Dualism has supposedly fallen out of favor in modern science. However, a new form of dualism has taken root in recent decades that bears striking resemblance to long disavowed theories of mind. In this first of three parts, we will very briefly explore dualism's origin.
To understand the current ways in which the brain is thought about by the neuroscientific community, and, by extension, the popular imagination, we need to appreciate some historical context. It is necessary, therefore, to back up quite far in the history of philosophy and biology, way back, in fact, all the way to Ancient Greece and the writings of Aristotle. He wrote that each extant thing is comprised of two conceptually distinct constructs, “matter” and “form”. These concepts, while distinct, are at the same time inextricably linked in Aristotle’s view of the universe, with his meanings of matter and form being, very simplistically stated, an object and its “essence”, respectively, each “thing” being simultaneously an extant body and abstraction, neither having hegemony over the other. One of his famous illustrative examples is that an axe is comprised of a wood handle and iron head, which is the matter, and it also possesses the ability to chop wood, its form. Previously, Plato proposed that objects existed in the abstract, that there was a perfect object that existed a priori in the ideal, but that the ideal was not attainable on Earth. Aristotle rejected this view, favoring his matter/form dichotomy. Each thing has both matter and form, although they are not necessarily immutable, as matter can change shape, and therefore the form may be altered as well, as one could, say, melt the axe head to make some other iron tool.
Applying this concept to biology, Aristotle called an organism’s form its psuchē. The word psuchē has been translated from Greek as ‘soul’, but our concept of soul is not anything like what Aristotle meant. To him, psuchē was the essence of being. It is what is responsible for growth, reproduction, and, in the case of humans, for cogitation and cognition. Every organism has a psuchē in his view, be it a philosopher or a weed growing through the cracks of a sidewalk. Importantly, there was no reference to religion or religiosity in his conception of psuchē.
Developing this concept further, he hypothesized that each of us has a life force running through our blood vessels (pneuma) that allows us everything from muscle contraction to sensory perception. Even though Aristotle thought, ultimately, that the center of thought lay not in the brain, but rather, in the heart, his writings about the flow of the life force throughout the organism led eventually to the hypothesis that the ventricles of the brain were the seat of mental function, a position whose foundation was laid by Galen in the 2nd c. and elaborated on by Nemesius in the late 4th or early 5th c. The ventricles are a series of interconnected cavities in the brain throughout which cerebrospinal fluid (CSF) flows. That this constant flow was what was ultimately responsible for our mental abilities seemed a reasonable conjecture, because flow requires energy. (This is especially poignant in light of the accepted theory of motion of the time, also Aristotle’s, that an object’s natural state was rest.) The energy imparted to the CSF, which seemed to come from somewhere magical (bear in mind, while the blood is pumped by the heart, no such organ exists to pump CSF--that job is accomplished by cilia that line the ventricles, but of course these men lacked microscopes to aid them), is perhaps what gives rise to our mental powers, where the life force lay.
Aristotle’s construction of soul was very forward thinking, and perhaps far ahead of his time. The unbreakable link he places on matter and form, body and soul, could conceivably even strike one as a precursor to a materialist worldview, although certainly Aristotle believed in the divine. Nominally speaking, materialism is the dominant worldview of the broad science community, but, as I shall show in the following parts of this column, there are still many covert dualists operating in science. More on that in a bit.
The main conceptual problem that troubled the ancients and continues to haunt us in modern times, the reason that the concept of a life force was needed to being with, is that each effect has a chain of causality, but thoughts seem to break this chain. What causes a thought, especially a seemingly original or whimsical one? Thoughts appear to be void of a physical cause. This problem was “solved” by Descartes in the 17th c. Obviously, Descartes was a polymath whose contributions to the modern world are enumerable, but many, though by no means all (for example he was the first person to speculate about inhibitory inputs to the nervous system), of his contributions to neuroscience were, flatly, incorrect.
In his Treatise on Man Descartes conceived of two very separate entities that comprise the person. First, there is the body. The body is the material part of the person and encompasses that part of the nervous system responsible for reflexes and involuntary movements (e.g. one’s heartbeat). Second, there is the “mind”, or what we may consider the immortal soul. In Descartes model of the person, the mind controlled all aspects of cognition and cogitation, and was also responsible for directing voluntary muscle movements. Unlike Aristotle’s concept of the relationship between form and matter, here, the mind holds hegemony over the body. Furthermore, Descartes even proposed how the two entities are connected, namely, the mind gains access to the body via a connection with a small brain structure known as the pineal gland. Upon death, the mind/soul separates from the body and enjoys eternal life. It is undying unlike the body, which is only a temporary vessel for our time on Earth. To Aristotle the soul was incorporeal because it was an abstraction, and thus didn’t “die” because it couldn’t; to Descartes the soul was incorporeal, but was a thing itself that didn’t die because it was immortal. This is a non-trivial conceptual difference.
Descartes argued that humans are the only creature with a mind (soul), and they are, therefore, the only organisms that can be described as conscious (although, curiously, all mammals have a pineal gland, I believe). With his view that mind and body are separate as well as separable, Descartes offers a solution as to how animals can act like humans act in some circumstances, via their reflexes and involuntary movements, while preserving a unique and higher position for humans, that of a conscious being. Importantly, this is one of the earliest times that humans or animals had been described purely mechanically, and Descartes thus helped found the field that became known as physiology.
This bifurcated view of humanity has become known as “dualism”, and scientists generally regard dualism as unscientific and more in the realm of religiosity than of empirical inquiry. Hard numbers about how the neuroscience community views dualism are difficult to find, but anecdotally, one can say with confidence that there is not much support, nominally anyway, for a dualistic conception of man. One survey found that only 36% of individuals who identified as “medical professionals” support the idea that we have a soul that is separate from our bodies , compared with a much higher number among the general population. One would have to imagine that if just brain scientists were surveyed, the number would likely be much, much lower.
Despite this, it has been suggested by some thinkers that a nouveau form of dualism has emerged out of modern neuroscience. Part of the problem with Descartes’ theory, and a problem which he identified himself, was that if it truly isn’t your eyes that are seeing, as is definitely the case if his mind/soul is what is actually conscious, but rather that the image that falls on your retina is reconstituted on your pineal gland so that your soul can perceive the image presented to it, then this automatically begs the question of who is seeing for your soul? Doesn’t your soul then need its own eyes and pineal gland inside of it? The cycle is never ending unless we permit the soul to be purely supernatural, which Descartes appears to have done; but, surprisingly, this is almost completely analogous to the language of modern neuroscience. Let’s examine this passage from Kurzweil, for example.
Is this any different from Descartes? Kurzweil firstly regards an activity as being carried out in a person’s brain.This begs the same question that if a brain thinks for the person, who thinks for the brain? This time we can’t summon magic as Descartes may have done. Cognition and cogitation are functions of man, not of our brains: This is the thrust of our misconception. Secondly, he regards unconscious activity as being purely mechanical, with the converse presumably being that conscious activity may have a component of free will. Replace “brain” with “mind” and we have classical dualism. I have chosen Kurzweil’s recent popular publication to pick on because this type of vernacular has seeped into the popular consciousness from the academic literature. The fact that it is in popular science shows how pervasive it has become, as popular writers take their cues from their scientific counter parts. In the next installment, we will address neodualismin academic neuroscience writings from such giants of the field as Kandel, Gazzaniga, and Crick, and I shall show that the brain has become the new mind/soul.
1. Demertzi, A., et al., Dualism persists in the science of mind. Ann N Y Acad Sci, 2009. 1157: p. 1-9.
2. Kurzweil, R., How to create a mind : the secret of human thought revealed2012, New York: Viking. 336 p.