Is it Already Time to Give Up on a Science of Consciousness? A Commentary on Mysterianism 

Abstract:This essay is an extended review of the book “The Mysterious Flame - Conscious Minds in a Material World” by Colin McGinn. After a brief introduction, the book is summarized. McGinn’s main thesis, that the problem of consciousness cannot be solved scientifically because of an intrinsic limitation of the human intellect, is then analyzed, particularly from the perspective of modern neuroscience. I discuss the criticism of Materialism, which constitutes a crucial part of the book, in light of the ideas of Churchland, Chalmers, and others, and I review a finer distinction in the mind-body problem between identity and causal relation. This leads to a discussion of the contribution of Mysterianism to the ontology of scientific theories. Finally, I comment on other critical passages of The Mysterious Flame and propose a thought experiment to shed light on some of the issues raised in the book.

The end of this millennium has seen the appearance of a plethora of books, articles, reviews, conferences and workshops on “consciousness”. This movement involves philosophers, but also psychologists, neurobiologists, physicists, ethologists, mathematicians, computer scientists and thinkers from many other disciplines. The participation of so many scientists in this debate contrasts sharply with the traditional view that conscious experience cannot be the object of scientific investigation because of its subjectivity, privateness, and irreplicability. Certainly it is hard (if at all possible) to approach matters such as qualia experimentally by the straightforward “Galilean” method, and an adequate epistemology needs to be developed (see e.g. [1]). One of the main reasons for the recent wealth of scientific contributions to the consciousness debate is the fast progress of neurobiology, brain imaging, and computer science. For example, recent discoveries concerning the “code” of neural patterns, i.e. the characterization of the spatial and temporal parameters by which neuronal activity represents, stores, and transmits information, have brought the discussion of what “perception” is to a more quantitative level than ever before [2-4]. The advancement of techniques such as multi-electrode recording, functional imaging, emission tomography, and magnetoencephalography (recently reviewed in [5-8], respectively) carries the hope and the expectation that in a not-so-distant future we will have a precise mapping of the neural correlates of any behavioral or cognitive state, down to the system, cellular, and (in principle) sub-cellular level. This new knowledge will integrate and complement the results obtained through classical studies on pathological states such as blindsight and split brains.

As this progress promises to bring some fresh perspective in the age-old question of the mind-body relationship, thinkers from different disciplines offer a variety of views on the current status of a science of consciousness. Opinions range from the statement that, as far as principles are concerned, we already know what consciousness is and how it arises, while all that is left to be discovered are details [9-11]; to a cautiously optimistic prediction that the problem is hard indeed, but as science and technology progresses, we will find the solution [12-14]; to the admission of the possibility that currently available physical and biological concepts might be unsuitable in and of themselves to tackle the problem, and that we should find and introduce radically new ideas and tools in our search [15-17]. In this spectrum of positions, Colin McGinn stands at an extreme. In his “mysterian” theory, he has argued for the cognitive closure of the human mind: we will never really know what consciousness is and how it arises, because the problem is beyond our intelligence. According to McGinn, scientists should recognize that the brain is structurally not equipped to “know” consciousness. Consequently, they should give up on trying to address the scientific problem of consciousness, and leave it to philosophers to mark the boundaries between what is in principle intelligible to humankind and what is bound to remain a mystery forever.

In The Mysterious Flame – Conscious Minds in a Material World, McGinn reviews the position of his mysterian thesis by collecting and summarizing themes largely discussed in his previous books [18-21]. An important merit of the current book is that it addresses the lay public. Philosophical jargon and long, technical discussions of classical authors are kept to a minimum, and arguments are usually accompanied by examples taken from everyday life, or often, from the television series Star Trek. The attempt to reach out to non-experts is praiseworthy, considering that consciousness can be described as what all human beings have and no one can define. All people, not just philosophers and scientists, should have access to the discussion of what we mean by consciousness, and what the first-person experience feels like. Unfortunately, however, The Mysterious Flame fundamentally fails to support its core thesis with solid arguments, and several critical passages are seriously flawed in ways I shall detail below.

The book opens with a definition of consciousness encompassing basic phenomenological experience, or the qualitative, subjective personal states usually referred to as qualia. The author decides to leave out what he calls “reflective” consciousness or self-awareness, reducing what he means by this term to higher order internal representations (such as thinking of having a sensation, emotion, feeling, or thought). The first chapter continues with the programmatic statement that will be elaborated in the book, namely that “the bond between the mind and the brain is a deep mystery, […] an ultimate mystery that human intelligence will never unravel” (p. 5). In order to delineate the terms mind and brain, McGinn reports an extract from a sci-fi story, where aliens exploring the Earth remain profoundly puzzled by how human beings can achieve consciousness with brain made out of meat. The problem is restated as an invitation to the reader to contemplate why (s)he should be conscious at all, while, say, steaks are not. This introduction ends with a discussion of the two “orthodox explanations” of consciousness, Materialism and Dualism, and why they “don’t work” (p. 18). This part of the book is actually critically important to the whole mysterian cause, as several subsequent chapters will crucially refer to the flaws of Materialism and Dualism outlined here. McGinn’s arguments against these two positions follow the classical philosophical debates: it is hard to swallow that the mind is what the brain does, because the first is subjective knowledge, the second is objective, and because the two really feel different. And it seems quite difficult to maintain that they are totally separate entities (which would also admit the possible existence of zombies, ghosts, and the like) against increasingly solid scientific and clinical evidence. After summarizing the remaining chapters, I will return to McGinn’s attack on Materialism, as it raises major concerns and affects much of the subsequent discussion.

The second chapter constitutes the central logical justification of the mysterian theory, and of the whole book. Here, all the evidence suggesting the unintelligibility of consciousness is gathered, and the reader is invited to give up on a deeper understanding. First, the author summarizes historical skeptical positions (how do you know you are not living in a dream, or in virtual reality?), and a series of questions which are impossible to answer are offered as concrete examples (how many ants were there in Africa in the year 1620?). Then he argues that the very structure of human intelligence naturally allows certain capacities (e.g., language), but not others (e.g., echolocation), while other animals find themselves in different situations. Given these circumstances, there is no reason, in principle, for theoretical sciences to be limited to the human species. The reader is invited to imagine an environment in which Evolution allowed the presence of species with a wide range of cognitive capacities: some creatures would be remarkably superior to humans in all aspects of scientific understanding, whereas others would exceed us in only some aspects of scientific thought. This exercise should show how human scientific intelligence might be limited in certain respects, and introduces the core of Mysterianism, namely the cognitive closure. If Hume had been right, and the only concepts humans could form were directly copied by the sensory input from the environment, then the atomic theory would be cognitively closed to humankind, simply because “you can’t see an atom” (p. 44). Now, McGinn argues, how do humans really form concepts? Either by introspection, such as when I contemplate my pain for a cut on my finger, or by “outer senses” e.g. smell and touch, possibly with technological aids such as microscopes. Consciousness can only be accessed through introspection, while the brain may only be investigated through observations outward. It is thus the “irreducible duality in the faculties through which we come to know” (p. 47) that fundamentally negates the possibility of understanding how mind and brain go together. 

Towards the end of the second chapter it is noted that, unlike the brain, consciousness might be quite simple after all. The author argues that the basic elements of consciousness are possessed by many species, and that it is hard to imagine that Evolution would have introduced a “complex” element all in one step. The chapter ends with what can be considered a manifesto of Mysterianism: ten points to explain why accepting that the mind-body relationship cannot be understood is not a “depressingly negative conclusion”, but rather a “palatable, even liberating” admission. These arguments are meant to suggest a broader discussion on the attitude towards life, knowledge, faith, and scientific investigation, and, the author emphasizes, should not be considered in logical support of Mysterianism. This portion stands out from the rest of the book, but it might have a great impact on philosophical thought, should the mysterian theory be proven right. The main lines of reasoning here are that knowing what we cannot know gives more power in interpreting what we do know, and it prevents wasting time and energy which could be used to study phenomena we may hope to understand; it helps demarcate the line between the rational acceptance of a scientific mystery, and the religious abandon to mystical and magical processes; knowledge is not necessarily pleasant, science and technology have a dark side, and the sense of awe is entertainingly fascinating; accepting your own limitation is noble and elevating rather than depressing; and a new branch of science might emerge from this position: can we modify (e.g., genetically) human beings so that they could “come to grips with consciousness” (p.76)?

In chapter three, other theories and positions about consciousness are considered. The mysterian conclusion is compared to the assumption of the existence of God, and to alternative variations of the dualistic view. More “outlandish” theories of the mind-brain link, called panpsychism and mentalism are introduced and criticized. The problems found in all these approaches, according to McGinn, encourage a more ready acceptance of Mysterianism. Chapter four is dedicated to discussion of the relationship between consciousness and space, which is a great favorite of McGinn’s [22, 23]. The non-spatiality of consciousness is troublesome, since classically, consciousness is seen as a phenomenon emerging from physical processes, with spatial components and spatial properties. McGinn argues that it seems reasonable to admit that our concept of space is inadequate and lacking, and that we need a radical breakthrough on this matter. However, he continues, no other concept of space is available to us, and rightly so, considering the way we act in space and the evolutionary path that led to our sensory modalities. We are like Flatlanders, intrinsically unable to perceive one or more dimensions of space, and therefore, to make sense of some phenomena involving these extra dimensions. The conclusion, once again, is that we are cognitively closed with respect to the true nature of space. 

Chapter five discusses a fine distinction between conscious and unconscious computation. It is argued that there is a hidden structure of consciousness that lies in between the surface of consciousness and the unconscious proper. Two categorical examples are given for the hidden structure. The first shows how common human logic makes use of hidden intermediate steps. In order to understand the paradox “the queen of America is bald” one has to accept the false premise of the existence of a queen of America. According to McGinn, this implicit assumption, which is not apparent in the grammatically correct sentence, is an example of the hidden structure of conscious thought. The second example concerns blindsight, i.e. the ability of people with lesions in specific brain areas to acquire visual knowledge while declaring they cannot see anything. McGinn concludes that in normal vision too there is a hidden component of conscious perception. Just as there is more to an object than I can perceive (its atomic structure, for example), so there is more to my visual experience than I can voluntarily reflect upon. The author continues the argument by claiming that “we cannot know ourselves, not all the way down.” (p.163). Letting go of this craving to explain, it is concluded, leaves space for the existence of free will. The notion of physical causality negates the possibility of making free decisions. Our decisions are not behavioral reactions, but at the same time they are not always superficially conscious either. They are “hidden”, and form part of the mystery.

Chapter six considers the possibility of conscious machines. As far as we know, it is argued, simulation of behavior does not imply inner consciousness, and the Turing test should be discarded as useless: animals are as sentient of pain as we can be, yet they would fail the Turing test; a “complicated” computer program could eventually pass the Turing test, yet it would still remain an unconscious algorithm. Maybe, McGinn hypothesizes, for a machine to be conscious we have to assume that it should be made out of organic matter (consciousness has never seemed to emanate from an inorganic source). And as far as how to build such a machine, this falls into the mysterian realm, since we do not know what makes consciousness emerge from the material world. No hard conclusion can be drawn at this stage, but a wise dosage of skepticism is advised. The same can be said about the inverse problem, i.e. whether or not there could exist a “smart” animal, a well behaved organism, which had no inner consciousness nonetheless. We do not know, and the chapter ends with this open question. Finally, the last chapter proposes a new role for philosophers, in line with the thesis offered in the Mysterious Flame: philosophers should delineate the boundaries of intelligible knowledge, liberating Science from the burden of mystery. Is all of what is usually termed “consciousness” really unintelligible? Not quite: only the purely subjective “inner” component is. So, although scientists should waste no time trying to understand the link between the feeling of pain and the electrophysiological activity of certain neuronal fibers, a careful philosophical analysis might find the limits of what components of pain, in terms of behavioral and intellectual knowledge, can be causally related to brain activity. 

Several central arguments presented in McGinn’s book seem critically flawed, and the result is poor logical support for the mysterian hypothesis. The first problems concern the discussion of Materialism. Here, the story of Jackson’s famous character Mary is retold, in order to show that the knowledge of a physiological state does not imply the knowledge of mental states (see also discussion in [16], and references therein). Mary is an imaginary, bright and well-equipped neuroscientist, who was born and raised, and always lived, in an artificially black-and white environment. She knows everything about her brain activity and functioning, at the system, cellular, and molecular level. However, she has never seen colored objects. Although she knows how her nervous system reacts when the retina is stimulated with electromagnetic waves, when she finally is allowed to see a red rose, she has to admit that there was something missing in her knowledge, which is the sensation of redness itself. One of the main problems with this argument is that there is no evidence whatsoever that Mary would have a sensation of redness, after she became adult in a black and white world. In fact, there is evidence that the visual system of mammals is extremely plastic, and, to a certain extent, adapts itself to perceive what the environment has to offer [24]. It is highly conceivable that human infants gradually learn to perceive the sensation of redness only after several sensory exposures to red objects. The only way Mary could really know everything about her brain, including how it represents red light, would be to actually have her retina stimulated with red light enough to allow the development of normal neural connections.

A similar argument used by McGinn in his critique of Materialism is borrowed from Nagel’s discussion of “what it is like to be a bat”. Since humans are not capable of echolocation, even if we understand the details of how bat brains achieve it, we will not be able to imagine how it feels. From the study of bat neurobiology, however, we might infer some qualitative relationship between the auditory, visual, and echolocation senses. This could, in principle, give us a rough idea of what an echolocation quale feels like. There is some clinical evidence involving human patients who lost their corneas to disease at around age 10 months. In adulthood, as the technology for cornea transplants was developed, these subjects underwent operations and acquired physiologically functioning eyes once again. Patients who, before the operation, had been trained to imagine visual sensation through touch and sound, were actually able to acquire a much more complete visual perception than others [25].

Jackson’s “Mary” and Nagel’s “bat” arguments lose much of their strength when analyzed in light of a more subtle analysis of Materialism, that McGinn addresses only tangentially, probably in order to leave his book more accessible to the lay public. This analysis concerns the distinction between identity and causal correlation. If we found, for instance, that a certain conscious experience C occurs if and only if a certain neural pattern N is present in the nervous system, could we conclude that the conscious experience is that neural pattern? Or shall we rather maintain that Ccauses N? Patricia Churchland is in favor of the identity hypothesis, and compares this scenario to other similar debates that accompanied previous scientific revolutions [26]. It is not that particle motion causes temperature. Particle motion is temperature, as strange as it may seem. It is not that the movement of electrons causes electricity. Movement of electrons is electricity, as strange as it may seem, and so forth. When we find what are the elements of neural patterns that correspond to conscious experience, we will get used to the idea of an identity, just because any other explanation would be too complicated: the mystery will vanish. In criticizing Materialism, Churchland claims, McGinn makes an unwarranted leap from “it is unimaginable” to “it is impossible”, and the logical gap between the two statements is usually filled with “dust which cloaks the fallacious core of the argument” [26].

The alternative position would argue that, unlike temperature and electricity, consciousness might be caused by brain states though not identical with them, given the objective/subjective gap that divides the two concepts [27]. Interestingly, in a now famous keynote paper, Chalmers admits the gap between C and N (what he calls the Hard Problem), and yet refuses to embrace McGinn’s Mysterianism [28]. In accusing the mysterian position of excessive pessimism, Chalmers believes that this is no place to give up, it is the place, rather, where things become interesting. Even if we are open to the possibility that reductive explanations fail to satisfy our curiosity about consciousness, he claims, the nonreductive approach needs to be explored. Chalmers’ ideas, and the subsequent discussions [29], constitute an extremely important alternative view to radical Materialism. This subject is inexplicably overlooked in the Mysterious Flame, and it deserves commentary here in that it seriously challenges the novelty and the depth of Mysterianism [17, 28]. Chalmers notes that it occasionally happens, in physics, that an entity is to be taken as fundamental. Most phenomena can be explained in terms of something simpler (such as electricity and temperature, mentioned above), but this is by no means universal. Examples of fundamental entities are charge, mass, or space-time. Regarding the aforementioned example of electricity, why is it that electrons are negatively charged, why is it that there should be such a property as charge at all, apparently with two states (positive and negative), and why is it that negatively and positively charged objects should attract each other, while objects with the same charge tend to repel each other? Similar fundamental questions can be formulated for mass and gravitation. Questions can become even more precise: why is the gravitation constant exactly what it is, and not, say, twice that amount?

When it turned out that electromagnetic processes could not be explained in terms of classical mechanics, Chalmers argues, scientists introduced novel fundamental components in the physical theory, including properties (charge) and laws that went with them. The ontology of physics itself underwent an expansion. This process lasted for decades and eventually led to the explanation of apparently uncorrelated macroscopic phenomena such as ferromagnetism. Similarly, according to Chalmers, a complete theory of consciousness will have to introduce some new fundamental properties. In order to delineate these properties, however, and the laws that coordinate them, we need to learn more about the branches of science related to conscious experience, namely neuroscience and behavioral psychology. The more we learn about the “easy” problem, the more we will be able to narrow in and nail down the characteristics of the entities to be eventually assumed as fundamental. 

What earlier physicists (mainly Galileo and Newton) did with mechanics was to recognize that many phenomena could be described in terms of a restricted number of laws and parameters. It was this process that led to the assumption of mass as a fundamental entity. What is Mysterianism really? If it were the admission that fundamental properties cannot be explained further, then it would be no novelty. But in The Mysterious Flame, the whole subject surrounding consciousness is regarded as a deep mystery, and in fact, there is no deep reason to do so. Even if we assume that there is something “mysterious” (or, perhaps better, “fundamental”) in the process of consciousness, then it would be important to carve out all we can describe quantitatively about the process, so as to leave a minimum set of equations and parameters. In order to do that, we need to study and describe which C corresponds to which N and vice versa. If we knew the neural correlates of consciousness, if we knew which properties of neural patterns correspond to elements of conscious experience, then we could outline a theory, inclusive of fundamental properties and laws, coherent with this knowledge. In his keynote article, Chalmers proposes a series of lucid programmatic steps to reach this point from the current status of neurobiology and experimental psychology. His main principles, namely structural coherence, organizational invariance, and the double-aspect theory of information [28], address several of the issues McGinn raises in The Mysterious Flame, and it is surprising that they are ignored in this book.

Chalmers’ analysis of the process leading to scientific theories can be reformulated in terms of quantitative equations describing the laws of nature. For example, Copernicus’ and Galileo’s observations on the motion of bodies were summarized in the two equations

F = m * a (1)

F = G * m₁ * m₂ * d ^-2(2)

where F is the (gravitational) force between two bodies of mass m₁ and m₂ separated by a distance d, and G is a (universal) constant. Experimental observations suggest that the mass referred to in equation 1 is actually the very same property as the mass referred to in equation 2, although there is no logical reason for it to be so. So, we assume that there is one fundamental entity of physical bodies called mass, and not two (inertial and gravitational)#. One can derive Copernicus’ laws from equations 1 and 2, and therefore Copernicus’ laws are usually not regarded as fundamental. There is an implicit principle of minimization of the fundamental equations here: natural theories should keep the number of fundamental equations (and also, fundamental parameters and universal constants) to a minimum##. For example, a great revolution in thermodynamics was achieved when equations such as 

P * V = N * K * T(3)

(where P is the pressure of a gas, V its volume, N the number of its molecules, K a (universal) constant, and T the temperature) could be explained in terms of equation 1 by assuming a statistical definition of P and T in terms of molecular mass and velocity [30]. The debate between radical Materialism (C is N) and Chalmers’ position (Ccauses N, and we have to understand how), can be restated as an argument about whether consciousness can be explained in terms of the presently accepted fundamental laws of physics, or whether we need additional fundamental laws. In either case, it is necessary to define and describe quantitatively both C and N before reaching a conclusion. From this perspective, Mysterianism looks like an unjustified third route.

The fact is, at this stage of neuroscience knowledge, we simply do not know enough to establish what the neural correlates of qualia are. The first chapter of The Mysterious Flame has a title that encapsulates one of the ideas encouraging Mysterianism: “Still unexplained after all these years”. It is true that the nature of consciousness has evaded philosophers’ grasp for thousands of years. But if we want to give neurobiology a chance, we must admit that we are just at the beginning. Are certain patterns of “neuronal activity” all there is to consciousness? We cannot give an answer, not necessarily because the question is cognitively closed to us, but because we have not learned enough about what the characteristics of those neural patterns must be. From this perspective, Materialism might be wrong, but equally, it might very well be true. As Churchland pointed out, it seems unreasonably early to give up on the attempt to find out how the brain performs its job: as long as experiments continue to produce results that so greatly advance our understanding, why not keep going [26]?

Science proceeds by collecting observations, and by connecting them to previously established laws (possibly at different scales or explanatory levels), or by establishing novel laws to accommodate them. In a way, it is the set of fundamental laws, parameters, and universal constants, that constitute the limit and the boundary of human knowledge. Is McGinn’s call for a unique role for philosophers in this process meaningful? Unfortunately, The Mysterious Flame leaves this entire body of questions regarding the ontology of science untouched.

The lack of discussion of Churchland and Chalmers’ claim that we do not know enough neurobiology yet to (dis)prove Materialism and/or to discover the fundamental entities that describe consciousness scientifically, constitutes the crucial flaw of The Mysterious Flame, and of Mysterianism in general. This same issue emerges, in one form or another, in several parts of the book. For example, in the core discussion in favor of the cognitive closure of the brain-consciousness relationship (pp. 49-53), McGinn argues as follows: “There is some property of the brain, let’s call it C*, that explains how consciousness emerges from neural tissue. […] If we look hard enough inside the crevices of the cortex, we will eventually come across the property C*. […] But this is pure fantasy. The key point here is that just as consciousness itself is not, as a matter of principle, visible in the brain, so C* - which constitutes the very essence of consciousness – is not visible either. […] To understand the general theory of consciousness we would need to understand how the specific forms of consciousness arise from particular sorts of brain property. But that would require us to be able to form concepts of types of experience we cannot in fact conceive.” In reviewing this passage, it is apparent how the key problem is not even stated: either C* actually explains consciousness in terms of other physical laws (much like the statistical interpretation of gas dynamics explains the relationship among temperature, pressure, and volume in terms of particle number and movement) or C* constitutes a radically new set of physical entities and laws (much like electrical charge had to be introduced in order to explain electromagnetism). McGinn has no satisfying reason why we should not be able to see C* as long as we define it as “the neural correlate of consciousness” rather than “the property that explains how consciousness emerges from the neural tissue”. 

In another crucial passage of chapter 2, one reads “Can we take the atoms of the brain (neurons and their parts) and combine them according to appropriate laws into conscious states? The answer is clearly ‘No’. When you have an experience of yellow, your conscious state does indeed depend for its existence upon what is happening in your neurons in the visual area of your cortex. But it is not true that your experience has such neural processes as its constituents. It is not made up of the processes that constitute its neural correlate. The conscious state does not have an internal structure that is defined by its physical underpinning. […] The kind of neural complexity that lies behind a conscious experience does not show up in its phenomenological character. Neurons are not the atoms from which consciousness is composed by means of lawlike combinations.” Again, there is a misconception here of what counts as an explanation. We accept the atomic theory in physics, even if not all the properties of a substance can be directly inferred by its atomic constituents. In fact, substances made up of identical atomic units are well known to chemists to have quite different properties, depending on how the atoms are arranged in the molecule. So, the hardness of diamond, the liquidity of water, and the viscosity of oil, are emergent properties of their constituents. In the end, it is possible to rationalize the properties of diamond, water, and oil, based on those of carbon, hydrogen, and oxygen, and thanks to our understanding of quantum and classical mechanics and electromagnetism. But it takes many logical steps to connect (extract) emergent properties of matter to (from) the atomic components. If we knew as little about the chemical elements as we know about neuronal processes, the emergent physical properties of substances would look quite mysterious even to the most careful observer. However, after the properties of the atomic constituents were finally understood, the whole macroscopic picture made sense altogether.

The above example is not the only source of confusion of what would count as a solution to the mind-body problem according to McGinn. In an early paragraph of the book, the molecular analogy is actually presented (p. 20): “all the facts about water are facts about H₂O, although the words ‘water’ and ‘H₂O’ do not mean the same thing: they are not synonyms.” One of the main theses of Mysterianism is that mind cannot be explained from brain like water from H₂O. However, towards the end of the book, the author outlines what we really need in order to explain the relationship between brain and consciousness (p. 217): “We can know, that is, that radically new concepts are necessary and that they would have to be connected to each other rather in the way that ‘bachelor’ is connected to ‘unmarried male’. […] If I am right, we are not going to come up with that solution”. The major flaw here is that the definition of bachelor contains the meaning of unmarried male. One can understand the logical relationship between the properties of water and H₂O without having to define one concept with the other. Again, a deeper discussion of identity and causal relation in physical laws would have helped clarify what is acceptable as “knowledge” about consciousness, and whether Mysterianism is really a necessity, or just a possibility.

Similarly, when the appearance of consciousness in evolution is discussed in The Mysterious Flame, the possibility that consciousness is a truly emergent property is not considered. McGinn writes (p. 63): “I like to imagine that day, many millions of years ago, when the first sentient organism came along, and a brand new ingredient entered the cosmos. […] It was early, primitive, and not especially smart. It almost seems as if evolution could not help producing consciousness once it discovered sensory processes. I therefore see no reason to believe that consciousness is any more ‘complex’ or ‘advanced’ than digestion or sexual reproduction.” McGinn’s belief here has no real scientific basis. In fact, many primitive organisms are known to lack a nervous system (which by the author’s own admission seems to be an essential substrate of consciousness), yet are able to digest and sexually reproduce. They can “sense” by means of chemoreceptors, but how can we possibly know that they have “consciousness”, if consciousness is defined as “the having of sensation, emotions, feelings, thought” (p. 2)? And if a saturated/unsaturated chemoreceptor is our threshold to admit “sensation”, then why should microchips not be sentient, or thermometers, or gas gauges? The subject of the appearance of consciousness in evolution is harder (and more meaningful) to discuss if we consider the emergent properties of information representation in nervous systems. This cannot be done until the neural correlates of consciousness are scientifically pinned down. 

Unfortunately, questions such as “What is the minimum complexity a representing system needs to have in order to allow a process such as consciousness?” are simply rejected in The Mysterious Flame: “The deeper question here is how a bunch of cells can become a self anyway: What converts biological tissue into that self whose existence so impressed Decartes? The fact is that there are no scientific criteria for the appearance of selves; all we have are shaky intuitions […]. Maybe, then, we cannot know ourselves, not all the way down. We can know we exist all right, but we cannot grasp our intrinsic nature” (p. 162). In this conviction, however, McGinn is neglecting many discussions in the scientific literature insisting on a role for complexity in the explanation of consciousness (see e.g. [31-32] among many examples). Given the title of the journal this essay is meant for, I cannot help but quote a passage from the very beginning of the book (p. 11): “Some people like to harp on the complexity of the brain, as if this gave a clue to its mental productivity. But sheer complexity is irrelevant: merely adding more neurons with more synaptic connections doesn’t explain our problem a bit. […] The trouble is that neural complexity is the wrong kind of thing to explain consciousness. It is merely a matter of how many cells a given cell can causally interact with.” Clearly, the author’s excessive simplification of the concepts of information and complex systems, prevents him from appreciating another possible perspective in the discussion of consciousness.

Much in the same way, the progress concerning adaptive neural networks, evolutionary algorithms, and computer models of brain portions is neglected in the discussion of the (im)possibility of conscious computers (p. 184-185): “The computer merely uses electronic pulses to rearrange its internal states; nothing in this implies that it is conscious. There is no more reason to believe a computer is conscious than a table is. […] A computer is a high-tech puppet: you pull the strings and watch it respond, but it no more has a mind than Punch and Judy do. And making it more complex is not going to alter its basic character. If symbol manipulations do not produce consciousness in simpler cases, why should adding more of them make any difference?” Again, it is unclear why McGinn does not recognize at this point the possibility for complex macrophenomena to emerge from simple microsystems. A single moving molecule does not “produce” temperature, or liquidity, why should adding more of them make any difference? And similarly, how can we explain the chaotic pattern of traffic from the characteristic of a single automobile?

The same superficiality of argument is apparent in the initial discussion of what self-awareness is (p. 3): McGinn only describes higher order states, particularly the ability to reflect on one’s own experience and to characterize oneself as conscious. The Mysterious Flame, it is said, is about the fact of consciousness, not its self-ascription. The author claims: “Many animals are in the same state: they have a conscious life, but they do not aspire to reflect on this fact. They do not, to put it another way, apply mental concepts to themselves. To have a conscious state is not the same as applying a concept of that conscious state to oneself, any more than to have a certain color hair is to describe oneself as having that color hair.” Here there seems to be a certain confusion about the formation of the concept of Self (for a more detailed discussion on this subject, see [33]), and about the relationship between this process and the ability to ascribe mental states to oneself. In fact, one could argue that self-consciousness is not equivalent to having a concept of self, any more than feeling pain is the same as having an abstract concept of pain. At this stage, it would have been extremely important to discuss the possibility that phenomenological consciousness, or qualia, are only possible when self-awareness is present [13, 33]. Again, several subsequent arguments in support of Mysterianism lose strength in light of this omission.

The possibility of creating artificial consciousness, discussed at the end of the book, represents the natural setup for a thought experiment with interesting consequences for Materialism and Mysterianism. McGinn chooses not to take this opportunity and to conclude that we cannot know whether or not artificial consciousness is a possibility. So, let us take up the discussion from where The Mysterious Flame leaves off. Since the mechanism by which single neurons function appears to be relatively understandable and to fall within the realm of “objective” science, we may think of creating artificial neurons, either physically in a microchip, or virtually in software. If neurons were believed to be too mysterious for this operation, we might in principle even start from sub-cellular components, such as dendritic branches and spines, axonal shafts and varicosities, somatic organelles, and neurotransmitter vesicles. If it were proven that quantum phenomena played a key role in the function of these components, we could implement or build the basic units with stochastic rules to reflect this fact. Of course, we would need various types of artificial neurons for the different classes of neurons present in the nervous system. If we had a precise map of all the input/output connections of a person’s brain at any time, we could start substituting one by one each neuron of his/her nervous system with an artificial analogue, until the whole subject’s brain would be replaced, essentially, by an artificial machine. Although, at the present stage of knowledge, this is just a thought experiment, we may nonetheless start asking questions: would the subject retain consciousness, or at which point in the process would (s)he start (and finish) losing it? It is unreasonable to state that this question will forever remain a mystery, because, in principle, there is no reason technology will not reach this goal sometime in the future. The thesis defended in The Mysterious Flame would be consistent with the position that the “artificialized” person would still be conscious, but we would still know nothing of the relationship between his/her consciousness and the ensemble of our chips (or virtual neuron-like algorithms). Let us then imagine carrying out the same operation of “brain artificialization” on a second individual. In principle, if we assume that the sensation of red (given the sight of the same red object) is similar or identical for the two individuals, we may map the “neural” state of one brain-machine to that of the other. For this purpose, it is not necessary for the two neural states to be identical. In fact, given the different individual histories of the two subjects, we would expect that the neural states corresponding to “identical” sensations should be somewhat different. (Incidentally, by studying the general analogies among the neural states of many such brain-machines in correspondence to a certain quale, we could find the neural correlate of that quale.) 

Perhaps before the simulation of an entire human brain, scientific progress will allow the simulation of a “virtual life”, which is the entire set of sensory inputs received by a human being in a life span (counting 10 images per second for a 600×600 pixel retina at 32-bit resolution, this would sum up to roughly 30 million GB of data, before compression, for 70 years of visual modality). Then we can imagine connecting the brain-machine individuals to the virtual life simulator. Naturally, the life simulator will have to be plastic, to adapt its outcome (that is, the sensory inputs to the brain-machine) to the behavior of the individual. The “behavior” of the individual, needless to say, might be purely virtual if we wish to disconnect the subject’s body from his/her brain machine. At that point, the individual will be living a purely virtual input/output existence. Needless to say, brain-machine would be plastic too (i.e. they would change their structure and properties through the interaction with the life simulator), because they represent accurate models of real brains. The advantage of this setup is that now all the variables of our thought experiment are completely controlled. That is, we can reasonably administer the very same input (or history of inputs) to each individual, and we can expect to elicit the same or similar conscious experience (in principle, this could only be true if brains were hooked up to the life simulator when the individual was born, but this detail does not really affect the thought experiment). At this stage, we may map the neural correlates of any conscious experience for each individual. Not only can we then control the individual conscious experience (by tuning the life simulator) and then monitor the neural correlate in the brain machine; we can also impose a specific neural pattern (by tuning the brain machine) and record the conscious outcome as a behavioral correlate in the life simulator. An even more extreme situation can be designed: we can have the “scientist” and the “experimental subject” both hooked up to brain machines and life-simulators. The scientist will be able to study the neural patterns of the subject and also experience personally his/her corresponding introspective states, by “replaying” the corresponding patterns on his/her own setup. This thought experiment shows that, if we believe that conscious experience is somehow exclusively related to brain activity (i.e. it emerges from brain activity, it is caused by brain activity, or simply is brain activity), which is not inconsistent with McGinn’s position, there seems to be no reason, in principle, that one could not study the relationship between the two aspects (qualia and neural correlates) both introspectively and objectively. This would lead in turn to answering many open questions in the philosophy of consciousness and in neurobiology, and would likely disclose the additional (if any) fundamental physical entities and laws necessary to describe consciousness scientifically.

An almost independent part of The Mysterious Flame deals with the “advantages” of Mysterianism mentioned above. Among these are the benefits that individuals can receive from recognizing their intellectual limitation and the enjoyment of a humble awe for Nature. This discussion is concentrated at the end of the second chapter (pp. 69-76) and several themes are then developed in later chapters. Particularly, McGinn suggests that Mysterianism, by rejecting the possibility that we will ever subsume consciousness to our understanding of determinism and causation, allows the possibility of free will (p. 168). And he illustrates how cognitive closure might relieve the fear of death, or at least how further knowledge about death could elicit even more unpleasant emotions (pp. 169-171). Aside from the statement that scientific progress comes with a dark side (nuclear weapons, pollution, excessive experimentation on humans), this discussion seems too personal to be analyzed at an objective level. Some readers will undoubtedly appreciate it, while others will probably find it inappropriate. Suffice it to say that some of the same “advantages” could in principle be obtained without embracing a mysterian position. The assumption that one day consciousness will be described and explained by physical laws still leaves space for awe in the contemplation of why there is matter, and why fundamental physical laws are the way they are (no matter what the mind is, never mind what matter is).

A last word needs to be said about the bibliography of The Mysterious Flame. From a book intended for the lay public, one would expect to be provided with an objective review of accessible works on the subject, i.e. both in favor and against the main thesis. In addition, when critical passages are only discussed superficially to allow easier and readier comprehension, all appropriate sources should be cited. McGinn exhaustively refers to his previous work, and only rarely quotes appropriate alternative views in the literature. A modern philosophical discussion of consciousness cannot be sustained without taking into consideration basic neuroscientific evidence, and this is completely lacking in The Mysterious Flame’s bibliography. In contrast, other recent books on the subject point readers to a valuable collection of publications with which they can continue their intellectual journey: the most striking case is Metzinger and Chalmers’ effort [34], but other examples include [35] and, for a completely non-technical book, [36].

To summarize, Colin McGinn’s The Mysterious Flame – Conscious Mind in a Material World is an accessible, well written book, containing a number of stimulating and provocative ideas and a radical central thesis. The overall impression it leaves the reader with is that “maybe” we will not understand what consciousness is in the end. However, many logical arguments presented in the book are simply not convincing. In particular, the discussion of Materialism and emergent phenomena is never brought to the relevant level of the ontology of science. The resulting conclusion we draw is that, quite positively, it is not yet time to give up on a science of consciousness.

Acknowledgments:I am indebted to Drs. Joe Grady and Rebecca Goldin for reviewing and commenting on the manuscript, to Dr. Paolo Biscari for several ideas on the subject, and to Drs. Jim Olds and Harold Morowitz for continuous support and encouragement.

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