BIOLOGICALLY, WE ARE PRIMATES, CLOSE RELATIVES OFchimpanzees, with which we have more than 98 percent of our DNA in common. In terms of genes, the kinship is even closer, as part of the difference concerns “junk DNA,” which has no coding function. Yet, mentally, the distance that separates us from our simian cousins is huge. In the past, this was explained by our having a soul that animals did not possess. Today, the explanation is that we have a bigger brain. What is it about this organ that explains the wonders of mental life?
In recent years, this question has become a central topic of research, sometimes referred to as the “last frontier,” involving some of the best neurobiologists, psychologists, cognitive scientists, computer experts, and philosophers in the world. The field is actively fermenting, and I can give only an interested but unspecialized onlooker’s view of its dynamic state.
Mind is in the head, sustained by the brain. That much we know from everyday experience. What modern science has taught us in addition is that mind and brain are intimately connected, anatomically, functionally, and historically, by linkages that are beginning to be understood. The two are indissolubly linked, leading to the notion that thoughts, feelings, and all other manifestations of the mind are products of the activities of neurons in the brain. The concept is not new. The same was said two centuries ago.
Thus declared the eighteenth-century French physician Pierre Jean Georges Cabanis. The German literature attributes a renal version of the saying to the nineteenth-century Dutch physiologist Jakob Moleschott, who is said to have written: “The brain secretes thought as the kidney secretes urine.” In the climate of the times, these affirmations were meant as provocative attacks on the religious belief in an immortal soul. At present, the words have lost their incendiary character and their substance is accepted by most neurobiologists.
How could they be faulted? The proofs are there, indisputable, that no manifestation of consciousness is possible without the normal functioning of cerebral neurons. Let this functioning be impaired by lack of oxygen, or by a drug or trauma, and loss of consciousness inevitably follows. Many cases are known in which deterioration of certain specific mental aptitudes, speech, for example, or musical memory, can be related to strictly localized cerebral lesions. Starting in the nineteenth century with the observations of the French physician Pierre Paul Broca and of the German psychiatrist Karl Wernicke, whose names have been given to the speech centers, a detailed mapping of the brain has been established on the basis of such data.
Whereas there can be no consciousness without normal neuronal function, the inverse is far from being true. All the acts of our vegetative life, the coordination of our movements, and many other complex activities are managed by our nerve centers without our being aware of this control or even without our being able to affect it in any way. Many consciously initiated gestures progressively transform, through learning and practice, into unconscious automatisms. We laboriously learn to walk, to ride a bicycle, or to play the piano, finally arriving at a situation in which the control of consciousness has become more a hindrance than a necessity. Even in reasonings, it is often difficult to distinguish the respective parts of the conscious and the unconscious. Whereas the mechanisms of these phenomena remain poorly understood, their structural basis is known.
The Latin word cortex means bark. As applied to the brain, it designates a thin, specialized structure that covers the entire surface of the organ. The cerebral cortex consists of a sheet of grey matter (rich in cells), about three millimeters thick, characteristically composed of six superimposed cell layers. A dense network of arborescences links the cells of these layers by a very large number of connections, which unfold transversely from one layer to another, and laterally within the same layer. This network is connected to the other parts of the brain and, thereby, to the whole organism by a tight mass of sensory and motor fibers (white matter). The former convey to it sensory impulses coming from all parts of the body, in particular the sense organs. The motor fibers send impulses to all the muscles. These inputs and outputs delineate on the cortex surface a set of specialized areas, which are now well mapped.
The cortex is the seat of consciousness; only signals that pass through it give rise to mental experiences. Below the cortex, numerous nerve centers bridge sensory and motor impulses by pathways that bypass the cortex and, for this reason, escape consciousness. The whole of vegetative life is thus regulated in an unconscious fashion. So are many automatic movements, such as those that command the position of the eyes, coordinate gestures, or control balance. Some of these automatisms are inborn. Others are created by learning, descending, so to speak, from the cortex, where they have been set into place, to deeper zones, where cortical surveillance dwindles.
It is remarkable that the structure of the cortex is essentially the same throughout the vertebrate series. What changes is its surface area, which reaches 2,200 cm2 for the human cortex, forcing it to make numerous infoldings, or convolutions, in order to fit within the skull. The surface area of the cortex is about 500 cm2 in chimpanzees. In rats, it is four to five cm2, which, corrected for body weight, would amount to some 180 cm2 for a human-sized rat. It goes on diminishing as we move down the animal scale, but there is the beginning of a cortex as soon as a true brain becomes distinguishable. Even in fish, there is a small cortical area, mainly linked with olfactory centers, which are particularly developed in these animals.
These facts suggest strongly that the characteristic, six-layer structure of the cerebral cortex is the generator of conscious experiences and that the richness of these experiences is somehow linked to the surface area of this brain structure. Expansion of the cortical area from 500 to 2,200 cm2, for example, is what extended the range of problems soluble by the brain, from fishing termites with a twig to sending a man to the moon or engineering life.
According to neuroanatomists, the organization of the cerebral cortex is subdivided into functional blocks, or modules, associated laterally in the plane of the cortex. The richness of mental experiences thus appears to be linked to the number of such modules, somewhat like the performance of a computer is linked to the number of interconnected microchips of which it is composed.
Much detail has been added in recent years to our understanding of this functioning, especially in the visual area. A key factor made possible by the increase in the number of the brain’s “microchips” seems to be the multiplication of parallel circuits carrying different aspects of the same information. Entry into the field of consciousness could be linked to some kind of resonance among those different circuits, by a phenomenon analogous, though of a different nature, of course, to what causes a crystal glass to burst into pieces under the influence of a sound whose frequency corresponds to one of its intrinsic frequencies, or a bridge to rupture when vibrating in phase with troops marching in step.
The underlying operations, in the course of which all kinds of circuits are tried and compared in more or less random fashion until the resonating combination emerges, are not conscious but could, when vigilance relaxes during sleep, “leak” into the cortical field. Dreams could thus, as first suspected by the founder of psychoanalysis, the famous Austrian neurologist Sigmund Freud, open a window into what is going on subconsciously in our brain.
Before moving on to the nature of consciousness, we must consider an important additional aspect of the functioning of the brain, namely its wiring. How does such a stupendously complex network of interneuronal connections arise in the course of development? Modern science has yielded valuable information on this topic.
The brain is estimated to contain on the order of 100 billion neurons, each of which is linked to other neurons by an average of 10,000 connections. In total, this amounts to one million billion interneuronal connections. The diploid human genome contains some five to six billion base pairs. Thus, it is obvious that the wiring of the brain cannot be written into the genes. It must occur epigenetically, that is, by superimposed processes that take place during development. Genes only provide a general framework, which delineates the main features of the characteristic cerebral structure of the species. All the details of the interneuronal connections are created, within the limits of this framework, under the influence of inputs that reach the brain both from the body itself and from the outside world.
The mechanisms involved in this wiring have been analyzed by the French neurobiologist Jean-Pierre Changeaux and by the American Gerald Edelman, who, after completely elucidating the chemical structure of an immunoglobulin, has become actively involved in neurobiology. In brief, what happens, according to these two investigators, is that growing neurons continually establish transient connections with one another in essentially random fashion. The connections are rapidly undone, unless some outside influx causes them to be utilized, in which case they are stabilized. The neuronal network is thus established in the beginning by usage and continues to be so throughout life by learning. There are two important aspects to this mechanism.
First to be noted is its analogy with the fundamental mechanism of Darwinian selection. Chance creates a wide diversity of connections, among which are selected, under the influence of environmental factors, those that are retained and amplified. Hence the name of “neuronal Darwinism” given by Edelman to this mechanism.1 Darwin is also cited by Changeaux in this sentence: “The Darwinism of the synapses takes over from the Darwinism of the genes.”2
A second important aspect of this mechanism is that it highlights the capital role of communication in the psychic development of children. The manner in which we treat our children from the day of their birth onward, perhaps even earlier, literally shapes their brains and, thereby, their personalities. All prospective parents must know this lesson and draw the necessary conclusions. If they wish their children to develop a rich neuronal network, the condition of a rich personality, they must talk to them from the very first day, let them hear music, sing to them, cherish and caress them, attract their visual attention, give them toys of various shapes and colors; in summary, provide the children with a multitude of sensory stimulations thanks to which they will be able to build the innumerable neuronal circuits that underly the blossoming of mental life. One should not, as was often done, wait until a child develops understanding of language to start communicating with it. Even if it does not understand, it records. That is what is important.
Thus, much progress has been made and will no doubt be made in the future in our understanding of the brain on a purely phenomenological level. While important, these advances leave unexplained the actual nature of consciousness and that of its relations to neuronal functioning.
To most of us, consciousness is a self-evident fact. It is something that goes on in our brains and allows us to think, feel, make decisions, and speak and act accordingly. It is at the core of our deep-seated feeling of self as the person in charge of our destiny. It is the foundation of morality and of the underlying notion of personal responsibility. This intuition is now increasingly being challenged by a number of neurobiologists and philosophers, who see it as an illusion, a trick played on us by natural selection, an expression of something derisively called “folk psychology,” as remote from the real thing as is “folk physics” from quantum mechanics. In the opinion of many of the greatest experts of our time, cerebral neurons do all the job and it makes no difference whether or not consciousness accompanies their activities. In the words of Crick, “you’re nothing but a pack of neurons.”3 By this paraphrase of Alice in Wonderland (“youre nothing but a pack of cards”), the co-discoverer, with Watson, of the double-helical structure of DNA, who has converted to neurobiology, sums up the currently fashionable view on the subject. Neurons do it all on their own, whatever may go on in the mind at the same time. Implicit in this view is the notion that consciousness—if it exists at all—is no more than an epiphenomenon, some sort of emanation produced by, or associated with, the activities of certain parts of the cerebral cortex but totally unable to influence these activities.
You may have the feeling of being in command of your ship and responsible for its running. But that, we are now told, is an illusion. When, at the end of sometimes agonizing ponderings, you finally resolve on saying “I believe,” “I love,” or “I will,” or decide on a gesture or an action, what you call your “self” has nothing to do with it. It is no more than a spectator, a puppet mistakenly imbued with a sense of importance, perhaps even a mere phantom, while, in fact, your neurons pull all the strings. Extreme defenders of the theory even go so far as to maintain that consciousness is itself an illusion, without real existence.
An important implication of the epiphenomenon-illusion theory is that there is no free will. The defenders of this view realize that their affirmation undermines the very basis of moral responsibility, a cornerstone of human civilization. But they argue that whether we do, or do not, enjoy free will in reality makes no difference in practice. What count are the behaviors and wired-in connections built around the free-will illusion. Seen as an implacable consequence of the determinism of the brain-mind relationship, this notion is now accepted, albeit grudgingly, by a number of scientists and philosophers. It is even cheerfully hailed as “liberating” by some. In the words of Susan Blackmore, already cited in the preceding chapter, “there is no truth in the idea of an inner self inside my body that controls the body and is conscious. Since this is false, so is the idea of my conscious self having free will.”4 And she concludes: “In this sense, we can be truly free.”5 A number of other experts have, in one form or another, expressed the same opinion, concluding that, such being the truth, we have no choice—incidentally, who is denied the choosing?—but to accept it and act accordingly.
Those who refuse to accept an affirmation that contradicts their most intimate inner experience are sent back to Darwin. They are told that natural selection has favored the awareness of self, the feelings of freedom and responsibility, because these traits determined a social behavior that was useful to the preservation of the species. Prehumans genetically disposed to feel responsible with respect to the group had, collectively, a greater chance to survive and produce progeny than those who lacked this feeling. To be useful, the feeling need not correspond to reality. An illusion would do just as well.
True enough. But there can be no illusion without a victim. If being a victim of an illusion is itself an illusion, one arrives at an infinite regression of illusions, of the “Russian dolls” kind. Note that the defenders of the illusion theory use the same image to attack the notion of self, which, they maintain, supposes a self that looks at it, and so on, ad infinitum. The self, however, can look at itself, closing the series; whereas an illusion without a victim is inconceivable.
It therefore seems reasonable to start with the assumption—most would call it conviction—that consciousness is a real thing. We are conscious beings. The whole richness of our inner life is linked to this faculty. On it depends our ability to reason, to create, to enjoy, to suffer, to love, as well as the power we have to act in accordance with those perceptions. However illusory such abilities and powers may be, our being conscious of them is not an illusion. The heart of the matter is not whether consciousness exists, but what it does. Put more clearly, what we want to know is whether consciousness is purely passive or whether it can play an active role.
In general, neurobiologists, together with a few “materialist” philosophers, tend to support the former view on the basis of what they know of the functioning of the brain. What they see is, indeed, nothing but a “pack of neurons,” interacting by a variety of physical and chemical signals and accomplishing stupendous feats of integration and coordination, most often without our even being aware of what they are doing. Take the cardiovascular system. At every instant, the brain and its associated nerve centers are deluged with messages coming from all over the body that may mean things like “send more blood,” “oxygen crisis,” “pressure reaches danger point,” and the like. The messages are decoded and sorted, and appropriate responses are sent telling the heart to beat faster or slower, or the blood vessels to dilate or contract. All this complex interplay is never put into words or disclosed to our consciousness. It all takes place automatically, thanks to wired-in circuits, somewhat, though in enormously more complex fashion, like a thermostat adjusting the heat output of a furnace in relation to the temperature of a house. Many other physiological regulations and manifestations rely similarly on occult polyneuronal activities, which are beginning to be unravelled thanks to the powerful new techniques of neurobiology.
Even when consciousness is involved, the brain may carry out a considerable amount of hidden processing before sending the information to consciousness. In vision, for example, more than 30 separate channels record different aspects, such as outlines, movements, colors, shades, and so on, of the image projected on the retina. All these messages are integrated into a coherent picture by a process known as binding, accomplished entirely unconsciously. This process, which has been compared earlier to the physical phenomenon of resonance, seems to be related to a synchronization of the various impulses, leading to a characteristic 35 to 75 hertz oscillation, which Crick and his German-American coworker Christof Koch believe to be the basis of consciousness. The final result of this complex process is what we “see.”
Even our reasonings may depend to a large extent on unconscious operations by which the neuronal phenomena that underlie concepts are sorted, combined, compared, weighed, and otherwise processed, before the outcome is delivered to consciousness to form what we experience as the substance of our thoughts. Add to this impressive sum of facts, which is growing almost daily, the notion that consciousness probably started with feelings associated with certain physiological activities, and you readily understand why consciousness is viewed by so many experts as an essentially passive epiphenomenon or correlate of certain polyneuronal processes, a manifestation that merely reflects the occurrence of those processes but lacks the power of influencing them in the manner implied by the existence of free will.
It has been objected that a purely passive consciousness can have no useful function and, therefore, no selective value. But this argument is not convincing. Suppose consciousness were just an inseparable concomitant of certain neuronal activities taking place in the cerebral cortex, a sort of “glow” or “hum,” so to speak, that happens to obligatorily accompany those activities. Its selection as such would then need no explanation. The usefulness of the activities that generate consciousness suffices.
A more serious difficulty with consciousness is that it cannot be explained in known physical terms. It is an inner experience, inaccessible to investigation from the outside. Consciousness cannot be recorded. All that can be done is to record the underlying electrophysiological and biochemical manifestations, to note the accompanying behaviors, and to try to establish correlations between those manifestations and behaviors and consciousness phenomena. Even this requires the participation of the individuals who lend themselves to the experiments and inform us of what is going on in their minds. All we can know of the minds of others we know from their testimony and by analogy with our personal experience. This, of course, is the main reason why consciousness is ignored by all those who believe that only what can be “objectively” observed, analyzed, or measured is validly addressed by scientific research.
A beacon that can serve as a guide in the fog of theories and speculations is the fact that consciousness gives access to abstract notions, such as truth and falseness, beauty and ugliness, good and bad, comprehensibility and mystery, and that it allows us to communicate to others, by way of language and artistic creation, our personal vision of these notions. These facts form the main basis of dualism, a theory that attributes consciousness phenomena to an immaterial entity, soul, or spirit, bound to the material body but distinct from it.
Instinctively, we are all dualists. We speak and act as persons, owners of a machine we call our body and over which we believe we have authority. Our entire affective and moral life is pervaded by this dualism, as when we complain that our body has betrayed us, regret having given in to its weaknesses, or, conversely, exult in our power to master them. But beware; this feeling, as we have just seen, may be only an illusion, a trick played on us by our neurons with the complicity of natural selection.
Many religions are dualist. Thus, Christian religions associate with the material and mortal body an immaterial soul that survives after death of the body. Here again, however, we must guard against simplistic ideas. Even though it is true that the immortal soul and the thinking self have long been considered as one and the same, and still are in the minds of many people, Christian thinkers are increasingly aware of the need to redefine the human soul in the light of discoveries in neurobiology.
Dualism is often linked to the name of the seventeenth-century French philosopher René Descartes, who defended a dualist conception of human nature in his celebrated Discours de la Méthode. It must, however, be noted that what is truly novel in the philosophy of Descartes is less dualism than mechanism. For Descartes, the human body, like that of all animals, may be considered a machine entirely subject to the laws of physics and explainable in terms of those laws. God has done no more than edicting the laws and creating the machine, subsequently letting nature take its course without other intervention. In this sense, Descartes rejects vitalism, which, without having been clearly formulated, was nevertheless implicitly present in all the thinkings of his time.
This conception was revolutionary. Descartes is well aware of this. As a good Catholic, anxious, moreover, not to suffer the fate of Galileo, who had just been condemned by the Holy Office, he insists on the purely imaginary character of his hypothesis. He presents it as a logical construction, entirely in accordance with reason, but hastens to add, in order to avoid getting into trouble, that things most likely happened differently.
In this perspective, Descartes’s dualism is less a new theory than a minimal concession of his mechanistic philosophy to doctrine—to which, incidentally, he entirely subscribes. His dualism applies exclusively to human beings, who are the only possessors of a soul, the seat of reason, which distinguishes them from animals. He postulates an interaction between the soul and the body-machine, assumed to take place in the pineal gland, which, by its location in the middle of the brain, clearly betrays its central role. There, the soul communicates with what Descartes calls “animal spirits.” Contrary to what this term might seem to suggest, these are material entities, present also in animals and described by Descartes as “a very subtle wind or, rather, a very pure and vivid flame, which, continually rising from the heart to the brain, will travel from there through the nerves to the muscles, and gives movement to all the limbs.”6 In animals, all is automatic. In humans, the soul manipulates the animal spirits in the course of their passage through the pineal gland.
Cartesian dualism has practically no defender left among contemporary scientists. There is a notable exception, the Australian John Eccles, an eminent neurobiologist, winner of the 1963 Nobel prize in medicine, who remained until his death in 1997 an unconditional exponent of a dualist theory of brain function. Needless to say, Eccles no longer spoke in terms of animal spirits manipulated in the pineal gland. He imagined the presence, at the level of synapses (the junctions between neurons), of “microsites” where neurons and consciousness could interact thanks to quantic fluctuations requiring no energy.
Phenomenologically, the mechanism conceived by Eccles has been met with skepticism by most cell biologists. As to the implication of quantum mechanics, we shall see that many investigators have tried to call on this discipline to explain the relationship between neuronal function and consciousness, without necessarily defending a dualist theory, at least explicitly.
Concerning this theory, I wish to point to what seems an intrinsic, logical flaw of Cartesian dualism. If matter and spirit are entities of truly different nature, the question arises as to how they can interact. This necessarily requires the participation of a hybrid form—a “matter-spirit connector”—sharing properties of both entities. But, if such is the case, matter and spirit join in a single entity . There can be no true dichotomy between the two. Thus, “hardline” dualism does not withstand logical analysis. Upon reflection, what lies behind dualism is a preconceived definition of matter. Even today, although dualism is widely rejected, the influence of this doctrine subsists in the conception most people have of matter.
According to a definition that goes back to Aristotle and represents the keystone of Cartesian dualism, we call matter what is inert, solid, and blindly subject to physical forces. We give another name to anything that does not fall within this definition. For the ancients, this was the case for many natural occurrences, such as astronomical phenomena, tempests, lightning and thunder, or volcanic eruptions, which they attributed to the strifes and caprices of imaginary gods, who combined magic powers with very human preoccupations. With the advances of physics, all these phenomena have been incorporated into the realm of matter.
Life was long viewed as an exception, but this is no longer so. Modern science has refuted vitalism by demonstrating that the basic phenomena of life are entirely explainable in purely physical and chemical terms. Thus life, in turn, has come to be seen as a manifestation of matter. This fact has not been recognized without difficulty and remains hard to accept by the average person, as it requires a widening of the a priori vision we have of matter as something gross, inert, and brute, and of life as “animated” matter.
There remains mind, the last bastion of animism. We have seen that this bastion is increasingly assailed by the advances of neurobiology. On the other hand, I have mentioned the logical problem raised by dualism. There is thus growing support in favor of a monistic (from the Greek monos, single) conception that tends to drive mind as well into the domain of matter. Even more upsetting than the rejection of vitalism, this conception forces us to widen our vision even further. We must loosen the stranglehold that the dualist intuition, reinforced by natural selection, has tightened around our definition of matter. Modern science has shown the way.
Before the invention of scientific instruments, we knew of matter only what is perceived by our sense organs, the products of a long evolution in the course of which natural selection has retained only what was immediately useful to the ability to survive and reproduce. We now know that the image of the world offered by our sense organs, if perfectly effective in everyday life, has little to do with true reality.
What appears to us as solid and impenetrable is mostly vacuum, within which atomic nuclei, which contain more than 99.9 percent of the mass of any object, are more distant from each other, relatively speaking, than are the planets of the solar system.7 The illusion of solidity arises from the fields of force generated by the tenuous clouds of electrons that lie between the nuclei. The latter are nothing but enormously concentrated energy packets—according to Einstein’s celebrated equation, e=mc2—whose power, dramatically revealed in the infernos of Hiroshima and Nagasaki, manifests itself more pacifically today in our nuclear power stations.
Our other perceptions of the outer world are equally misleading. We saw in Chapter 3 that our eyes perceive only an infinitesimal fraction of the radiation emitted by matter. Our vision of the world would be totally different if another window were opened to us in the spectrum of electromagnetic radiations. A similar selectivity affects the sounds detected by our ears and the chemical substances discerned by our sense of smell.
Thus, our intuitive definition of matter is completely distorted by the filters our sense organs interpose between an object and us. It is an essentially pragmatic definition, based on the kind of information that proved most useful in the search for food, the fight against predators, and reproductive success. As means of knowledge, this information is almost valueless. It has needed the long road of scientific investigation to bring us progressively closer to true reality. This reality has proved so strange as to preclude any sort of mental representation, except by way of an abstruse, multidimensional mathematical formalism that is inaccessible to most of us and untranslatable in terms of ordinary experience, even by those who understand it.
These discoveries give a completely different meaning to the philosophical doctrine known as “materialism.” Opposed to spiritualism, this doctrine has long been brandished, whether aggressively by its proponents or defensively by its opponents, as signifying that there is “nothing but” matter. Monism affirms the same thing, but redefines matter as including the “spirit”. It is interesting to find this opinion defended, under the name of “metarealism,” by a distinguished Catholic philosopher, Frances Jean Guitton, who died in 1999. In a 1991 book titled Dieu et la Science (God and Science), which relates his conversations with two physicists, the brothers Igor and Grichka Bogdanov, Guitton writes: “If spirit and matter have a common origin, it becomes clear that their duality is an illusion, due to the fact that one considers only the mechanical aspects of matter and the intangible quality of spirit.”8 And he concludes: “Spirit and matter form a single and same reality.”9 Under the pen of a practicing Catholic considered one of the most eminent Christian thinkers of our time, such a sentence is both surprising and revealing.
A number of experts, dissatisfied with the apparently inexorable determinism of the brain-mind linkage, have taken refuge in the indeterministic haze opened by quantum mechanics and by the famous “uncertainty relations” uncovered by the German physicist Werner Heisenberg, which, they believe, open the door to conscious choice without violating the laws of physics. To Kenneth Miller, the Catholic biochemist quoted in Chapter 12,10 quantum indeterminacy forms the bridge between science and religion. It is the element of uncertainty deliberately introduced by God into the laws of His creation so that human beings can be free to choose between good and evil and bear responsibility for their actions.
Attempts have even been made to identify the cellular sites and mechanisms of these quantum events. I have already mentioned the “synaptic microsite” theory put forward by Eccles. The British mathematician and theoretical physicist Roger Penrose has, in collaboration with the American cytologist Stuart Hameroff, proposed a model based on “quantum gravity” and involving microtubules, which are tubular structures, about 25-millionths of a millimeter in diameter, made of protein units known as tubulins.11 Details of this theory are too complex to be examined here. Let it simply be recalled that microtubules are present in all eukaryotic cells, not just in neurons. Thus, a unicellular protist or a single sperm cell would already possess the structural basis of consciousness. So would plant cells.
I must leave it to the specialists to judge the possible relevance of quantum mechanics to brain function. As a mere spectator, interested but lacking the required expertise, I can only make two remarks of a general nature. First, it seems to me that all explanations based on quantum mechanics retain a strong aroma of dualism. It is always the spirit that manipulates matter, with only the added clarification that it does so by taking advantage of matter’s indeterminacy at the fundamental level. We are no longer dealing with the soul influencing animal spirits, but it amounts to the same thing.
The second point that strikes me is that quantum events are invoked mainly to “cheat thermodynamics.” They are introduced as a means of breaking the deterministic chain of polyneuronal activities without the expenditure of energy, thus opening the door to free will. But free will does not necessarily mean “free lunch.” There is no objective reason for assuming that the brain would generate consciousness and the ability to choose without spending energy. The opposite appears much more probable.
Expressions such as “mental power” or “willpower” are part of everyday language. Yet, they have become almost dirty words in science, largely, I suspect, because they too readily raise the specters of telepathy, extrasensory perception, spoon bending, and other spurious claims. Not that such manifestations should be ruled out a priori . That would be unscientific. What distinguishes the paranormal from the normal is not its intrinsic impossibility—how often has a phenomenon been declared impossible until it was observed!—but the total lack of credible proof of its existence. Whenever a so-called paranormal phenomenon has been subjected to rigorous scientific control, either nothing has been found or a fraud has been uncovered. Adding the fact that the paranormal serves as a screen for a gigantic commercial exploitation of public gullibility, which sometimes, notably in the medical domain, may have dramatic consequences, one understands the hostility of scientists. In the case under discussion, however, we are not dealing with paranormal phenomena, but with perfectly normal phenomena in search of an explanation. This is very different.
In my opinion, to declare consciousness an irrelevant concomitant of polyneuronal functioning in the cerebral cortex, let alone dismiss it altogether from our preoccupations, for the sole reason that it is inaccessible to objective analysis, is not a satisfactory intellectual attitude. It ignores the whole gamut of subjective states; the countless sensations, feelings, moods, and emotions that color our lives; the thoughts, reasonings, speculations, and fantasies that flit through our minds; the ability we possess to focus our attention, to concentrate on a single topic to the exclusion of all others. It also disregards all the products and achievements of our mental activities; the innumerable expressions originating, through science, philosophy, poetry, music, the visual arts, religion, and other forms of culture, from our inner experiences; the increasingly effective tools and technologies, up to sophisticated computers, interplanetary spacecraft, nuclear power stations, biotechnologies, and other fruits of human ingenuity, developed with the help of our knowledge; all the richly textured social fabrics, which now envelop the entire planet, created by the sharing of experiences with the help of language and other means of communication. Finally, it belies our deep-seated conviction of being in charge of our fate and morally responsible for our actions. Such sacrifices for the sake of intellectual coherence and materialistic comfort seem to me excessive and unwarranted.
Looking at the question with the simple, if not simplistic, eyes of a biochemist, I see it as a transduction problem. On one hand, there are the neurons accomplishing their complex functions by mechanisms that are explainable in known physical and chemical terms and open to objective scientific investigation and description. On the other, there are the associated subjective manifestations of consciousness, of unknown nature but presumably likewise explainable, which can be uncovered only by introspection and interpersonal communication. Joining neuronal activities and conscious experiences, there is a special six-layered arrangement of the neurons involved—characteristic of the cerebral cortex—that seems to be the specific transducer of the ones into the others. Interconnected neurons do all kinds of things in our brains. But, as far as is known to me, only those of the cerebral cortex generate conscious experiences, presumably by virtue of the special way in which they are associated into modules, which, themselves, are linked into a dynamic web of highly specific topography.
Biology knows a number of transducers. To begin with, there are those that use metabolic energy to assemble ATP. Then, there all the others that, most often by way of ATP but sometimes also by other means,12 convert this energy into other forms of chemical energy, as in biosyntheses; or into the active transport of molecules or ions, as in membrane transporters and pumps; or into mechanical work, as in myofibrils, cilia, and flagella,13 or into light, as in the emitters of fireflies; or into electric discharges, as in the electric organs of torpedo fish. In all cases, one form of energy is converted into another. It seems not unreasonable to assume that, as with other biological transducers, the operation of the cortical transducers also involves an energy conversion. In fact, the opposite would be surprising, as it would amount to the generation of something without the expenditure of energy, in violation of the laws of thermo-dynamics (supposedly circumvented, as we saw above, by quantum effects).
It thus becomes at least plausible that consciousness represents some sort of physically energized state and that the particular configuration of neurons in the cerebral cortex serves as generator and supporter of that state. If so, what becomes of the energy thus invested? Its fate could be to be simply dissipated as heat, in which case, consciousness would indeed be a mere epiphenomenon. But the possibility may also be envisaged that a greater or lesser part of the energy could be returned—the transducer being reversible—to the neuronal mechanisms from which it has emerged. This would be the phenomenon of mental causation so vigorously denied by much of modern neurophilosophy.
Such notions fit naturally within biochemical thinking and should not, it seems to me, encounter serious objections. But, if we wish to account for our mental life and have it be more than an illusion, we must go one step further. We must assume that the state of consciousness may, between energization and de-energization, undergo certain internal rearrangements—the mind at work?—with as a consequence modifications of the neuronal mechanisms by consciousness . There would thus occur a sort of to-and-fro interchange between neurons and consciousness, in the course of which our thoughts and feelings would be elaborated with the help of the metabolic energy of the neurons.
The bothersome aspect of this kind of model is that it implies the existence of some unknown physical manifestation. But is that so reprehensible? The truth is that we do not know the nature of consciousness. To call it physical is no more than following the monistic principle that we have seen as logically necessary. To consider it energy-dependent is in accord with thermodynamic principles and more readily acceptable, at least to me, than the image of an entity that somehow escapes thermodynamic constraints by the magic of quantum fluctuations. The history of physics is replete with instances where advances in knowledge have imposed radically new notions. Just think of gravitation, atomism, electromagnetism, wave-corpuscule duality, relativity, matter-energy equivalence, elementary particles and their binding forces, not counting such exotic entities as quarks, muons, bosons, charm, and the like. Perhaps biologists, who were so successful in proving the nonexistence of “something else,” should also, like the physicists, have the audacity to envisage something that is not included in the known properties of matter. Such audacity seems to me more valid, in any case, than relegating that something to the realm of the illusory simply because we do not understand it.
We may never know the key to the riddle of the brain. On the other hand, if, as seems to me almost mandatory, mind depends on some kind of energy-dependent physical manifestation, I see no reason why it could not some day prove accessible to physical interferences that would allow probing of the underlying mechanism. In the meantime, I prefer to entertain a hypothesis that accounts, without being implausible, for my most intimate experiences—including my feeling of personal freedom and responsibility—rather than trying to convince myself that those experiences, including the effort of convincing myself, are no more than an illusion created—how?—by a “pack of neurons.”
Remember Lucy? She is the young female australopithecene whose fossilized remains were discovered in 1974, in Ethiopia, by the American Donald Johanson and the Frenchman Yves Coppens.14 Now, go back in mind some three million years and imagine the living Lucy resting, after a long day’s trek through the savannah. The hunt has been successful and a few fruits have added a welcome dessert to her meal. A dozen of her congeners of both sexes are lying around her, providing a warm feeling of togetherness and security. Contentment fills her body. Fleeting images of the day’s activities pass through her rudimentary mind, concerned mainly with food, sex, care of the young, and companionship. Her eyes, through slowly closing eyelids, are absently gazing at the stars lighting up in the darkening sky.
Suddenly, just as she is falling into a slumber, she has a vision. Of sparks springing from two stones hitting each other, of shadowy forms on the walls of a cave dancing, in some flickering light, at the sound of grunts that seem to mean something, of larger-than-life figures raising sticks to the skies and wailing around a dead body, of a hairless newborn staring at her in touching helplessness. Awe, fright, and bewilderment alternate in the unformed recesses of her consciousness, giving place, in a brief moment, to a strange, evanescent sentiment of pure joy, never experienced before, inexpressible in the crude language with which she communicates with the other members of the band. Then, everything dissolves into sleep. The next morning, nothing but a vague memory of something uncommon, desirable, but unattainable, remains of her dream. She is back in her familiar world.
Today, we can interpret Lucy’s reverie. With some 700 cm2 of cerebral cortex surface area, she has been granted a nebulous glimpse of what would some day be accomplished with three times as much. The glimpse was crude, perforce limited to what she could attain by stretching her mental powers to the utmost. She could not possibly foresee our sciences, our arts, our societies, or our religions, share our thoughts or our emotions. She would have needed more cortical modules for that.
What, we may now ask, would happen if the surface area of our cerebral cortex should triple once more? If we extrapolate from the past, it is obvious that we can no more answer this question with our present mental means than Lucy could have done with hers three million years ago. We can only dream, like her, but without the vague premonitory glimpses our hindsight has given to our reconstruction of her reverie. All we can imagine is that those of our faculties that were born most recently have the greatest chance of developing further. We may assume, in this perspective, that science would become less laborious and impenetrable than it is today. Children would learn relativity theory in kindergarten, if learning was at all needed. Everybody would juggle black holes and superstrings as we now play with crossword puzzles, and handle the genetic vocabulary as we now do the alphabet. Minds would see reality beyond the appearances accessible to the sense organs and, perhaps, communicate with each other without need of speech or writing. Emotions similarly would be experienced without the necessary participation of sight or hearing. Perhaps, the blissful vision of love claimed by some rare mystics will be everyday experience.
All this, of course, is fanciful and necessarily shaped by elements of present reality and experience. By definition, our vision cannot include what to us is unthinkable. The difference between 6,000 and 2,000 cm2 of cerebral cortex surface area is most likely to be as drastic as the difference between 2,000 and 700 cm2. Whatever it implies, this thought is worth keeping in mind as we look into the future of our species and of the living world. This we shall do in Chapter 16. Before we do so, however, we must consider some recent technical developments that radically alter any sort of view we may have of our future.