WHAT SHOULD WE EXPECT FROM A THEORY OF CONSCIOUSNESS?

Patricia Smith Churchland
Philosophy Department,
University of California San Diego

I. INTRODUCTION:
Within the domain of philosophy, it is not unusual to hear the claim that most questions about the nature of consciousness are essentially and absolutely beyond the scope of science, no matter how science may develop in the twenty-first century. Some things, it is pointed out, we shall never ever understand, and consciousness is one of them
(Vendler 1994, Swinburne 1994, McGinn 1989, Nagel 1994, Warner 1994). One line of reasoning assumes that consciousness is the manifestation of a distinctly nonphysical thing, and hence has no physical properties that might be explored by techniques suitable to physical things.

    Dualism, as this view is known, is still to be found among those within the tradition of Kant and Hegel, as well as among some with religious convictions. Surprisingly, however, strenuous foot-dragging is evident even among philosophers of a materialist conviction. Indeed, one might say that it is the philosophical fashion of the 90's to pronounce consciousness unexplainable, and to find the explanatory aspirations of neurobiology to be faintly comic if not rather pitiful. The very word, "reductionism" has come to be used more or less synonymously with "benighted-scientism-run-amok", where scientistm apparently means "applying scientific techniques to domains where they are inapplicable."

    McGinn, perhaps the most unblushing of the naysayers, insists that we cannot expect even to make any headway on the problem. (p. 114) Ironically perhaps, here we are at a conference in honor of Dr. Herbert Jasper who was a great pioneer in moving neuroscience forward on this problem, and where results will be presented allegedly showing additional progress on the problem. Because I am quite optimistic about future scientific progress on the nature of consciousness, my aim here, as a philosopher, is to address the most popular and influential of the skeptical arguments, and to explain why I find them unconvincing. Thus the overall form of the paper is negative, in the sense that I want to show why a set of naysaying arguments fail. The positive part of the story derives from the actual progress being made on the topic, but I shall leave it to my neuroscience colleagues to present the data and details on that. Section II will focus on skeptical arguments raised essentially in protest to reductionist programs, and Section III will examine a range of skeptical arguments arising from consideration of what we do not yet know.

II REDUCTIONISM -- SHOULD WE EXPECT AN EXPLANATION AT ALL?

As a framework for my discussion, I shall first characterize the notion of scientific reduction, as we understand it from examples in the history of science. In its starkest description, a reduction is an explanation of some macrolevel phenomenon in terms of the organization and constituents of some lower level microphenomenon. That is, the macro properties are discovered to be the outcome of the nature of the elements at the microlevel, together with their dynamics and interactions. In the classic examples, this means that the causal powers of the macro phenomenon are explained as a function of the dynamics and causal powers of the micro phenomenon. Is the function a simple function -- such as that the "whole is nothing but the sum of the parts"? Virtually never. Summation is a supremely simple function, and macro properties such as temperature in a gas, or reflection of light or being a visible spark or inheriting red hair are anything but simple functions of their causally potent underlying structures.

    What does the history of science reveal about reductive explanations that might be helpful in understanding the issue before us? Let me t ry to answer this by briefly discussing three cases. The first concerns the discovery that we could identify temperature in a gas as the mean kinetic energy of its constituent molecules. This then permitted coherent, unified explanation of temperature phenomena such as conduction, of why temperature and pressure are related in the way they are, of why heated things expand. The first success with gases allowed the extension of the explanatory framework to embrace liquids and solids, and eventually plasmas and even empty space. As a theory, it was far more successful than the caloric theory, which postulated a subtly compressible fluid as increasing in volume when a things temperature increases. Substances differ in the rate at which caloric can flow through them, and at which they can acquire or lose caloric. The explanation of the nature of light can be seen as another successful example of scientific reductionism. In this instance, the macro theory (optics) came to be seen as explainable in terms of micro theory (theory of electromagnetic radiation); visible light turned out to be EMR, along with X-rays, utlraviolet rays, radio waves, and so forth. Note also that here, as elsewhere, further questions always remain to be answered, and hence there is a sense in which the reduction is typically incomplete.

     If the overarching mysteries are resolved, however, that is usually sufficient for scientists to consider an explanation -- and hence a reduction -- to be essentially in place. Reductions can be very messy, in the sense that the mapping of properties from micro to macro can be one: many or even many: many, rather than the ideal, 1:1. While the case of light reducing to EMR is relatively clean, the case of phenotypic traits and genes is far less clean. Genes, as we now know, cannot be counted on to be single stretches of DNA, but may involved distinct segments of DNA. Additionally, a given gene may participate in different macro properties as a function of prior conditions. (Kitcher 1984)

     Nevertheless, many molecular biologists see their explanatory framework as essentially reductive in character, mainly because a causal route from base-pair sequences to traits such as Huntington's disease can be traced or at the very least, sketched in outline. The details can be expected to be filled out as experimental results come in. On the other hand, the lack of a clean line has prompted some philosophers, for example Philip Kitcher, to propose that perhaps these messy cases are best thought of not genuinely reductive. I view that as essentially a semantic recommendation, which promises some clarity in understanding, but which also has the drawback that in fact most scientists view molecular biology as impressive instance of reductive explanation -- incompleteness, messiness, and complexity notwithstanding. I am inclined to stick with the word 'reduction', despite the complications in the biological domain, because there is really nothing suitable to take its place, and because linguistic inertia is usually a sign that current usage is in fact useful. Given this general characterization of reduction and reductionism, I shall now address five skeptical problems.

1. SHOULD WE EXPECT CONSCIOUSNESS TO "GO AWAY"?

One difficulty, according to the skeptics, is that if consciousness is reduced to neuronal activities, then we are landed in the absurd position of saying that my pains, tastes and so forth are not real. (Searle, 1993) This worry is, in my view, based on misinformation concerning what reductions in science do and do not entail. The short answer to the topic question, therefore, is "No: pains will not cease to be real just because we understand the neurobiology of pain." That is, a reductive explanation of a macro phenomenon in terms of the dynamics of its microstructural features does not mean that the macro phenomenon is not real or is scientifically disreputableor somehow explanatorily unworthy or redundant. Even after we achieved an explanation of light in terms of EMR, theory of optics continues to be useful, to discover new things. Nobody thinks light is not real, as result of Maxwell's equations. Rather, we think we understand more about the real nature of light than we did before 1873.

     Light is real, no doubt about it. But we now see visible light as but one segment of a wider spectrum that includes x-rays, ultraviolet, and radio waves. We can now explain a whole lot at the macro level that we were unable to explain before, such as why a beam of light passed through a narrow slit shows a two-smudge interference pattern. Somewhat similar comments can be made concerning the aftermath of the reductive achievement of statistical mechanics.

     Temperature is taken to be a real property, and the study of the macro level itself remains in good standing. Thermodynamics continues to be capable of revealing new and interesting scientific truths, despite the existence of statistical mechanics, and indeed it is well-aided by its undergirding. Sometimes, however, hitherto respectable properties and substances do turn out to be unreal. The caloric theory of heat, for example, did not survive the rigors of science, and caloric fluid turned out not to be real. The theory was explanatorily problematic, especially when it had to address this problem: if heat from rubbing is to be explained by release of caloric in the spaces between the atoms, it should run out after a while. But, oddly for the theory, rubbing can be continued indefinitely and the heat does not stop being produced. If anything, rubbed things get hotter the longer they are rubbed. The molecules-in-motion approach could explain this quite simply: macro motion is translated into micro motion.

    Caloric theory also stumbled in its energy calculations for steam engines. On the caloric accounting, some caloric had to have disappeared by the end of a period of steam-engine activity, but the data proved otherwise. The molecules-in-motion theory got the accounting correct, because it claimed that the micro motions (heat) were transformed into macromotions -- movement of the engine wheel. In the end, caloric fluid was no match for molecular motion as an approach to thermal phenomena. Theories range themselves on a spectrum of how little or how much of the macro theory comes to be modified as a result of increasing explanatory reach of the micro theory. Revision of hypotheses is a major hallmark of science and how it makes progress, so it is no surprise to see revision as reductive macro-micro progress is made. The degree of revision required will obviously vary from case to case, and will depend on how the facts fall out. What will be the fate of our current conception of 'consciousness' as we discover more about the nature of the brain will depend on the facts of the matter and the long-term integrity of current macrolevel concepts. (See P. M. Churchland 1994)

     Some revisions to the concept of consciousness, as it stood circa 1950, are already in evidence owing to the impact of data on core beliefs about consciousness. The discovery by Sperry and his colleagues concerning the effects of commissurotomy did, I think, make it evident that unity in conscious experience has a lot to do with connections in brain wiring, and hence was not a kind of transcendental necessity. Research on sleep and dreaming revealed that there was far more dreaming going on the introspection was led to believe, and that even in matters of dream content, considerations of learning and "neural housekeeping" probably play at least as important a role as conflict-resolution or wish-fulfillment. In addition, the regularity in nightly cycles of behavioral state and their control brain stem mechanisms such as the locus ceruleus and the giant neurons on the pons strongly implicate a neurobiological, rather than a psychological explanation.

     The discoveries concerning the biological parameters of dreaming has been critical in shifting our understanding away from a Freudian or Jungian conception of the nature and significance of dreaming to a more biologically based conception. (E. g. Hobson, 1988) Blindsight constitutes another phenomenon where research revealed something very disruptive to our a priori assumptions: conscious, deliberate behavior could be based on visual signals of which the subject had no visual experience (Weiskrantz 1986, 1997). Initially, many philosophers found this so counter-intuitive as to be a violation of rationality itself, though it has now become accepted as s puzzling phenomenon whose empirical basis can be studied.

     Of comparable significance is the discovery that even in perception, introspective data can mislead us concerning the nature of the psychological processes involved. There are many examples here, but perhaps an especially dramatic one is the finding that in visual perception, only a tiny area (about 2 degrees) of the visual field is foveated and hence perceived in crisp detail at any given moment. Saccades, made about every 300 msec, and neuronal integration of signals across saccadic movement, contribute to the illusion full-field detail. Additionally, a whole range of data from neurology -- from anosognosia to the amnesias to Balint's syndrome -- showed that conscious belief structures are not organized strictly according to the canons of logic.

     The possibility that conscious experience may well be an assortment of various capacities flying in loose formation is now uncontroversial, but a mere twenty years ago it seemed outrageous. By the 1990's, it has been generally acknowledged that quite different phenomena, such as (a) perceptual awareness, (b) something like metacognition (knowing that you do not know how many second cousins you have) and (c) knowing that you want to convert your bonds to stocks, may be subserved by rather different neurobiological mechanisms. In sum, the short answer to the lead question, "should we expect consciousness to go away?" is this: "No." The various phenomena we group together as conscious phenomena will not, of course, go away. Nevertheless, we may come to conceptualize them in somewhat different -- and perhaps even very different -- ways.


2. SHOULD WE EXPECT CONSCIOUSNESS TO BE EMERGENT?

As a prelude to warning neuroscience off the topic, we are often told that consciousness is an emergent property. But what does it mean to call a property 'emergent'? On one version, it means that there can be no explanation of that property in micro terms. Consequently, if it is then claimed that consciousness cannot be explained because it is emergent, that simply comes to this obviously circular hypothesis: consciousness cannot be explained because it cannot be explained.

     To avoid the circularity, some (Broad 1951, Popper 1978) have suggested a more careful meaning of 'emergent': if a property is emergent, then it cannot be predicted from knowledge of the microproperties. For example, it is alleged that even if you did know all the microproperties of water, you could not predict that it would be wet. If the macroproperty cannot be predicted from knowledge of the micropoperties, the story goes, then science will never be able to explain it as the outcome of microproperties. This view tends to see prediction and explanation as two sides of the same coin.

     Philosophers have objected to this on grounds that prediction and explanation are not in fact complementary, as the metaphor implies. It is generally considered that physics does have an explanation for the wetness of water, whether or not anyone could have predicted it from the micro properties. Additionally, there is a logical reason why predictability does not work very well as a criterion for eventual explainability: the very same ideas that support the hunch that something cannot be explained are invoked to support the premise that no one could predict the macro property even if they knew the microstructure. Thus there is a circularity here as well. Broad thought it would help if you took the predictor to be an archangel, and others have suggested an omnipotent god might serve in that role. Thought-experiments that depend on agreeing what a very smart archangel might or might not be able to predict tend to lack credibility and certainly lack consensus, and I confess I do not find them very helpful as a index of anything.

     Perhaps the most sophisticated argument on this approach is owed to the Australian philosopher Frank Jackson (1982). In sum, Jackson's idea was that there could exist someone, call her Mary, who knew everything there was to know about how the brain works but still did not know what it was to see the color green (suppose she lacked "green cones and wiring", to put it crudely.) This possibility Jackson took to show that qualia (the visual experience itself) are therefore not explainable by science. That is, if qualia were just patterns of neural activity, then if Mary knows what neural activity allegedly constitutes having a visual experience of green, then she should know what green qualia are like. There are various weaknesses in this argument, but the main problem with the argument is that to experience green (have green qualia), certain wiring has to be in place in Mary's brain, and certain patterns of activity have to obtain. Since, by Jackson's own hypothesis, she does not have that wiring, then presumably the relevant activity patterns in visual cortex are not caused and she does not experience green. Her knowing all of the relevant neurobiology (not unlike Broad's imagined archangel) presumably involves propositional knowledge, and probably the learning is widely distributed in the brain.

     Who would expect her visual cortex -- V4, let us suppose -- would be activated in the "green qualia" pattern just by virtue of her propositional (linguistic) knowledge about activity patterns in V4? Not me, anyhow. Jackson's argument has to assume that either knowing the neurobiology of "green qualia" somehow will bring about experiencing green qualia or that qualia are not scientifically approachable. But both alternatives are probably false. I suppose knowing the neurobiology of "green qualia" could somehow or other bring about experiencing green qualia, but I see no reason to expect that it should. Via channels bypassing the color circuits, Mary can have propositional knowledge, including the knowledge of what her own brain lacks in terms of "green-qualia-wiring". As Paul Teller (1992) puts it, the subjectivity of the experience is just the having of the experience, not some ineffable kind of knowledge. Nothing whatever follows about whether science can or cannot explain qualia. Within neuroscience, there is a useful and nonmystical notion of emergence: a property is emergent if it is a network property -- if it is the outcome of the intrinsic properties of the neurons, together with the way they interact. In this less metaphysical sense, the rhythmicity of the stomatogastric ganglion of the lobster is an emergent property.
(Selverston and Moulins 1987) One reason to prefer this more neutral meaning of "emergent" is that it leaves open the question of whether a property is emergent because it is an explainable network property, or because it is an unexplainable nonphysical property. (See Bechtel and Richardson 1993 for a general discussion of these issues. )


3. SHOULD WE EXPECT THAT I COULD KNOW WHAT YOU EXPERIENCE?

This question is most pointedly raised in the context of the inverted spectrum problem, and I shall address it in that form. To illustrate, consider the possibility that your color experiences (color qualia) might be systematically inverted relative to mine; e. g. where you see red, I see green, and so on. Noting that there could be systematic behavioral compensation that would cover experiential differences, skeptics have urged that even looking inside would be unavailing . Allegedly, no conceivable test could ever reveal similarity or inversion in our color experiences. The lesson we are invited to draw is that consciousness is intractable scientifically because inter-subjective comparisons are impossible. Some philosophers think that this is not merely a problem about what we can and cannot know, but evidence that consciousness is a metaphysically different kind of thing from brain activity. In addressing this issue, I shall make one assumption: that conscious experiences are in some systematic causal connection to neuronal activity. That is, they are not utterly independent of the causal events in the brain.

     To deny the assumption is to slide into a version of dualism known as "psycho-physical parallelism", meaning that mental events and physical events are completely independent of each other causally, and just happen, amazingly enough, to run in parallel "streams". Normal human color vision is known to depend three cone types, each of which is tuned to respond to light of particular wavelengths. Cone inputs are coded by color-opponent cells in the retina and lateral geniculate nucleus, and project to double-opponent cells in the parvocellular-blob pathways of the cortex. Cells in cortical area V4 appear to code for color regardless of wavelength composition of the light from the stimulus, and appear to subserve the perceptual phenomenon known as color constancy. Lesions to the cortical area known as V4 result in achromatopsia (loss of all color perception), in humans and monkeys. Also relevant to behavioral determinations of differences in experience is the fact that the relations between hue, chroma (saturation) and value (lightness) define an asymmetric solid (Munsell color quality space). This implies that radical differences in perception should be detectable behaviorally, given suitable tests. That is, "A is more similar to B than to C" relations between colors are defined over the Munsell quality space, and if there is red/green inversion, the similarity relations to yellow, orange, pink etc. will not remain the same.

     Given the progress to date, it seems likely that the basic neurobiological story for color processing can be unraveled. For similar reasons, it looks likely that the basic story for touch discrimination and its mechanisms in the somatosensory thalamus and cortex can also be unraveled. For example, it seems evident that if someone lacks "green" cones, or lacks "red/green opponent cells, or lacks a V4, they will not experience the visual perception of green. Comparable circuitry and comparable behavioral discriminations seem to be presumptive of comparable experiences; that is, comparable qualia. (Clark 1993) The skeptic, however, insists that no data -- not behavior, not anatomy, not physiology -- could ever reveal qualia inversion. Incidentally, what is at issue here is not that minor differences in such things as hue or brightness might go undetected, but that even huge differences, such as red/green inversions or brightness/dullness inversion, might be in principle absolutely undetectable. To approach this matter somewhat indirectly, let us first consider a vivid example where it is evident that a perceptual inversion is likely detectable, namely, inverted "shape" qualia. Could Alphie have "straight qualia" whenever Betty has "curved qualia" (and vice versa) and the difference be absolutely undetectable? In this example, because two modalities -- vision and touch -- can access the external property, it seems easier to agree that together, behavioral data and wiring data permit us to make a reasonable determination of similarity and differences. That is, the problem is not essentially less tractable than determining whether two people digest food in the same way or wherther two cats in free fall right themselves in the same way.

     Much the same is usually conceded for pleasure/pain inversion, and within vision, of near/far inversion in stereopsis. Random dot streograms are already a very reliable determinant of (a) whether a subject has stereopsis at all, and (b) whether there is an inversion between two subjects. If we factor in data from "near/far" cells in V1, then insisting upon absolute undetectability begins to look unreasonable. It seems a bit like insisting that it is absolutely undetectable whether the universe was created five minutes ago, complete with all its geological records, its fossil records, history books, and my memories etc.

     Skepticism carried to that extreme just ceases to be scientifically intersting, and becomes philosophical in the pejorative sense of the term. In the case of "shape inversion", the skeptic can remain a skeptic by going one of two ways, neither of which helps his sweeping anti-reductionist defense: (1) no qualia -- not shape, not temperature, not pain not any qualia-- can be compared across subjects, even to a degree of probability. They are one and all, absolutely incomparable. For all I could ever know, you might experience the color red when I experience pain. (2) The neurobiology of shape qualia (rough/smooth, etc.) can be compared, and perhaps even the neurobiology of stereopsis, but color vision is different. The first appears to depend only on an anti-reductionist resolve, without any independent argument. In that case, we really are looking at a circular argument. The only escape from the circle is to fall into the embrace of dualism -- and worse, of the deeply implausible psycho-physical parallelism rendition of that already implausible doctrine. The second makes a major concession so far as qualia in general are concerned. Having conceded that some qualia are scientifically approachable, the skeptic no longer shields subjectivity as such, but only subjectivity for certain classes of experience, namely color vision. This looks far less powerful that the original position, and it starts the skeptic down a slippery slope. For having made this concession, it now becomes easier for the reductionist to push hard on the point that comparisons in receptor properties, wiring properties, connectivity to motor control, and so forth, will augment -- as it already does -- behavioral data, and allow us to compare capacities across individuals. And similar arguments can be made for other single modality experiences: stereopsis, sound, pain, temperature, feeling nauseous, feeling dizzy etc. That is, as long as awareness of color has a causal structure in the brain -- as long as it is not a property of soul-stuff utterly detached from all causal interaction with the brain -- data from psychology (e. g. the color-hue relationships ) and neuroscience (tuning curves for the three cone types in the retina, wiring from the retina to cortex and intracortically) predicts that big differences in color perception will correlate with big differences in wiring and in neuronal activity. In the context of a more detailed knowledge of the brain in general, rough comparisons between individuals ought to be achievable, subject to the usual qualifications unavoidable in any science. (For a more thorough examination of this matter, see Austen Clark's outstanding book Sensory Qualities, 1993).

4. SHOULD WE EXPECT EXPLANATIONS OF WHAT IS GOING ON IN SOMEONE'S MIND, MOMENT BY MOMENT?

The question of how detailed a theory has to be in order to count yielding an explanation is not straightforward, and varies with the motivations for wanting an explanation. The desire to control a phenomenon, or to predict exactly what will happen next, may require more detail that the desire to grasp the general go of it. Thus we basically do understand the weather, but because it is a complex dynamical system with many variables, we cannot predict exactly where a tornado will form or where within inches or even kilometers it will move once formed. On the other hand, sometimes good intervention in a phenomenon can be achieved with minimal understanding, as when lithium salts werefound to bring manic-depression under control but almost nothing was understood about how this was achieved. The complexity of the human nervous system makes detailed, moment-to-moment prediction highly unlikely. Additionally, intervention in the system to obtain the data on the relevant parameters, perhaps neuron by neuron, would change the basic conditions and frustrate the prediction. Certainly at this stage we have no non-invasive technology at the neuronal level of resolution to achieve that end.

     The same, however, is true of predicting exactly where Tony Gwynn will hit a baseball. Measurements to obtain the data will change the data, and there are too many variables to compute. As a practical matter, therefore, thought-by-thought monitoring looks unlikely. Consequently, I suspect that determining from his neuronal profile, moment by moment, whether someone will choose a Ford Bronco or a Chevy Yukon is not a reasonable goal for the near future, though for all one can be sure now, advances in technology may improve predictions.

    As with predicting the weather, data does narrow the range of possible outcomes, and together certain general assumptions, reasonably close predictions are possible. Predicting such matters as attentional shifts or coming to a decision may well be possible, just as one can make a very good guess where Gwynn will hit if you know Gwynn's batting history, the strengths and weaknesses of team in the field, the pitcher's repertoire and his history in this game, and who is on base.

5. SHOULD WE EXPECT A REDUCTION ROM THE BEHAVIORAL LEVEL DIRECTLY TO THE NEURONAL LEVEL?

Nervous systems appear to have many levels of organization, ranging in spatial scale from molecules such as serotonin, to dendritic spines, neurons, small networks, large networks, areas, and systems. Although it remains to be determined empirically what exactly are the functionally significant levels, it is unlikely that explanations of macro effects such as perceiving motion will be explained directly in terms of the most micro level. More likely, high-level network effects will be the outcome of smaller networks, and those effects in turn of the participating neurons and their interconnections, and those in turn of the properties of protein channels, neuromodulators and neurotransmitters, and so forth. One misconception about the reductionist strategy dubs it as seeking a direct explanatory bridge between highest level and lowest levels. This idea of "explanation-in-a-single-bound" does stretch credulity, but neuroscientists are not remotely tempted by it. In contrast, the view I am advocating here prefers to predict that reductive explanations will proceed step-wise from highest to lowest, always agreeing of course that the research should proceed at all levels simultaneously.
(Churchland and Sejnowski 1992)

III USING IGNORANCE AS PREMISE

Perhaps the most common argument of those skeptical of neurobiological progress consists in stressing what we do not know, and using this as a basis for arguing about what we cannot know. McGinn, for example, repeatedly insists that the problem of how the brain could generate consciousness is "miraculous, eerie, even faintly comic" (p.
99). Finding the problem difficult, he concludes, "This is the kind of causal nexus we are precluded from ever understanding, given the way we have to form our concepts and develop our theories." (P. 100). McGinn is by no means alone here. Fodor too thinks he can already tell that the question is unanswerable -- not just now, not just given what we know so far, from unanswerable ever. Vendler mocks the ambitions of neuroscience by saying that it is obvious, from, the nature of sensation, that our sensing selves "are in principle beyond what science can explain." That we are trying to unravel the mystery is, in Vendler's view, a consequence of the overweening assumption that there are no questions science cannot answer. In general, what substantive conclusions can be drawn when science has not advanced very far on a problem? Not much.

     One of the basic skills we teach logic students is how to recognize and diagnose the range of nonformal fallacies that can undermine an ostensibly appealing argument: what it is to beg the question, what a non sequitur is, and so on. A prominent item in the fallacy roster is argumentum ad ignorantiam -- argument from ignorance. The canonical version of this fallacy uses ignorance as the key premise from which a substantive conclusion is drawn. The canonical version looks like this: We really do not understand much about a phenomenon P. (Science is largely ignorant about the nature of P.) Therefore: we do know that:
(1) P can never be explained or (2) Nothing science could ever discover would deepen our understanding of the phernomenon P. or (3) P can never be explained in terms of properties of kind S.

     In its canonical version, the argument is obviously a fallacy: none of the tendered conclusions follow, not even a little bit. Surrounded with rhetorical flourish, much brow furrowing and hand-wringing, however, versions of this argument can hornswoggle the unwary. From the fact that we do not know something, nothing very interesting follows -- we just don't know. Nevertheless, the temptation to suspect that our ignorance is telling us something positive, something deep, something metaphysical or even radical, is ever-present. Perhaps we like to put our ignorance in a positive light, supposing that but for the Profundity of the phenomenon, we would have knowledge. But there are many reasons for not knowing, and the specialness of the phenomenon is, quite regularly, not the real reason. I am currently ignorant of what caused an unusual rapping noise in the woods last night. Can I conclude it must be something special, something unimaginable, something.... alien ... other-worldly? Evidently not. For all I can tell now, it might merely have been a raccoon gnawing on the compost bin. Lack of evidence for something is just that: lack of evidence. It is not positive evidence for something else, let alone something of a humdingerish sort. That conclusion is not very glamorous perhaps, but when ignorance is a premise, that is about all you can grind out of it. Now if neuroscience had progressed as far on the problems of brain function as molecular biology has progressed on transmission of hereditary traits, then of course we would be in a different position. But it has not. The only thing you can conclude from the fact that attention is mysterious, or sensorimotor integration is mysterious, or that consciousness is mysterious, is that we do not understand the mechanisms. Moreover, the mysteriousness of a problem is not a fact about the problem, it is not a metaphysical feature of the universe -- it is an epistemological fact about us. It is about where we are in current science, it is about what we can and cannot understand, it is about what, given the rest of our understanding, we can and cannot imagine. It is not a property of the problem itself. It is sometimes assumed that there can be a valid transition from "we cannot now explain" to "we can never explain" , so long as we have the help of a subsidiary premise, namely, "I cannot imagine how we could ever explain..." . But it does not help, and this transition remains a straight-up application of argument from ignorance. Adding "I cannot imagine explaining P" merely adds a psychological fact about the speaker, from which again, nothing significant follows about the nature of the phenomenon in question.

     Whether we can or cannot imagine a phenomenon being explained in a certain way is a psychological fact about us, not an objective fact about the nature of the phenomenon itself. To repeat, it is an epistemological fact -- about what, given our current knowledge, we can and cannot understand. It is not a metaphysical fact about the nature of the reality of the universe. Typical of vitalists generally, my high school biology teacher argued for vitalism thus: I cannot imagine how you could get living things out of dead molecules. Out of bits of proteins, fats, sugars -- how could life itself emerge? He thought it was obvious from the sheer mysteriousness of the matter that it could have no solution in biology or chemistry. He assumed he could tell that it would require a Humdinger solution. Typical of lone survivors, a passenger of a crashed plane will say: I cannot imagine how I alone could have survived the crash, when all other passengers died instantly. Therefore God must have plucked me from the jaws of death. Given that neuroscience is still very much in its early stages, it is actually not a very interesting fact that someone or other cannot imagine a certain kind of explanation of some brain phenomenon.

     Aristotle could not imagine how a complex organism could come from a fertilized egg. That of course was a fact about Aristotle, not a fact about embryogenesis. Given the early days of science (500 BC), it is no surprise that he could not imagine what it took many scientists hundreds of years to discover. I cannot imagine how ravens can solve a multi-step problem in one trial, or how temporal integration is achieved, or how thermoregulation is managed. But this is a (not very interesting) psychological fact about me. One could, of course, use various rhetorical devices to make it seem like an interesting fact about me, perhaps by emphasizing that it is a really really hard problem, but if we are going to be sensible about this, it is clear that my inability to imagine how thermoregulation works is au fond, pretty boring. The "I-cannot-imagine" gambit suffers in another way. Being able to imagine an explanation for P is a highly open-ended and under-specified business. Given the poverty of delimiting conditions of the operation, you can pretty much rig the conclusion to go whichever way your heart desires. Logically, however, that flexibility is the kiss of death. Suppose someone claims that she can imagine the mechanisms for sensorimotor integration in the human brain but cannot imagine the mechanisms for consciousness. What exactly does this difference amount to? Can she imagine the former in detail? No, because the details are not known.


     What is it, precisely, that she can imagine? Suppose she answers that in a very general way she imagines that sensory neurons interact with interneurons that interact with motor neurons, and via these interactions, sensorimotor integration is achieved. Now if that is all "being able to imagine" takes, one might as well say one can imagine the mechanisms underlying consciousness. Thus: "The interneurons do it." The point is this: if you want to contrast being able to imagine brain mechanisms for attention, short term memory, planning etc., with being unable to imagine mechanisms for consciousness, you have to do more that say you can imagine neurons doing one but cannot imagine neurons doing the other. Otherwise one simply begs the question. To fill out the point, consider several telling examples from the history of science.

     Before the turn of the twentieth century, people thought that the problem of the precession of the perihelion of Mercury was essentially trivial. It was annoying, but ultimately, it would sort itself out as more data came in. With the advantage of hindsight, we can see that assessing this as an easy problem was quite wrong -- it took the Einsteinian revolution in physics to solve the problem of the precession of the perihelion of Mercury. By contrast, a really hard problem was thought to be the composition of the stars. How could a sample ever be obtained? With the advent of spectral analysis, that turned out to be a readily solvable problem. When heated, the elements turn out to have a kind of fingerprint, easily seen when light emitted from a source is passed through a prism. Consider now a biological example. Before 1953, many people believed, on rather good grounds actually, that in order to address the copying problem (transmission of traits from parents to offspring), you would first have to solve the problem of how proteins fold. The former was deemed a much harder problem than the latter, and many scientists believed it was foolhardy to attack the copying problem directly.

     As we all know now, the basic answer to the copying problem lay in the base-pairing of DNA, and it was solved first. Humbling it is to realize that the problem of protein folding (secondary and tertiary) is still not solved. That, given the lot we now know, does seem to be a hard problem. What is the point of these stories? They reinforce the message of the argument from ignorance: from the vantage point of ignorance, it is often very difficult to tell which problem is harder, which will fall first, what problem will turn out to be more tractable than some other. Consequently our judgments about relative difficulty or ultimate tractability should be appropriately qualified and tentative.

     Guesswork has a useful place, of course, but let's distinguish between blind guesswork and educated guesswork, and between guesswork and confirmed fact. The philosophical lesson I learned from my biology teacher is this: when not much is known about a topic, don't take terribly seriously someone else's heartfelt conviction about what problems are scientifically tractable. Learn the science, do the science, and see what happens. When McGinn says we have been working on the problem of consciousness for a long time, he seems surprisingly innocent of what it takes to even begin to study the brain basis for the phenomenon. Whereas groundbreaking discoveries in astronomy could be made with a crude telescope, as when Galileo discovered the moons of Jupiter, Figuring out how neurons do what they do requires high-level technology. And that, needless to say, depends on immense infrastructural science; on cell biology, advanced physics and twentieth century chemistry. It requires sophisticated modern notions like molecule and protein, and modern tools like the light microscope and the electron microscope.

     Most importantly, making progress in how brains work depended on understanding electricity. This is because what makes brain cells special is their capacity to signal one another by causing micro changes in each others' electrical state. Living as we do in an electrical world, it is sobering to recall that as late as 1800, electricity was typically considered deeply mysterious and quite possibly occult. Only after discoveries by Ampere and Faraday at the dawn of the 19th century was electricity clearly understood to be a physical phenomenon, behaving according to well-defined laws, and capable of being harnessed for practical purposes. Finally, consider Vendler's admonition: we cannot expect to solve all problems, answer all questions. Let's agree with him -- some questions may never be answered. What follows from that so far as this problem -- the problem of the neurobiology of consciousness -- is concerned? Absolutely nothing. Suppose this problem is really very hard. What follows from that? Nothing. We cannot tell, from the vantage point of ignorance, that a given problem cannot be solved. Problems do not come with the information "I am unsolvable" pinned to their shirts.

IV CONCLUSIONS:

Given the current state of cognitive science and neuroscience, it is reasonable to expect we shall understand more about the nature of consciousness as more is revealed about how in general the brain works (Llinas and Pare 1996). In particular, with increased understanding of the nature of sensory systems, attentional mechanisms, short term memory, working memory, dreaming, imagery, planning and so forth, probably the neurobiology of consciousness will come into focus (Crick 1993; Paul M. Churchland 1994, 1996). Clearly, we need to understand in detail the role of back projections (re-entrant signaling) in such phenomena as filling-in and complex pattern recognition (Edelman 1992).

     We need to understand the meaning of the physiological data on binocular rivalry (Leopold and Logothetis 1996), as well as the significance of neuropsychological phenomena such as illusions of body-image and confabulation (Gazzaniga and LeDoux 1978; Ramachandran et al. 1996). Undoubtedly there will be many surprises along the way, and some discoveries may cause us to reconceptualize the very problem itself. Though each the of the skeptical arguments considered here command powerful intuitive appealing and for that reason alone must be taken seriously, none commands significant credence once examined and analyzed. That they are flawed does not, of course, show that neuroscience will in fact be successful in expanding our understanding of consciousness, only that the skeptics conclusions regarding the mere possibility are unconvincing.

REFERENCES:

Bechtel, William and Robert Richardson (1993). Discovering Complexity: Decomposition and Localization as Strategies in Scientific Research. Princeton: Princeton University Press.
Broad, C. D. (1951). The Mind and its Place in Nature. London: Routledge & Kegan Paul.
Churchland, Patricia S. And Terrence J. Sejnowski (1992). The Computational Brain. Cambridge, MA: MIT Press.
Churchland, Patricia S. (1996). "The hornswoggle problem." Journal of Consciousness Studies. @@
Churchland, Paul M. (1987). Matter and Consciousness, Second Edition. Cambridge MA: MIT Press.
Churchland, Paul M. (1994). The Engine of Reason, The Seat of the Soul. Cambridge MA: MIT Press.
Churchland, Paul M. (1996). "The rediscovery of light". Journal of Philosophy. 93: 211-228.
Churchland, Paul M. and Patricia S. (forthcoming). "Recent work on consciousness: philosophical, theoretical and empirical." Seminars in Neuroscience.
Clark, Austen (1993). Sensory Qualities. Oxford: Clarendon Press.
Crick, Francis (1994). The Astonishing Hypothesis. New York: Scribner's.
Dennett, Daniel C. (1991). Consciousness Explained. New York: Little, Brown.
Edelman, Gerald (1992). Bright Air, Brilliant Fire. New York: Basic.
Flanagan, Owen (1992). Consciousness Reconsidered. Cambridge MA: MIT Press.
Flohr, Hans (1992). "Qualia and brain processes." In: Emergence or Reduction. Ed. By A. Beckermann, H. Flohr, J. Kim. New York: Gruyter. 220-240.
Gazzaniga, M. S. and J. E. LeDoux (1978). The Integrated Brain. New York: Plenum Press.
Hobson, Allan (1988) The Dreaming Brain. New York: Basic Books.
Jackson, Frank (1982). "Epiphenomenal qualia". Philosophical Quarterly. Vol. 32. 127-136.
Kitcher, Philip (1984). "1953 and all that. A tale of two sciences." Philosophical Review 43: 335-74.
Leopold, David A. and Nikos Logothetis (1996). "Activity changes in early visual cortex reflect monkeys' percepts during binocular rivalry." Nature. 379: 549- 553.
Llinas, R. R. And D. Pare (1996). "The brain as a closed system modulated by the senses." In: The Mind-Brain Continuum. Ed. By R. R. Llinas and P. S. Churchland. Cambridge MA: MIT Press. 1-18.
McGinn, Colin (1989) "Can we solve the mind-body problem?". Mind. 98:349-66. Reprinted in: The Mind-Body Problem: A Guide to the Current Debate. Ed. by R. Warner and T. Szubka (1994), Oxford: Blackwells. 99-120.
Nagel, Thomas (1994). "Consciousness and objective reality." In: The Mind-Body Problem: A Guide to the Current Debate. Ed. by R. Warner and T. Szubka (1994), Oxford: Blackwells. 63-8.
Popper, Karl. (1978) The Self and Its Brain: Part I. New York: Spring-Verlag.
Ramachandran, V. S., L. Levi, L. Stone, D. Rogers-Ramachandran, R. McKinney, M. Stalcup, G. Arcilla, R. Zweifler, A. Schatz, and A. Flippin. (1996) "Illusions of body-image: What they reveal about human nature." In: The Mind-Brain Continuum. Ed. by R. R. Llinas and P. S. Churchland. Cambridge, MA: MIT Press. 29-60.
Searle, John (1992). The Rediscovery of the Mind. Cambridge MA: MIT Press.
Selverston, A. I. And M. Moulins (1987). The Crustacean Stomato-gastric System: A Model for the Study of Central Nervous Systems. Berlin: Springer-Verlag.
Swinburne, Richard (1994). "Body and Soul". In: The Mind-Body Problem: A Guide to the Current Debate. Ed. by R. Warner and T. Szubka (1994), Oxford: Blackwells. 311-316.
Teller, Paul (1992). "Subjectivity and knowing what it's like". In: Emergence or Reduction. Ed. By A. Beckermann, H. Flohr, J. Kim. New York: Gruyter. 180- 200.
Van Gulick, Robert (1995). "What would count as explaining consciousness?" In: Conscious Experience. Ed. by T. Metzinger. Lawrence, Kansas: Allen Press.
Vendler, Zeno (1994). "The ineffable soul." In: The Mind-Body Problem: A Guide to the Current Debate. Ed. by R. Warner and T. Szubka (1994), Oxford: Blackwells. 317-28.
Warner, Richard (1994). "In defense of a dualism". In: The Mind-Body Problem: A Guide to the Current Debate. Ed. by R. Warner and T. Szubka (1994), Oxford: Blackwells. 343-354.
Weiskrantz, Laurence (1986). Blindsight: A Case Study and Implications. Oxford: Oxford University Press.
Weiskrantz, Laurence (1997). Consciousness Lost and Found. Oxford: Oxford University Press.

Patricia Smith Churchland

 Born: July 16, 1943
 Citizenship: USA/Canada
 Permanent Resident U.S.A.
 Married: Paul M. Churchland, Ph. D.
 Children: Mark M. Churchland (1972)
 Anne K. Churchland (1974)

 Address: Philosophy Department 0119
 University of California San Diego
 La Jolla CA 92093
 Telephone: 619-534-6811
 Internet: pschurchland@ucsd.edu

Fields Of Specialization
Philosophy of Neuroscience
Philosophy of Mind
Philosophy of Science
Environmental Ethics

Educational History
University of British Columbia, 1961-65, B.A. (hons.)
University of Pittsburgh, 1965-66, M.A.
Oxford University, 1966-69, B. Phil.

Employment History
Assistant Professor, University of Manitoba, 1969-1977
Associate Professor, University of Manitoba, 1977-82
Visiting Member, Institute for Advanced Study, Princeton, 1982-83
Full Professor, University of Manitoba, 1983-84
Full Professor, University of California, San Diego, 1984 -

Academic Awards And Grants
Woodrow Wilson Fellow, 1965-66
British Council Fellow, 1966-67
Canada Council Fellow, 1967-69
Canada Council Research Grant, 1975-76
Woodrow Wilson Faculty Development Award, 1978
Social Sciences and Humanities Research Council Leave Fellowship, 1979-80
Social Sciences and Humanities Research Council Research (SSHRC) Grant, 1979-80.
University of Manitoba SSHRC Research Grant, 1980
University of Manitoba SSHRC Research Grant, 1980-1
Philosopher's Annual (one of ten best articles) 1980
SSHRC Research Time Stipend, 1981-83
Rh Institute Research Grant for Outstanding Contributions to Inter-Disciplinary Research and Scholarship, 1981
SSHRC Department of International Relations Grant, 1982
Soc. Sc. & Hum. Research Council Leave Fellowship, 1983-84
Soc. Sc. & Hum. Research Council Research Grant, 1983-84
UCSD Senate Research Grant 1984-84
UCSD Senate Research Grant 1985-86
UCSD Senate Research Grant 1986-87
USCD Senate Research Grant 1987-88
National Science Foundation (NSF) Research Grant 1987-1989
James S. McDonnell Research Grant 1988-89
Faculty Research Lecture Award (UCSD) 1988
Chancellor's Associate Award (UCSD) 1988
James S. McDonnell Research Grant 1989-90
UCSD Senate Research Grant 1990-91
Adjunct Professor, Salk Institute, 1989-
UC President's Fellowship in the Humanities 1990-91
MacArthur Foundation Research Fellow, 1991-96
Elected, Academy of Humanism, 1993
Honorary Doctor of Letters, University of Victoria, 1996
 

Publications

Books
Neurophilosophy: Toward a Unified Science of  the  Mind-Brain.  (1986)  Cambridge, Mass.: MIT Press.

The Computational Brain.  (1992)  P. S. Churchland and T.J. Sejnowski.  Cambridge, Mass.: The MIT Press.
_____Italian Translantion, Il Cervello Computazionale (1995)  il Mulino: Bologna

Neurophilosophy and Alzheimer's Disease.  (1992)  Ed. by Y. Christen and P. S. Churchland.  Berlin:
Spinger-Verlag.

The Mind-Brain Continuum  (1996). Ed. R. R.  Llinas and P. S. Churchland. MIT Press.

On the Contrary : Critical Essays 1987-1997. (1998 ). Paul M. Churchland and Patricia S. Churchland. MIT
Press

Articles:

In Press:
‘The Mind-brain problem’ (with Paul M. Churchland). In: The Brain of Homo Sapiens. Vol. 4 of Frontiere della
Biologica (Istitutio della Enciclopedia Italiana Trecanni). (French and English edition also forthcoming.) Ed. By E.
Bizzi, P. Calissano and V. Volterra.
‘The Brain-built self’. Ars Electronica. Austria

1998

‘Computation and the brain’ (with Rick Grush)(1998) . In: The MIT Encyclopedia of Cognitive Science. MIT
Press.

‘What can we expect from a theory of consciousness?” (1998) In: Advances in neurology: Vol 77.
Consciousness: At the Frontiers of Neuroscience. Eds. H. Jasper, L. Descarries, V. Castellucci, S. Rossignol.
Philadeplphia: Lippincott-Raven. 19-32.
 

1997
Recent work on consciousness: Philosophical, Empirical andTheoretical . Seminars in Neurology. 17: 101-108.
(With Paul M. Churchland).

Reprinted inCognitive Studies: Bulletin of the Japanese Cognitive Science Society.. 4: 45-55.

'Brainshy: Nonneural theories of conscious experience.' (1997). In: Consciousness -- Papers for Tucson II. Edited
by S. Hameroff, J. Laukes et al.

1996
'Toward a neurobiology of the mind." (1996) In: The Mind-Brain Continuum. Ed. by Llinas and Churchland.
Cambridge, MA: MIT Press. 281-303.

'The Hornswoggle Problem' (1996) Journal of Consciousness Studies. 3:402-8.

1995
'Machine Intelligence'.  (1995)  P. M. Churchland and P. S. Churchland.  Aniversary volume of Scientific American.
'Gaps in Penrose's Toiling'.  (1995)  R. Grush and P. S. Churchland. Journal  of Consciousness Studies.
(1995) In: Conscious Experience. Ed. by T. Metzinger.  Berlin: Schoningh-Verlag.
'Feeling Reasons', (1995). In: Decision-Making and the Brain. Ed. by A. R. Damasio, H. Damasio  and Y.
Christen. Berlin: Springer-Verlag.
(1995) Reprinted in Mind and Brain in the 21st Century. Edited by C. Maar. Berlin:
Rowohlt Verlag.
Relies to The Churchland and their Critics  (1995).  P. M. Churchland and P. S. Churchland  Ed. by R. N.
McCauley. Oxford: Blackwells.
'Can neurobiology teach us anything about consciousness?' (1995). (Expanded version of 1993). In: The Mind, The
Brain, and Complex Adaptive Systems. Ed. by H. J. Morowtiz and J. L. Singer. Reading, Mass.:
Addison-Wesley.
(1995). Reprinted in Conscious Experience. Ed, by T.
Metzinger. Berlin: Schoningh Verlag.
'Intertheoretic-reductionism: A neuroscientist's field-guide.' (reprinted from 1991). In: Nature's Imagination. Ed. by
John Cornwell. Oxford: Oxford University Press.

1994
'Filling  In:  Why  Dennett  is  Wrong'.  (1994).   P.S. Churchland  and  V.  S. Ramachandran.  In Dennett  and
His Critics.  Ed. Bo Dahlbom.  Oxford: Blackwells.
Reprinted in Vancouver  Studies  in  Cognitive  Science.  (1994).  Ed. S. Davis and K. Akins.  Oxford:
Oxford UP.
'A Critique of Pure Vision'.  (1994).  P. S. Churchland, V. S. Ramachandran, and T. J. Sejnowski.  In Large-scale
Neuronal Theories of the Brain.  Ed. C. Koch.  Cambridge, Mass.:  MIT Press.
'Consciousness  and  the  Neurosciences:  Philosophical  and Theoretical  Issues'.  (1994).  I. Farber and P. S.
Churchland  In The  Cognitive Neurosciences.  Ed. Michael Gazzaniga.  MIT Press.
'Could a Machine Think?' Paul Churchland and Patricia Churchland. Reprinted in Thinking Computers and
Virtual Persons. Ed. E. Dietrich Academic Press.
'Inter-theoretic reduction: A neuroscientist's field guide' (reprinting) Paul Churchland and Patricia Churchland.  in:
The Mind-Body Problem: A guide to the current debate. Ed. by R. Warner and T Szubka. Oxford:
Blackwells. 41-54.
1993
'Can Neuroscience Teach us Anything About Consciousness?' P. S. Churchland (1993) Presidential Address,
Pacific  Division of the American Philosophical Association. In Proceedings of the APA.

1992
'Introduction:  Neurophilosophy and Alzheimer's Disease'.  (1992).  Introduction to Neurophilosophy and
Alzheimer's Disease.  Ed. Y. Christen and P. S. Churchland.
'Aristotle  on  Memory'.  (1992).  Patricia Smith Churchland and Georgios Anagnostopoulos.  For The
Encyclopedia of Learning and Memory.  General Editor, L. Squire.
'Silicon brains'.  (1992).  T. J. Sejnowski and P. S. Churchland.  Byte, October, 1992.
'Computation in the Age of Neuroscience'.  (1992).  T.  J.  Sejnowski and  P. S. Churchland .  The New
Computation.  Ed. D. Hillis. MIT Press.
1991
'Intertheoretic reduction:  A neuroscientist's field guide'.  (1991).  Paul M. and Patricia S. Churchland.  Seminars in
the Neurosciences.  2: 249 - 256.
_____Reprinted  in Neurophilosophy and Alzheimer's Disease (1991).  Ed. Y. Christen and P. S. Churchland.
Springer-Verlag.
_____Reprinted in Modelos Cognitivos de la  Mente:  Investiga-cion  Interdicplinaria en Ciencia Cognitiva.
(1992)  Ed. J. L. Diaz and E. Villanueva. Universidad Nacional Autonoma de Mexico
'Our Brains, Ourselves:  Reflections on Neuroethical Questions'.  (1991).  In Bioscience and Society. Ed. D.J.
Roy, B. E. Wynne, and R. W. Old.  Wiley & Sons.
1990
'Is  neuroscience relevant to philosophy?'.  (1990).  In Canadian Philosophers.  Ed. D. Copp.  University of
Toronto Press.
_____Reprinted  as  'Les Neurosciences Concernent-Elles  La Philosophy?'  (1991). In: Philosophie De L'Esprit Et
Sciences Du Cerveau. Ed. Jean-Noel Missa. Librarie Philosophique J. Vrin. (Paris)
'What is computational neuroscience?'  (1990).  With T.J. Sejnowski and C. Koch.  In Computational
Neuroscience.  Ed. E. Schwartz.  Cambridge, Mass.: MIT Press.
'Could a machine think? Recent arguments and new  prospects'.  (1990).  With P.M. Churchland.  Scientific
American.
_____Reprinted in The Intentionality of Machines.  Ed. E. Dietrich.  Oxford: Blackwells.
1989
'Neural  representation and neural computation'.  (1989).  With T.J. Sejnowski.  In Biological Computation and
Mental  Representation.  Ed. L. Nadel.  Cambridge, Mass.: MIT Press, 15-48.
_____Reprinted in Philosophy of mind and action theory  (1991).  Ed. James Tomberlin, Ridgeview Publishing:
Altascadero, CA.
_____Reprinted in From  Reading to Neurons.  (1989).  Ed. A. Galaburda. Cambridge,Mass.: MIT Press,
217-254.
'Brain and cognition'.  (1989).  With T. J. Sejnowski.  Foundations of Cognitive Science.  Ed. M. Posner.
Cambridge, Mass.: MIT Press.
'From Descartes to neural networks'.  (1989).  Scientific American 261: 118.
1987-1988
'Reductionism and the neurobiological basis of consciousness'.  (1988).  In Consciousness  in Contemporary
Science.  Ed. A. M. Marcel and E. Bisiach.  Oxford: Oxford University Press, 273-304.
'The  significance  of  neuroscience  for  philosophy'.  (1988).  Trends In Neurosciences, 11: 304-307.
'Replies to Corballis and to Bishop'.  (1988).  Biology and Philosophy 3, 393-402.
'Computational neuroscience'.  (1988).  T.J. Sejnowski, C.  Koch, and P. S. Churchland.  Science,
241:1299-1306.
_____Reprinted in Encyclopedia of Neuroscience (1988).
_____Reprinted in Connectionist Modeling and Brain Function:  The Developing Interface.  C.  R. Olson.
Cambridge, Mass.: MIT Press.
'Perspectives  on cognitive neuroscience'.  (1988).  P. S. Churchland and T. J. Sejnowski.  Science 242:741-745.
_____Reprinted in From Molecules To Minds.  (1990).  Ed. Katrina Kelner, American Association for the
Advancement of Science.
_____Reprinted in Perspectives on Cognitive Neuroscience.  (1991).  Ed. Lister and Weingartner.  Oxford:
Oxford University Press. 3-23.
'Epistemology in the age of neuroscience'.  (1987).  The Journal of Philosophy, 84, 544-552.
1983-86
'Replies to Commentaries on Neurophilosophy'.  (1986).  Inquiry, 29,  241-272.  (This issue of Inquiry is devoted
to a symposium on Neurophilosophy.)
'Psychology and the study of the mind-brain:  Reply to Carr, Brown, and Sudevan'. (1984).  Neuroscience 13,
1401-1404.
'Stalking the wild epistemic engine'.  (1983).  With P. M.  Churchland.  Nous,  17, 5-18.  (Symposium for the
American Philosophical Association, Western Division, Chicago, March 1983.)
_____Reprinted in Mind and Cognition.   (1990).  Ed. W. Lycan.  Oxford: Blackwells. 300-311.
'Consciousness: The transmutation of a concept'.  (1983).  Pacific Philosophical Quarterly 64, 80-95.
'Content:  Semantic and information-theoretic'.  (1983).  With  P.  M. Churchland  The Behavioral and Brain
Sciences.
'Is the visual system as smart as it looks?'  (1983).  In Proceedings of the Philosophy of Science Association,
SymposiaVol 2.    541-552.
'Ojemann's  data:  Provocative but  mysterious'.  (1983).   The Behavioral and Brain Sciences  6, 211-212.
'Dennett's  instrumentalism:  A frog at the  bottom  of  the mug.'  (1983).  The Behavioral and Brain Sciences 6,
358-9.

1980-1982
'Mind-brain  reduction:  New light from  the  philosophy  of science'.  (1982). Neuroscience 7, 1041-1047.
'Is determinism self-refuting?' (1981).  Mind 90, 99-101.
'On  the  alleged backwards referral of  experiences  and  its relevance  to  the  mind-body  problem'.  (1981).
Philosophy  of Science. 165-181.
'How many angels?' (1981). The Behavioral and Brain Sciences 4, 236.
'Functionalism, qualia and intentionality'.  (1981).  With P.  M. Churchland. Philosophical Topics 12, 121-145.
_____Reprinted  in Mind, Brain, and Function. (1982).  Ed. R. Shahan and J. Biro. Norman, OK: University  of
Oklahoma Press.
'The  timing of sensations: Reply to Libet'.  (1981).  Philosophy of Science 492-497.
'A perspective on mind-brain research'.  (1980)  The Journal  of Philosophy 77, 185-207.
_____Reprinted in The Philosopher's Annual.  (1981).  Ed. D. L. Boyers, R. Grim and T.  J.  Saunders.
Ridgeview California: Ridgeview Publishing Co., 1-24.
'Language, thought, and information processing'.  (1980).  Nous 14, 147-170.
'Neuroscience and psychology: Should the labor be divided?'  (1980).  The Behavioral and Brain Sciences 3,
133.
1974-1978
'Fodor on language learning'.  (1978).  Synthese 38, 149-159.
'The virtuosity of the sensory cortex and the perils of common sense'.  (1978).  With P.M. Churchland.  The
Behavioral and Brain Sciences 1, 144.
'Internal states and cognitive theories'.  (1978).  With P.M. Churchland.  The Behavioral and Brain Sciences 1,
348.
'How Quine perceives perceptual similarity'.  (1976).  Canadian Journal of Philosophy 6, 251-255.
'Logical form and ontological decision'.  (1974).  The Journal of Philosophy 71 (Abstract) 599-600.
Reviews
Review of Memory and Brain by Larry Squire.  (1990).  Philosophy of Science.
Review of Computer models of mind by Margaret Boden.  (1988).  Nature 334, 22-23.
Review of Philosophy and the Brain by J. Z.  Young.  (1987).  Nature 326, 905-906.
'Leap frog over the brain'.  (1987).  Review commentary in multiple book reviews of Vaulting  Ambition by Philip
Kitcher.  The Behavioral and Brain Sciences 10, 73.
Review of From Folk Psychology to Cognitive Science by Stephen P. Stich.  (1985).  The Philosophical
Review, 418-420.
Review of Mind and Brain, ed. J. Eccles.  (1984).  The Quarterly Review of Biology 59, 55-56.
Review of Human Inference:  Strategies and Shortcomings in Social  Judgment  by Richard Nisbett and Lee
Ross.  (1983).  Canadian Philosophical Reviews 2, 240-242.
Review of Psychological Models and Neural Mechanisms by Austen Clark.  (1982). The Journal of Philosophy
79, 98-111.
Review of The Language of Thought by J. A.  Fodor.  (1980).  Nous 14, 120-124.
Review of Anatomy of Knowledge, ed. M. Grene.  (1969).  Oxford Magazine, 15-17.

Professional Societies
Society for Neuroscience
Philosophy of Science Association
American Philosophical Association
Society for Philosophy and Psychology
Offices
President, 1984-85, Society for Philosophy and Psychology
Board of Governors, Philosophy of Science Association 1985-87.
Program Committee 1984, Philosophy of Science Association
Board  of Governors,  Canadian  Philosophical  Association 1978-1980.
President,  American  Philosophical  Association  -  Pacific Division. 1992-93.
Chair of Executive Board, Institute for Neural Computation (UCSD) 1994 -- __
Editorial Boards
Cognitive Science 1986-88
Journal of Cognitive Neuroscience
Theoretical Medicine
Neural Computation
Television Appearances:
 Visions; Channel 4, London January 1989
 Nightwatch; (Charlie Rose) CBS, February 1990
 Bill Moyers; April, 1990
 KCET, Los Angeles (Discovery Channel) ; November 1990
 RTBF, Charleroi (Belgium) Odyssey of the Spirit (first and sixth broadcast.) Recorded April 1991, for
1992-93 season.
 PBS - New York: AI and Neural Nets (February 1992)
 Channel 4 London - The Mind/Brain (April 1992)
 CNN - Changing our Minds (series on environmental issues) (1994)  repeated on TBS (1994)
  Discovery  Channel  -- The  Brain:  Our  Universe  Within (1994)
 PBS -- The Human Quest (1995)