10. The gap between matter and mind: the mind-body problem

10.1 Origin of dualism of mind and matter

The idea that there is a world of matter and a world of spirit, and that mind and body are in some way ontologically separate from each other has permeated most human cultures¹. The term mind has often used as a synonym with soul, spirit, psyche. For example, José Manuel Rodriguez Delgado writes, “In present popular usage, soul and mind are not clearly differentiated and some people, more or less consciously, still feel that the soul, and perhaps the mind, may enter or leave the body as independent entities.”²

Prehistoric cultures began to represent images on walls of caves probably as far back as 50,000 years ago, marking the beginning of sharing experiences beyond the present³. Leaving an external representation of personal experiences led to the postulated existence of a world beyond the immediately observable. It has been easy to think of highly imaginative personal experiences as belonging to other worlds. Christianity has tended to see the mind, the logos, or logistikon (mind, nous, or reason) as distinct from the soul (Greek psyche; Latin anima) and sometimes further distinguished, the spirit (Greek pneuma). This view can be traced back to Plato⁴ and Aristotle⁵ and schools of Hindu philosophy. The parts of the soul proposed by Plato are supposed to be in different regions of the body: logos, in the head, is related to reason and regulates the other parts; thymos or thumetikon (emotion, spiritedness, or masculine) is in the chest region and underlies emotions; eros, or epithumetikon (appetitive, desire, or feminine) is located in the stomach and houses the desire for physical pleasures.

Galen developed the idea that psychological modes are related to four primary humours: chole (bile), melanchole (black bile), sanguis (blood) and flegma (phlegm). These were associated with the four basic elements: fire, earth, air, and water, which in turn were the bases of all things, according to Aristotle’s general cosmological theory.

The idea that the worlds of matter and of mind are fundamentally distinct in their nature was formalised by René Descartes in the mid 1600s with his distinction between (1) the “res extensa”, the external world, made of matter in space accessible to objective directly shared experience; and (2) the “res cogitans”, the world of subjective experience, the inner world inner world of the mind, often described as the intangible, spiritual/mental/psychic world only accessible to personal subjective experience⁶. This view came to be referred to as the Cartesian dualism. 

There were several motivations for Descartes to propose an unbridgeable gap between mind and body. The fact that this vision survived is, in my view, due to a series of historical misunderstandings. In the mid 1600s, when Descartes proposed the dualistic conception, the executions of Giordano Bruno by the Roman Church was still a fresh memory. Bruno was burned a live in Rome in 1600, because of his religious heresies that included postulating against an infinite divinity. A few years later, the heretical condemnation of Galileo Galilei for his astronomical interpretations denying the centrality of the Earth in the solar system was another reminder to Descartes about the dangers of testing the power of the Church. 

Descartes’ book The World had become ready for publication in 1633. The world system he had adopted in the book assumed, as did Galileo’s, the heliocentric Copernican model. Upon hearing of the church’s condemnation of Galileo in the same year, Descartes decided against its publication. In a letter to Marin Mersenne, (November 1633), Descartes expresses his fear that if he were to publish the volume The World, he would suffer the same fate as Galileo.

Another important reason for Descartes to maintain his dualism what that although his simplistic idea of the functions of the nerves as a hydraulic process was inadequate to explain the richness of the activities of the mind, he had developed a mechanical conceptual framework for understanding the function of living organisms, a framework that would later be referred to as Physiology.

However, even an intellect like Descartes could be excused for not be able to conceive how the mind could be grounded in physics. At the time of the formalisation of dualism between mind and body by Descartes in the 1600s, physics consisted only of mechanics. The existence of the electromagnetic force was not even suspected, and chemistry did not yet exist as a science. 

His view that the external world of the res extensa was concrete, visible, touchable, accessible to all, while the inner world of the res cogitans, that of the thinking, of the mind, was invisible, intangible, apparently not extended in space, and moving so fast to appear practically instantaneous and not accessible to others, was taken as evidence of the fundamental different nature of these two worlds. He considered the brain important for most higher functions. However, he could not see how his res cogitans, the world of the mind could be directly related to the mechanical parts of the brain, as, at first glance, the soft homogeneous appearance of the brain matter (no microscopy was available yet) could not contain the otherwise almost infinite number of ‘ideas’. Thus, anything that appeared intangible, invisible, and could not be conceived in space was assumed to exist in some other world.

Yet the issue of how the world of the thinking could interact with the world of extended matter, including the brain, had already been raised by Descartes’ admirer, Queen Christina of Sweden, who pointed out to him the unsatisfactory explanation of how an immaterial mind could affect the material body! Descartes did not have a suitable answer.

The Cartesian dualism, with an irreducible the gap between mind and matter, remained well embedded in the conceptual framework of scientists well after Descartes, not least because Platonic-Aristotelian philosophy, reinterpreted by Christianity, had imposed an absolute separation between the perishable material body, and the immaterial eternal soul. Omitting immortality and immateriality of the soul from any cosmological view of the world was a safer view if one were to avoid dangerous clashes with the Church.

Over the next two centuries following Descartes, at least three main views were developed to attempt to explain the relation between these two separate worlds. 

John Locke, in An Essay Concerning Human Understanding (1689), argued for the mind’s initial resemblance to “white paper, void of all characters,” with “all the materials of reason and knowledge” derived from experience. David Hume, another empiricist, agreed with the view that nothing is in the brain except what enters from sensory inputs from outside. The brain is metaphorically a tabula rasa (clean slate). This view taken to extremes eventually ended denying an independent existence of a mental world or at least for Locke that only divine revelation could enable us to understand how ‘perceptions’ are produced in our minds by material objects. 

Conversely George Berkeley, and other idealists, doubted of the existence of an external world, which was assumed to be our creation and thus concluded that the world out there depends on us observing it, hence his dictum “esse est percipi” (“to be is to be perceived”). Berkeley was probably on the correct track by realising the role of the observer in defining what exists, but his religious allegiance compelled him to involve God’s creation of an absolute world beyond human perception.

Gottfried Leibnitz, while keeping both worlds separate and in parallel via a kind of pre-established harmony, postulated the existence of a supreme being (the Christian God) that ensures their perfect coordination, with no direct interaction between them. 

The dual nature of human experiences have been characterised as primary or objective, as opposed to secondary or subjective experiences. Thus, primary qualities are thought to be properties of objects that are independent of any observer, such as solidity, extension, motion, number and figure. These characteristics convey facts and are measurable aspects of physical reality. They exist in the thing itself, can be determined with certainty, and do not rely on subjective judgments. Conversely, secondary qualities are thought to be properties that produce sensations in observers, such as colour, taste, smell, and sound. They can be described as the effect things have on certain people.

This distinction was originally proposed by Galileo Galilei when he wrote in 1632: “I think that tastes, odours, colours, and so on are no more than mere names so far as the object in which we locate them are concerned, and that they reside only in the consciousness. Hence if the living creature were removed, all these qualities would be wiped away and annihilated”⁷. He argued that primary qualities were those qualities that are susceptible of being handled by mathematics and geometrical formulas. Both Descartes and Newton also agreed on the clear distinction between primary and secondary qualities. Finally, Immanuel Kant argued effectively that space and time are categories constructed by the mind to interpret the world, and thus primary qualities are inherent properties of material things⁸.

During the 1700s, the scene was set to address experimentally the nature of mental processes by a mysterious nervous force called ‘vis nervosa’. There were numerous attempts to explain the nature of neural processes, including initial experiments by Jan Swammerdam who generated contractions of a frog muscle by irritating its nerve supply, thereby supporting the idea that behaviour is based on stimuli. At the end of the 1700s, two Italian scientists, Alessandro Volta, a physicist, and Luigi Galvani, a biologist, argued about the nature of animal electricity, significantly advancing the field. In Bologna, Galvani’s classic experiments demonstrated that frog leg muscles contracted when touched by two metals and concluded that this was due to a kind of ‘animal electricity’. Meanwhile, in Pavia, Volta maintained that the animal electricity proposed by Galvani was merely the result of electricity generated by the metals used in the experiments. The result of their intense public debate was observed with much interest in the rest of Europe, underpinning the development of two major modern disciplines. Volta’s work led to the invention of the battery, almost identical to many still used nowadays, and the associated development of the modern era of electricity. Galvani opened the field of what became known as neurophysiology leading to modern neuroscience. 

It would take another 150 years from the argument between Volta and Galvani for the complex electrochemical nature of the neural processes within the nervous system to be revealed. In addition, evidence that living organisms consisted in enormous clusters of individual living cells was extended to the nervous system. At the end of the 19^th century, there was a serious debate between the reticular view sustained by Camillo Golgi and cellular view sustained by Ramon y Cajal. Cajal maintained that there was sufficient evidence to regard the nervous system as a collection of separate nerve cells connecting with each other via small gap⁹. This gap, since called the “synapse”, was demonstrated by Charles Sherrington on functional bases. Despite opposing views, both Golgi and Cajal received the Nobel prize conjunctly in 1906, mainly because Golgi developed the staining methods to visualise in great detail individual neurons, and Cajal used this method to develop convincingly his “neuron theory”. It was only with the advent of electron microscopy in the mid 20^th century that neuroscientists could visualise the very narrow synapse between neurons, confirming Cajal’s neuron theory with the nervous system being fundamentally composed of chains and circuits made of separate cells.

The idea that higher mental functions reside in and depend on the activity of the nervous system (brain) has emerged over the past recent centuries has been widely accepted by neuroscientists (see Section 4). 

However, although the physical bases of the nervous system are well grounded both in mechanics and in electrochemistry, the gap between the two worlds of Descartes, the Cartesian dualism, according to some philosophers, remains unbridgeable. For example, Edmund Husserl in the early 1900s, declared that mental and spiritual reality possess their own reality independent of any physical basis, and that a “science of the mind” (Geisteswissenschaft) was to be established as a foundation of a ‘Transcendental Psychology’ regarded to be as scientific as the natural sciences. In a way this reinforced the Cartesian impossibility of reconciling the two worlds. 

More recently, the Australian neuroscience Nobelist Sir John Eccles, a Catholic, held a dualistic view with an immaterial soul affecting the brain and thus the body¹⁰.

Although it is now widely accepted that mental functions including awareness, self-awareness and phenomenal consciousness have some neural bases, the Cartesian Dualism of an inner world of the mind and an external physical world still permeates much of modern philosophical discussion. Indeed, this idea persists as the ‘brain-mind’ or ‘mind-body’ problem with its ‘epistemic gap’¹¹.

In 1996, a young influential Australian philosopher David Chalmers asked, “How and why do neurophysiological activities produce the “experience of consciousness?”¹² John Searle asks a similar question: “How exactly do neurobiological processes in the brain cause consciousness?”¹³

Chalmers pointed out that finding the neural correlate of consciousness would simply solve the ‘easy problem’ even assuming that the meaning of ‘correlation’ is agreed and accepted. However, a ‘hard problem’ would remain to explain why a subjective feeling should arise at all from such brain activity. He claimed that the problem requires us to consider that the subjective feeling of having such experiences is beyond the physical neural processes underlying states of consciousness and therefore cannot be investigated by physics.

The problem of the relation between brain and mind has been put succinctly by Colin McGinn who wrote in 1989: “I do not believe we can ever specify what it is about the brain that is responsible for consciousness, but I am sure that whatever it is it is not inherently miraculous. The problem arises, I want to suggest, because we are cut off by our very cognitive constitution from achieving a conception of that natural property of the brain (or of consciousness) that accounts for the psycho-physical link. This is a kind of causal nexus that we are precluded from ever understanding, given the way we must form our concepts and develop our theories. No wonder we find the problem so difficult!”¹⁴ 

With the advent of Christianity with a God who designed and made the world according to ‘laws’, the first task of humans was to ‘read’ the mind of God to discover such rules. An increasingly more humanistic perspective, which described the nature of ‘things’ as a function of human experience, has begun to remove many of the psychologically and philosophically biased ideas of the past. The importance of the observer as part of the understanding some phenomenon is now well understood and integral to all modern science, starting from quantum mechanics and extending all the way to psychology.

Indirectly the issue of interaction of mind and brain has also been addressed as part of the development of a branch of medicine, psychosomatic medicine that attributes mental causes to disturbances of the body. 

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1. P Boyer (2001): Religion Explained: The Evolutionary Foundations of Religious Belief. Basic Books;
   E Cohen et al. (2011): Cross-cultural similarities and differences in person-body reasoning: Experimental evidence from the United Kingdom and Brazilian Amazon. Cognitive Science 35, 1282–1304;
   M Roazzi et al. (2013): Mind, soul and spirit: Conceptions of immaterial identity in different cultures. International Journal for the Psychology of Religion 23, 75–86.
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2. JMR Delgado (1969): Physical control of the mind; toward a psychocivilized society. Harper and Row. ↩︎
3. See my videos on Art and Science: https://marcellocosta.au/wp/videos/from-art-to-science-painting-science-the-brain/ ↩︎
4. EA Duke et al. (eds.1995): Plato Opera Volume I. Euthyphro, Apologia, Crito, Phaedo, Cratylus, Theaetetus, Sophista, Politicus. Oxford University Press. ↩︎
5. H Robinson (1983): Aristotelian dualism. Oxford Studies in Ancient Philosophy 1, 123–144. ↩︎
6. R Descartes (1637/1998): Discourse on Method and Meditations on First Philosophy. 4th edition, Hackett. ↩︎
7. G Galilei (1623): The Assayer. ↩︎
8. I Kant (1783): Prolegomena to Any Future Metaphysics That Will Be Able to Present Itself as a Science. ↩︎
9. M Cobb (2021): The idea of the Brain – a History. Profile Books London;
   E Pannese (1999): The Golgi Stain: Invention, diffusion and impact on neurosciences. Journal of the History of neurosciences 8, 132-140;
   GM Shepherd (1999): The legacy of Camillo Golgi for modern concepts of brain organization. Journal of the History of the Neurosciences Basic and Clinical Perspectives 8, 209-214. ↩︎
10. JC Eccles (1994): How the Self Controls Its Brain. Springer Verlag. ↩︎
11. D Chalmers (1995): Facing up to the problem of consciousness. Journal of Consciousness Studies 2, 200–219. ↩︎
12. D Chalmers (1996): The conscious mind: In search of a fundamental theory. Oxford University Press.  ↩︎
13. J Searle (2017): The basic reality and the human reality. Harvard University Press. ↩︎
14. C McGinn (1989): Can we solve the mind-body problem? Mind 98, 349-366. ↩︎