh argument that Block defends. If the mesh argument works (I don’t think it does, at least not in favor of overflow), then we have an answer to the perfect experiment. We say that there is unaccessed consciousness in the isolated brain region because that is the (allegedly) the best over-all interpretation of the data coming in from neuroscience and psychology. Just to repeat, I DO NOT think that there is overflow but I do think that the above kinds of arguments need to deal with the mesh argument directly so I don’t find Cohen and Dnnett’s paper to advance the debate.

The Problem of Zombie Minds

So I am finally done teaching summer school and am ready to settle in to my two weeks of ‘vacation’ before the Fall semester begins. Just as I am about to switch on the PS3 I am struck by the following line of argument…let me know what you think of it…

Those who know me know that I am fond of an argumentative strategy that I call ‘deprioritizing’ when it comes to a priori arguments against (or for) materialism. The idea is taken from the police. When something is deprioritized we still recognize it is a legitimate thing but also recognize that it is not a high priority. So if we are deprioritize the a priori arguments we can still acknowledge that in principle we can tell a priori what is what but for us it will be an empirical discovery. By the time a priori methods will be useful it will be too late. I do this by introducing shombies and zoombies. A shombie is a physical duplicate of me that has consciousness in the absence of any non-material properties. I have claimed that when we are conceiving of a shombie world we are NOT conceiving a a zombie world. But how do we know that it is not? I tend to think of the shombie world as the close possible world where some kind of higher-order theory is true and we have consciousness just like we do in the actual worlds.

This got me to thinking. How does the other side know that consciousness is absent at the zombie world? According to them to know that one is consciously seeing red is to be acquainted with a red quale in such a way as to have it partly constituting my belief or judgment. So to know that we have consciousness, or to know that it isn’t lacking at the actual world, requires being acquainted with it. So how do we know that it is lacking at the zombie world? Sure can conceive of a word with our physics at some future date but all we can ‘see’ is that there are beings there who look like us, talk like us, etc. It would seem that we have no way to tell from the third-person whether these ‘zombies’ really do lack consciousness and since that is the only way for us to know about zombies we are led to a contradiction. In order to conceive of zombies we must know that they lack consciousness, but it is impossible for us to know that they lack consciousness, thus zombies are inconceivable. We can sum this up in the following argument.

1. If zombies are ideally conceivable then we can know that they (the zombies) lack consciousness
2. We cannot know that they lack consciousness
3. Therefore zombies are not ideally conceivable

An opponent might respond that it is just stipulated that there is no consciousness at the zombie world but this is exactly the reason why physicalist claim that the zombie argument is question begging or that it builds into the very concept of consciousness that it is non-physical.

Some Thoughts About Color

I just returned from an interdisciplinary workshop on color (More or Less: Varieties of Human Cortical Color Vision). Unfortunately I was not able to attend the conference that followed. Below are a few scattered (jet-lagged) thoughts in reflection of what happened.

The workshop began with presentations by Michael Tye and Alex Bryne on the philosophy of color. Tye went over the basic positions in the metaphysics of color, viz. realism (colors exist on the surfaces of objects), irrealism (colors exist in the mind of the perceiver), and super-duper irrealism (colors do not exist anywhere). The talks were uninteresting if you, like I, were already aware of this stuff and the arguments on each side but it would have been useful (if that is the right word) for, say, a scientist who wasn’t.

During the discussion Tye and various commenters, were arguing about the relative costs and benefits of the various theories. Tye seemed to think that we should opt for the theory with the most benefits and the least costs. Byrne objected and memorably said “the truth has no costs”. If, for instance, color physicalism is true (colors just are physical properties of the surfaces of objects) then there are no costs in accepting that theory. As a group we may not know which theory is true but, he went on, this is compatible with some particular philosopher, or even a scientist I suppose, knowing the truth. I am pretty sure that it was this line of argument which prompted some unnamed scientist to quip that “the philosophers here are arrogant” later that day. But at any rate what are to make of this debacle?

It has always seemed to me to be obvious that realism and irrealism are true in this case. We use color words interchangeably for both properties of surfaces and also for the conscious color experiences we enjoy. So, when someone asks the question ‘what is red, really?’ they are asking a question which is ambiguous. ‘Red’ really is some physical property of a surface if what you are asking is ‘what is the perceptible property red?’ and it really is a property of some conscious experience if we are asking the question ‘what is the perceived property red?’ Each of these deserves to be called ‘the color red’. But, as between the various ways of spelling out the former or latter who knows? Is perceptible red a complex or primitive property? If primitive is it metaphysically primitive or only nomologically? My money is on complex non-primitive because of considerations about science but this is an open question for me.

It seems to me that the main reason for objecting to this common sense way of thinking about the color red is because of theoretical concerns about transparency. If one is convinced that one can *never* become aware of properties of our conscious experience but, instead, are only able to become aware of the properties ‘out there’. I thought that some of the interesting empirical results about synesthesia presented by Noam Sagiv called this into question. Some synesthetes see the color of a given number, say, as being ‘on the number’ (associators) whereas others see the color not on the number but rather as a property of their experience of the number (projectors). Of course, to get subjects to make this distinction took training, and so no one should deny that in teh first instance what we are usually aware of are the properties of objects but with training we can become aware of properties of our experiences. This distinction also nicely illustrates the way that we use color words to apply to both kinds of things (objects and experiences).

Charles Hayward and Robert Kentridge presented interesting data on cerebral achromatopsia, which is color blindness due to cortical damage rather than any deficiency in the eyes or LGN. One of their main points seemed to be to distinguish CA from blindsight for color. So, cerebral achromatopsics are unable to access or use any information about the color of objects. It is not, like blindsight, that they (seem) to lack phenomenology but are able to use the information to make judgements that are mostly accurate. These subjects lack any ability to access color information. Most interestingly there was one patient who had CA but who did not notice the deficit at first. Presumably this person had all of the color phenomenology just vanish and yet he did not seem to notice. Perhaps even more surprising was the fact that it was not until there color vision had been restored that they noticed that it had been gone in the first place!

There is a lot more that happened (like Mel Goodale’s talk which was excellent) but I’ll have to think about that later!