So how do material entities relate to mental entities? Or to be more precise, how does neuronal activity relate to the intergenerational mental process of asking questions and posing answers? So far I have I outlined conflicting empirical traditions in the history of philosophy: materialism, which is based on the reducibility of belief to ‘material systems,” that can be directly observed via human perception; and idealism, which is based on the reducibility of belief to “mental systems,” that can be directly observed via “introspection” of consciousness. Our beliefs about the relationship between materiality and mentality have been influenced by a set of philosophical puzzles known as the mind-body problem. The various answers to this cluster of issues have involved drawing notoriously fuzzy lines of demarcation between: mind and body, internality and externality, introspection and external observation, and psychology and biology.
The thread that binds the various manifestations of the mind-body problem can be historically traced to Rene Descartes, the great seventeenth-century rationalist philosopher. Most philosophy students immediately recognize his famous dictum, “I think, therefore I am.” Known as the father of “modern philosophy,” Descartes is historically accredited with having initiated an intellectual “revolution” that turned the course of continental European philosophy and psychology “inward” toward the introspective analysis of consciousness. Actually, what he did was postulate the existence of two interacting metaphysical subsystems: material substance and mental substance. Since then, inquiry into the nature of this mind-body relationship has kept generations of psychologists and philosophers and their students busy inquiring.
There is, of course, a longstanding tradition of mind-body dualism in Western philosophy that goes back at least to the early Greek philosophers and the early Judeo-Christian theologians that acknowledged that the physical bodies of all living things are composed of non-living material substance. Of course, Sir Isaac Newton discovered the universal laws that govern the motion of non-living material substance. Therefore, by the seventeenth century, most scientists were engaged in extending
metaphors into other areas of scientific endeavor, including psychology,
politics, and economics. Newton
In order to extend that materialistic paradigm into psychology many early psychologists adopted the high-level theory that the human body, like the rest of material nature, is more-or-less organized like a “machine;” that is to say, a closed mechanical system ruled by internally programmed deterministic laws. In order to discover these laws, philosophers and scientists agreed that they must observe the material processes that take place within the body’s various sub-systems and fit those observations into a mathematically elegant model.
In the quest to explain, predict, and ultimately control psychological phenomena, scientists aspired to identify the material and/or biological structures responsible for the traditional content of psychological inquiry: feelings, thought, perception, and behavior. According to the Cartesian formula, this “instinctive” and “reflexive” material aspect of living things could ultimately be reduced to the laws of physics as modeled by Newtonian mechanics. By the seventeenth century, Descartes and his successors believed that this research project entailed the empirical study of the human brain, the central nervous system, and the flow of matter and/or energy within that material system.
However, Descartes’ attempt to bring psychology and philosophy in line with the Newtonian worldview was complicated by the fact that he was unable to completely break away from the constraints of hundreds of years of orthodox theological and philosophical tradition. One of the most thoroughly entrenched beliefs in the Western philosophical and theological traditions has been the belief that human beings are unique among living entities. Traditional Christian theology is woefully anthropocentric in that it embraces the simplistic belief that human beings, by virtue of a divine act of “special creation,” possess a non-material eternal soul. (I’ll get back to the “human-animals puzzle” later.) This godlike soul provides the foundation for the Judeo-Christian concepts of individuality, rationality, free will and personal responsibility.
Much of the Judeo-Christian tradition is anchored in a theory of the afterlife. After you die your immaterial soul either transmigrates to heaven (only if you’ve been good) or hell, (only if you’ve been bad). The concept of sin is predicated upon the idea that human beings can know what is good, but do not always choose to do what’s good: hence the distinction between knowing and willing. Sin consists in knowing the Good but deliberately neglecting to do the Good. Although, God punishes sinners, he generously accepts apologies. Western Liberalism reformulated many of these theologically-based concepts (such as free will, and responsibility) and injected them into the social and political philosophy of the Western Enlightenment. Over time, philosophers and scientists gradually abandoned the old value-laden, theologically embedded, concept of “soul” in favor of the seemingly more value-neutral, objective, and scientific concept “mind.” Although, there was a change in verbiage, much of the traditional conceptual baggage remained intact. After all, intellectual systems do have a history!
According to Descartes, scientific knowledge of the subsystems of the human mind (in contrast to the brain) must be based on the “internal” observation of conscious mental entities and/or mental processes. (Again, why do we metaphysically conceptualize mind as internal?) This method of inward observation of mental substance is called “introspection.” Introspection is an individual, private, and, therefore, subjective experience. I can observe my own (so-called) internal consciousness, but I cannot directly experience your internal consciousness and you cannot experience mine. We can, however, get together and at least apparently share our common feelings, thoughts, and perceptions by describing those private experiences via our common language. Even if we speak different languages we can communicate via a translator. Cartesians typically maintain that the primary datum of psychology is inexorably internal and ultimately private. Subsequent Cartesians have sought to find the common ground that might serve as the basis for converting subjectivity into something objective and scientific.
The empirical question, therefore, arises: “How can we transform a ‘private internal mental event’ into something that can be publicly verified and/or falsified via long-term collaborative observations performed by a scientific community?” Or simply, “How can there be an organized cooperative scientific community of psychologists that objectively study feelings, thoughts, percepts, and behavior when the scientists are locked into their own individual subjectivity?”
This puzzling logical relationship between the perceivable external material world and the conceivable internal mental world drives the traditional mind-body problem. Since the seventeenth century, the materialist tradition, essentially, has taken the existence of the external material world (more or less) for granted and has assumed that at least some of our feelings, thoughts, and percepts are (more or less) copies of material things and that originate in that external world. So when we feel, think about, or perceive the world, at least some of those events originate in externality and/or “correspond” to what’s going on in that external “objective reality.” Unfortunately, not all of our feelings, thoughts, and percepts connect to the real world. Whenever I talk to my sisters I’m amazed at what they believe they remember about our childhood. Are they manufacturing the past or do I just have a short memory?
Subjectivists acknowledge that we (at least) seem to be experiencing the same world. But then again, everything that we experience is in our own private consciousness, and unfortunately, we have no obvious direct empirical evidence of that external material world or whether it is really “out there.” This same logic raises doubts as to whether we can know that other minds exist. “I know I exist, but I don’t know about you!” Cartesian subjectivism had serious implications for those who sought to establish psychology as an empirical science. Descartes’ critics argued that this idea of grounding psychology in privately experienced mental substance undermines the observational requirement for the establishment of scientific theories. Worse than that, how can there be a scientific community composed of individual minds locked into their own private worlds?
Of course, the obvious problem here would be how to describe the mechanism by which material systems and mental systems interact to form a single, unified, mind-body entity? Descartes’ “solution” to the mind-body problem, usually called two-sided interactionism, seems intuitively plausible enough, even today. In acts of volition, the human mind causes changes in the human body (My mind commanded my brain to command my finger to touch letter “Z” on my laptop computer.); and, in sensation the human body causes changes in the human mind (When I touched the stove I felt something hot on my hand because my spinal cord sent information to my brain, which in turn relayed that message to my mind.) Since Descartes believed that animals lack mental substance, he concluded that animals lack consciousness, free will, and sentience (or the capacity to experience pain and pleasure). He admitted that they possess a limited amount of intelligence. For centuries, this anthropocentric line of inquiry and the religious doctrine of special creation have justified unspeakable cruelty to both animals and the environment. (Am I being cynical again?)
Of course, Descartes realized that if composite human beings constitute a single system, the mind must somehow connect to the body. He thought that the essential mind-body connection was located at the pineal gland, which contemporary psychologists summarily dismiss as simply empirically false. However refutation of Descartes’ theory is not quite that simple. The mind-body problem is really an epistemological puzzle. Even if Descartes is “really” right about the existence of a mind-body interface structure located somewhere within the human brain, how could psychologists know whether it is located at the pineal gland, or some other structure” After all, psychologists can’t observe a causal interface between material substance and mental substance? Think about it. How can we observe the causal interactions between a “material entity” that exists in a particular place at a particular time and has observable and measurable physical properties (size, shape, color, weight, etc) and a “mental entity” that has no observable physical dimensions, nor spatial and temporal coordinates? In short, how can these mental entities be located “somewhere” and therefore connect with the body, if they lack physical dimensions (size, shape, color, weight, etc). In fact, if you think about it, mental substance has exactly the same attributes as “nothingness.” So how can “something” interact with “nothing?” So here’s the mind-body problem in a nutshell: “How can we observe and subsequently describe causal interaction between a material entity and a mental entity?”
Many philosophers and psychologists have focused their criticism of Cartesian dualism on this epistemological problem that arises in the context of mind-body causality: that is, how can we “know” that material causes produce mental effects; and, how can we “know” that mental effects produce material effects? But as far as the scientific status of psychology is concerned, the more basic question is: “How can we scientifically observe the connection between mind and body? Is it a material connection elucidated by the observation of external material entities and processes; or, is it an internal mental connection observable via introspection?”
Historically, the mind-body problem has proven to be enormously resilient. You can still buy philosophy books and journals that argue about these questions. It’s even in this book! For centuries, subsequent philosophers and psychologists have sought to reduce Descartes’ dualistic ontology to a single system. However, that effort has also spawned a variety of alternative schools of thought, which have made it very difficult for psychologists to organize their science and themselves under one single paradigm. Two forms of monistic reductionism have dominated the debate. Material reduction simply denies the independent ontological status of mental systems and therefore seeks to reduce mentality to material systems that exchange matter and/or energy. Hence, based on this paradigm, psychology must restrict itself to the empirical observation of material entities. Today, biology and neurology represents the most widely accepted forms of material reduction in psychology.