Douglas Groothuis
Interactionist dualism has certainly fallen out of philosophical fashion, despite some noteworthy exceptions.1 Even some theistic philosophers argue that the soul is neither biblically sanctioned nor philosophically required for an intelligible discussion of resurrection claims about personal identity. Rather than defending dualism against its many modern foes, I will discuss several of Richard Taylor’s salient criticisms of dualism which serve as roadblocks to an intelligible presentation. After discussing these, I will briefly turn my attention to a response which attempts to avoid the problems of both dualism and materialism by making the notion of a "person"—rather than mind or body—the primitive and primary reference.
For Richard Taylor, humans are living organisms and no more than material bodies. There is no mental component or soul or mind to be added to the corporeal configuration. The mind-body problem is solved by dropping the mind. Taylor finds the idea of a distinct soul as unnecessary to explain the human capacities often invoked by dualists as evidence for the soul. Matter will do just as well, thank you. But will it?
Taylor says that it "it is quite plain" that "the difficulties of simple materialism are not overcome by any form of dualism."2 This is because of (1) the difficulty in associating a nonphysical spiritual or mental substance with a very different physical body and because (2) there are just as many problems in ascribing "personal and psychological predicates and descriptions"3 to minds as there are in ascribing them to bodies. We will first address this rather novel second move and then consider whether the supposed problems with associating mind and body render interactionism indefensible.
Taylor thinks that "all forms of dualism arise from the alleged disparity between persons and physical objects."4 People, unlike rocks and weeds, can think, believe, feel, wish and the like. We have mental states unascribable to nonliving physical objects. We may think of a rock, but a rock may not think of us. Hence the dualist argues that these unique mental states indicate something different about humans, that we have minds that think, believe, feel, and wish. The assumption is that mental predicates cannot rightly affix to material objects.
To this, Taylor argues that we have no reason not to affix these predicates to material objects because the "real difficulty here is in seeing how anything at all can deliberate, choose, repent, think, be virtuous or wicked, and so on."5 This difficulty, Taylor thinks, is not overcome by positing an immaterial "thinker." The proper perspective is just that humans are like other physical objects in some senses—they have weight, dimension, color, etc.—and unlike other physical objects in other senses—they think, choose, hate, etc. Since it is the case that humans have physical bodies—even the dualist will grant this—it is better to assume that humans are physical bodies, and that "some bodies think, feel desire, choose, etc." Taylor thinks this argument is just as good as the dualists’ argument and avoids "a morass of problems concerning the connections between soul and body."6
Such a materialism, Taylor realizes, is open to the charge that certain mental states cannot be adequately explained in simply physiological terms. The mental cannot be reduced to the material without remainder. Taylor gives examples of intentional mental states where a person has a desire for something or has a fear of someone. That is, the mental state is about something or concerns something outside itself. Dualists have often appealed to such states as inexplicable on materialist grounds alone. Can a material object or process—say, alpha brain waves—be afraid of spiders or fall in love with someone? Taylor grants that this "referential character" of certain mental states poses a problem for materialists. He says:
It is fairly well known, for example, what physiological changes a person undergoes when in a state of fear; but when these changes are artificially invoked, the person does not experience fear in the usual sense. He describes his state as being vaguely like fear but finds that he is not afraid of anything.7
The "referential character" of fear is not replicated through physical inducement alone. Something is missing. The dualist says the mind is missing, the materialist something else.
Taylor’s solution is to posit "unfamiliar states of matter"8 which are, in his words, "identical" with psychological states. Our "ordinary methods of biology, chemistry, and physics" may not pick up this covert corporeality, but it is there to be found, nevertheless--lest materialism fail us. Taylor insists that this is not question-begging because the "soul philosophers" always appeal to unobservable states of the soul and because nothing nonmaterialistic follows from the fact that every psychological state has yet to be correlated with a bodily state. Further:
From the fact that a certain state is in some respect unusual it does not follow that it is a state of an unusual thing, of a soul rather than a body, but rather, that if it is a state of body it is an unusual one, and if it is a state of the soul it is no less unusual.9
Taylor’s argument seems to be that the dualist explanation is no better than the materialists’, and the materialist is not freighted with somehow connecting a soul with a body. For Taylor, then, we are ultimately no more than "a meat computers"10 of great sophistication and—as far as our present scientific knowledge is concerned—of great mystery. Taylor is really arguing for a "matter of the gaps" solution to the mind-body problem. There are gaps or explanatory lacunas in our ability to adequately describe mental states in purely physical terms. In dealing with intentional or referential mental states we are, as yet, at a loss as to how to describe them physically.
The dualist wants to give a "mind of the gaps" solution to the same problem in that merely physical explanations can never fill in all the gaps between mental states and physical descriptions. There is an irreducible mental element in human beings called the mind or soul which is not identical to any material state. This alone explains the kind of referential states described by Taylor, as well as any mental state.
What should we make of Taylor’s argument thus far? First, his claim that mental states are just as easily predicable to bodies as to minds is less than compelling. The issue at hand is how to explain the unique attributes of mental life. In no other cases of material objects do we predicate rational calculation, hope, faith, love, etc. A rock is not loving; a bed is not hateful. These attributes are uniquely human. As Hasker puts it, the materialist explanation makes no gain in simplicity if, after rejecting a mental substance, "we must then ascribe to the physical substance properties quite unlike those it is known to have in all other contexts."11 There is, I argue, a difference in kind between mental and physical states which has ontological implications.
A difference in kind involves two considerations. First, when two things differ in kind, one "possesses a defining characteristic not possessed by the other."12 For instance, odd numbers cannot be evenly divided by two into whole numbers while even numbers can be so divided. Second, there is no intermediate ground between two things that differ in kind. There is nothing "between" an odd number and an even number. A number is either one or the other. Or, in the case of animals, there is no intermediate between animals that fly and those that are earth bound. They differ in kind. There is no halfway house between flying and not flying. Mortimer Adler summarizes the distinction:
The impossibility of intermediates constitutes the discontinuity or discreteness of kinds: the only things that differ in kind differ discretely or discontinuously. . . . Thus, for example, a whole number is either odd or even. There is no third possibility of tertium quid.13
A difference in degree, on the other hand, admits of intermediaries. Something may be more or less bright, dark, long, short, big, small, etc. Two power-hitters in major league baseball may differ from another in degree (of homerun-hitting proficiency) if one hits forty-one homeruns in a season and the other hits thirty-nine the same season. Both hitters differ in kind from the baseballs they so readily power out of the park. Adler says that unlike difference in kind, "two things that differ in degree continuously, not discretely."14
My claim is that mental states and physical states differ in kind, not in degree. Thus they cannot be identical, given this very simple—and, I think, uncontroversial—principle of identity: "Whatever differs in kind cannot be identical." One could also grant the principle, "Whatever differs in degree can not be identical," given Leibniz’ law; but applying this to the mind-body problem could give materialists a wedge to argue that mental states are really highly complex or rarefied physical states. They could argue that mental states differ in degree of complexity from other physical states but not in kind, and can so be viewed as essentially identical physical states. To forestall this ploy, I will argue from the more intuitively certain principle that whatever differs in kind cannot be identical. Then I will argue that mental and physical states differ in kind, not degree.
The following discussion is meant to show that there is no metaphysical halfway house between mental and physical states. They are just too different. What one lacks, the other has, and vice versa. There is no graduated spectrum of states between the mental and the physical. In fact, mental states lack the defining properties of physical states; and physical states lack the defining properties of mental states. Contradictory properties cannot attach to the same thing.
It must be granted that thoughts are not round or square, weigh a certain amount, smell like roses, or are colored. A thought about a rose isn’t red; a thought about a rough road isn’t rough; a thought about the smell of steak doesn’t smell like steak. Yet Taylor wants to maintain that thoughts are, in some sense, identical to material states. He thinks we can, at least in principle if not in present day science, find the physical state of affairs that explains the as yet mysterious referential mental states. This is a kind of promissory note for future science. Such explanations should be, or at least can be, discovered by a more advanced scientific procedure. They are in principle knowable. Karl Popper calls this "promissory materialism" which "consists, essentially, of a historical (or historicist) prophecy about the future results of brain research and of their impact."15 But does this promise make any sense?
Even if a particular mental state is correlated with a particular brain state this does not mean that the mental state is identical to the brain state. Most basically, the experience of joy can never be adequately or completely described by reference to physical states. Brain waves aren’t joyful; neither are they melancholic or anhedonic. Rather, people experience these emotions, people who differ drastically from nonhuman, physical objects.
Further, any objective report about any physical brain state can never explain without remainder any corresponding mental state which is necessarily subjective. The subjective state and the objective state are not identical. To put it another way, my first person mental experiences—of pain, joy, fear, ratiocination, etc.—are not reducible to third person objective descriptions concerning brain waves, neurons, etc. Hick points out:
For there is the inescapable difference that our own mental states are known by us directly whilst our brain states are known to us indirectly, on evidence. Thus whilst it is entirely plausible that something going on in my brain causes my consciousness of the night sky, sustains it, and is indispensable to it, the claim that my consciousness of the night sky literally is—exclusively and without remainder—my gray matter functioning in a certain way is a claim that two things which are apparently different in kind are really one and the same.16
The advocates of mind-brain identity often claim that the mind just is the brain in the same sense that lightning just is the motion of electrical charges. They are two different descriptions of the same thing. While Taylor doesn’t give this analogy, his position seems to force him into something similar if a person is nothing but a collection of physical states; that is, if mental states are reducible to physical states. The lightning is identical with the motion of electrical charges because everything true of lightning is true of electrical charges. The fact that two different names are used implies nothing about the intrinsic identity of lightning/electrical charges. I may be called Doug or Mr. Groothuis and still be the same person just as George Bush and the President of the United States are (on December 10, 1990) the same person.
With astronomical insight we discern that the morning star and evening star are identical. With some scientific savvy we discover that lightning and the motion of electrical charges are identical. But as Hick points out, the lightning/electrical charge identity or the morning star/evening star identity analogies refer clearly to one physical object understood under two different descriptions. Hick says: "To assume that such cases offer a valid analog for the identity of a physical event with a mental event is simply to beg the question at issue, which is precisely whether physical and mental events can be identical."17 These sorts of analogies don’t get us very far because they exclude the very sorts of mental states that are at the heart of the issue.
Therefore, even if we grant some super-science that would satisfy Taylor’s materialistic quest for covert corporeality, mental states and physical states would remain distinct and irreducible to each other. As Moreland points out, a brain surgeon may have far greater knowledge of my brain (physical states) than I do or ever will, but she cannot know my mental life as well as I do. She cannot feel my fear at going under her knife nor my hope that I will reawaken after the operation.18 So, if brain states are identical to mental states it must be the case that whatever is true of one is true of the other. But it is certainly not the case that my first person subjective experience (mental state) of testing syllogisms for soundness and validity is true of the brain state I am in when I work on logic. There may be correlation, but there can be no identity. Neither is there a difference in degree between the experience of thinking logically and the physical description of the brain state one is in while during so. No brain state is semi-logical, not any mental state semi-physical. As Leibniz noted, if we liken the human brain to a factory, we could see any number of movable parts, but we could never see the thinking. To suppose we can equate brain states with mental states is a category mistake of the first order, as Berkeley noted: "To expect that by a multiplication or enlargement of our faculties we may be enabled to know a spirit [soul or mind] as we do a triangle, seems as absurd as if we should hope to see a sound."19
The point here is that mental experience in the first person is logically distinct from third person observations Thus mental and physical events are not equivalent or identical. Consider one more case: A research scientist was born without the sense of smell. His area of interest is olfactory responses and processes in humans. He knows more about the physiological components of smell than any living researcher. Yet he has never smelled anything in his life. Can we say he knows what it means to smell because he has such a wide knowledge of the physical processes involved in smell? I think not. But if through a new operation—which he himself helped develop, given his encyclopedic knowledge of the subject—his olfactory faculty was restored, he could then be said to have experienced smell in the first person for the first time. He can then experience the mental state of smelling everything within his nose’s glad grasp.20 The physical correlates of smell are not identical to the mental state of smelling. If they were, our scientist would have had no new, post-operative experience.
Some future science may find that every mental state is correlated with a particular brain state or several possible brain states, but this would establish no more than the contingent correlation of these two very different kinds of states. It would show that the states are existentially inseparable (given what we know), but it would not show that they are ontologically identical.
Still Taylor may argue that while matter may have odd properties only found in humans, the supposition of a separate soul or mind in order to explain mental events puts us in no better position than the mysteries of materialism. So we are on safer ground to say that mental and physical states are equivalent in some way yet to be discovered. But, interestingly, several scientists specializing in brain function have concluded that there is more to the person than the brain alone. The existence of a distinct mind better explains, they think the scientific findings. This claim is in direct odds with Taylor’s hope for a super-scientific materialist explanation. But what sort of scientific evidence, if any, could support dualism?
Dr. Wilder Penfield was known for his ground-breaking work with epilepsy. His work involved stimulating brain tissue in conscious patients in order to find the causes of epilepsy. During these sessions Penfield found that the prodding of certain areas of the brain triggered vivid memories of past events. The patients reported remembering clearly such things as the taste of coffee. One patient, while on an operating table in Montreal, Canada, remembered laughing with cousins on a farm in South Africa.21 What amazed Penfield was that his patients, who were not under anesthetic, were simultaneously conscious of the re-experienced memories and of being prodded by an electrode in an operating room. Penfield called this a "double consciousness" wherein a memory was stimulated physically but was attended to and recognized as a memory by a conscious patient. Penfield likened this to the patient watching a television program while remaining aware that it wasn’t now happening.
Penfield repeated these results on hundreds of epileptic patients and concluded that a separable mind was able to track what the brain was doing as a result of the artificial stimulation. One’s mind in a sense could transcend the operations of the brain, monitoring memories without actually placing oneself in the situation remembered. Penfield noted that "The mind of the patient was as independent of the reflex action as was the mind of the surgeon who listened and strove to understand. Thus, my argument favours independence of mind-action."22 Penfield also stated that if we liken the brain to a computer, it is not that we are a computer, but that we have a computer.23
Penfield, who began his research as a materialist, switched to dualism after extensive research with epileptic patients. He said, "Something else finds its dwelling place between the sensory complex and the motor mechanism. . . . There is a switchboard operator as well as a switchboard."24
Although nonepileptic patients do not respond similarly to brain stimulation, other researchers, such as Sir John Eccles, a neurobiologist, have similarly concluded that the brain alone cannot account for a many phenomena. Eccles’
Hypothesis is that the self-conscious mind is an independent entity that is actively engaged in reading from the multitude of active centres in the modules of the liaison areas of the dominant cerebral hemisphere. The self-conscious mind selects from these centres in accord with its attention and its interests and integrates its selection to give unity of conscious experience from moment to moment.25
Thus, Eccles’ conclusions agree with Penfield’s, and his areas of research extend farther than that of epileptic patients. Eccles deems the "monist materialist" hope for an eventual physical explanation for mental events as wrongheaded in principle because mental events are not "simply derivative of aspects of nerve endings. There is no evidence for this whatever."26 Further, Eccles argues that his "strong dualist-interactionist hypothesis . . . has the recommendation of its great explanatory power. It gives in principle at least explanations of the whole range of problems relating to brain-mind interaction."27 Eccles notes that it has been impossible to develop a materialist explanation of "how a diversity of brain events come to be synthesized so that there is a unified conscious experience of a global or gestalt character."28 Given this impasse, Eccles proposed that "the self-conscious mind" serve to integrate the apparently disparate brain processes into a unified consciousness.29
My aim is not to give a detailed account of the evidence cited by the likes of Penfield and Eccles but to note that eminent, experimental scientists believe that dualism better accounts for the phenomena than does materialism. Mental activity seems to transcend that which is describable with reference to brain states or processes alone. Of course, Taylor could simply wait for the discovery of some subtle state of matter to explain these phenomena (the "matter of the gaps" approach), but we shouldn’t evaluate materialism according to its post-dated checks. Eccles claims that his interactionist idea is a genuine scientific hypothesis "because it is based on empirical data and is objectively testable."30 If so, Taylor would have to judge it on its own merits instead of dismissing interactionism in favor of materialism—which still awaits a scientific explanation of the mysterious "referential states." While the materialist hopes for a future explanation for facts not presently explicable on materialist grounds, Eccles and others offer theories that claim to account for a full range of phenomena by virtue of the existence of the mind.
Taylor may here simply deny such attempts a priori, given the problems he finds with how an immaterial mind can be understood to interact with matter. But this need not cripple the interactionist endeavor. As Mortimer Adler has pointed out, if there is good reason to question materialism and to grant the immateriality of mental states, the problems of interaction should be considered after the fact. These kinds of puzzles should not disqualify interactionist while there exists arguments and evidence in favor of it.31 There are any number of puzzles and conundrums concerning the activity of sub-atomic particles whose existence is, nonetheless, well established. If interactionism were logically contradictory or hopelessly unintelligible, arguments for it would be disqualified on that basis alone. But this does not seem to be the case. (Taylor admits that his own materialist position is not without mystery.)32
As mentioned above, even if a fuller physical explanation for various mental phenomena were discovered, this in itself would still not bridge the gap between subjective and objective reports. Jerome Shaffer remarks that if it were discovered that "each particular mental event occurs if and only if some particular brain event occurs" this
would not establish the [materialist] identity theory, which holds not just that mental and neural events are correlated in some regular, lawful way but that they are one and the same event, and, moreover, that these events are, basically, physical.33
When the gap between the subjective and the objective consists in a difference in kind, it is not just difficult to bridge but impossible. G. K. Chesterton’s quip has no little philosophical punch:
It is obvious that the materialist is always a mystic. It is equally true that he is often a mystagogue. He is a mystic because he deals entirely with mysteries, in things that our reason cannot picture; such as mindless order or objective matter becoming subjective mind.34
To this point, some may readily agree: "The reduction of persons to material properties is fundamentally misguided. Reductionism is wrongheaded." Yet the further retort would be: "Drop all the references to minds or souls being somehow in persons. We reject Taylor’s materialism but we also reject interactionism. Let’s rather speak of persons as the logically primitive term." We will call this perspective personalism.
Personalists agree that something has gone wrong if we assume that the "brain secretes thought as the liver secretes bile," as a Philosopher once said. Bodies don’t think, hope, will, desire, fear, or do mathematics. People do these things. But why split the person into a distinct soul and body, considering all the traditional difficulties in such a dichotomy? Persons think, not minds in bodies. The personalist need not appeal to scientific interpretations attempting to distinguish mind and body. We know that persons have unique properties without recourse to scientific experiments. That is enough.
While this position is superior to materialism, because it is more in harmony with ordinary language, it still leaves some important questions unanswered regarding the nature of these unique persons.
First, it doesn’t seem odd to inquire as to what part of a mechanism accounts for a particular function. If asked what part of the car carries the gasoline we answer that the gas tank in the rear of the car does. If asked what part of the car illuminates the road ahead we answer that the head lights do. If asked what part of the car turns the car we answer that the front wheels do. We can still say, of course, that "my car holds twenty gallons of gas" or "my car lights up the road at night" or "my car turns" but when pressed for a more particular and specific explanation we appeal to certain aspects of the car in question which explain functions: the gas tank, the head lights, and the front wheels.
Similarly, we might say that our professor thought long and hard before giving out the grades in the graduate seminar. Here the personalist chimes in, "Right! The professor, the person, thinks, Say no more." But must we stop here? Yes, the professor thinks. We don’t want to say that the brain produces thought as the stomach digests food. But it seems natural to ask what it is about the professor that allows him to think when the chair on which he sits can do no such thing. If we say, "Well, he’s a person. People think and chairs don’t," we really haven’t explained anything except the difference between the professor and the chair—something that was already understood before the question was asked. We haven’t explained the reason for the difference. The issue is: What makes people different? What accounts for their unique mental abilities?
The personalist will say that persons have mental abilities and that’s all there is to it. This seems somewhat analogous to saying a car carries gas, illuminates the road, and turns—and that’s all there is to it! But we want more. What is it about the car that carries gas, illuminates the road, and turns? How are these functions fulfilled? What makes them possible?
The interactionist, of course, will say that the person thinks because of the mind’s capacity to think. It is just this factor that distinguishes humans from nonhuman material objects. The function of thought is best explained by reference to an organ of thought distinct from the body alone. My elbow does not think, neither does my toe. I think But what do I think with? I think with the mind, a nonmaterial part of me. So for the interactionist, a person is both physical and mental. The mental aspect accounts for the unique properties of mental states. In other words, the mental states are states of something, of an entity called the mind. Similarly, physical states are states of various objects or bodies, including my own body. There is a parallel. States of affairs or properties are states of affairs or properties of something. Weight, color, mass, and texture are, indisputably and uncontroversially, states of physical bodies. Hope, fear, joy, and love are states of the mind, not physical bodies. The mental states are not reducible to the physical states. Mental states entail something that produces them in persons—the mind.
Taylor objects that an unusual state (a mental state) does not imply the existence of an unusual thing (the mind) . But this seems wrong. If, as argued, mental states are not identical with physical states, they cannot be states of matter, even Taylor’s "unfamiliar states of matter."35 Materialism cannot explain the difference in kind between mental and physical states. It only makes sense, then, to understand mental states as states of mind. They are states of that kind of thing, and it is not material. Therefore, contra Taylor, these "unusual" states do imply the existence of an "unusual thing"—the mind.
But Taylor’s terms shouldn’t throw us off the philosophical trail. Mental states are not unusual at all. We all experience them. They are only unusual when one is boxed in my materialistic constraints. To conceive of matter thinking is indeed unusual, to say the least. To conceive of a mind thinking is not.
The personalist will argue that the material/immaterial disjunct is illegitimate. We should rather speak of physical objects in some cases and persons in other cases. There is no need for immaterial minds. But the interactionist resounds that there must be something different about persons, something more than just their physical complexity, that renders them so different from nonpersons. The factor missing from a rock that prohibits it from thinking is a mind. Persons do think. They think with their minds.
If the personalist believes that the death and dissolution of the body is the end of the person (unless there is a later resurrection), then it becomes difficult to see just how she differs from the materialist. Persons can’t exist apart from bodies. There is no separable soul. So whatever makes a person different from a mere impersonal body, it must simply be a more complex organization or form of physical states, since the person is terminated with the cessation of bodily functioning.
The interactionist—however he responds to the classical problems of his position—appeals to the soul as the deciding factor accounting for human mentality. And it is just this, as classically understood, that endures bodily death.36 For the interactionist, then, there arise no problems of personal identity on account of gaps in existence between the pre-mortum (pre-resurrected) and post-mortum (post-resurrected) persons. The soul continues to exist until re-embodied or resurrected. There is then no gap to be bridged. Likewise, there is no gap to be bridged when all of my bodily cells have been replaced over a ten year period but I consider myself the same person despite this comprehensive physical overhaul.37
Copyright 2001 Douglas R. Groothuis. All rights reserved. International
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File Date: 4.11.01