SECOND RESPONSE

A.K. Moschovakis: Contribution to Round 2.

1. To judge from the first responses to the question posed by Andreas Papanikolaou, the participants of this Symposium have reached a consensus: presently, there is no final, completely satisfactory neurophysiological account of consciousness. However, opinions diverge as to the conclusions to be drawn from this. In contrast to the contents of paragraph 1 of the "Beginning of round 2" (in short Br2), the consensus reached so far is more illusory than real. At one extreme is the position that such an account is not only possible in principle but its form (albeit not the details) is already available (espoused by Tzavaras, Karavatos, Skaliora, Zarkadakis, Kouvelas, Kribas and myself). At the other extreme is the position that such an account is in principle impossible because the stuff that makes minds is fundamentally different from the stuff that makes brains (elaborated by Giorgos Papadopoulos) or because no conceivable methodology will ever allow us to flesh it out (elaborated by our host Andreas Papanikolaou and by Helen Savaki). All other positions lie somewhere in between.

2. The short answer to the question "Is there any data unavailable to Socrates that would compel a reasonable fellow to accept the theory which says that as the strings of the lyre produce the sounds of music, so does his brain produce his thoughts?", is yes, by the bushel. But to understand why, one needs a longer answer which is convoluted and rests on three epistemological arguments, concerning: 1) The relationship between theory and data. 2) The structure of scientific explanations. 3) Intertheoretic reductions and their implications.

2.1. Is it just a matter of weighing the empirical evidence, the whole empirical evidence and nothing but the empirical evidence that enables one to decide between two alternative theories? Actually not, for several reasons elaborated independently by the likes of Kuhn, Hall, Lakatos, etc. Data by itself was apparently not good enough to decide the issue for general relativity. So why should data such as that provided by Elias Kouvelas, Irini Skaliora and myself be good enough for the cerebral theory of consciousness? In contrast to what Irini seems to think, this "inherent inadequacy of the data" is not due to the particular thinking habits, conceptual resistances, religious convictions or spontaneous philosophy of any particular scientist you may care to name. Instead it is due to the fact that data acquire leverage and become persuasive only when used to evaluate the truth content of sentences, in an error statistical sense and in relation to the distance between the hypothesis tested and the rest of the theoretical corpus of the field. Although a circumscribed data set (say the results of a Matrices test presented to the mute hemisphere of commissurotomized patients) may be taken into account to test a statement (s) in Psychology (P, seP; say, that the right hemisphere can be conscious), a huge amount of data lurks in the background (data supportive of our notion of the corpus callosum, data supportive of our experimental design, data supportive of our data treatment, etc.). It goes without saying that the same is true of any statement in the Neurosciences. Although a hypothesis tested (say, that the spike trains of a certain neuron in V3 encode such and such an amount of disparity) is seemingly unrelated to sodium currents (in the sense that potassium, lithium, calcium, you name it, could very well underlie the action potentials of the V3 neuron in question), the choline data (meaning the data generated by Hodgkin and Huxley to test Bernstein's hypothesis re the breakdown of cell membranes during action potentials) lurks in the background (in the pedestrian sense that sometimes the relevant knowledge must be taken into account to design proper electrodes, and in the not so pedestrian sense that we have to be sure that spikes are for real before we start counting them, timing them, etc.). Although the focus shifts, relegating some data to the background while others are brought to the foreground, a huge amount of data is in play while a hypothesis is tested. It is due to this inherent relationship to hypotheses, that a huge amount of data comes to bear on the task in hand (test a hypothesis), although it may not seem to be so, superficially. Testing the hypothesis that the brain is sufficient for consciousness is no exception.

2.2. To to decide between alternative hypotheses, it is customary for their proponents to state what it is that they would count as relevant evidence. Accordingly, I would ask the dualist and the agnostic to tell us what it is that they would count as evidence in favor of a cerebral theory of consciousness. After all, shouldn't we know what it is that we are looking for before embarking on a quest to find it? Conceivably, our host did so in demanding a generative model of qualia. A related question was posed by Tzavaras, in passing ("What is it that counts for an explanation in Psychology?"), and by a close friend (Theodore Tomaras, who makes a living addressing questions in cosmology and quantum mechanics), in private ("What is it that counts for an explanation in neuroscience? How does it compare to the case in Physics?"). Following Hempel (1965), one could pose the more general question: "What is it that counts for an explanation in Science?". As very eloquently argued by Pefanis, the demand for a "generative model of consciousness" is misplaced. However, I do not think Pefanis is right in laying the blame on the third (consciousness) rather than the first two (generative model) words which collectively phrase the demand (provide a "generative model of consciousness"). He seems to think that consciousness is somehow strange and that we should be striving for some peculiarly stochastic, acausal account of the consciousness of a single individual. In contrast I think that part of the problem lies in requirement R1, one of Hempel's logical conditions of the adequacy of scientific explanations: "the explanandum must be a logical consequence of the explanans; in other words, the explanandum must be logically deducible from the information contained in the explanans; for otherwise the explanans would not constitute adequate grounds for the explanandum" (Hempel, 1965). Do scientists armed with general laws (the axioms of the discipline) apply laws of logic (say predicate calculus) to deduce phenomena and events (in the world) as theorems (of the discipline)? I do not think so and I am not alone in this. A book length argument against this notion was elaborated by Thompson (1989) as regards biology in particular (largely devoted to Mendel's laws of inheritance), and science, in general. Instead of providing generative models of what it is they deal with, scientists generate possible models of a theory and test the claim that a given empirical system (the "real world") is a model of the theory (see (Bickle, 1998) for a formulation of this argument as it applies to the Mind/Body problem). Thus, Hempel's deductive nomological account of science applies to no science and it would be surprising if it applied to neuroscientific accounts of consciousness. In other words, we lack a generative model of qualia and consciousness, not because consciousness is in principle beyond the reach of neuroscience or because the neuroscientific account of consciousness must be a stochastic, acausal one, but because no science has ever elaborated a meaningful generative model of whatever it is that it deals with, period.

2.3. It is possible to follow a different tack (a formal one at that) to argue that a full blown neuroscientific account of consciousness (however you choose to define it) is not needed for someone to think that it is possible in principle. Let me make one more effort to explain how the argument goes. Psychology (the science that deals with the mind) is being reduced to Neuroscience (the science that deals with the brain) as we speak. This applies to much of Psychophysics and most of Ethology (thus creating the modern field of Neuroethology) but other branches of Psychology (say Neuropsychology) are not immune (examples of this were presented by Elias Kouvelas, Irini Skaliora and myself as regards learning, memory, vision, action, etc.). Although local, this successful response to the "put-up or shut-up" argument has global consequences. The reason is that epistemological reduction (of theories concerning learning, memory, sensation, perception and action to theories concerning neural events) implies (to judge from the public record) ontological reduction (i.e., that the mind and the brain are made of the same stuff). In other words, successful neurophysiological accounts of Hering's Law imply that consciousness will be accounted for in a similar manner whatever one might choose to say (or not to say) about qualia. This is pretty much the point made by Thanasis Tzavaras in particular near the end of his description of the affair between zebras and eucalyptus trees: "Just as with consciousness, (Wisconsin et al., ) although there is no information about the precise mechanisms involved, I suppose that only a general Darwinian theory can account for this phenomenon".

2.3.1. How could one counter this argument? One possibility is to follow Kerassidis in his claim that "there has never been any reduction anytime in the course of human history". I doubt that Kerassidis objects to my use of the term reduction to characterize the special relationship between certain pairs of theories (optics-electromagnetism, laws of ideal gases-statistical mechanics, action potential-Kirchoff's laws, etc.). The public record contains too many examples of such intertheoretic reductions for this to be a viable objection. Alternatively, Kerassidis may be unwilling to underwrite the more general metaphysical commitments implied when using the term "reduce". These are rather minimal, but to explain why I need to backtrack a bit (borrowing heavily from Frank Jackson (1997). The metaphysics of materialistic reductionism is unexceptional in that it is about what there is and what it is like. Just like other metaphysics, it seeks a comprehensive account of a subject matter (the sun, the kidney, the mind, etc.) in terms of a limited number of ingredients. Accordingly, some features of the world do not figure explicitly in the story to be told about it. In other words metaphysics is both discriminatory (about what to include and what to exclude from the list of ingredients) and aims at completeness (in the sense that whatever is not included must be accounted for in terms of whatever is included). Take solidity, for example. One might be tempted to add it to the list of fundamental ingredients about the world, and insist that being solid requires being everywhere dense in addition to resisting encroachment. Alternatively, one could consider objects as nothing but aggregates of molecules held in a lattice-like array by various intermolecular forces. Does this imply that nothing is solid? Obviously not. One could go on to invoke Pauli's exclusion principle, thanks to which the lattice-like arrays of molecules prevent each other (exclude each other) from encroaching on each others' space. So resisting encroachment explains the stubbing of toes on misplaced stones and it becomes unnecessary to insist that toes and stones must have anything more in order to be solid. Scientific stories about the world are chock full of reductive accounts of this sort. Otherwise, scientific practice would offer little more than ever increasing lists of ingredients drawn from local, disjoint territories of regularized observations. This is clearly not the case.

2.3.2. An alternative means to counter the argument would be to grant the existence of intertheoretic reductions but withhold the claim that they entail ontological reductions. This is pretty much the stance adopted  by Searle who subscribes to causal reductionism (the causal powers of the reducing entity are entirely explainable in terms of the causal powers of the reducing phenomena), and admits that "In general in the history of science, successful causal reductions tend to lead to ontological reductions", but claims that consciousness is an exception to the rule: "When we come to consciousness, we can not perform the ontological reduction" (Searle, 1997). Unaccompanied by arguments the merits of which can be evaluated independently, Searle's opinion would be just another case of begging the question (lipsi tou zitoumenou). Searle invokes two arguments to buttress his point of view: 1) The knowledge argument (third person accounts even if exhaustive, leave out all subjective features of experience), 2) Kripke's argument. In #2.3.2.1. and #4.2.2. I intend to demonstrate that these arguments are also cases of question begging, albeit better camouflaged ones.

2.3.2.1. The knowledge argument has the form of a reductio which goes roughly as follows (Nagel, 1974; Jackson, 1986). Mary is a blind neurophysiologist who knows everything about light and vision. Her vision is restored thanks to a remarkable new operation following which she realizes what it feels like to see a deep red. Thus, contrary to the premise, her knowledge left a lot to be desired.

        Three objections have been raised against the knowledge argument. a) It cashes on the ambiguous use of the verb "to know", namely "to know of something" and "to know about something" (Churchland, 1995). One need not assume that mastery of Neuroscientific statements (to know in the latter sense) entails prelinguistic representations of redness in mechanisms of noninferential discrimination (to know in the former sense). b) It begs the question as there is nothing to demonstrate that Mary qua blind can not actually imagine what it feels to see red (Churchland, 1995). c) Remarkably, it is Searle who phrased the third objection in the form I summarise below (Searle, 2000). He pointed out that the argument "if science is by definition objective and consciousness is by definition subjective, it follows that there can be know a science of consciousness" commits the fallacy of ambiguity over the use of the subjective-objective distinction. In one sense of the distinction, the epistemic one, science is said to be objective in that it seeks truths that are equally accessible to any competent observer (say that "George W. Bush Jr. weighs 70 kg") and that are independent of his feelings and attitudes which can be subjective (he may claim, however misguidedly, that "George W. Bush Jr. is a good president"). However, there is a second sense to the subjective-objective distinction, the ontological one. Some entities, such as pains, sounds and colors have a subjective mode of existence in that they exist as experiences of conscious subjects (whatever this means; I will have more to say about this later on). Others such as pens, fountains and rocks have an objective mode of existence in the sense that they do not depend on the presence of anybody else. In making this distinction, Searle wishes to draw attention to the fact that the scientific requirements of epistemic objectivity do not exclude ontological subjectivity as a domain of investigation. To use his words, "There is no reason whatever why we can not have an objective science of pain, even though pains only exist when they are felt by conscious subjects". This much suffices to demonstrate that the knowledge argument begs the question in more ways than one. I will have more to say about pains and pens in #4, below.

3. While waiting for the dualist and the agnostic to tell us what it is that they would count as evidence in favor of reductionist, materialist monism, and in the name of symmetry, I would ask the interactionist dualist to provide information about the non-material stuff that he claims minds are made of and to describe the processes which allow the immaterial soul to interact with the material brain. I would also ask the agnostic to demonstrate that the material basis of consciousness is in principle unknowable (i.e., that we stand re the mind/problem "as a dog" stands re "the concept of a square root" as Kerassidis phrased it). How do these alternative positions fare when faced with the task in hand?

3.1. Take, for example, the arguments of Giorgos Papadopoulos which are typical of those espoused by interactionist dualists. He claims that the mental phenomena are based on a substance which is radically different from mater and that it can not be understood with the methods used to study the material world. Further, he claims that the immaterial substance is not unreal, is not causally inert and is not produced by the brain. Finally, he claims that the effects of brain lesions and stimulation can not support the notion that the brain produces mentation. Papadopoulos provides no facts or reasons to support his claims. Actually, there is evidence which contradicts his claims. For example, since brain lesions abolish mental phenomena and brain stimulation evokes mental phenomena both the sufficiency and the necessity criteria of Galilean causality are satisfied re the brain-mind relationship. This conclusion is far from outlandish. It is espoused among others by Stelios Kerassidis, who right from the start admits that the brain is necessary for the mind (I would not be so sure; consider the prospects of AI if this were correct) and near the end of his response states that "neural phenomena are probably sufficient for the production of mental phenomena". Interested readers  can find arguments in favor of the notion that the brain is both necessary and sufficient for the mind in Searle (2000). A final cautionary remark is in order: the interactionist dualist position is not for the light hearted in that its adherents need to do more, not less, work than proponents of alternative responses to the mind-body problem. Given his concerns, the onus is on the interactionist dualist to provide an account of the processes which allow the immaterial soul to interact with the material brain. Giorgos Papadopoulos is not the first of a long series of like-minded thinkers who fails to do this.

3.2. Helen Savaki offers a list of 32 neurophysiological/computational mechanisms reportedly underlying consciousness to claim that since not all these mechanisms can be simultaneously true they must be false and thus that the basis of consciousness can not be material. I hasten to add a 33rd mechanism namely that tension tunes corresponding pairs of fibers in the two optic nerves to vibrate in unison so that separate images in the two eyes are united (bound) into a single sensation. I also hasten to disclaim priority on this one. Credit must go to Mr. William Briggs, a fellow of Corpus Christi College, who included it in his copy of the "New Theory of Vision" sent to Newton in 1685 (it first appeared in the Philosophical Collections 6: 167-177, 1682).

3.2.1. What does this expedition demonstrate besides the ingenuity and fallibility of human beings? Arguably, it proves that the binding problem was not solved in Newton's time. As I argued before (in paragraph #4.2. of my first response regarding the fallacy of this so-called "argument from ignorance"), positing large numbers of scientific hypotheses is not an admission of defeat. It only implies that a new field has opened up for exploration. In his "Proofs and Refutations" Lakatos goes through the history of the branch of mathematics that deals with polyhedra to demonstrate that all hypotheses that can be formulated are actually formulated (Lakatos, 1976). Certainly, most of them end up in the trash-heap of history. Per 2.2. above, a certain neurophysiological account of consciousness can fail because (1) it is not a model of the theory (neurosciences), despite claims to the contrary, or (2) because it is not a model of what it purports to be a model, or (3) because the test designed to evaluate the claim that something in the real world (some sort of conscious experience) is a model of the theory was not done right. For example, the claim that the high frequency oscillations in the cortex underlie solutions to the binding problem is a Type 2 failure as argued by Hardcastle (a summary of her arguments can be found in paragraph #4.2. of my first response). Similarly, Newton's objections to Brigg's pet theory can be found as a prefix to the Latin version of Brigg's paper, bound together with other material in the second edition of Brigg's Ophthalmographia which came out in 1685. All of the remaining 31 neurophysiological/computational mechanisms reportedly underlying consciousness could have been evaluated in a similar fashion. This would have contributed to the field and I wish somebody invested the time needed to do this. However, even if one were to demonstrate that every single one of the remaining hypotheses fails for type 1, type 2 or type 3 reasons, this effort would fall far short of making a case for agnosticism. Instead one should prove that the material basis of consciousness is in principle unknowable.

3.3. Andreas Papanikolaou also subscribes to agnosticism (Br2.14) and he also falls far short of establishing that the material basis of consciousness is in principle unknowable. The crux of his argument is based on the premise: "Given our shared assumption that neither we nor anyone else is able to demonstrate whether and how the brain's micro and macro machinery creates qualia..." and reaches the conclusion: "...the following (among many other) alternatives are equiprobable: (i) the material brain produces qualia, (ii) an extra-material agency manifests itself by using the cerebral machinery... Or, as likely, that (iii), there are no such things as purely material or purely immaterial entities but that ... every speck of matter in the universe is full of qualia albeit in a nascent (for us) form, in which case the relation between brains and qualia is not a relation between two radically distinct layers or strata or reality". As I intend to show in #3.3.1.-3.3.3, this conclusion would be unwarranted even if the premise were true. But the premise is false as I intend to show in #4.1. 

3.3.1. Our host's argument is an argumentum ad ignorantiam - an argument from ignorance. Borrowing heavily from Churchland (1997) the canonical version of the argument looks something like this:

        We really do not understand much about phenomenon Q (say qualia)Therefore, we do know that:

        1) Q can never be explained in terms of properties of kind B (say brain events); (staying closer to Br2, paragraph 30: you will never be successful in constructing a model that will show how the brain produces Q).

        2) Factors other than brain events may be necessary for the production of Q (Br2-6)

        3) An extra-material agency manifests itself by using the cerebral machinery to produce Q (Br2-16)

        Certainly, none of the conclusions follows from the premise. Nothing follows from the fact that we do not know something. We just don't know. I have no idea what caused that banging noise from just beyond the fence. Am I at liberty to conclude it must be something special, alien, otherworldly? Evidently not. For all I know it could be two cats fighting over the meatballs I discarded yesterday. This is not a very deep conclusion, but when ignorance is a premise this is about as much as you can grind out of it (Churchland, 1997).

3.3.2. The three options, (i) the material brain produces qualia, (ii) an extra-material agency manifests itself by using the cerebral machinery, (iii) every speck of matter in the universe is full of qualia albeit in a nascent (for us) form, are not equivalent when it comes to testing them. To prove (i) one would need to demonstrate that something inside the brain can account for a quale. To prove (ii) one would need to find the extra-material agency and show how it interacts with the brain. To prove (iii) one would need to demonstrate that something out there in the world can account for a quale.

3.3.3. The three options listed in 3.3.2. are also not equivalent when it comes to gauging the empirical support they receive from the data in hand (data such as that described in 4.1.). Let's go back to Mach bands. Per Hartline's (1940) account they are due to lateral interactions between adjacent photoreceptors of Limulus eyes (or to the photoreceptor, horizontal cell, bipolar cell circuit if one wishes to consult the later efforts of Werblin, Dowling and Bob Miller regarding mammalian retinae) when shone with step functions of light intensity. So (i) has a fair chance of proving correct (the odds are much better now than in the times of Socrates due to data that was not available to him). In contrast there is nothing to recommend (ii) to us. If anyone out there knows anything whatever about the extra-material agency and its Mach band generating interactions with the retina, please do not keep it a secret; you could be much closer to Stockholm than you may think. Nor is there any info about the "nascent (for us) form" of a step signal of light so that it generates Mach bands whatever the eyes it strikes; therefore, the prospects of (iii) are nowadays as slim as they were 200 (or 2000) years ago.

4. More generally I intend to demonstrate that, (1) in contrast to paragraph 2 of Br2, qualia come in lots of sorts (in the sense that the pieces of an exploded homunculus can be found here, there, and elsewhere), (2) there already exist models (albeit not generative ones) of some kinds of them, and (3) qualia is trivial in whatever sense it is in principle impossible to have a neurophysiological account for.

4.1. Not only are there neurophysiological accounts of qualia but some of them have withstood the test of experiment and time. Phenomena such as color constancy, Mach bands and vection are subjective experiences in the strictest sense of the word yet successful neurophysiological accounts of these phenomena have already been provided. And this is not the end of the story. There are many more theories, hypotheses and models which address additional features of subjective experience and whose neurophysiological substrate is being explored as we speak. For example, thanks to the work of Dale Purves (1999), we know that the Craik-O'Brian-Cornsweet effect, namely, the subjective impression that the central one of three parallel gray ribbons is perceived as darker or lighter than the flanking ones, depending on the luminance waveform of the regions separating them, despite the fact that all three ribbons reflect the same amount of light (per construction), depends on long range interactions between visually responsive neurons. Moreover, thanks to the work of Charlie Gilbert (1979) we know that V1 pyramidal cells deploy the requisite terminal fields. However, we do not know yet whether the former is indeed necessary and/or sufficient for the latter. In other cases, the data is specific enough to exclude some possibilities but are not specific enough to pinpoint the precise mechanism. For example, thanks to the work of Bela Julesz (1971), we know that our subjective experience of the Mueller-Lyer illusion does not depend on neurons peripheral to V1 but we do not know the identity of the neurons it does depend on. Whatever the present empirical status of these and other models of subjective experience, they collectively demonstrate one thing, namely that in contrast to the claims of our host "...no matter how heterogeneous the brains and the qualia may be, their deeper nature must be one, whole, homogeneous and undivided..." fragments of different sorts of qualia emerge from different sorts of neural nets. There is no qualia problem. Instead, there are lots of local quale problems.

4.2. How is pain related to neurons? It would seem that certain subjective aspects of pain (such as whether it is deep and diffuse or acute and penetrating) depend on the activation of different sorts of fibers (C and Ad, respectively). To some extent, it also seems that the difference between a bellyache and a toothache (i.e., our ability to localize pain) depends on whether it is this or that fiber that gets going; further, one first order pain fiber can influence the wrong second order pain fiber so localization through pain is not as veridical as through touch. Clearly, pain can be caused without C (or Ad) fiber activation; Held's central pain is one of the many syndromes subsumed under the rubric neuropathic pain (in this case, presumably due to thalamic activation). Nor is the link between C fiber activation and pain an obligatory one. Hemi-section of the spinal cord (i.e., in patients suffering from the syndrome of Brown-Sequard) renders insensitive half of the body, the half that lies below the cut on the opposite side; in cases such as this, C fibers can still fire in response to painful stimuli applied to the appropriate part of the body but no pain is felt. More interestingly as I said in my first response concerning the subjective quality of pain, subjects suffering from lesions of the anterior cingulate report that they feel pain but that they no longer mind it (Vogt et al., 1992). So, what is it that we can conclude from these facts?

4.2.1. It does not do justice to pain to think that it has no existence independent of the subject experiencing the pain ("A pain and this pen I am now holding, appear to me radically different in that the first is a sensation that, though localized in a part of my body has no other content than itself, whereas the second appears as an object independent of me", to quote our host). We have no trouble dealing with the notion that pain is real even if we do not experience it. Otherwise the concept would not be used in statements such as "Nick doubled over in pain" or "the discharge of C fibers is crucially relevant for pain". Moreover, the pain feels piercing or pressing, pulsing or steady, it is characterized by a certain intensity, duration, etc. In other words pains display the qualitative characteristics that we experience and do so depending on the manner in which C fibers (and other neurons) discharge. Similarly, pens are characterized by their weight, color, length, etc. Their appearance depends on the density of the material they are made of, how they compare to standard lengths, etc. Pens signify the presence of an object out there, but they do so only if one makes a commitment to realism. It is the same commitment to realism (and not physicalist or eliminativist positions) which allows pain to signify that something is not O.K. somewhere in an ailing body out there.

4.2.2. Let us see how these facts square with a classical anti-physicalist argument (Kripke's (1980). It has been argued that putative mental-physical identities (of the form "Pain = the firing of C fibers") differ importantly from those deriving from other scientific reductions (of the form water = H2O). The argument requires us to think of a different world where either or both statements could be false (since neither is known a priori this is indeed conceivable). Yet, if they were true, they ought to be necessarily true. It has been claimed that the apparent contingency can be reconciled with the actual necessity in the latter case but not in the former. The reason is that when we think of a world where water is not H2O, we in fact imagine a substance which superficially behaves like water (ethyl alcohol might do in an odorless world of the proper temperature, populated by humans endowed with the proper liver, etc.) but is not H2O. In contrast, it has been claimed that imagining a situation in which one is experiencing a state superficially resembling pain just is to imagine a situation in which one is experiencing pain. Per 4.2. above, I would not be so sure. When we are asked to imagine a situation in which one is experiencing a state superficially resembling pain, are we asked to imagine a situation in which one is experiencing Ad-fiber pain or C-fiber pain. Presumably asking somebody to imagine a situation in which one feels Held's pain is to ask too much of a normal subject who is thus unlikely to have experienced anything of the sort. The same is true of asking somebody to differentiate between "mindful" and "mindless" pain (per #4.2., accompanied and unaccompanied by anterior cingulate activation). Or is such imagining not superficial enough for the purpose of the thought experiment? In which case, what is the difference between superficial imaginings of water and pain and what is the assertion that "imagining a situation in which one is experiencing a state superficially resembling pain just is to imagine a situation in which one is experiencing pain" other than begging the question?

4.3. Are neural processes such as those brought up in 4.2. all that there is to pain? Absolutely not. Pains and other subjective experiences are woven together with other sensations, wishes, reminiscences, flashes of desire and intentions into the thick fabric of everyday mentation. We hold them dear because of their capriciousness, that seems to defy the laws of logic and nature, and the idiosyncratic way in which they combine disparate elements (the way letters are combined into words). Is there anything mysterious about the letters of this alphabet? Again, not. They are the emotions, decision processes, illusions, veridical perceptions, and memories neuroscientific accounts of which are being elaborated. It is their combination that makes them as unique as works of art, and they can be studied as such (this is pretty much the point made by the two psychoanalysts in our group). However, the first person narrative and the scientific discourse about the first person narrative are two different things. Only when the two are confounded, are subjective experiences presented as problematic for scientific accounts of the mind.

4.4. Are the neural processes brought up in 4.2. cum the quasi-narrative, quasi-intentional and quasi-evaluative processes brought up in 4.3. all that there is to pain? I would say ay, but the agnostic and the dualist would presumably say nay. If as I claim, the neurophysiological basis of the qualitative character of experience (the saturation of a color seen, the intensity of a pain felt,the sweetness of a nutrient ingested, the pitch of a sound heard, the apparent movie like impression generated by a fast enough sequence of still frames, etc.) is being worked out, the concern expressed in the opening sentence of 3.2.2. which I quote from Br2 must be either (1) that the processes alluded to in 4.2 and 4.3. could be happening without any feeling whatsoever, or (2) because it is something other than the qualitative characteristics of subjective experience (e.g., the intensity, acuteness, duration, etc. of pain) that the dualist or the agnostic wishes to understand. In the technical literature, (1) is known as the "absent qualia" or "zombie" argument. Not to draw the wrath of Tzavara's vehement objections towards far fetched thought experiments, I address it in 4.4.1.2. only tangentially; besides, to do so fully I would need to deal with a different aspect of consciousness, namely awareness. Suffice to say, that the neurophysiological basis of awareness is nowadays considered a legitimate field of exploration; whether relevant efforts prove successful and if so how soon, remains of course to be seen. I do intend to address (2) in 4.4.2. because it allows one to comment on qualia some more (namely, deal with point 3 of #4.).

4.4.1. Our host does not seem to think it likely that he will encounter qualia looking down one of his imaging devices. I share his skepticism but I beg to differ as to why. I think that imaging techniques suffer from an inherent trade-off between resolution and signal to noise ratio. Increasing the former puts a heavy burden on the latter and vise versa, so improving the technique to his satisfaction and mine could prove a long and arduous expedition. Yet, I do not see any a priori insurmountable difficulty in taking advantage of imaging or other techniques to pin-point brain events underlying subjective conscious experiences. Consider for example the following experiment done by Nikos Logothetis and his colleagues (Logothetis and Schall, 1989) and alluded to in #5.4. of my first response. Thanks to it, we know that the discharge of neurons of the temporal lobes of monkeys is related to the conscious perception of movement rather than to the characteristics of the visual stimulus. To explore this issue, rhesus monkeys were shown moving visual stimuli that were rivalrous for the two eyes (downward in the one, upward in the other) and the monkeys were asked to make a rapid eye movement to one spot if they perceived downward motion and to another spot if they perceived upward motion. About 1:5 of the neurons in the superior temporal sulcus responded to the presence of the stimulus they preferred irrespective of the monkey's choice. However, about half as many cells discharged only when the perceptual choice of the monkey corresponded to their preferred direction irrespective of the stimulus configuration. Our host would advise us to withhold the conclusion that these cells are related to the subjective experience of perceiving the movement of objects for two reasons, namely: (A) the first round of experiencing may confound the second, etc. (B) we can conceive of monkeys capable of perceiving (and reporting) the motion of an object while experiencing nothing subjectively.

4.4.1.1. Reason (A) is a rephrasing of the "uniqueness" argument and it doesn't hold water. As I already implied in my first response, unique instances (say electron #1256392936538976355484909, carboxyl group #1256392936538976 or cat #1256392936538) have not been in the providence of physics, chemistry and biology, respectively (Hempel, 1965), so I don't know why the brain and conscious experiences of human #1256392 ought to be in those of Neuroscience and Psychology, respectively. To repeat a point alluded to in my first response, the physics-engineering spectrum of human activity is about thermodynamics, Carnot's cycle and internal combustion engines. The malfunction of the engine of car #1782837465480404866 is for the car mechanic. To get back to minds and brains, suppose human #1256392 feels angst badly enough to seek psychoanalytic treatment. With the help of a specialist he will attempt to reconstruct his biography in a way that rings true, resolve inner conflicts, rid himself of symptoms, etc. To proceed, the psychoanalyst must be proficient in the techniques and theoretical corpus of the science he studied (in this case re mechanisms of defence, neuroses, transference, etc.). But one should not confuse the science part of the endeavor (which is about concepts such as projection, and statements about diseases, the structure of the psyche and its development) with the therapeutic art (which is about enabling free associations, ensuring catharsis and in final analysis putting together a biography in narrative form) that goes with it.

4.4.1.2. It is reason (B) that gets us to the "absent qualia" argument. In general it has the following form: a realization of our functional organization is proposed to occupy some bizarre medium, following which an appeal is made to our intuition that "that" can not possibly be conscious. For example, it has been pointed out that the organization of our brain might be simulated by the Chinese nation (Block, 1978). If we got every person in China to simulate a neuron and equipped them with radio links to simulate synapses then the functional organization of our brain would be in place. Surely, this baroque system would not be conscious (it would be a brain that contains about 100 times fewer neurons than ours but this is not why it could not possibly be conscious). There are several objections to this argument. I will summarize the one elaborated by Chalmers (1996) which is in the form of a reductio ad absurdum. Consider that one of the neurons in your brain is replaced by a sophisticated chip that preserves all functions and input output connections of that neuron. Surely, you would remain conscious. Suppose that you repeat the process a second, third, etc. times till all neurons are replaced by similar chips. Either you predict that at some point consciousness is lost (it is not at all easy to think that this would be the case as there is no discontinuity in the process envisaged) or that it is not, in which case a machine (the aggregate of chips that now is your brain), can be conscious. What does this reductio demonstrate besides the weakness of conceivability arguments? It shows that in the absence of independent empirical evidence assertions such as "reporting a percept need not be accompanied by any subjective feeling whatsoever" is just question begging ("lipsi tou zitoumenou" anon).

4.4.2. So what is it other than the intensity, acuteness, duration, etc. of pain, that the dualist or the agnostic wishes to understand? What else is there that constitutes the deeper nature of subjective experience? I suspect nothing. If they think there is, the onus is on the dualist and the agnostic to tell us what it is. While waiting for their response, which will hopefully contain a better one, I'll adopt the list supplied by Dennett (1999). It contains the items: (1) ineffable, (2) intrinsic, (3) private, and (4) directly apprehensible in consciousness, all of which I think are trivial (interested readers should consult Dennett (1999) for an eloquent argument in favor of quinning the whole lot). If nothing else, about a hundred years worth of experience with psychoanalysis, should have rendered us suspicious towards our utterings in particular as regards the contents of our thoughts. So, whatever it is that one might wish to claim about something apprehended directly in consciousness, "direct apprehension in consciousness" is not one of them. If anything, "ineffability" is more of a practical issue. Our ability to verbalize the appeal of certain tastes has to do with our gastrimargic predilections and can improve with frequent excursions to a good restaurant (preferably with a good thesaurus in hand). There is also nothing extraordinary about item (3) on the list (private). Our privacy is exhausted in our idiosyncrasies (per #4.3. above); but, our idiosyncratic discrimination profiles can be rendered public through the usual objective testing procedures (Dennett, 1999). Finally, consider "intrinsic". I am staring at a bluish, pyramidal, fairly heavy, glass paper weight that belongs to a colleague. All of its secondary properties are relational or extrinsic ones except for the first one which is claimed to be intrinsic. It is far from clear what that means. Intrinsic to the paper weight I am staring at, intrinsic to my mind, intrinsic to what? It is instructive to consider how the brain evaluates colors (Land, 1959). To figure out the color of the said pyramid, I measure how much it differs from all other colors in the visual scene (along the red-green, blue-yellow, dark-light axes in neural discharge space). Thus, color too is a relational property although it may not seem to be so superficially. Until the agnostic or the dualist come up with a better list of qualia, it is fair to say that the qualitative properties of experience are trivial in whatever sense it is in principle impossible to have a neurophysiological account for.

5. A final cautionary remark is in order. Nothing whatever is gained if the Cartesian distinction "res extensa/res cogitans" is replaced with that between "sensibilia" and "intelligibilia". The latter may sound familiar as it has been repeatedly emphasized by Plato and Aristotle. It is also a distinction to be debated between opponents and proponents of British empiricism (the latter were reluctant to entertain it). However, unless one limits it to objects apprehended by us (thus leaving alone the rest of the world), in which case it is rendered secondary to the distinction res extensa/res cogitans, the existence of everything is made to depend on the presence of feeling (sensibilia) and thinking (intelligibilia) subjects. To reconcile the first and third person perspectives, proponents of this substitution presumably want us to consider everything from a first person perspective. This maneuver is unlikely to generate a stampede, least of all among materialist monists. For one, it is not as innocuous as it looks. Besides a theory of measurement and a theory of inference (deploying one of each is common practice when doing science these days) one is asked to formulate a theory of sensing and a theory of knowledge. All this before taking a single step in the long voyage to explore the world. I am sure that anyone who has spent time going through the Dialogues can see how frustrating and self-defeating this demand is. Maybe this is why the classics were substandard when it came to science despite the fact that they were as good as anybody in terms of mathematics, art, engineering and philosophy.

6. To summarise, the quest for a generative model of qualia starting from brain entities is a case of barking under the wrong tree, for several reasons: 1) Whatever it is that science does, this does not include the elaboration of generative models. 2) Choosing qualia as a starting point for a philosophical exploration is not particularly challenging because their neurophysiological underpinnings is being worked out as we speak. 3) The risk of being led astray is higher when treating qualia rather than when treating say the action potential, speciation or leptons, largely because of confusion and linguistic ambiguities. In any case, putting together a reductive materialistic theory of the mind is a worthy endeavor and using qualia as a starting point is as good as any. Besides, generating scores of experimental results re vision, audition, action, etc., the materialist monist can rely on a powerful epistemology (that of structural analysis of theories and intertheoretic reductions) to buttress his world view. To contribute to the field, dualists would have to elucidate the immaterial stuff that makes the mind and explain how it interacts with the material stuff that makes the brain. Instead, the best they have had to offer so far, is a list of unsubstantiated negative claims about the mind and anti-physicalist arguments that beg the question. To contribute to the field, agnostics would have to demonstrate that consciousness is in principle beyond the ken of human understanding. Instead, they have not not advanced beyond an argument from ignorance. So, to judge from the first responses, the materialist position is the only game in town.

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