A dialog between Donald MacKay and Mario Bunge, printed in the journal Neuroscience over the course of two years beginning in 1977, provides a conscise summary of MacKay’s views on the mind-body relationship. In this dialog, MacKay contrasts the dualistic interactionism theory of Popper and Eccles with Bunge‘s emergentist materialism theory, and then builds a case for a third alternative based on the notion of mental events embodied in, but not identical to, brain events. Although neuroscience has made tremendous progress in the past two decades, MacKay’s attempt to trace a path between interactionism and materialism is still worth considering.
Twenty years ago a remarkable book entitled The self and its brain: An argument for interactionism (Popper & Eccles, 1977) was published by two eminent philosophers of science, Sir Karl Popper and Sir John Eccles. This book ignited a firestorm of controversy among neuroscientists and philosophers of science because it presented, for the first time in decades, a serious defense of the dualistic theory of mind-brain interactionism. The publication of the book provoked a dialog between Mario Bunge, a distinguished philosopher of science at McGill University, and Donald MacKay. This dialog spanned two years. Because it took place in the pages of the journal Neuroscience, it is not as well known to American philosophers and psychologists as are some of MacKay’s other writings. Yet in my opinion MacKay’s contribution to this dialog contains one of the clearest statements of his views on the mind-body relationship. I will attempt to show how MacKay used this dialog to trace a path between interactionism and materialism–a path that acknowledges the central concern of each of these perspectives, while denying that either view has an exclusive claim to the truth.
The starting point of the dialog was Bunge’s commentary on the book by Popper and Eccles (Bunge, 1977). Bunge dismissed the notion of interactionism as a failed idea and concluded that one particular form of materialism, which he referred to as emergentist materialism, is the only rational alternative. MacKay countered with a commentary of his own, questioning Bunge’s conclusions and presenting a third option (MacKay, 1978). The dialog concluded with a rebuttal by Bunge and a final response by MacKay (Bunge, 1979; MacKay, 1979). Let’s examine the arguments that were set forth in this dialog.
In their book, Popper and Eccles argued that the prevailing central assumption of brain scientists was fundamentally misguided. What was this central assumption? That the human brain is a physically determined system in the same sense as any other body organ–that is, the causes of any significant events in the brain could be found in the physical relationships among the components of the brain itself. Against this assumption of materialism, Popper and Eccles sought to bring back Descartes’ notion that there are two distinct worlds of reality, and that World 1 (the physical mechanical world) was open, in the brain, to the influence of World 2 (the world of mental states, including conscious thoughts and decisions). Popper explained, “I think that the self in a sense plays on the brain, as a pianist plays on a piano or as a driver plays on the controls of a car,” while Eccles asserted, “The self-conscious mind acts upon … neural centres, modifying the dynamic spatio-temporal patterns of the neural events” (Popper & Eccles, 1977, p. 495) . Although Popper and Eccles rejected Descartes’ view that the pineal gland is the organ through which the interaction of the mind and brain takes place, they maintained that some special point of interaction between the two worlds was necessary. Popper suggested that “the action of the mind on the brain may consist in allowing certain fluctuations to lead to the firing of neurones” (p. 541), and Eccles proposed that the point of interaction may be in the probabilistic operations of the synaptic junctions between neurons.
In Bunge’s commentary in Neuroscience (Bunge, 1977), he set this Popper-Eccles dualistic mind-body interactionism against a hard-headed reductionist materialism that denies the existence of mental events or reduces them to “nothing more” than physical neural events. Bunge seemed as uncomfortable with reductionist materialism as he was with dualism. He agreed with Popper and Eccles that subjective mental events are real and are a legitimate subject for scientific investigation. However, he maintained that the mind is not different from the brain. Mental events “emerge” from the cellular events and processes of the brain in much the same way that breathing emerges from the cellular processes of the lung; mental events do not have a separate existence apart from the brain any more than breathing exists apart from the lung. Bunge argued that his view, which he called emergentist materialism, “turns psychology into a natural science instead of a supernatural one” (p. 507). Bunge appeared to believe that this view converts the “mind/body” problem into a “brain/rest-of-the-body” problem.
MacKay’s commentary began by applauding Popper and Eccles’ boldness in challenging the fundamental assumption of modern neuroscience, and the breadth of evidence they present in support of interactionism. MacKay affirmed their stated motivation for opposing materialism and mechanistic determinism, namely a desire to preserve the significance of human existence and the moral imperative of human responsibility. MacKay was also sympathetic to Bunge’s concern that interactionism, if it were taken seriously, would undermine the rational basis for physiological psychology. But at this point MacKay distanced himself from both interactionism and materialism, and proposed a third option which he called comprehensive realism, which fits on the monism/dualism continuum at a point between the positions represented by Bunge and by Popper/Eccles.
MacKay argued that we should begin not by emphasizing the primacy of matter nor the primacy of the mind, but rather we should “start from our immediate experience of what it is like to be a person” (MacKay, 1978, p. 601). Being a person means having a flood of conscious experiences, and the data from these experiences is the ground on which all our knowledge must rest. But for each of these conscious experiences there is a corresponding change in the state or activity of the brain. This leads to MacKay’s first main point: we have two different kinds of data about ourselves. We have the data of our own experience as conscious agents, and the data about our correlated brain-activity and brain-states. These data could be lined up in parallel columns, as shown in Table I.
MacKay acknowledged that a materialist such as Bunge might argue that the I-story terms are not a separate form of data from the brain activity, but rather are simply our way of expressing in words the particular states of neural activity occurring in our brains. Against this view, MacKay maintained that these two columns represent a genuine and irreducible duality. These two columns are correlated, but are not the same. Here are some reasons why: (1) The I-story is essentially private (that is, not available to outside observers unless I decide to tell them), while the brain-story is, in theory, open to inspection by outside observers. (2) Every change in the I-story is accompanied by a change in the brain-story, but the reverse is not necessarily true; some changes in brain activity are not detectable by our conscious experience. (3) The I-story is immediate and compelling (and has been available throughout history to every human of normal intelligence), while the brain-story is obscure, needing special instrumentation available only in this century; we would know nothing of the brain-story if it were not for the I-story .
Having established the duality of data about ourselves and our brains, MacKay next asked whether this duality implies dualism–parallel worlds that would require some form of interactionism in order to influence each other, as Popper and Eccles claimed. MacKay here made his second main point, arguing that the duality of data does not imply parallel worlds–that is, a material world for the brain and a non-material world for the mind. MacKay used one of his favorite analogies, that of a computer running a program to solve a mathematical equation, to argue against both Popper and Eccles and against Bunge. In one sense, we could say that the behavior of the atoms inside the computer chip is determined by the particular equation being solved. In another sense, we could say that the solution to the equation is determined by the laws of physics governing the behavior of the atoms inside the computer chip. But this reciprocal determinism does not require us to postulate that computers have pineal glands or any other organ of interaction between the material world of the computer chip and the non-material world of the equation, nor does it require us to declare that the equation is identical to, or merely a name for, a particular pattern of activity within the computer chip.
Ludwig, Thomas E., Philosophical Psychology