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1.  Mind and Matter

We begin with our journey with an examination of the relationship between conscious minds and physical matter (traditionally called the “mind-body problem”).

Historical Roots

Before launching into a discussion of modern views on the mind-body problem, it is helpful to consider the historical processes that gave rise to those views. In particular, an historical perspective will enable us to understand the almost religious vehemence with which some positions are held.

In the history of human thought up until surprisingly recent times, it was much more common to attribute mental or psychological properties to seemingly inanimate matter than it is today. Jonathan Shear, the founder and editor of the Journal of Consciousness Studies, notes that the problem of accounting for the existence of conscious experience that confronts modern science was not a problem for the ancient Greeks, as they viewed the material world as being imbued with mind, which served as a force governing the behavior of matter (Shear, 1995).  For instance, Thales of Miletus (died c. 546 B.C.E.) claimed that inanimate objects possessed a psyche allowing them the possibility of self-motion.  A century later Empedocles asserted that all elemental bodies were endowed with thought and sensation (Nash, 1995a).  Epicurus (341-271 B.C.E.) held that atoms have free will and could initiate collisions by swerving from their path, which was believed to be predetermined by such atomists as Democritus and Leucippus (Skrbina, 2005).  This idea has been revitalized many times over the course of development of Western thought.  Even as late as the turn of the last century, Ernst Haeckel (1899/1929) argued that in order for molecules to be attracted to one another, each must somehow “feel” each other’s presence.

 Aristotle taught that the natural state of any body was one of rest.  He asserted that the crystalline spheres which carried the planets and stars on their celestial voyages in his cosmology were associated with incorporeal “movers” that provided the force needed to maintain their motion.  He viewed these movers as being spiritual in nature and conceived of the relation of a mover to its sphere as “akin to that of a soul to its body” (Mason, 1962, p. 42).

Aristotle’s view was given a Christian interpretation by Christian philosophers such as Dionysius in the fifth century and Thomas Aquinas in the thirteenth century, with Aristotle’s “movers” being equated with the angels described in the Scriptures.  Aristotle also attributed psychological properties to baser matter, ascribing the tendency for a terrestrial object to fall to the Earth to its “aspiration” to reach its natural place.

Even as late as 1600, William Gilbert, an English physician and the founder of the scientific study of magnetic phenomena, proclaimed that the Earth has a magnetic soul analogous to the “magnetic soul” that Gilbert believed governed the behavior of lodestones. According to Gilbert, the rotation of the Earth and the inclination of its axis of rotation with respect to the sun were both caused by a desire on the part of the Earth’s soul to avoid extreme temperatures and to cause seasonal variations.  Almost two centuries later, in 1777, the English chemist Joseph Priestley asserted that physical matter was akin to “spiritual and immaterial beings” because of its properties of attraction and repulsion.

  These animistic views of matter gradually crumbled under the onslaught of scientific advances. The law of the conservation of angular momentum (earlier called the doctrine of “impetus”) led John Philoponos in the sixth century and William of Ockham in the fourteenth to deny the need to assume the existence of angels to keep the planetary spheres in motion. After all, if you spin a top, it keeps spinning by itself. (Philoponos was rewarded for this observation by being denounced as a heretic by the Church.)  

In rejecting Aquinas’ angels, William of Ockham was led to formulate his famous injunction “not to multiply entities beyond necessity,” which has since become known as “Ockham’s Razor.”  In fact, Ockham’s Razor, which was originally formulated to justify the exclusion of a class of spiritual beings (Aristotle’s angelic movers) is still one of the primary justifications used by modern scientists and philosophers to deny the existence of a realm of mental experience that is independent of physical events in the brain.  With regard to Ockham’s original application of his principle, the historian of science Herbert Butterfield (1957) viewed the impetus doctrine (in the form of the modern laws of conservation of momentum) as the primary factor underlying the banishment of a spiritual realm from scientific accounts of the world and the establishment in seventeenth century of the view of the universe as material clockwork-like mechanism.  The Calvinist John Preston proclaimed in 1628 that “God alters no law of Nature” (Mason, 1962, p. 181).  Divine intervention by deities or angels was no longer permitted; events were seen to be predictable from, and governed by, the laws of nature alone.   

 Vestiges of divine intervention persisted at least into the 18th century. Issac Newton asserted that divine intervention was necessary to reestablish the regular order of the planets’ orbits, which were constantly being deranged due to gravitational forces among the planets and comets and to a supposed gradual reduction in orbital velocity due to “ether drag” (Christianson, 1978).  However, in general the picture of the universe that emerged from the seventeenth century (at least in Western philosophy) was one of a huge impersonal machine governed by strictly mechanical principles.

Once the picture of the physical universe as a soulless machine gained ascendancy, not only did matter get stripped of its mental and spiritual aspects, so did living organisms. For instance, while Ernest Haeckel used an analogy between the growth of salt crystals and that of living cells to proclaim that all matter had a spiritual aspect, his contemporary Carl Nageli used precisely the same analogy to deny that biological cells were associated with a spiritual force, instead arguing that their growth was due to simple mechanical forces. The chemical synthesis of organic compounds in the laboratory, exemplified by Friederich Wöhler’s synthesis of urea in 1828, further undermined the vitalistic philosophies that insisted that a spiritual force governed biological processes.

Antoine Lavoisier had earlier demonstrated that the ratio of emitted heat to carbon dioxide was the same for candle flames as it was for animals, suggesting that respiration was a purely mechanical process.

While vitalism is not dead, its few modern advocates, including Arthur Koestler (1972, 1978) have been regarded as fringe thinkers by the scientific establishment.   

One of the contributors to this mechanistic cosmology was, paradoxically enough, the seventeenth century philosopher and mathematician Rene Descartes, who is widely regarded as being the prototype of the modern dualist (a dualist being one who regards the realms of mind and matter as having independent reality).  Among the phenomena that had most strongly indicated a mental aspect to matter were those suggestive of the operation of action-at-a-distance, such as gravitation and magnetism.  Descartes was able to eliminate this stumbling block on the road to a totally mechanistic outlook by proposing theories of magnetism (the vortex theory) and gravitation (the plenum theory) that avoided the problem of action-at-a-distance by assuming that these two types of force were transmitted through a physical medium.

Descartes extended his mechanistic philosophy to encompass living creatures as well as inanimate matter. He viewed animals as mere machines.  He did not, however, question the existence of minds in humans; indeed, he thought one’s primary and most direct knowledge was of one’s own mind. He viewed mind as a totally different kind of entity from matter. In Descartes’ view, one’s mind (or ego) was indivisible and hence lacked a basic character of matter—that of extension in space.  Thus, the mind inhabited a different plane of existence from the physical world and could not be said to have a spatial location.

Despite their different natures, Descartes proposed that the mind interacted with the physical body by deflecting the motion of the “animal spirits” flowing through the brain. He thought the pineal gland was the area of the brain in which this mind-matter interaction took place (as the pineal gland was the one structure that was not duplicated in the cerebral hemispheres and thus seemed appropriate to house a unitary and indivisible mind).  Because Descartes’ law of inertia held merely that the total quantity of motion in a system remains constant (but not necessarily its direction), he proposed that the soul acted upon the body by altering the direction of motion of the animal spirits, while not changing the intensity of that motion. 

The mathematician G. W. Leibniz, however, demonstrated that Descartes was in error and that directionality was conserved in the law of momentum.  Thus, Leibniz demonstrated that the physical body (as modeled by Descartes) was a deterministic system. There was therefore no room left for an influence of the mind on the body, and the mind was totally excluded from influence on the physical world. (It should be noted that mind retained a place in Leibniz’ own “monad” cosmology, although that cosmology never gained ascendancy in Western thought.)

As a deterministic clockwork physical universe allows no room for mind-action, it is not surprising that Cartesian dualism soon yielded to the materialism of Hobbes and La Mettrie (and more recently of Watson, Skinner, Dennett and the Churchlands). 

Once again, an application of the law of inertia led to the exclusion of the spiritual realm from scientific models of the world, only this time it was not angels being banished from the heavens, but the human soul itself being banished from its body. Indeed the historian of science Richard Westfall (1977) viewed the rigid exclusion of the psychic from physical nature as the “permanent legacy” of the seventeenth century.

However, since the emergence of the theory of quantum mechanics early in the last century, the brain is no longer viewed as a deterministic system. Thus, the argument from determinism no longer works, and there is now the possibility that an immaterial mind could interact with a physical brain by selecting which quantum state the brain enters out of the many states that are possible at any given time. 

The philosopher Michael Lockwood (1989) has noted that the prejudice in favor of matter was grounded in the apparent solidity of the former in the Newtonian worldview. Lockwood points out that the solidity of matter has disappeared in the theory of quantum mechanics (material particles exist as probability waves in an abstract mathematical space until they are observed) and that mind and matter are now both equally mysterious.

The tenacity with which some scientists resist the idea of an autonomous realm of mind is perhaps understandable in light of history. The emerging mechanistic picture of the world was fiercely resisted by the religious establishment, notable examples being the condemnation of Galileo for the crime of propounding the heliocentric (sun-centered) model of the solar system and the resistance to the theory of biological evolution that is still being mounted by Christian fundamentalists. Thus, any mention of an immaterial soul may raise fears of a descent back into religious irrationalism (and a consequent lack of funding) on the part of many scientists.

Edge (2002a) in fact attributes Descartes’ proposal of his theory of mind-matter interaction in part to his desire to remove the authority of the Church over the scientific investigation of matter.  Edge notes that science could only investigate matter with the tools available in the seventeenth century and that it was (and still is) “not equipped” to deal with mentalistic phenomena.   Edge (2002b) also attributes science’s embrace of the ancient Greek philosophy of atomism (in which the universe is conceived as being composed of microscopic, discrete elementary particles) as another move to reject, or circumvent, the authority of the Church.   

Let us now turn to an examination of modern views on, and “solutions” of, the mind-brain problem.

Monistic Philosophies

Monistic solutions to the mind-brain problem are those that postulate that the universe is composed of only one type of “stuff.” That “stuff” is usually taken to be mind, matter, or some sort of “tertium quid” having both mental and physical properties. Monism stands in contrast to dualism and pluralism, which comprise those philosophical positions that postulate the existence of two or more distinctly different types of “stuff,” with one of them typically being mind and another being matter.

Idealism. The monistic position that contends that the world is composed solely of minds and mental events goes by the name of idealism.  According to idealists, all that exists is mental experience. People consciously or unconsciously construct the hypothesis of a physical world in order to account for certain regularities in their sensory experience, but this is only a convenient fiction. The contention that the physical world may be an illusion is logically irrefutable.  For instance, you may think you are a human being holding a book on the mind-brain problem in your hand, whereas in fact you may be a nucleon-based life form on the surface of a neutron star who has gone into the analogue of a movie theater where strong pion fields have been applied to your brain both to induce amnesia for your real existence and to create in you the illusion that you are some two-legged elongated oxygen-breathing carbon-based being on a remote planetary body for the sole purposes of entertainment.  More simply, you could be merely dreaming or hallucinating. Following the Taoist philosopher Chuang Tzu, the reader might legitimately wonder whether she or he might be a butterfly temporarily dreaming about being a human being reading a sentence about butterfly dreams. I can remember arguing with someone against this position. I maintained that I could not be dreaming because of the clarity and consistency of my sensory experience. Imagine my surprise when I woke up. (This actually happened to me.)

All you can be certain of is your own existence. Seeking certain knowledge, Descartes found that he could not doubt his own existence as a thinking being.  In perhaps his most famous quote, he was led to exclaim, “I think, therefore I am.” All you can be absolutely certain of is your own existence and that you are now thinking certain thoughts, remembering certain memories, feeling certain feelings and sensing certain sensations. The inferences you make about your external environment based on these mental events may not be valid, as you may be hallucinating, remembering falsely, having groundless feelings and thinking delusional thoughts. The doctrine that only one’s self exists or can be proven to exist is a special case of idealism that goes by the name of solipsism.

  The various agencies presumed by idealists to be responsible for producing the illusion of the physical world have included God (in the view of the prototypical idealist, the eighteenth century philosopher Bishop George Berkeley, for whom Berkeley University was named), a collective mind or collective unconscious, and the illusion-producing state of craving and ignorance (according to certain schools of Buddhism).

The reply of most modern scientists and philosophers of science to idealism is that scientific theories that postulate the existence of an objective physical world have produced more exact predictions about possible human observations than have idealistic theories and therefore should be preferred over the latter for that reason. (Such theories are even covertly preferred by most solipsists, who seem strangely reluctant to step in front of illusory oncoming trains. Dr. Samuel Johnson said of idealism, “I refute it thus,” and then he proceeded to kick a rock with his foot. Johnson’s “refutation,” while actually proving nothing, did show his dedication to the anti-idealist cause.)

Idealism is not merely an historical curiosity, but even has its advocates today. Within parapsychology, for instance, Edgar Mitchell (1979), a former Apollo astronaut who once walked on the moon, suggested that an idealistic philosophy may have to be adopted in order to account for the evidence for psychokinesis (the alleged ability of mind to directly influence material objects and systems that are remote from the body.)  The physicist Amit Goswami (1993) has contended that an idealist conception of the world is required in order to render modern theories of physics, in particular quantum mechanics, coherent.

Radical Materialism. Radical materialism is the polar opposite of idealism. Radical materialists deny the existence of mental events, insisting that the world of physical matter is the only reality.  Incredibly enough, this philosophy held sway in the discipline of psychology itself in the early part of this century (at least in the United States).  Behaviorism emerged as the dominant force in psychology in this country as a reaction against the fallibility of the method of introspection that predominated in the earliest days of psychological investigation. Behavior was publicly observable and scientifically measurable, whereas the vague mental images that form, say, a particular individual’s idea of the number seven are not. Some of the leaders of the behaviorist movement, such as John Watson (1924/1970) and the earlier versions of B. F. Skinner (e.g., Skinner, 1953), went so far as to deny the existence of mental events altogether.  This denial of course flies in the face of the fact that the reader and I (if I am not a figment of the reader’s imagination) have directly experienced such mental events as sensations, thoughts, feelings and memories. Skinner’s position essentially contains its own refutation. Skinner could not consistently claim that he believed that mental events do not exist, as that belief would itself constitute a mental event. Therefore by his own theory (and reportedly by his own contention), Skinner’s expressions of belief in the doctrine of radical materialism were merely forms of physical behavior than he had been rewarded for displaying in the past (through royalties, academic honoraria, etc.).  If the books produced by Skinner are in fact merely the product of conditioned typewriter-pecking responses and the sentences within them do not express ideas, there is no need to take these books seriously.  It should be noted that Skinner did eventually retreat from this early radical version of his theory.

Materialism is not dead as a philosophy in modern cognitive neuroscience, however. The philosopher Paul Churchland has recently proposed doing away with “folk psychology” (talk of mental events such as beliefs and desires) in all human discourse (Churchland, 1989, 1995).  He would replace “folk psychology” with a strictly neural account of behavior. Thus, instead of a wife telling her husband that she is really angry at him, she would say instead, “The neurons in my amygdala seem to be firing at an unacceptably high rate.”   

Churchland has in fact gone so far as to assert that truth might cease to be an aim of science! This assertion is implicitly based on the assumption that the concept of truth presupposes the existence of propositions capable of being true or false, which in turn presupposes the existence of mental events such as thoughts, ideas and beliefs that are expressed in such propositions. Churchland proposes that scientific theories should no longer be expressed in terms of sentences but rather in terms of patterns of connections among neurons (or among the pseudoneurons in a computerized “neural net,” as discussed below). But now we are right back where we started. Unless human knowledge is to be given up entirely, Churchland must at least be able to entertain propositions such as “neural net A diagnoses diseases more accurately than does neural net B.” Such propositions, however express beliefs. If Churchland seriously wishes to give up the “folk psychological” concept of belief, then his philosophy self-destructs in the same way that Skinner’s did.

Skinner, incidentally, was by no means the last modern thinker to deny the very existence of private conscious experience, or “qualia” in the terminology of philosophers. The prominent materialist philosopher Daniel Dennett has asserted that “contrary to what seems obvious at first blush, there simply are no qualia at all” (Dennett, 1988, p. 74).  This statement may go a long way toward explaining Dennett’s reasoning.  However, I imagine that reader (like me) has personally experienced a great number of qualia, such as brilliant patches of red and pangs of hunger.  Qualia may be both beautiful and horrifying.  Dennett doesn’t know what he is missing.

Quasi-dualistic materialism. More sensible versions of materialism concede the existence of mental events, but contend that mental events arise solely from physical events and that a complete scientific description of the world can be given in terms of physical processes alone. In one version of this theory, mental events are thought to be brain events experienced from the “inside.” This view goes by the names “central state materialism” and “neural identity” theory, among others. A related doctrine is double-aspect theory. Double-aspect theorists contend that mental and physical events are merely two aspects of a single underlying reality. As the vast majority of double-aspect theorists implicitly or explicitly assume that this single underlying reality is essentially physical matter, this theory is basically equivalent to the previous two. 

Panpsychism.  A similar doctrine is panpsychism, which asserts that all matter, not just living organisms, has a mental aspect.  This view has been advocated by the prominent Western philosopher Alfred North Whitehead (1929/1978), among others.  

Panpsychism, with its contention that rocks and toothbrushes enjoy some form of consciousness, strikes one as absurd at first brush (or even more clearly upon a secondary cursory inspection of one’s toothbrush).  However, when you carefully consider it, the doctrine begins to grow on you.  

A prominent recent proponent of this position is the philosopher David Ray Griffin (1988a, 1988b, 1994, 1997), although he prefers to call his doctrine “panexperientialism” rather than “panpsychism,” as he does not contend that rocks and other inanimate collections of material particles possess a highly unified and structured consciousness, but rather ascribes only vague “feeling-responses” to them.  More highly complex and structured forms of consciousness, in Griffin’s view are restricted to “compound individuals.”  Such compound individuals are composed of, or arise from, a hierarchical collection of more primitive selves or “individuals.”  For instance, a neuron would be a compound individual in relation to its individual constituents such as molecules, and a “suborgan” such as the hippocampus of the brain that is composed of neurons would be a compound individual somewhat further up the hierarchy.  All such “individuals” would have both mental and physical aspects under the panexperientialist view, although only hierarchically-ordered structures would be assumed to have a highly organized and structured consciousness.  Less well-organized structures, such as rocks, would be ascribed only vague “feeling responses” according to Griffin’s panexperientialist theory.   

David Skrbina (2003, 2005) has recently provided a comprehensive and brilliant defense of the doctrine of “panpsychism.”  Skrbina argues for instance that an electron must somehow sense the presence of a proton in order to respond to its attractive force.  (An electron may even enjoy a certain degree of freedom of action due to quantum indeterminacy and may be able to sense a quantum field that is highly complex and global in nature.)  

As does Griffin, Skrbina associates more complex forms of consciousness with aggregates of matter, such as single neurons, or large assemblies of neurons such as hippocampi and cerebral hemispheres.  (However, it should be noted that, as discussed in the previous chapter, such aggregates of matter, much like one’s personality and physical body, do not persist over time and thus cannot form the basis of a continuing self.  Also, fields of consciousness appear to be unitary and indivisible, much more like a quark than like a molecule or a neuron.)

 As Skrbina points out, the panpsychist position solves the problem of “emergence” or the need to account for how organisms acquired consciousness in the course of evolution (i.e., how insensate matter gave rise to consciousness).  As he notes, there is no definitive line of demarcation that can be drawn between conscious and nonconscious organisms, in either the present world or in the course of evolution.  If all matter is imbued with consciousness or if fields of consciousness are fundamental constituents of the universe that have existed throughout its history, then the problem of evolution of consciousness (and of how a three-pound “hunk of meat” like the human brain could generate conscious experiences in the first place) does not arise.

It should, however, be noted that panpsychism still faces the difficulty of accounting for the emergence of a unified mind and global consciousness out of a myriad of psychic elements, as was pointed out long ago by William James and, more recently, by William Seager (1995).

Epiphenomenalism.  Epiphenomenalism is technically a form of dualism, insofar as it grants separate reality to the realms of mind and matter; however, I will classify epiphenomenalism as a form of quasi-dualistic materialism, as it denies that mental events have any influence whatsoever on the physical world. Mental events are considered to be mere “epiphenomena” of physical events in the sense that, while mental events are caused by physical events, they are themselves incapable of causing or influencing physical events. A prominent advocate of epiphenomenalism was the biologist Thomas Henry Huxley (1874, 1877), the grandfather of the noted writer Aldous Huxley,  who was perhaps most noted for his tireless defenses of Darwin’s theory of evolution (so much so that he earned the nickname “Darwin’s Bulldog”).

  Several writers, including the noted mathematician Roger Penrose (1987b) and Karl Popper and John Eccles (1977) have noted that epiphenomenalism in fact goes counter to Darwinism. Why should a conscious mind have evolved, they ask, if it did not play an active role in benefiting the organism? 

Also, and perhaps most amusingly, the mere existence of epiphenomenalist theories is in itself sufficient to refute the doctrine of epiphenomenalism.  After all, epiphenomenalism was developed as an attempt to explicate the role of mental events; therefore, the theory has been created in response to (i.e., has been caused by) mental events; otherwise, epiphenomenalism could not claim to be a theory of mental experience.  Thus, the theory of epiphenomenalism is refuted by the fact of its own existence.  

The physicist Heinz Pagels (1988) raised the question of whether the universe could be a giant computer, much as a personal computer screen can become transformed into a mini-universe with quasi-organisms evolving on it when a program realizing mathematician John Conway’s “game of life” is run on it.  This idea had previously been suggested by Ed Fredkin of M.I.T. and explicitly endorsed by Tomasso Toffoli (1982).  This view has been most recently revived by the noted mathematician Stephen Wolfram (2002), who suggests that universe is best understood as a giant cellular automaton (computerized grid of cells following prescribed rules of behavior).  If this suggestion that the universe is in fact the product of a giant computer has any validity, we cannot equate ourselves with the godlike programmers who created the universe and assume that we have simply each become entranced in the life of one of our three-dimensional creations (which we have come to regard as our physical body). Because of the arguments against epiphenomenalism, we cannot be mere spectators in the world. Our consciousnesses have a more active role in the universe than that.   

Physicalism.  The philosophical positions that I have grouped together under the heading of quasi-dualistic materialism would seem to be equivalent to one another as scientific theories, insofar as they all apparently make the same scientific predictions (mainly that no violations of the known laws of physics will occur in the brain and that no successful predictions regarding the behavior of the brain can be generated from theories involving nonphysical entities such as souls or minds that could not in principle at least be derived from theories referring solely to physical entities and processes).

The empirical findings that most directly challenge the doctrine of physicalism derive from the parapsychologists’ investigations of ostensible psi phenomena such as the clairvoyant reading of ESP cards and psychokinetic influence of the fall of rolling dice.  Because of their importance in this debate and because of the controversies surrounding parapsychological research, these findings and their implications will be discussed in some detail in Chapters 3 through 5.  However, as we have seen in Chapter 0, this evidence is not needed in order to build a strong case that one’s individual self or consciousness is something other than one’s physical body and may be capable of surviving the death of that body, or (perhaps more likely) of departing the body and becoming associated with a new physical system well prior to the death of the body.   

It is commonly held, both by parapsychologists and skeptics, that psi phenomena are inexplicable on the basis of current physical theories and are thus evidence against the doctrine of physicalism, if the latter is construed as the contention that all phenomena can be ultimately accounted for in terms of present theories of physics or relatively minor extensions thereof.

 Joseph Banks Rhine (the researcher who is largely regarded as the progenitor of modern parapsychology and who established the first major research program in experimental parapsychology at Duke University in the 1930s) in particular was highly skeptical that psi phenomena could be explained on the basis of any physicalistic theory. In fact, Rhine suggested that psi was nonphysical in nature, due to the lack of dependence of experimental psi-scoring rates on spatial or temporal separations and the lack of attenuation of the psi signal by physical barriers between the percipient and the target object (e.g., ESP card or die) that would block most known forms of physical signals (such as electromagnetic radiation).  Rhine also cited the fact psi success appears to be independent of the physical nature of the target object, as well as the apparent backward causation in time involved in precognition (and, we might now add, retroactive psychokinesis), as further evidence against any physicalistic explanation of psi phenomena.  At one point, Rhine (1972) postulated the existence of “nonphysical energy” in order to explain psi, a concept that the noted dualist philosopher John Beloff considered to be oxymoronic (Beloff, 1981).

Michael Levin (2000) has made the argument that if psi abilities are based on physical processes grounded in the biomechanical properties of the body, then surely these abilities would be selected for in the process of evolution and would by now be readily apparent in animals’ behavior.  The fact psi is an elusive and rarely observed ability, Levin asserts, constitutes further evidence that it is not derived from the biomechanical workings of animals’ bodies. 

Because it appears to be difficult to account for psi phenomena on the basis of known physical theories or principles, it is often believed that the existence of psi phenomena would falsify physicalism (where “physicalism” denotes the class of theories encompassing radical materialism and quasi-dualistic materialism). As the vast majority of working scientists subscribe to some form of physicalistic solution to the mind-body problem, it should not be surprising that they would choose to reject the claims of parapsychology, insofar as those claims tend to threaten their worldview. 

Some of the resistance of establishment science toward accepting the existence of psi may stem back to the fact that Western science has relatively recently (in the vast scheme of things) emerged from a battle with the Church over who would hold the authority regarding determining the nature of reality, the trial of Galileo being only one prominent example.  There are those who believe that some sort of truce should be declared between science and religion, such as Stephen J. Gould, who asserted that science and religion should be considered as “separate magisteria,” with science holding reign over matters of empirical fact and religion holding reign over ethics and matters of the spirit (Gould, 1999).   However, despite Gould’s contentions, science and religion are in many cases still in conflict over empirical questions, as is evident in the ongoing battle of religious creationists in the United States to have Dawrwin’s theory of evolution either removed or downplayed in high school biology curricula.

This conflict continues to underlie much of the scientific establishment’s resistance toward accepting the findings of parapsychological investigations.    For instance, in a scathing attack on parapsychology, Nicholas Humphrey (1996) asserts that the questions of the existence of souls and of the existence of paranormal powers are not independent issues and that the possession of a soul would imply the existence of such powers. On the other side of the fence, as psi phenomena suggest the existence of a nonphysical aspect to the mind, many people who would prefer to believe in the existence of an immortal soul may tend to adopt a belief in psi phenomena in support of their position. Indeed, John Beloff (1983) even asserted, in a Presidential Address to the Parapsychological Association, that the existence of an afterlife is contingent on the existence of psi, in seeming agreement with Humphrey’s position.  This is undoubtedly too strong an assertion, however, as it is quite conceivable that a mind or soul (or more likely a field of pure consciousness) could survive death even if the living person (or surviving trace) did not possess the powers of ESP and PK.

Even if it is assumed that the explanation of psi phenomena will require the postulation of entities and principles beyond those currently known to physicalistic science, it may be a mere issue of terminology whether such entities are to be considered material or nonmaterial.  If the former, the physicalist can claim victory; if the latter, the dualist can claim the same. Obviously, if mind and matter interact, they form one united system.  Whether one chooses to call that system the physical universe may be a matter of semantics rather than substance. (Some of the theoretical concepts already employed by physicists, such as the quantum-mechanical wave function discussed in the next chapter, already seem more mind-like than material in any event.)

Strangely enough, J. B. Rhine himself disavowed any position of dualism. John Beloff (1981) traces Rhine’s eschewal of dualism to his difficulty in seeing how such dissimilar things as mind and matter could interact, although Beloff himself sees no reason why a cause must necessarily be of the same nature as its effect.   Beloff suggests that Rhine’s position may have been motivated by a desire to avoid charges of supernaturalism as well as a desire to leave the door open for an ultimate cosmology that would embrace both mind and matter.  Beloff notes that Rhine recognized that psi might potentially be given an explanation in terms of quantum mechanics and that Rhine only wished to state the incompatibility of psi with “conventional” physics. Interestingly enough, Frederick Dommeyer (1982) has classified Rhine as a double-aspect theorist, presumably referring to a version of double-aspect theory in which the common substance underlying mental and physical events is something other than matter as currently understood.  

Several other parapsychological theorists have proposed versions of the double-aspect theory. Edmund Gurney, one of the early pioneers of psychical research, proposed that some third form of existence or “tertium quid,” in addition to mind and matter, would be required in order to explain mental phenomena and to bridge the gap between mind and brain (Gurney, 1887).  In more recent times, Carroll Nash (1976, 1995b) has proposed a double-aspect theory to explain psi phenomena.  Nash proposes that mind and matter are each aspects of some tertium quid, or neutral substance, that is not governed by space, time or causality, thus allowing psi to occur (as well as providing the basis for mystical experiences). Nash’s theory does not, however, appear to be sufficiently developed to enable testable predictions to be derived from it.  

Susan Blackmore (2001) has noted that psi phenomena are frequently invoked in support of the contention that consciousness plays some fundamental role in the universe.  She argues that, in view of the fact that psi is often considered to operate primarily at a subconscious or unconscious level, the assertion that psi phenomena are evidence for a fundamental role for consciousness is unwarranted.

Machine Consciousness. Most people would grant consciousness to seemingly intelligent animals such as chimpanzees, elephants, whales and dogs, although there are still those who follow Descartes’ lead in denying consciousness to all animals other than human.  (Descartes thought that “lower” animals were mere machines, from whence springs the opinion expressed by some people today that animals can not suffer or feel pain, thus rationalizing the mistreatment of such animals.)  Most people, aside from the panpsychists, would draw the line between conscious and nonconscious beings somewhere “down” the “hierarchy” of living and nonliving things, perhaps before one gets to ameobae, petunias, or slabs of granite.  

What about humanly-manufactured machines that exhibit more complexity and activity than does, say, a slab of granite?  Do thermostats feel a twinge of pain when the thermometer passes the set point and the furnace is not yet turned on? The famous neurophysiologist W. Grey Walter constructed mechanical “tortoises,” which ambulated about his house randomly until they ran low on power, at which point they would proceed to the nearest electrical socket to recharge themselves. Were Walter’s tortoises conscious?  Did they feel “hunger” for electricity?  What about modern computers that can defeat any human at chess?

Many people argue that, if a machine or computer were able to duplicate human thought processes, there is no need to postulate the existence of an immaterial mind or soul to explain human thought, as human-manufactured computers are presumably not endowed with such ethereal entities as souls or minds.

Roger Penrose (1987b), David Layzer (1990) and John Searle (1990), have argued that, even if computers were to prove capable of simulating human behavior, this would not imply that computers possess awareness or have conscious experiences. Rather, they see the biochemical “wetware” of the human brain as having specific properties necessary for the production of consciousness that the hardware of a typical digital computer lacks.  On the other hand, their assertions that the particular properties of biological wetware are necessary for the generation of conscious experience are not in general supported by any convincing argument.  It would be desirable, therefore, to have a more or less objective test to determine whether a computer or robot is conscious.

Just such a test was proposed by the mathematician Alan Turing (1950, 1964) in the form of an imitation game (which has since become known as the Turing test).  If a human being communicating with a computer and with another human being through a teletype machine (or, these days, a computer monitor) cannot tell which is the computer and which is the human being, then the computer should be deemed conscious (in other words, if you are willing to ascribe consciousness to the human being on the basis of her behavior, you should extend the same courtesy to the computer).

Could a computer successfully pass the Turing test? Computers operate by following mathematical algorithms (fixed, mechanical procedures for solving a problem or producing output).  Roger Penrose (1987b, 1989, 1994) has argued that human thought does not rely exclusively on such algorithms. Penrose bases his contention that human thought must have a nonalgorithmic component in part on mathematician Kurt Gödel’s famous incompleteness theorem. In 1931, Gödel shocked the mathematical world by demonstrating that there exist statements within any reasonably powerful mathematical axiom system that are true but which can never be proved to be true within the axiom system itself. To oversimplify slightly, such a statement might read as follows: “This theorem is not provable.” Let us call this statement Theorem X. If Theorem X were provable, a contradiction would result, as Theorem X asserts its own unprovability. Therefore, if the mathematical axiom system is consistent, Theorem X could never be proven. Consequently, Theorem X is true, as it simply asserts its own unprovability. Computers, being driven by algorithms, are equivalent to mathematical axiom systems. Hence, a computer would be unable to perceive the truth of its own Theorem X, as it would only regard as true those statements that it could prove.  Humans, on the other hand, are readily able to perceive the truth of such statements as Theorem X.  Hence, Penrose argues, human thought is not algorithmic and therefore could not be simulated by an algorithmic computer. The chief difference between the computer and the human in this regard might be that the human can understand the meaning of the statements involved, whereas computers just blindly manipulate symbols according to prescribed rules without any idea of what those symbols might mean.

Penrose has further argued that, as human awareness must be noncomputational in nature and as current laws of physics are essentially computational systems, new principles of physics may be required to explain humans’ capacity to achieve direct insight into mathematical problems and to understand the meaning of language. 

Penrose (1994) observes that Kurt Gödel himself maintained that the mind was not identical to the physical brain, as Gödel felt that the physical brain would necessarily be a computationally-based system.  Gödel was thus a dualist.  As we shall see, Penrose has come to view consciousness as intimately connected to nonlocal quantum processes in the brain.  He sees such noncomputable quantum processes as being a prerequisite for consciousness.  Any system based entirely on simple computation must be nonconscious in Penrose’s view.

Paul Churchland (1995), perhaps the foremost defender of radical materialism in the modern era, has expressed agreement with Penrose’s position that human reasoning is nonalgorithmic.  Churchland does not, however, see such nonalgorithmic reasoning as emerging from arcane quantum mechanical processes, but rather from the continuous, analog nature of the human brain (as compared to Turing machines, which operate by entering one discrete state after another).

Philosopher John Searle (1987, 1990) has argued that even if a computer were to successfully simulate human behavior, this would not imply consciousness on the part of the computer. As an analogy, he considers the case of a person who does not speak Chinese who sits alone in a room with a book of rules instructing him how to respond to strings of Chinese characters. While a speaker of Chinese may think he is engaging in a dialogue with this person by swapping notes back and forth under the door to the room, the person inside the room does not in fact understand what the Chinese speaker is saying or what he himself is saying, as he does not know what the symbols mean. Similarly, Searle argues, computers are engaged in a purely syntactic manipulation of symbols and have no idea of what those symbols mean. 

Christian Kaernbach (2005) recently tested Searle’s Chinese room argument by having human subjects simulate addition and multiplication modulo 5 (i.e., “clock” arithmetic on a five-hour clock in which 3 + 4 = 2, for instance) by following a “look up” table similar to that provided to the subject in Searle’s Chinese room.  Kaernbach found that his subjects gained no insight into the meaning of their symbolic operation unless they were specifically informed of the connection to mathematical operations.  Kaernbach’s results would appear to substantiate Searle’s intuition.

In his later publications, Searle does concede that a robot might be said to have semantic and not just merely syntactical understanding of linguistic symbols if the robot were provided with sensing devices (such as TV cameras) and motor apparatus (such as robot arms). In such a case, the robot could develop a sensory “awareness” of the outside world and could gain an inkling of “insight” into the fact that words refer to objects and events in an outside world.

 It may be argued that, even if a computer could simulate human thought, humans quite possibly possess psi abilities that may be indicative of a spiritual or immaterial aspect to human beings.  Computers, being mere machines, would presumably be incapable of demonstrating such psi powers. Actually, Turing himself considered this objection in his original proposal of the imitation game. He suggested that computers might be able to manifest, or least simulate, psi powers if a random event generator (REG) were included in the computer’s design.  Such REGs, which are a common tool of the parapsychologist’s trade, are essentially electronic “coin flipping” devices, often based on quantum mechanical uncertainty.  For instance, “heads” might be defined to occur if a Geiger counter recorded the first decay of a strontium 90 atom in as occurring during an odd microsecond, and “tails” might be defined to occur if the first decay occurred during an even microsecond. Such quantum mechanical decay is based on the Heisenberg uncertainty principle and is (according to standard theories of physics) truly random.  Even a physicist with complete knowledge of the REG system (which must be less than complete in any event due to the Heisenberg uncertainty principle) could not predict when such a decay will occur.

Once the REG system is implanted in the computer, the computer might appear to have psi powers (at least if humans themselves have such powers).  For instance, in a telepathy experiment, the “sender” (e.g., person looking at an ESP card and attempting to transmit its identity to the computer) could subconsciously use his psychokinetic (PK) powers to influence the REG in such a way as to make it appear that the computer has ESP.  Various PK tasks posed to the computer might be performed inadvertently through the experimenter’s use of her own PK abilities (especially if the experimenter was rooting for the computer).  Thus, to all appearances, the computer would have psi powers. 

To pursue this line of thought even further, it would be interesting to speculate what would happen if a large number of quantum-mechanically based REGs were installed in the computer.  If minds are to be equated with the “hidden variables” that govern the outcome of quantum decisions, perhaps such a largely nondeterministic computer would be able to acquire a mind.  Of course, it would no longer be the sort of deterministic, algorithm-following sort of computer that is known as a Turing machine. Instead, it might be something approaching a silicon-based life form.

In the end, the real test of consciousness in automata such as robots and computers may be to wait to see if such machines spontaneously express curiosity and wonderment about their own inner experience, much as human philosophers of mind do. Presumably, a nonconscious computer would not develop a preoccupation with the machine equivalent of the mind-body problem.

Dualistic Philosophies

We are thus led to consider dualist positions, which grant independent reality to both mental and physical events. We will begin with parallelism.

Parallelism. Parallelism is a peculiar form of dualism in that it insists that the realms of mind and matter are totally separate and do not interact at all. One of the foremost advocates of this doctrine was the seventeenth century mathematician and philosopher Gottfried Willhelm Leibniz (1714/1965), who asserted that God had placed the physical and mental realms in “preestablished harmony” so that they are forever in correspondence with one another, much as two synchronized clocks continue to display the same time as one another. Parallelism seems to have one more realm than it needs.  After all, the reason that we postulate the existence of a physical world in the first place is to explain certain regularities in our sensory experience. If the physical world is not the cause of our sensations, there is really no reason to postulate its existence at all. Which brings up…

Interactionism. Interactionists, as their name implies, assume that the mental and physical realms do in fact interact with one another. Unlike epiphenomenalism, in interactionism the causal highway is a two-way street. Not only do events in the physical realm cause mental events, but mental events are capable of influencing physical events as well.  As we have mentioned, since the advent of the theory of quantum mechanics, the brain is no longer considered to be a completely deterministic system and therefore could be open to influence from a mental realm. (In this context, however, it should be noted that some die-hard materialists such as philosopher Daniel Dennett (1991) continue to reject dualism on the basis of arguments involving the outmoded concept of a deterministic brain system.)  In fact, the brain seems almost designed in such a way as to maximize its receptivity to such influence from a nonmaterial mind. Neurophysiologist John Eccles has called the brain just “the sort of a machine a ‘ghost’ could operate,” as its functioning is dependent on minute electrical potentials and the motions of neurotransmitter molecules and calcium ions (Eccles 1953, p. 285).  Several prominent physicists, including Niels Bohr (1958), Arthur Eddington (1935), Henry Margenau (1984), Euan Squires (1990) and Henry Stapp (1992), have explicitly proposed that the mind interacts with the brain by influencing the outcome of quantum processes within the brain.  

Roger Penrose (1987a) has suggested that the “oneness” or “global” quality of consciousness may be related to nonlocal quantum connections between neural processes in the brain, and he further notes that neurons, unlike the elements of deterministic computers, are subject to quantum mechanical influences.  In the more recent versions of Penrose’s theory, he proposes that water molecules in the microtubules composing the cytoskeletons of widely separated neurons could exist in a quantum-mechanically coherent state. As the configuration of such cytoskeletons could influence the synaptic connections between neurons, this would provide a nonlocal means of unifying neural activity over wide regions of the brain. In fact, Penrose equates the operation of free will with quantum mechanical decisions influencing the configuration of such microtubules.  It should, however, be noted that Penrose objects to the dualistic view that an immaterial mind external to the physical brain system can influence the outcomes of quantum mechanical processes in the brain.  Rather than being caused by conscious awareness, Penrose proposes that quantum mechanical state vector reduction occurs when the energy difference between the alternative physical outcomes becomes sufficiently great (Penrose, 1994).  Penrose’s theory is based in part on Stuart Hameroff’s proposal that the cytoskeletal microtubules within neurons may be centrally involved in the computational activity of the brain. Hameroff, incidentally, concurs with Penrose’s view that conscious experience may involve nonlocal quantum connections between microtubules in widely separated neurons.  Hameroff thinks that such connections may help to bind diverse neural activity into unified perceptions and experiences and to provide a unified sense of the self. He also sees such connections as providing the indeterminism necessary for the operation of “free will” (Hameroff, 1994).   

In particular, Penrose has contended that water molecules in widely separated microtubules could exist in a quantum-mechanically coherent state and that nonlocally correlated changes in cytoskeleton configurations could alter synaptic connections between neurons. He sees such conformational changes as being intimately associated with the experience of “free will” (Penrose, 1994).  However, Rick Grush and Patricia Churchland (1995) have argued that microtubules are not in close enough proximity to the synaptic complex to influence synaptic transmission.  They also note that the gout drug colchicine depolymerizes microtubules, disrupting any quantum mechanical coherence that might be present, but is not associated with any loss of consciousness.   In reply to Grush and Churchland, Penrose and Hameroff (1995) counter that very little colchicine enters the brain and that most brain microtubules are hardened and do not undergo cycles of polymerization and depolymerization. They also note that the drug does in fact cause impairments in learning and memory.

  David Hodgson (1991) has seconded Penrose’s assertion that consciousness is intimately dependent on nonlocal connections between spatially separated brain events.  In his view, such connections help forge a united perception of an object from its separate features.  He conjectures that nature had to provide such nonlocal connections in order for consciousness to exist.  He further contends that only indeterministic systems are associated with consciousness, as conscious minds would be of no use to a mechanistic system.  Physicist A. J. Leggett  (1987a) has even suggested that new quantum principles may be needed to describe the behavior of complex systems such as brains.  Penrose (1994) agrees with this position of Leggett and proposes that new laws of physics will be required to explain noncomputational brain activity.

There has even been an attempt to subject the theory that nonlocal quantum processes undergird conscious thought to an experimental test.  Nunn, Clarke, and Blott (1994) found that when a record was made of the electrical activity of one of the brain’s hemispheres, performance on psychological tasks involving that hemisphere was enhanced.  More specifically, they found that subjects’ performance in a button-pushing task was more accurate if EEG recordings were made of the motor areas of the brain involved in the task than if recordings of other areas of the brain were made.  Presumably, the making of an EEG recording assisted in collapsing quantum mechanical state vectors, resulting in more efficient cognitive performance.  

There have been many who have had difficulty conceptualizing how such different entities as mind (which Descartes and many subsequent philosophers regarded as immaterial and lacking any spatial extension) could interact with matter.  For instance, in regard to Descartes’ notion that the mind interacted with the human brain through the deflection of the animal spirits as they passed through the pineal gland, the philosopher Thomas Metzinger says: 

Something without any spatial properties cannot causally interact with something possessing spatial properties at a specific location.  If Descartes had taken his own premises seriously, he could never have come up with this solution, which is so obviously false.  If the mind truly is an entity not present in physical space, it would be absurd to look for a locus of interaction in the human brain.  (Metzinger, 2003, p. 381.  Emphasis in original.) 


As each of us seems to be somehow “stuck” in a human brain, however temporarily, it would in fact seem that the self, construed as a field of consciousness, does have some spatial properties, if only the property that it is, at least temporarily, somehow stuck to (or under the panpsychistic hypothesis, part of) a human brain occupying a particular region in space.

From this it does not follow that the self in its entirety is confined to a spatial location in the human brain or circumscribed region of space.  As we shall see in the next chapter, even the elementary particles of matter such as electrons and protons typically do not have any particular spacetime location until they are forced to adopt one through an act of observation.  Even physical matter lacks the material properties ascribed to it by Metzinger.

The British psychologist and philosopher John Beloff (1998) notes that under the general theory of relativity, matter influences and is influenced by spacetime, despite the fact that material particles and spacetime continua are radically different types of entities.  If their different natures do not prevent matter and spacetime from mutually influencing each other, argues Beloff, then there is not reason why mind and matter could not also interact despite their seemingly different natures.  Similarity in properties may not be a necessary condition for causal interaction.

Another conceptual objection to interactionism is that mind-brain interaction would involve violations of the laws of physics.  Many writers, including Mohrhoff (1999), Wilson (1999), Levin (2000), Jaswal (2005) and Clark (2005a), have argued that any action of a nonphysical mind on the brain would entail the violation of physical laws, such as the conservation of energy and momentum and the requirement that the outcomes of quantum processes be randomly determined.

Levin (2000) argues that dualist interaction would involve a violation of the law of the conservation of energy.  However, the noted philosopher Karl Popper has suggested that the mind may have its own source of (presumably physical) energy.  Under this view, the mind would be a sort of quasiphysical object that might be capable of greater influence on the brain than that allowed by the Heisenberg uncertainty principle of quantum mechanics. Popper even went so far as to assert that the law of energy is only “statistically valid” (Popper & Eccles, 1977, p.541).  Without going to this extreme, it could be argued that mind is capable of exerting some force on some of the material particles in the brain.  Also, we are a long way from having measured with precision every minute energy transaction in human brains. In the process of doing so, it is conceivable that some unexpected energy transaction may be observed. If science should progress to the point where the action of spheres of consciousness on energy transactions within the brain can somehow be mathematically (or otherwise) described, this might be a victory for the contention that immaterial minds can exert physical force.  If such spheres of consciousness are identified with known material particles and system, the physicalists could claim victory.  If not, the dualists could so declare.  

If spheres of consciousness could exert some sort of physical force, it is likely that they would be declared as a new form of physical matter or energy, resulting in a victory for the physicalists.  If the present day physicalists opine that all physical particles have already been discovered, this may only be evidence for the psychological tendency toward premature closure, in that they fervently wish to believe that they already possess virtually complete understanding of the universe.  But such a declaration could only be the worst form of arrogance in view of the fact, already noted, that physicists have only recently discovered the existence of dark energy, which is now believed to comprise three-quarters of the matter-energy in the universe.

Many writers (e.g., Beck, 1994; Bohr, 1958; Eddington, 1935; Hameroff, 1994; Hodgson, 1991, 2005a; Leggett, 1987a, 1987b; Margenau, 1984; Penrose, 1994; Squires, 1990; Stapp, 1992, 1996; Walker, 2000) have noted that the classical deterministic theory of Newtonian physics has been replaced with the indeterminism of quantum mechanics, in which many possible futures may arise from a given present state of the universe, and have suggested that the conscious mind or “free will” may act on the brain by selecting a particular quantum state (i.e. forcing the quantum mechanical state vector to “collapse” to a desired outcome).  In fact, Eccles (1953, p. 285) noted that the brain is just “the sort of machine a ‘ghost’ could operate,” as its functioning is dependent on minute electrical potentials and the motions of neurotransmitters and calcium ions.  Thus, in Eccles’ view, at least as expressed in his later writings (e.g., Eccles, 1989), changes in macroscopic brain activity may be brought about without violating the limits of indeterminacy allowed under the theory of quantum mechanics.

A similar view has been expressed more recently by physicist Henry Stapp (2005b), who asserts that quantum mechanical laws must be used to describe the process of exocytosis (the emission of neurotransmitters into the synaptic cleft), citing empirical research in support of this assertion (Schwartz, Stapp & Beauregard, 2005).  In particular, Stapp notes that the “quantum Zeno effect” (maintaining a quantum state through repeated observation) provides a means whereby conscious minds could act on the physical brain, namely by holding the brain in a particular state.  He cites William James’ observation that the role of conscious attention is to preserve brain states in support of this view.  He also notes that Pashler (1998) has observed that consciousness may act as an information-processing bottleneck in this regard.   

Contrary views have been expressed by Jaswal (2005) and Clark (2005a), among others, who argue that any such influence on quantum mechanical processes would lead to a violation of the statistical predictions of quantum mechanics and the principle that the outcome of quantum mechanical processes are randomly determined.  Such influence would therefore constitute a violation of the laws of physics.   

First of all, it should be noted, as many observers have argued, that description of the universe afforded by the laws of quantum mechanics is incomplete.  Also, no one has provided, or likely ever will provide, a complete description of the quantum state of any brain at any time.  We may discover new entities or processes that may be identified with the so-called “hidden variables” that determine the outcomes of quantum processes.  Also, quantum mechanical outcomes may indeed be random in simple physical systems, but may be less random in certain complex systems, such as human brains, in which the observing consciousnesses may have a more vested interest.  It may also be that such consciousnesses enjoy a closer physical proximity to physical brains, on the view that quasi-physical spheres of consciousness may be, at least, temporarily, somehow “stuck” in physical brains.  

Thus, it might turn out that the outcomes of quantum processes inside complex systems such as brains are not randomly determined but are governed by fields of consciousness, whereas those in simpler systems are not so governed.  Also, many parapsychological researchers, going back to Schmidt (1969, 1970), have produced evidence that conscious minds may be capable of determining, or at least biasing, the outcomes of quantum processes, as will be discussed in more detail in subsequent chapters.  

Having discussed the general framework, we will now consider specific versions of dualistic interaction that have been proposed in recent times.  Thus discussion will be an introductory one, and a more detailed discussion of some of the philosophical and scientific issues raised by modern models of dualistic interaction will be postponed until Chapters 2, 5 and 7.

Eccles’ theory of mind-brain interaction.  There are few adherents to the doctrine of dualistic interaction among working scientists today.  John Eccles was perhaps the most prominent example of such a scientist in the second half of the twentieth century.  Eccles was a renowned neurophysiologist, who in 1963 shared the Nobel prize in medicine and physiology with his coworkers A. L. Hodgkin and A. F. Huxley.  The prize was awarded for their studies of the axons of the giant squid, establishing the membrane theory of nerve conduction and demonstrating the exchange of sodium and potassium ions across the membrane (which has come to be recognized as the basic mechanism of nerve impulses).

Eccles progressively elaborated his dualistic model in a series of publications spanning several decades (e.g., Eccles, 1953, 1970, 1977, 1979, 1980, 1983, 1987, 1989; Eccles & Robinson, 1984; Popper & Eccles, 1977).  Eccles felt that it is necessary to postulate the existence of a mind separate from the brain in order to explain the integration of mental activity.  In particular, Eccles felt that the integrated perception of objects and visually presented scenes cannot be explained in terms of known neurological processes, in view of the fact that the nervous impulses related to visual experiences appear to be fragmented and sent to divergent areas of the brain. For instance, Christof Koch and Francis Crick count from 30 to 40 different cortical areas specializing in different aspects of visual processing (Koch & Crick, 1991). Similarly, Wilson, Scalaidhe and Goldman-Rakic (1993) have described the separation of the neurons dealing with the spatial location and identity (color and shape) of an object in the prefrontal cortex of the brain of a monkey.  Hodgson (2005b) notes that red circles are experienced as a whole (or “gestalt”) despite the fact that the neurons “reporting” “red” and “circle” are located in different areas of the brain.

In view of the fact that the perception of any single object involves the firing of neurons in widely dispersed areas of the brain, it is difficult to understand how this neural activity can possibly result in a unified perception of an object.  This conundrum is generally termed the “binding problem” (Koch & Crick, 1991). In Hodgson’s view, the experience of gestalts such as his example of the red circle indicates that consciousness may be nonlocal in the quantum mechanical sense (Hodgson, 2005b).  The relationship between quantum nonlocality and consciousness will be revisited several times in the chapters to follow.

 Stacia Friedman-Hill, Lynn Robertson and Anne Triesman (1995) report an instance in which a breakdown of this perceptual unity was apparent in a patient who miscombined colors and shapes from different objects and who was unable to judge the locations of objects. This patient had bilateral lesions in the parietal-occipital areas of the brain, suggesting that these brain regions may be centrally involved in generating unified perceptions of experience.  

Francis Crick (1994) ascribed the unity of perception to rhythmic oscillations in the brain resulting in the synchronous firing of large populations of neurons.  

Two other neurophysiologists, Gerald Edelman and Giulio Jononi (1995), have contended that the binding of perceptions and the unity of experience is achieved thorough reentrant signaling pathways in the brain.

Eccles, on the other hand, saw the integration of neural activity as the raison d’être of an immaterial mind, and he suggested that the evolution of consciousness may have paralleled the emergence of the visual processing mechanism.  He endorsed William James’ conjecture that brains may have had to acquire conscious minds because they had grown too complex to control themselves.

Eccles proposed that another role of consciousness is to assist in the solving of nonroutine problems (as opposed to the execution of overlearned and routine skills such as tying one’s shoes). Eccles’ view of the role of consciousness is similar to that of many cognitive psychologists in this regard.

Eccles contended that the mind interacts with only certain groups (or “modules”) of neurons, which he called “open neurons.”  He used the term “liaison brain” to refer to the regions of the brain containing these open modules, and he asserted that this liaison brain lies in the cerebral cortex rather than in the deeper areas of the middle brain. In support of this site, he cited a study by Bard (1968) indicating that cats who have had their cerebral cortex removed behave as if they were mindless automata.

In his earlier writings, Eccles maintained that the liaison brain was generally located in the left cerebral hemisphere, due to the fact that language ability is usually located in that hemisphere and the fact that split-brain patients typically report (from the left hemisphere where their language skills are located) that they have experienced no discontinuity in their sense of self following their commisurotomy (an operation that involves severing the corpus callosum, a bundle of nerve fibers that connect the two hemispheres of the brain and provide the primary means for communication between them).

Some evidence in favor of Eccles’ theory that the left brain is the site of consciousness was provided by a study by Efron (1963b) indicating that flashes presented to the left and right visual fields were judged to be simultaneous only when the flash on the left occurred several thousandths of a second before the one on the right, suggesting that the judgment of simultaneity was made on the basis of the simultaneous arrival of the neural messages at a site in the left hemisphere. (Strangely enough, information about the right visual field is sent directly to the left hemisphere and information about the left visual field to the right.)

Another piece of evidence in favor of locating the liaison brain in the left hemisphere is the fact that migraine attacks and brain injuries are more often associated with a loss of consciousness when they occur in the left hemisphere than when they occur in the right (Miller, 1990).

In his earlier writings, Eccles tended to see linguistic ability as a prerequisite for self-consciousness, and he consequently denied self-consciousness to most nonhuman animals and even to the right hemisphere of the human brain following commisurotomy.  He later recanted this position, citing Gallup’s (1977) research demonstrating self-recognition by chimpanzees when confronted by their images in a mirror (they cleaned spots off their faces) and research by Sperry, Zaidel and Zaidel (1979) demonstrating the ability of the right hemisphere in split-brain patients to recognize pictures of themselves (the patients, not the hemispheres!).  Eccles maintained that consciousness is restricted to birds and mammals, the brains of lower animals such as bees and frogs being too small to support consciousness in his view. (Interestingly, Eccles has assigned consciousness to precisely those animals that sleep. Could there be some significance to this?)

In Eccles’ earlier writings, he expressed doubt that influences at the quantum level would be sufficient to explain the influence of the mind on the brain, as he felt that quantum events would be too random to account for the “precisely causal” events in the mind-brain interaction. In his later writings, he changed his mind, observing in particular that the exocytosis of synaptic vesicles (a primary mechanism in the transmission of nervous impulses from one neuron to another) involves energies within the range of the Heisenberg uncertainty principle of quantum mechanics (and thus would allow the mind to influence the brain by determining the outcomes of quantum decisions).  Although Eccles cagily avoided referring to parapsychology in most of his writings, as least on one occasion (Eccles, 1977), he used the word “psychokinesis” to describe the mind’s action on the brain.

The prominent philosopher of science Karl Popper, with whom Eccles wrote his most encyclopedic volume, The Mind and Its Brain, also endorsed a quantum-mechanically based theory of mind-brain interaction; however, at one point in the book Popper suggested that the mind may have its own source of (presumably physical) energy (Popper & Eccles, 1977).  Under this view, the mind would be a sort of quasi-physical object that might be capable of greater influence on the brain than that allowed by the Heisenberg uncertainty principle of quantum mechanics. Thus, the conscious mind proposed by Popper is a powerful one indeed.

Penfield’s theory of mind-brain interaction. Another prominent neurophysiologist to propose a dualistic model of mind-brain interaction in the second half of the twentieth century was Wilder Penfield. The most complete exposition of his model was given in his posthumously published book The Mystery of the Mind (Penfield, 1975).  Unlike Eccles, Penfield did not locate the site of mind-brain interaction in the cerebral cortex, but rather in the evolutionarily older region of the higher brain stem (diencephalon).  (Such a site would make evolutionary sense if immaterial minds are to be attributed to more “primitive” organisms that lack a neocortex.)  As one piece of evidence in favor of this localization, Penfield cited the fact that injury to this site typically removes consciousness and results in a coma.  Interestingly, Penfield did not believe that the site of mind-brain interaction lies in the reticular activating system of the brain stem, despite the fact that injury to this area also produces unconsciousness. This was due in large part to the fact that Penfield assigned a central role to the diencephalon in the integration of brain activity.  In particular, he cited the vast number of two-way connections between the diencephalon and the cerebral cortex as evidence for such a central role. 

The neurophysiologist Robert Thompson agreed with Penfield that the higher brain stem may be centrally involved in integrating behavior.  In support of this assertion, Thompson cited research indicating that injuries to this region produce deficits in a wide range of learning and problem-solving tasks as well as evidence indicating that memories may be stored in this region (Thompson, 1993). 

The physicist Nick Herbert (1993) locates the site of consciousness a bit further down, in the reticular formation of the brain stem.  Herbert sees this area as having a central role in the integration of sensory information and the regulation of behavior.  He sees the cortex as a peripheral device that is not associated with consciousness.

John Eccles (in Popper & Eccles, 1977) explicitly took issue with Penfield’s proposed site of mind-brain interaction, arguing that injury to the brain stem merely removes the background excitation of the cerebral cortex that is necessary for consciousness to occur.   As evidence against Eccles’ localization of the site of mind-brain interaction in the cerebral cortex, Penfield cited the fact that large portions of the cerebral cortex can be removed without loss of consciousness.

As further evidence in support of his proposed site of interaction, Penfield cited the fact that epileptic seizures in the higher brain stem cause a person to behave as a mindless automaton, carrying out preprogrammed motor acts without a later memory of them. Penfield saw conscious attention as a prerequisite to the storing of memories.  In this, he agreed with Eccles, who cited an experiment by Held and Hein demonstrating that active exploration of the environment is associated with learning in kittens, whereas passive exploration (being carried around a room) is not (Eccles, 1979, discussing the experiment reported by Held & Hein, 1963).  However, in cases of multiple personality, secondary personalities seem to be capable of storing memories when the primary personality is distracted or unconscious (although such memories are not generally accessible to the primary personality).

As evidence that the conscious mind lies outside of the brain mechanism, Penfield cites the fact that movements or other activity produced by electrical stimulation of the brain are experienced as ego-alien and involuntary. For example, if Penfield applied an electrical stimulus to a patient’s brain causing her to raise her arm, she typically experienced the raising of the arm to occur independently of her will. Electrical stimulation of the brain never resulted in a sense of volition. (Of course, a materialist could object that this merely proves that the brain can discriminate arm movements initiated by it in an unmolested state from those caused by the application of an outside electrical impulse.) Penfield specifically declined to use the word “immaterial” to describe the mind, perhaps because he viewed such a term as implying a total separation between mind and matter.

Other views on mind-brain interaction. Many other theorists have forwarded their own hypotheses regarding the nature and location of mind-brain interaction. The number of sites proposed is legion, and at times it seems that no area of the brain will prove to be exempt from being designated as the site of the soul.  

V. S. Ramachandran (1980) sees the frontal lobes as the likeliest candidate for the site of mind-brain interaction, partially due to the fact that persons with frontal lobe lesions frequently report a loss of coherence and continuity in their sense of self. 

Joseph LeDoux (1985) equates consciousness with language use and thus associates it with the linguistic apparatus of the brain. He therefore denies consciousness to the right hemisphere in split-brain patients unless it possesses a linguistic capacity, in which case LeDoux would ascribe a dual consciousness to the patient. 

John O’Keefe (1985) sees consciousness as primarily concerned with the construction of mental representations of the world. He would therefore locate consciousness in the septohippocampal region of the brain, insofar as the neurophysiological evidence suggests that “cognitive maps” may be located in this area (certain neurons in a rat’s hippocampus may fire when the rat is in a particular location). O’Keefe also notes that conscious attention is necessary for the storage of episodes and narratives in memory, and certainly the hippocampus must be intact in order that such memories be stored.  Patients with damage to the hippocampal region are generally unable to form new episodic memories. Such a patient may for instance believe he is still a soldier in Korea, having formed no memories of events occurring in the years since he received his head injury.

O’Keefe further notes that consciousness is especially involved in dealing with novel events. The conscious mind, he asserts, selects actions to be carried out, but is not involved in the details of these action programs (such as the specific steps involved in tying a shoe). These action programs instead tend to be automatic and occur outside of awareness. He does note that consciousness is involved in the initial learning of such programs. Conscious attention is also activated when the result of a motor action is unexpected and deviates from the fixed action plan. He observes that certain neurons in the hippocampal area tend to fire when an organism is confronted with a novel situation, which he takes as further support for the hippocampus as the site of consciousness.

Like O’Keefe, David Oakley (1985a, 1985b). asserts that the conscious mind is intimately involved with the creation of cognitive representations of the world. He notes that the hippocampus and neocortex must be intact for such representations to emerge, as opposed to simple conditioned responses.   In an article written with Lesley Eames, Oakley suggests that two or more domains of consciousness may coexist within a single person (Oakely & Eames, 1985). Oakley and Eames note, for instance, that associative learning occurred separately for each of the alternate personalities in the “Jonah” case of multiple personality (Ludwig, Brandsma, Wilbur, Bendfeldt & Jameson,1972), whereas Pavlovian conditioning, which they view as noncortical and automatic, was shared among the different personalities.  Oakely and Eames also attribute a dual consciousness to split brain patients, although they see “self-awareness” as usually being restricted to the left hemisphere.

Benjamin Libet (1989, 1991a) views the supplementary motor area (SMA) of the cerebral cortex as being one of the primary areas that is involved in voluntary acts.  In this he agrees with Eccles, who at one point went so far as to say that “there is strong support for hypothesis that the SMA is the sole recipient area of the brain for mental intentions that lead to voluntary movements” (Eccles, 1983, p. 45).  Libet notes that patients with damaged supplementary motor areas are often incapable of spontaneous voluntary movement; while they may listlessly respond to suggestions from others, they seldom initiate movements on their own. In this sense their will is curtailed. Libet’s view is underscored by Goldberg’s observation that lesions of the supplementary motor area lead to repetitive hand movements, such as buttoning and unbuttoning a shirt, that are experienced as ego-alien and occurring independently of the subject’s will (Goldberg, 1985).  Libet further observes that blood flows into the supplementary motor area when movements are merely being contemplated.

Libet’s own experiments indicate that subjects’ decisions to initiate motor movements (flexing the hand) typically do not occur until 350 milliseconds after a readiness potential has begun to build in the brain, indicating that the brain itself has already been preparing for movement at the time of the subject’s experienced decision.  Libet notes, however, that mind-brain interaction must be a two-way street, and he found that subjects could change their mind about flexing their hands during the final 150 milliseconds preceding the actual physical act.  He also found that this veto decision seemed to coincide in time with a drop in the voltage of the readiness potential.  Libet infers from this that the conscious mind has the ability to block an already initiated movement or to let it occur.  In this view, the brain is seen as generating courses of action, while the mind or a “free will” decides on the options. He sees the inhibition of action as one of the central roles of a conscious mind.  

Levy (2005) has interpreted Libet’s results in a somewhat different manner.  Levy notes that Libet’s subjects may have delegated the task of deciding when to flex their hand to processes occurring in the “unconscious” regions of their minds.  Levy also notes that it is reasonable to doubt whether Libet is correct in identifying the unconscious brain activity with the intention to or decision to act rather than with the generation of an urge or desire to act.

To explicate the process of mind-brain interaction, Libet (1994) postulates the existence of a “conscious mind field” (CMF), which he sees as being produced by brain activity. The CMF is not capable of being detected by physical measuring devices, nor is it reducible to neural processes; nevertheless, Libet proposes that the CMF is capable of exerting a causal influence on brain processes and that it provides the means whereby diverse neural activity can give rise to unified perceptions and experiences. Libet contends that his view of the CMF is compatible with a variety of different philosophical positions on the mind-body problem.  Libet’s views are discussed in more detail in Chapter 7.

The staunch defender of materialism Paul Churchland (1995) has proposed the intralaminar nucleus of the thalamus as the brain site responsible for producing a “unified consciousness.” (Yes, even that ardent proponent of reductionist materialism Paul Churchland has been forced on occasion to use the word “consciousness” in a nonpejorative sense.)  Churchland bases his claim on the fact that this brain site possesses two-way projections to diverse areas of the brain as well as the fact that the various senses are represented polymodally in this area. He notes that his colleague Antonio Damasio (1994) has nominated the right parietal lobe of the brain for a similar role, as this area must be intact in order for a continuous sense of the self to exist.   

Jean Burns (1993) has suggested that the synchronous firing of large assemblies of neurons underlies conscious experience and forms the interface for mind-brain interaction. Burns’ theory is based on brain wave records and recordings from single neurons showing that such synchronous firings are involved in acts of conscious perception.  Burns’ view in this regard is very similar to that of Koch and Crick, discussed above.

Indeed, it would almost seem that no region of the brain has been omitted from the list of brain regions that form the primary center of consciousness according to one researcher or another.  In addition to the candidates listed above we have the thalamus (Cotterill, 1995), nonrandom, coherent deviations of the brain’s electromagnetic field from its resting state (John, 2003), and, last but not least, quantum-mechanically entangled water in the microtubules composing the cytoskeletons of neurons (Penrose, 1994; Hameroff, 1994).  Each of these authors presents a cogent argument in favor of their candidate for the area of the brain (or brain process) that is the center of consciousness (or of the interaction between consciousness and mind).

With this many candidates for the primary center of consciousness (or of interaction between the conscious mind and brain), it may begin to seem that no center is primary, that many different brain centers and processes may be associated with their own conscious activity, and that these centers of consciousness may not be mutually accessible to one another, at least in a direct sense.  This possibility will be discussed in much further detail in Chapters 5 and 7.


Last, but by far not least, there is strangely appealing doctrine of “mysterianism,” whose most notable proponent is Colin McGinn (1999).  McGinn contends that the biological wetware of our brains has evolved to enable us to reason about and understand the physical world rather than to solve such esoteric problems as the nature of consciousness and the fate of the soul.  Our globs of 1011  pulsating amoeba-like neurons are more likely designed to discover how to better secure a stone axe head to a stick to beat upon our neighbor’s brain than to enable us to understand the realms to which our neighbor’s consciousness has fled after we have completed our handiwork.

 In McGinn’s view, the role of consciousness and the nature of the soul will forever remain beyond our cognitive grasp as our primate brains have evolved to seek fruit and elude tigers and deal with other concrete concerns in the physical world.  McGinn opines that the nature of consciousness and its relation to the physical world must remain outside of the grasp of consciousness, at least of those consciousnesses inhabiting our primitive primate brains, which are unequal to the task of understanding their true nature.  Perhaps McGinn is right.  Perhaps that is why consciousness is often referred to as the “hard problem” of philosophy.  But, unlike our ape brethren, we have been to the moon and plumbed the creation of the universe down to the first femtosecond.  It is premature to give up trying to understand the nature of our conscious mind.  As we shall see, such understanding may require us to relinquish core beliefs about the nature of our selves and the quasi-permanence of our association with any particular body.

 Once we have shed our present body and the “self-cocoons” we have wrapped around us to keep us firmly fixed to our present personalities, who knows what wonders may await us? 

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