by Dr. J. P. Moreland
As Megan stood in the checkout line at the grocery store, a magazine caught her eye. On its cover a voluptuous blonde posed nude, certain body parts concealed only by strategic positioning. Sharp anger mixed with grief at the display of “just a body” provoked Megan to complain to the manager. The words “just a body” echoed in her thoughts all the way home.
Once, Megan hadn’t realized that she’d treated herself like “just a body.” Without regard for her soul (though she’d never deny possessing one), Megan’s behavior demonstrated a physicalist “if it feels good, do it” mentality. She never thought to consider the damage her choices might do to her innermost being. A purely physical self-concept guided Megan into decisions that destroyed her marriage and almost destroyed her self-worth in the process.
Throughout human history, the majority of people, educated and uneducated alike, have been dualists, at least in the sense that they consider a human as a being who experiences life beyond physical death (whether as the very same individual, or as some sort of spiritual entity that merges with the “All”). Some form of dualism appears to be the instinctive response to what people know about themselves through introspection and in other ways.
Many philosophers who deny dualism admit that it is the commonsense view. Nonetheless, the thinking that a person is “just a body” (physicalism) permeates a culture without much awareness. Such a pattern of thought can cause individuals like Megan to make moral choices that damage the soul. Though physicalism is one of philosophy’s most complex and challenging topics, understanding its issues in connection with dualism can help a person make constructive choices based on all facets of body and soul.
Part 1 of this series presented the case for property dualism by showing how the mental properties that make up one’s stream of consciousness are not physical, but genuinely mental. Part 2 built a case for substance dualism by arguing that a human being’s soul, or self (e.g., a mother’s soul), is immaterial. This third and final installment rounds out the case for body and soul dualism with two steps: first, by offering a response to the frequently stated objections to property/substance dualism and, second, by critiquing important versions of physicalism.
Response to Typical Objections
Those who argue against property and substance dualism raise objections that fall into one of two classes: scientific problems and philosophical problems. In one way or another, some scientific objections imply that, while possible, evidence makes dualism unlikely. But this claim is hard to substantiate.
Various arguments in philosophy of mind literature (see the arguments presented in Part 1 of this series) make evident that science cannot formulate and address, much less resolve, most of the body and soul issues. For example, even if a certain mental state (such as Megan’s desiring a hug) depends upon a specific region of the brain, a dualist can explain the dependence as a form of correlation or causation, rather than as some sort of identity relation. It is not science per se, but philosophical or methodological naturalism that becomes the main dualist opponent here. Dualists justifiably argue that naturalists beg important questions in their employment of science to justify physicalism.
Typical of physicalists, Nancey Murphy admits that while advances in science do not disprove substance dualism, they do show it as a weak position. Murphy asserts, roughly, that physicalism is stronger because it is not primarily a philosophical thesis but rather the hard core of a scientific research program for which ample evidence exists. To what evidence does she refer? “Biology, neuroscience, and cognitive science have provided accounts of the dependence on physical processes of specific faculties once attributed to the soul.”1 No such evidence, as Murphy acknowledges, provesdualism false—a dualist can always appeal to correlations or functional relations between the soul and brain/body¾but advances in science make it a view with little justification.
To uncover the flaws in this claim, one may note first that people have both actual properties and potential properties. The former are traits already actualized in a person (e.g., Megan’s blue eyes); the latter are genuine potentialities that would be actualized by a person if certain circumstances were to obtain them. If some entity X changes so as to exemplify some property F, then prior to X’s exemplifying F, X must be the type of thing that has the property of being potentially F. A little girl does not have the actual property of being shaped like a woman; but even while she is a little girl, she already has the property of being potentially shaped that way.
Both actual and potential properties characterize a person. Moreover, a faculty of a particular person is a natural grouping of resembling capacities or potentialities possessed by her. For example, the mind—a faculty of Megan—consists in a range of naturally resembling potentialities of thought and belief. It follows, therefore, that her faculties characterize Megan, or give her identity. Further, a potentiality gets its identity and proper metaphysical categorization from the type of property being actualized. The nature of a capacity to exemplify F is properly characterized by F itself.
However, as revealed in Part 1 of this series, the capacities for various mental states (e.g., desiring relationship) are mental and not physical capacities. Thus, the faculties constituted by those capacities are mental and not physical and may not always coincide. Thus, as Megan physically matures from a young girl into a woman, her emotional and intellectual faculties may or may not also mature.
A person is the kind of being she is in virtue of the actual and potential properties/faculties essential and intrinsic to her. Thus, a description of the faculties of Megan provides accurate information about her. A description of her capacities/faculties provides more accurate information about what kind of person she is than does an analysis of the causal/functional conditions relevant for her to behave in various ways. This is because the causal/functional conditions relevant to her actions can either be clues to her intrinsic nature or else information about some other entity that she relates to in exhibiting a particular causal action.
For example, if Megan wears clothes that attract attention, information about the precise nature of those clothes and their role in her action may not tell us much about the nature of Megan (except that she is dependent in her functional abilities on other things, that is, her appearance). A conclusion cannot ensue that the actual and potential properties of her clothes are clues to her inner nature.
In the same way, functional dependence on/causal relations to the brain are of much less value in telling Megan who she is than is a careful description of the type-defining mental capacities described in Part 1. In this case, physicalism and dualism are empirically equivalent theses (i.e., consistent with the same set of empirical observations of the brain and body) and, in fact, there is no theoretical virtue (e.g., simplicity, fruitfulness, kindness) that can settle the debate if it is limited to being a scientific debate.
Thus, it is not simply that science cannot prove dualism to be false. Rather, science provides little evidence for settling the issue. This is especially true in light of insights about the relative merits of human faculty descriptions (who Megan is) as opposed to analyses of causal/functional dependencies related to that person (how she appears).
Science is a wonderful tool for explicating various relationships between mind and body and it needs to be said that the mind/soul affects the brain/body and not just vice versa. But, in this author’s opinion, science offers little to resolve the main ontological questions of the mind/body problem. These issues remain distinctively and primarily philosophical and even theological in nature.
Turning from scientific to philosophical criticisms of dualism, two problems stand out: first, the problem of knowing other people’s minds and, second, the problem of causal interaction. According to the first problem, dualism makes knowledge of other minds impossible or seriously challenged. In a dualist construal, the mental states of other persons are always underdetermined by knowledge of the relevant physical facts about those persons (e.g., brain states and body movements) and, thus, knowledge of the physical facts does not yield knowledge of other people’s mental states.
Many times Megan determined her male friends’ thinking by their physical actions; however, she often underdetermined their mental states. They had no intention of marrying her even though their actions led her to believe they were on that path.
Dualists respond to underdetermination in two ways. First, they view this problem as, in fact, a reality—one that forms the basis for the knowledge argument as well as for the argument from first person indexicals (indicators of “I”¾see Part 1). So from the dualist perspective, underdetermination represents a virtue and not a vice. (While in Megan’s case it might have been helpful to accurately read her boyfriends’ minds, more often than not such ability would lead to significant problems¾no one would be able to entertain private thoughts.)
Second, dualists see the physicalists’ skepticism as going too far: physicalists presuppose that if it is logically possible for some knowledge claim to be mistaken, then one cannot have knowledge (or justified belief) regarding the claim, at least not until the skeptic is refuted. So understood, the problem is not dualism, but skepticism in general. The dualist argues that an individual can have knowledge or justified belief even if it is logically possible that she is mistaken, or that she offers a defeasible account of knowledge of other minds.
Thus, when Megan’s boyfriend slipped an engagement ring on her finger, she was justified in believing that he wanted to marry her, even if he might eventually take the ring back, and even if no amount of knowledge of his brain or body guaranteed that he was not just another philanderer. Space forbids further elaboration, but dualists Richard Swinburne and Alvin Plantinga have proffered accounts of knowledge of other minds adequate to rebut the physicalist challenge.2
Regarding the problem of causal interaction, one should note that Christian theism involves dualist interactionism regarding God Himself. God, an immaterial spirit, is capable of causal interaction with the material world, and if God can part the Red Sea, it is unclear why Megan (made in His image and possessing an immaterial spirit) cannot interact with the material world in such a way as to place a ring on her finger by willing it there.
Very few people, especially Christian theists who raise this objection, have objected to the intelligibility of divine miracles. Even if one does not believe such miracles ever occurred, still, the very idea that if there were a God, He could interact with the material world He created seems intelligible to most people. But if the problem of causal interaction is one about the very nature of spirit and matter, then it counts against divine interaction just as much as it does against human interaction. And if the former is intelligible, as most theists and atheists acknowledge, then the latter is as well.
More justification exists for believing that causal interaction takes place than for accepting the assertion that mind/body interaction is “problematic.” Megan is aware of the fact that rejection causes a mental event of pain or that a decision to put a ring on her finger is causally responsible for the ring being there. Adequate evidence reveals that the interaction takes place even if one has no idea how it occurs.
The preceding paragraphs provide a brief response to the main objections against dualism. The discussion now turns to an evaluation of some major forms of physicalism.
A Critique of Physicalist Alternatives to Dualism
Physicalism reduces the mind and body to virtually a body. To understand contemporary versions of physicalism, one must understand the five distinct types of “reduction” to which physicalists appeal:
- Individual ontological reduction: One object (a macro-object like Megan) is identified with another object or taken to be entirely composed of parts characterized by the reducing sort of entity. This type of reduction argues, for example, that living things are identical to or composed entirely of collections of physical/chemical parts arranged in a certain way; thus, living things do not possess a soul or vital entity that accounts for their unity and status as living things. (Megan as a person may be reduced to the components of her physical body.)
- Property ontological reduction: One property (Megan’s attractiveness) is wholly identified with another property (Megan’s body).
- Linguistic reduction: One word or concept (loneliness) is defined as or analyzed in terms of another word or concept (being alone). These kinds of reductions may be found in the dictionary or specialized vocabulary of a particular discipline.
- Causal reduction: The causal activity of the reduced entity is entirely explained in terms of the causal activity of the reducing entity (e.g., Megan’s mental life is entirely explained by her brain).
- Theoretical or explanatory reduction: One theory or law is reduced to another by biconditional bridge principles (e.g., Megan will find a husband if and only if her physical body attracts one). Terms in the reduced theory connect with terms in the reducing theory by way of biconditionals. This relationship identifies the properties expressed by the former terms with those expressed by the latter. Supposedly, the laws of thermodynamics can be reduced to the laws of statistical mechanics and, on that basis, Megan’s body can be identified with her ability to find a husband.
Individual ontological reduction is affirmed by virtually all physicalists.3 Whether or not functionalists accept property reduction is debatable, but physicalists generally believe that in the actual world, all properties exemplified by people are physical properties in some sense or another.
Causal reduction is hotly disputed by physicalists. Part of the debate involves the causal closure of physical phenomena (roughly, the notion that if one traces the antecedent causes of a physical event, he never has to leave the physical domain; there is no room for something nonphysical to cause things to happen in a chain of physical events) and the reality of so-called top/down causation. In other words, Megan is what her body does. It is safe to say that, currently, most physicalists accept causal reduction.
With the demise of philosophical behaviorism and positivist theories of meaning, linguistic reduction has been virtually eliminated from the debate. Theoretical reduction, however, remains as the main type of reduction employed in classifications of physicalism and, unless otherwise indicated, descriptions of physicalism, whether labeled as reductive or nonreductive should be understood to employ it.
Type identity Physicalism
Currently, the main version of reductive physicalism is type identity physicalism. These physicalists accept both theoretical reduction and property ontological reduction. In this view, mental properties/types are identical to physical properties/types (e.g., Megan is her body).
Moreover, identity statements asserting relevant identities are construed by physicalists as contingent identity statements employing different yet co-referring expressions. For example, the statement “Megan is identical to the tall blonde woman” is contingently true (while true, it could have been false, unlike “2 + 2 = 4” which is a necessary truth). The terms “Megan” and “tall blonde woman” both refer to the same thing (namely, a specific person) even though the terms do not have the same exact definition. Likewise, “heat is identical to mean kinetic energy” is allegedly a contingent identity statement. The truth of these identity statements is an empirical discovery, and the statements are theoretical identities.
Two main objections seem decisive against type identity physicalism. First, it is obvious that mental and physical properties differ from one another (see Part 1). Physicalists have not met the burden of proof required to overturn this deeply ingrained intuition.
They respond that in other cases of identity (e.g., Megan is not the tall blonde woman), intuitions about nonidentity turned out to be wrong, and the same is true in the case of mental properties. However, for two reasons, this response fails. For one thing, these other cases of alleged property identities are most likely correlation of properties cases.
Second, as philosopher Saul Kripke argued, the reasons why intuitions were mistaken (granting that they were mistaken, for the sake of argument) can easily be explained, but a similar insight does not appear in the case of mental properties.4 Since there is a distinction between Megan and how she appears (the tall blond woman), intuitions about nonidentity confused appearance with reality. But since mental properties such as loneliness are identical to the way they appear, no such source of confusion is available. Thus, intuitions about their nonidentity with physical properties remain justified.
The second difficulty with type identity theory is called the multiple realization problem, though a more accurate label would be the multiple exemplification problem, since according to dualists, mental properties are exemplified and not realized. Organisms with very different brains and bodies can all be in pain.
Largely in response to this latter type identity problem, a version of (allegedly) nonreductive physicalism—functionalism—has become the prominent current version of physicalism. Functionalists employ a topic neutral description of mental properties, or states, in terms of bodily inputs, behavioral outputs, and other mental state outputs. “Topic neutral” refers to a characterization of a mental state in terms that are neutral as to whether the state turns out to be physical or mental. Such a characterization depicts a mental state in terms of its functional role in behavior, not in terms of its intrinsic attributes.
For example, loneliness is whatever state is produced by being alone and which causes a tendency to desire relationship. The state of desiring companionship is, in turn, spelled out in terms of other mental states and bodily outputs (e.g., Megan’s activities designed to find someone to love her).
Mental properties are functional. Machine functionalists characterize the various relations that constitute a functional state in terms of abstract computational, logical relations, and causal role functionalists spell them out in terms of causal relations. Either way, a mental property such as loneliness turns out to be the second order property of being alone (a second order property is a property of a property, for example, having blond hair is a property of being Megan), of having a property that plays the relevant functional role “R.” In other words, “mental properties” are treated very much like computer software. Type identity physicalism is a hardware view; functionalism is a software position. (For more on functionalism, see sidebar.)
Token physicalism is a hard view to classify. Fundamentally, proponents of this view claim that even though there is no smooth property identity for mental types, every token (that is, particular) mental event is identical to a particular physical event. For example, there is not a single type of physical property that people must have to consider themselves lonely. But, with this view, every time any person is lonely, that particular physical “being alone” event will be identical to some brain event or other. Beyond that, things are not so clear and it is beyond the scope of this article to probe this viewpoint more deeply. However, it is safe to say that for most physicalists, token physicalism is not a distinct viewpoint; rather, it is just one specification of a full-blown physicalist functionalism in which mental properties are seen as functional types and particular physical events as token realizers of those types. So understood, the objections raised against functionalism also apply to token physicalism.
Finally, eliminative materialists assert that mental terms get their meaning from their role in folk psychology (roughly, a commonsense theory designed to explain behaviors, such as searching for a husband by attributing mental states such as loneliness to them), and, that like Phlogiston theory, folk psychology will eventually be replaced with some neurophysiological theory. Thus, they say, the various mental terms of folk psychology fail to refer to anything and should be eliminated. Some eliminative materialists apply this view to all mental states (including sensations, such as pain) while others limit it to propositional states, such as beliefs and thoughts.
Eliminative materialism has garnered only limited acceptance. First, it inappropriately treats dualism as primarily a theory, which it is not (much less a replaceable one); rather, dualism is a descriptive report of the mental self and the mental states with which one is acquainted through introspection. Second, it simply seems implausible to say that no one ever actually has a sensation or belief. Third, some argue that in effect, eliminative materialism is self-refuting in that it advocates the belief that there are no such things as beliefs.
Some eliminative materialists have sought to avoid the self-refutation charge via verbal gymnastics. While admitting their view does in fact reject the existence of beliefs, they argue it allows for a physical replacement that plays the same role as beliefs, and that the theory advocates this replacement. However, many critics remain skeptical of this response on the grounds that if an entity is found that actually plays the same role as a belief, it will simply be a belief by another name. If it plays a different role, then self-refutation may be avoided only at the expense of proffering an inadequate revisionism.
An emerging supervenient position views mental properties as distinctively new kinds of properties that in no way characterize the subvenient physical base on which they depend. So understood, supervenience is actually a form of property dualism. Structural supervenience views mental properties as structural properties entirely constituted by the properties, relations, parts, and events at the subvenient level. Functionalism is currently the most popular version of structural supervenience.
Supervenient physicalism alone is not a distinct viewpoint. It fails to capture property dependence (the dependence of mental properties on physical ones) and, instead, only expresses covariance between mental and physical properties. In this respect, it is consistent with substance dualism, type physicalism, and epiphenomenalism. In fact, it allows for cases where A supervenes B, yet B in some sense depends on A. Personhood supervenes being human, but arguably, this genus/species relation depends ontologically on its genera for existence and identity.
In order for supervenience to express the dependence of mental properties on physical properties and, thus, to be adequate for at least minimal physicalism, it must be supplemented with two further principles:
- The anti-Cartesian principle: There can be no purely mental beings (e.g., substantial human souls) because nothing can have a mental property without having a physical property as well.
- The principle of mind-body dependence: Whatever mental properties an entity has depend on and are determined by its physical properties.
By employing arguments already given in Part 1 of this series, property and substance dualists will reject both principles (1) and (2). Moreover, since the anti-Cartesian principle is strictly a metaphysical thesis, no scientific evidence justifies it, so the authority of science cannot be claimed on its behalf. Regarding the principle of mind-body dependence, some scientific evidence does exist for the dependency expressed; however, scientific evidence also exists showing that mental states causally affect brain states. In any case, substance dualist arguments presented in Part 1 (e.g., the modal argument and the argument from libertarian freedom) provide counterexamples to the principle of mind-body dependence.
In sum, philosophical naturalism supports physicalism; science does not. And while the mind/body issues addressed in this series have been presented in a brief form, some solid philosophical grounds for rejecting physicalism and for accepting property and substance dualism have been established.
Megan turned away from physicalist thinking when she turned her attention to spiritual matters. When she embraced the truth claims of Jesus Christ she began contemplating more deeply the body and soul issues. Through introspection and Bible study, she gained insight into both their distinctions and connectedness. Megan began to recognize herself as an individual of inestimable worth¾much more than just a body—a soul designed in the image of God.
Understanding the implications of substance dualism, even though she was unfamiliar with the exact terms, added value to her existence and reason to safeguard her soul against the damage inflicted by an “if it feels good, do it” approach to life. The understanding that she’s not just a body set Megan’s spirit free and gives her hope that others might discover the same freedom.
- Nancey Murphy, “Human Nature: Historical, Scientific, and Religious Issues,” in Warren S. Brown, Nancey Murphy, and H. Newton Malony, Whatever Happened to the Soul? (Minneapolis: Fortress Press, 1998), 17. Cf. 13, 27, 139-43.
- See Richard Swinburne, The Evolution of the Soul, rev. ed. (Oxford: Clarendon Press, 1997), 11-16; Alvin Plantinga, Warrant and Proper Function (NY: Oxford University Press, 1993), 65-77.
- Type identity physicalists affirm property reduction, token physicalists avoid it, and others simply eliminate it.
- Saul Kripke, Naming and Necessity (Cambridge, MA: Harvard University Press, 1972), 148-55.
- Dualism: In metaphysics, the view that some reality consists of two fundamentally different entities (e.g., mental and physical).
- Eliminative materialism: The view that mental terms referring to thoughts and beliefs are like the term “phlogiston,” namely that they don’t refer to anything real and therefore may be eliminated.
- Epiphenomenalism: The view that mental states are caused by brain states but do not themselves cause anything.
- Functionalism: The view that types of mental states such as being in pain can be characterized totally in terms of their role in behavior.
- Mental holism: The view that a particular mental state gets its identity from its entire set of relations to all the other mental states in one’s life.
- Methodological naturalism: The view that science can only seek natural explanations for phenomena.
- Physicalism: The view that human beings are simply material objects.
- Property dualism: The view that ostensibly mental properties are genuinely mental and not physical properties.
- Substance dualism: The view that a human consists of an immaterial substantial soul and a physical body that is not identical to the soul.
- Subvenient: A property, for example being a wavelength, on which an emergent property, for example being a color, depends.
- Supervenient physicalism: The view that mental states are emergent properties that depend on the brain.