The Soul is Alive and Well, by D. Jeffreys

Theology and Science, Vol 2, No. 2, 2004 (dx.doi.org/10.1080/1474670042000261105 )

The Soul is Alive and Well:
Non-reductive Physicalism and Emergent Mental Properties

DEREK S. JEFFREYS

Abstract Non-reductive physicalism denies the soul's existence, arguing that cognitive functions emerge from evolutionary processes. Focusing on Nancey Murphy, this paper argues that non-reductive physicalism has an inadequate conception of causality. Murphy defends downward causation, but like many modern and postmodern philosophers, she pays insufficient attention to the metaphysics of causality. Drawing on Thomistic philosophy, this article maintains that lower-level entities like neurotransmitters lack the causal power necessary to produce higher-level cognitive operations. In defending emergence, Murphy performs a metaphysical sleight-of-hand through which cognitive powers inexplicably appear. The paper ends by urging contemporary thinkers to develop richer metaphysical understandings of causality, and to use them to enhance the dialogue between religion and science.

Key words: Non-reductive physicalism; Nancey Murphy; Thomism; The soul; Causality; Emergence

Non-reductive physicalism is shaping important debates about religion and science, promising a new integration of fields as diverse as neuroscience and theology. Its appeal rests on its vision of the person, whose mental life emerges from physical processes. This means that, in Nancey Murphy's words, "statements about the physical nature of human beings made from the perspective of biology or neuroscience are about exactly the same entity as statements made about the spiritual nature of persons from the point of view of theology or religious traditions."¹ This view enables Christians to welcome scientific developments, rather than viewing them as hostile to Christian faith and practice.

Despite its attractiveness, however, non-reductive physicalism also challenges elements of traditional Christian doctrine.

For example, it denies the existence of the soul, arguing that advances in modern science render it obsolete. What does this mean for Christian practice? The Nicene Creed, a part of weekly worship in many Christian denominations, states, "we look for the resurrection of the dead and the life of the world to come." However, without a soul, how can Christians await the resurrection, which seems to require continuity between our present lives and the "life of the world to come?"

Non-reductive physicalists are aware of these questions, and they have addressed them in several books and conferences. However, they usually discuss them without awareness of the rich philosophical traditions in Christianity and other religious traditions. This is particularly true when it comes to causality. Non-reductive physicalists write extensively about causality, championing top-down causality, and describing how God acts causally. However, they rarely consider historic treatments of the topic. For example, they seem entirely unaware of the Buddhist tradition's extraordinary account of causality, which challenges many of their presuppositions about cause and effect. Likewise, they disregard the Aristotlean-Thomistic tradition, superficially analyzing Aristotle and Thomas without understanding their writings. As a result of this historical carelessness, non-reductive physicalists manage to avoid significant philosophical challenges.

In the hope of developing a richer dialogue about the soul and causality, in this article, I present a Thomistic challenge to non-reductive physicalism, arguing that its understanding of causality is metaphysically defective. I choose Nancey Murphy as my interlocutor, for she has been a leader in developing non-reductive physicalism in the last decade. First, I outline how she uses the concept of supervenience to undermine reductionism, noting how she combines it with downward causation. Second, I discuss how Murphy denies the soul's existence, describing why she thinks neuroscience accounts for cognitive functions traditionally attributed to the soul. Third, I critically examine Murphy's commitment to physicalism, arguing that she offers little philosophical justification for it. Fourth, using W. Norris Clarke's arguments, I maintain that non-reductive physicalism fails to explain how higher mental functions emerge in evolutionary processes because it violates a fundamental rule of causality that no effect can be greater in perfection than its cause. Fifth, I discuss the metaphysical justification of this Thomistic causal principle, describing how causality is intimately linked with natures. I argue that Murphy ought to adopt the Thomistic account of causality, noting that she cannot reject its idea of perfection or affirm an alternative regularity conception of causality. She cannot make any of these objections because she explicitly defends the idea that entities have natures with causal powers. Sixth, I urge contemporary scholars in religion and science to pay more attention to metaphysics, noting that it provides indispensable tools for engaging modern science. I conclude by maintaining that without a more sustained treatment of causality, non-reductive physicalism amounts to a metaphysical sleight of hand.

Nancey Murphy and reductionism

Drawing on a rich array of scientific and philosophical resources, Murphy mounts an impressive attack on reductionism. She notes that it admits of several, distinct meanings. Methodological reductionism is a "research strategy for analyzing the thing to be studied into parts."² For example, a doctor may study a disease by analyzing biochemical processes. In contrast, causal reductionism "is the view that the behavior of the parts of a system (ultimately the parts studied by sub-atomic physics) is determinative of the behavior of the higher-level entities."³ A causal determinist might argue that the brain causes behavior. Ontological reductionism asserts that higher-level entities are "nothing, but the sum of their parts."⁴ One kind of ontological reductionism rejects the idea that we need new elements in order produce higher-level entities from lower-level ones. For example, we need not appeal to the soul to explain how consciousness emerges in evolutionary history. Reductive materialism is another form of ontological reductionism. It maintains that the lower-level entities are the "really real." Exemplifying this approach, late-twentieth century philosophers known as "eliminative materialists" attempted to eliminate mental language altogether, consigning it an unscientific approach to the mind called "folk psychology."⁵

Among these forms of reductionism, non-reductive physicalism carefully treads its way. First, it retains ontological reductionism without embracing reductive materialism. Higher-level entities, Murphy maintains, are just as real as lower-level ones. Second, non-reductive physicalism rejects the idea that we need a soul or vital force to explain consciousness. However, it also repudiates causal reductionism, refusing to reduce mental states to physical ones. Murphy characterizes non-reductive physicalism as "the acceptance of ontological reductionism, but the rejection of causal reductionism and reductive materialism."⁶ Applying it to the mind, she argues that it "denies the existence of a nonmaterial entity, the mind (or soul) but does not deny the existence of consciousness (a position in the philosophy of mind called eliminative materialism) or the significance of conscious states or other mental (note the adjectival form) phenomena."⁷ For Murphy, "the human nervous system, operating in concert with the rest of the body and its environment, is the seat of consciousness."⁸ Religious experience, higher-level cognitive processes, and moral awareness all emerge from the nervous system's operations.

To block causal reductionism, Murphy uses the concept of "supervenience." As she points out, supervenience originated in ethics, finding its way into that discipline with G. E. Moore and R. M. Hare. Murphy introduces it with the vague idea that "every mental event (state, property) is related to some brain event."⁹Philosophers often describe this relation as one of identity or causality; mental events are either identical to brain happenings or caused by them. In either case, we cannot avoid reductive materialism. To preclude these consequences, Murphy proposes a different relation between mental and brain events, a complex hierarchy of systems governed by "supervenience." Here are Murphy's definitions of this idea, which she takes to be equivalent:

Property S is "supervenient" on property B if and only if something instantiates S in virtue of (as a non-causal consequence of) its instantiating B under circumstance c.

Property S is "supervenient" on property B if and only if something's being B constitutes its being S under circumstance c.¹⁰

For Murphy, when we have a mental event, say a thought about God, we have a brain event or function. The supervenience relation between the mental and the physical is not causal; we cannot say that when a mental event is instantiated, specific brain happenings always cause it. Similarly, it is not an identity relation because "supervenient" properties are multiply realized; if "S supervenes on B (given circumstance c), then something being B entails its being S, but its being S does not entail its being B."¹¹ Technically, this means that S cannot be identical to B because B does not entail S. For example, we may have a brain function related to several kinds of thoughts. By indexing supervenience to circumstances, Murphy shows that it is not an identity relation.

The causal reductionist must demonstrate that brain states constitute mental events in all circumstances. Murphy maintains that she cannot do this, and therefore, the reductionist project fails. She acknowledges, however, that some philosophers of mind define supervenience without paying attention to circumstances, thus making reduction easier. However, she argues that her account does greater justice to cases in the philosophy of mind. For example, a mental set in perception is closely indexed to circumstances. Murphy uses the example of an electrical shock. Two subjects receive shocks, which are physical happening. However, one may experience the shock as a burn, another as ice-cold. In each case, the shock could be realized as a variety of "perceptions of the environment (ice-cube tray on the counter, burn ointment), or the result of statements by the experimenters, or any one of an unbounded set of other devices resulting in what we can only meaningfully describe at the mental level as the expectation of heat or of cold."¹² With examples like these, Murphy argues that her account of supervenience holds great promise for explaining the relationship between mental states and the brain.¹³

What does supervenience explain?

Supervenience may undermine causal reductionism, but how much does it really explain about how the mind and brain interact? Jaegwon Kim, once one of its strongest advocates, has recently questioned whether it illuminates the philosophy of mind.¹⁴ Supervenience, he notes, is consistent with a variety of approaches to the mind, and both emergentists and epiphenomenalists have appealed to it.¹⁵ By itself, Kim maintains, supervenience "leaves unaddressed the question of what grounds or accounts for it—that is the question why the supervenience relation should hold for the mental and the physical."¹⁶ It simply states patterns of "covariation" between mental and physical traits, pointing out a dependency relation between the two. Mind-body supervenience "states the mind-body problem—it is not a solution to it. This means that non-reductive physicalism must look elsewhere for its metaphysical grounding; supervenience itself is not capable of supplying it. Any putative account of the mind-body relation that accepts mind-body supervenience must specify a dependence relation between the mental and physical that is capable of grounding and explaining mind-body supervenience."¹⁷

I think Kim is right that by itself, supervenience may eliminate some theories of the mind, but leaves undetermined which one we ought to adopt. In fact, within religion and science debates, we find thinkers who appeal to it for different purposes. For example, Philip Clayton uses it to defend an emergent monism that includes both spiritual and physical properties.¹⁸ Furthermore, simply stating that mental and neurological properties "exist" gives us very little information. For example, the Thomistic tradition distinguishes two fundamental modes of being, esse reale and esse intentionale. Esse reale is characterized by activity and self-communication, while esse intentionale is a dependent form of being that requires esse reale to actualize it.¹⁹ On this view, existence has modes, and we must specify what kind of existence an entity enjoys. Similarly, Yogacara Buddhism, a philosophically rich tradition from fourth and fifth-century India, famously maintains that the mind has three "aspects," the imagined, the relative, and the perfected. The relative enjoys a privileged existence, and is "simply identified with mind, mind understood as experience in toto."²⁰ In contrast, the imagined aspect is the way in which "experience constructs a world for itself," and the perfected aspect is characterized by the absence of dualism.²¹ On a common interpretation of Yogacara Buddhism, it is a form of philosophical idealism that grants the physical a shadowy existence, but sees the mind as the "really real." These examples show that existence is a philosophically complex concept, and we cannot uncritically appeal to it as if we all know what it means. Responding to this challenge, Murphy argues that higher-level laws and properties exert "top-down" or "whole-part" causality. Top-down causation means that higher-level variables in a system have genuine causal impact. Citing considerable evidence from biochemistry, ecology, and other sciences, Murphy argues, "interactions at the lower levels cannot be predicted by a look at the structure of those levels alone."²²Undoubtedly, laws and properties at lower levels affect those at higher levels, but higher-level developments also shape lower-level ones. Levels enjoy quasi-autonomy; some lower-level changes never affect higher levels, while some higher-level properties emerge from lower ones. Murphy establishes this quasi-autonomy by arguing that there are no laws at the neurological level that determine all mental events.²³ Absent these laws, we can conclude that the mental is more than epiphenomenal because it exerts causal influence. By defending top-down causation, Murphy goes beyond supervenience to establish that higher-level properties exist.

Non-reductive physicalism and the soul

Although Murphy insists that higher-level properties exert causal influence, she rejects the idea that a "soul" unifies them. Instead, she believes that modern science can explain the traditional faculties attributed to the soul. Brain localization research impresses her most, the attempt to find "the regional structure or distributed system in the brain responsible for such things as language, emotion, and decisionmaking."²⁴ As scientists increasingly associate functions of the "soul" with brain happenings, it becomes "more and more appealing to say that it is in fact the brain that performs these functions."²⁵ CAT scans, PET scans, and MRI technology enable neuroscientists to map the location of brain damage, correlating it with thoughts and behavior. They can also link language use and emotions. For Murphy, brain localization research provides "dramatic evidence for physicalism."²⁶

Murphy uses this research to criticize Thomas Aquinas' understanding of the soul, systematically correlating its faculties with neurological processes.²⁷ For example, Thomas defines the soul as the "life principle," but Murphy explains it in terms of "neural activity."²⁸ Similarly, what he attributes to the nutritive soul, she explains using DNA and neurochemicals. Finally, Thomas makes the soul responsible for higher mental functions, but Murphy notes how we now know that they all involve language, which we can correlate with particular brain regions. Summarizing her critique of Thomas, Murphy argues, "science has provided a massive amount of evidence suggesting that we need not postulate the existence of an entity such as a soul or mind in order to explain life and consciousness."²⁹ Thomas invoked the soul in order to explain the capacities he thought biologically inexplicable, but today, Murphy writes, this "hypothesis has been shown to be unnecessary."³⁰

Without a soul, however, how do human beings acquire reasoning, love, and knowledge of God? For Murphy, throughout evolutionary history, these attributes gradually emerge from the physical. Emergence "refers to the appearance of properties and processes that are describable only by means of concepts pertaining to a higher level of analysis."³¹ Religious experience, for example, is neither applicable nor reducible to the neurological level of analysis, but emerges from it. Murphy argues for autonomous "higher-level laws" governing emergent properties within a system.³² They explain how higher-level cognitive capacities emerge from specific parts of the brain. To account for these developments, critics can always appeal to the soul, but Murphy sees such appeals as desperate attempts to protect an antiquated idea.

Why adopt physicalism?

By using emergence, top-down causation, and supervenience, Murphy hopes to undermine traditional doctrines of the soul that see it as an immaterial entity. Supervenience, as William Hasker suggests, guarantees that "the mind cannot vary independently from the body, and this seems an inescapable implication of the physicalist claim that the physical facts determine all the facts."³³ However, why adopt physicalism in the first place? Murphy offers very little in the way of argument to support it. First, she rarely defines exactly what she means by the term "physical." As Hasker notes, the "task of framing a general definition of the physical is not a trivial one."³⁴ Is physicalism a methodological claim requiring us to accept only knowledge that the sciences generate? Or is it an ontological claim that restricts the physical to what is "built up out of the fundamental particles and energies that we have discovered in the natural world?"³⁵ Charles Taliaferro discusses four definitions of the physical, including what contemporary physics describes, what an ideal physics would describe, what is publicly observable, and what no subject is better placed to know than any other subject.³⁶ Each of these definitions has philosophical implications. For example, if we restrict the physical to what an ideal physics would describe, we establish that the tools of physics are the means for studying consciousness. However, such an approach ignores first-person elements of consciousness, leaving out "the crucial features that distinguish mental from non-mental phenomena."³⁷ I think we can define the physical without confronting insurmountable obstacles, but any definition has epistemological and ontological implications.³⁸ Murphy seems unaware of this point, uncritically and imprecisely appealing to the physical.

Murphy often supports physicalism by simply citing scientific research. She knows, however, that this approach is open to an obvious objection. Dualists can always claim that "there is a substantial mind and that its operations are neatly correlated with brain events."³⁹ In fact, a Thomist would expect to discover just the kinds of mental-physical correlations Murphy describes. Thomas argues that the soul integrates thoroughly with bodily functions. It is the "form of the entire body and of each of its parts."⁴⁰ Unlike some modern dualists, Thomas posits an intimate relationship between soul and body. The soul can exist without the body, but needs it in order to perform certain vital functions, particularly those relating to gathering information about the world. This approach to soul and body undermines many of the stock criticisms of dualism, particularly those that focus on why the soul needs a body and how it relates to the body. It also recognizes many correlations between the soul's activities and brain functions. Murphy seems to acknowledge the inadequacy of her appeal to scientific developments when she notes that Sir John Eccles, an outstanding neuroscientist, used neuroscience to support dualism. She notes, "it has long been recognized that substance dualism cannot be disproved by empirical evidence."⁴¹ However, if this is true, simply citing advances in neuroscience and cognitive science will not do. Murphy must provide good metaphysical arguments for physicalism.

Responding to this objection, she suggests we "look at the epistemological status of non-reductive physicalism, not as a philosophical thesis, but as a scientific theory."⁴² It is a research program, a "vast network of theories, logically related to one another and supported by a variety of data. What unifies it is a "hard core," a thesis, "often of a metaphysical nature, about the character of the part or aspect of reality under investigation."⁴³ The metaphysical "hard core" of Murphy's research program is her commitment to physicalism. For Murphy, a research program also includes a plan that specifies work to be done. Non-reductive physicalism sets forth the plan to "explain physicalistically the operations once attributed to the mind or soul."⁴⁴ Researchers in theology, philosophy, neurology, psychiatry, anatomy, and other sciences will corroborate it by explaining "mental" phenomena physicalistically.

I think Murphy's appeal to the idea of non-reductive physicalism as a research program amounts to an evasion. If its hard core is metaphysical, it would seem that we need to defend it metaphysically, not scientifically. Obviously, if we assume that physicalism is true, we will find considerable evidence for it by using the sciences. However, this is exactly the issue in dispute between physicalists and non-physicalists. Without explaining why physicalism should constitute the hard core of a research program, Murphy provides no reason to adopt it.

Non-reductive physicalism and causality

Nevertheless, by proposing physicalism as the hard core of her research program, Murphy provides us with the means of evaluating its success. Does it explain physicallistically "all of the operations once attributed to the mind or soul?" I think it fails to do so because it lacks a clear conception of causality. Murphy proposes that mental properties emerge from the physical, but the causal mechanism of emergentism is quite mysterious. How exactly does this happen? In evolutionary history, we have organisms lacking a moral awareness and religious experiences. At some point, these properties emerge when hominids evolve. Similarly, neurologically, we have neurotransmitters and brain activity out of which emerge rational thought and the capacity to love. What causes these dramatic changes? Without discussing causality, emergence has a magical quality, with higher-level properties popping into existence without explanation.

Perhaps further scientific research will discover how mental properties emerge from physical ones. After all, non-reductive physicalism is a young research program, and we should give it time to corroborate its hypotheses. Murphy often counsels us to wait while the sciences do their work. For example, she writes, "The version of physicalism I espouse argues that, just as life appears as a result of complex organization, so too sentience and consciousness appear as nonreducible products of biological organization. To conceive of how it is possible to get "mind" out of matter one needs to appreciate homeostasis, through goal-directness, information processing, goal evaluation, consciousness, and sociality to self-consciousness."⁴⁵ She seems to think that scientific research will eventually explain how mind emerges from matter. This theory faces the same types of problems as a theory based upon the "God of the Gaps."

How can the higher emerge from the lower? Thomism and causality

The "God of the gaps" strategy is clearly conceptually bankrupt, but I think there are good metaphysical reasons to doubt whether non-reductive physicalism will ever demonstrate how higher-level functions emerge from lower-level ones. Recently, W. Norris Clarke, S. J. has noted how non-reductive physicalism violates Aristotelian-Thomistic principles of causality. Higher-level properties like rationality supposedly emerge from lower-level neurological happenings, but this suggests that an effect can be greater than its cause, an idea Thomism has traditionally rejected. For Thomists, an effect cannot be "qualitatively superior in perfection to its efficient cause or to the sum total of efficient causes which produce it."⁴⁶ Shortly, I will indicate why I think contemporary philosophers ought to embrace this idea, but now, let me simply explain it. If an effect were qualitatively more perfect than its cause, the cause would have to give something it lacks. The new, "higher" properties would appear to come from nothing, but this is clearly impossible in terms of Thomistic causality. Often, philosophers appeal to the impressive history of evolution, arguing that it is now self-evident that higher forms of life emerge from lower ones.⁴⁷ However, this is an assertion, not an argument. We need to explain how it occurs; otherwise, we commit the fallacy of "post hoc, ergo proper hoc (after this, therefore, because of this)."⁴⁸

Obviously, this argument rests on a Thomistic understanding of causality, and why should contemporary philosophers embrace it? Often, Murphy treats Thomism like an antiquated relic of a naive, pre-scientific age. For example, she rejects hylomorphism, the view that material beings are composed of form and matter. She describes the historical shift from hylomorphism to atomism, noting that the "development of modern physics meant the rejection of animal (and plant) souls, understood as the substantial forms of their bodies."⁴⁹ This change, she maintains, "made it impossible to understand the soul as the form of the body."⁵⁰ Unfortunately, she does little but assert this point, without explaining exactly how modern sciences undermine the idea that the soul is the form of the body. Similarly, she traces how Newton and other early scientists abandoned Aristotelian causality. Replacing substance with event causation, they argued that, contra Aristotle material beings are passive, rather than active. Murphy acknowledges that, "since the demise of the Newtonian worldview, philosophical accounts of causation have not kept pace with science."⁵¹ However, she has little confidence in Aristotelian modes of thinking, noting how "we are left without a clear scientific answer to the question of causal nature of matter. Neither do we have an agreed-upon philosophical analysis of causal concepts."⁵²

It is precisely this state of affairs, I think, that ought to lead Murphy to reconsider the Aristotelian-Thomistic conception of causality. Simply rehearsing the history of Renaissance and eighteenth-century rejections of Aristotelean/ Thomistic philosophy of nature may be of historical interest, but tells us little philosophically. Many of these criticisms were unsound at the time they were made, but gained support because they reflected a general cultural revolt against all things Aristotlean/Thomistic. Moreover, they reflected modern science's lack of interest in final and formal causality.⁵³ If, as Murphy suggests, there is no contemporary consensus around what constitutes a good causal explanation, we are free to ask if these facile rejections of Aristotelian/Thomistic causation are justified. Murphy is a champion of a postmodern epistemological holism, which is highly critical of elements of modern thought. She ought, therefore, to be open to the suggestion that the modern rejection of Aristotelian/Thomistic causality was a significant philosophical error. I argue for a retrieval of the Thomistic understandings of causality, and will begin laying out what I mean by examining a few of Thomas' texts. I will then illustrate why they are philosophically important.

Writing about grace, Thomas states, "nothing can act beyond its species, since the cause must always be more powerful than its effect."⁵⁴ Exploring the sacraments, he insists, "the greater is not brought about by the lesser, for nothing acts outside its species."⁵⁵ For Thomas, causality involves "that which contributes positively to the being of another."⁵⁶ Thomas distinguishes between a principle, which implies some order among beings, and a cause, which involves an influx of being. The "term principle implies an order or sequence, whereas the term cause implies some influence on the being of the thing caused."⁵⁷ Thomas adopts Aristotle's account of four kinds of causation (formal, material, efficient and final), developing detailed accounts of each. My interest here is in the efficient cause, which is a kind of influence or influx involving action and productivity.⁵⁸ It is "that which by its action makes something to be, or come into being, either in whole or in part. It answers the question, who or what made this."⁵⁹

Thomas links the technical term "species" (the lowest unit of classification) with causality, focusing on the powers or capacities a being possesses. In order to exercise causality, an entity must have a nature, "an abiding center of action and being acted on."⁶⁰ A nature limits what a being can do and have done to it. For example, without technical assistance, a human being cannot fly. Nor can she be boiled in water without losing her unity. These examples illustrate that "what particulars are liable to undergo and what they are able to do are determined by their natures since they are manifestations of their natures."⁶¹ Natures possess sets of causal powers or capacities, many of which enable them to exert efficient causality. A power is a "disposition to a specific form of behavior to something, together with an unspecific reference to the nature or constitution of the thing or material concerned."⁶²

We see, then, that the Thomistic idea that "no effect can be greater than its cause" is not an arbitrary restriction on causality that makes no sense in the contemporary world. Instead, it originates in the idea of natures with limited capacities to act and be acted upon. Given this ontology, something qualitatively inferior in perfection simply cannot produce something qualitatively superior to itself. In other words, "a being cannot act by its own proper virtue alone in a manner superior to its nature. This would be to destroy the proportion that must exist between the agent and its effect and would make an effect nobler than its adequate and proper cause, an obvious contradiction."⁶³

This causal principle certainly allows for emergent properties. Naturally, there will be features of a whole or of a system that are not features of its individual parts. John Searle helpfully calls these features "system features," those we can deduce or figure out by considering constituent parts.⁶⁴ Lower-level entities can certainly produce system features, but for a Thomist, these cannot qualitatively exceed them in perfection. Searle describes "causally emergent system features" that we must explain by describing causal interactions among elements.⁶⁵ Here, again, a Thomist would have no objection as long as some active potency exists within the parts giving rise to a feature of the whole. Hasker, a defender of "emergent dualism," acknowledges that these active potencies must exist, noting, "the theory [emergent dualism] requires us to maintain, along with the materialist, that the potentiality for conscious life and experience really does exist in the nature of matter itself. At the same time we have to admit, as Colin McGinn has pointed out, that we have no insight whatever into how this is the case."⁶⁶ Despite such comments, however, Hasker continues to defend emergence, failing to recognize that the problem he identifies is metaphysical, not scientific. Unless we show that events at the neurological level have the adequate efficient causality to produce mental activity, no amount of research in neuroscience and cognitive science will advance Murphy's research program. We will continue to have the contradictory assertion that by themselves, qualitatively inferior natures produce qualitatively superior ones.

Objections

Murphy might object to the idea of degrees of perfection implied by the Thomistic account of causality.⁶⁷ It presupposes higher and lower degrees of perfection among creatures. Perhaps such language is a relic of a philosophy of being that has no relevance in a post-Darwin world. In fact, sometimes Murphy uses quotation marks when referring to "higher" human faculties, suggesting a reluctance to see them as superior in perfection.⁶⁸ She can avoid the Thomistic critique by simply denying that there are qualitative differences in perfection among creatures.

This response is certainly available to eliminative materialists, who jettison mental language altogether. However, I cannot see how a non-reductive physicalist can use it. Murphy adopts the language of higher and lower-level properties, making it integral to her account of supervenience. For example, she analyzes religious experiences by classifying them in terms of higher and lower levels. Using supervenience to good effect, she argues that religious experiences are supervenient on psychological or neurological events. However, she never defends the idea that religious experience occupies a higher level than neurological activity.⁶⁹ Why classify a level as "higher?" Why not reject hierarchy altogether, or develop one that locates neurological happenings at the summit? Perhaps Murphy means that the higher is more complex than the lower. Alternatively, perhaps she means that the higher encompasses more of a whole than the lower. These are the two criteria she employs when discussing the hierarchy of the sciences.⁷⁰ However, can we really argue that every mental event is more complex than every neurological event?⁷¹ In what way does moral awareness encompass more of a whole than its neurological base? I can make little sense of these ideas, and cannot, therefore, see that the complexity and range of mental events make them "higher" than neurological activities. By employing a hierarchy, Murphy implies some conception of perfection, even if she fails to define it. Her classification is parasitic on older ideas that religious experience, moral awareness, and advanced cognitive activities are qualitatively more perfect than neurological and other bodily activity.

Furthermore, as a Christian theologian, Murphy cannot reject a hierarchy of perfection without paying a very heavy price. She carefully defends an account of divine action in which God acts at the quantum level. A being that acts in this fashion has extraordinary knowledge and power, and Christian theologians have usually described these divine attributes as perfections. In virtue of God's nature, God is more perfect than creatures. St Augustine, Anselm, Thomas, John Calvin, and many others develop Christian anthropologies linking the divine perfection with the biblical idea that we are made in God's image. The imago dei is not simply a more complex or more encompassing set of higher-level attributes, but is also a participation in divine perfection. A Christian theologian cannot reject this participation in perfection without jettisoning important theological intuitions and axiological claims. I, therefore, cannot see how Murphy can avoid the Thomistic challenge by rejecting its understanding of perfection.⁷²

Murphy might also respond to the Thomistic account of causality by rejecting it altogether, embracing either Humean skepticism or a regularity conception of causation. Bertrand Russell profoundly influenced Anglo-American philosophy by attacking the idea of cause, and many of its practitioners adopted his skepticism about causality. Russell maintained that the word "cause" is "so inextricably bound up with misleading associations as to make its complete extrusion from the philosophical vocabulary desirable."⁷³ Carefully discussing efficient causality, he denies that it possesses productive power. Thinkers dissatisfied with his skepticism often adopt a nomic understanding of causality, which sees it as a regularity relation, governed by laws of nature that can generate counterfactuals. For example, philosophers of science Ernest Nagel and Carl Hempel defend influential nomic accounts.⁷⁴ They banish productivity from causality, replacing it with a cause-effect relation characterized by regularity, spatial contiguity, temporality, and asymmetry.⁷⁵

Both nomic and Humean accounts of causality confront significant philosophical difficulties, which I will not enumerate here.⁷⁶ What is important is that Murphy cannot use them to evade the Thomistic critique. Obviously, an advocate of top-down causation who writes frequently about divine action cannot endorse Humean skepticism. In fact, Murphy often criticizes Hume, arguing that he presupposes the need to defend a foundationalist epistemology.⁷⁷ She also wants to establish that God acts at the quantum level, developing an intriguing and in my view, persuasive account of how God might act.⁷⁸ However, with this aspiration, Murphy cannot coherently embrace a Russell-like skepticism about causation.

Murphy could adopt a nomological account of causality, but she expresses significant misgivings about it. She worries about an ontology that includes laws of nature, preferring instead to discuss the "law-like character" of the natural world.⁷⁹ She argues that contemporary scientific practice assumes no common conception of causation. For example, she suggests that without a Prime Mover initiating motion, we must assume, "contra Descartes and Newton, that matter is inherently active."⁸⁰ Entities appear to have inherent capacities for kinds of motion. Similarly, Murphy argues that although many philosophers embrace event-causation, scientific language is ambiguous about what constitutes a causal explanation. If A causes B, is it the event bringing about change that requires causal explanation, or is it B's existence we must explain? If we understand causal laws in terms of laws of nature and initial conditions, as Hempel argues, what exactly is the cause? Is it A, or is it the laws of nature? For Murphy, scientific language provides no consistent answer to this question. She concludes (as I noted earlier), "we are left without a clear scientific answer to the question of causal nature of matter. Neither do we have an agreed-upon philosophical analysis of causal concepts."⁸¹ From this analysis, it appears that Murphy rejects a nomological understanding of causality.

Given these reservations about contemporary understandings of causality, Murphy ought to pay more attention to the Thomistic account of causality, particularly because she argues that entities have natures with causal powers. Writing about divine action, she insists that what God creates:

Has a measure of independent existence relative to God, notwithstanding the fact that God keeps all things in existence. To put the point another way, if God were completely in control of each event, there would be no-thing to keep in existence. To create something, even so lowly a thing as an electron, is to grant it some measure of independence and a nature of its own, including inherent power to do some things rather than others.⁸²

At all levels of creation, God creates "genuine individuals, with his or her own integrity, created powers, capacities, and typical behavior" that enable them to participate in creation.⁸³ Moreover, God never overpowers God's creatures, acting instead to sustain and influence them within their nature and powers. Thus, at the quantum level, God respects the "rights" of sub-atomic particles, acting within their inherent powers to actualize "one or another of the quantum entity's innate powers at particular instants."⁸⁴ Through this "bottom-up" causation, God shapes macro-events.

Writing about top-down causation, Murphy again affirms the idea of natures, arguing that in order to understand divine causation, we must "know what are the intrinsic capabilities" of higher-level entities.⁸⁵ This will determine the limits of divine activity on a particular entity. For example, "cats can be taught to play games and eat onions when incorporated into a household; pet rocks cannot, no matter how stimulating the company."⁸⁶ The type of entity God creates constrains God, and if God acts beyond such constraints, God must create a new nature. God, for example, might create a being that looks like a stone but acts like a cat. However, we would no longer call such a creature a stone, but would have to find another way of classifying it. These passages provide strong evidence that Murphy endorses a conception of causality linked to natures and their capacities. Whether she affirms the contemporary notion of "natural kinds," or an older idea of natures, I cannot ascertain. Nevertheless, she closely links powers and natures; otherwise, her talk of God respecting inherent natures would make no sense. For Murphy, causation appears to be not simply a regular relation of events, but involves types of entities with powers and capacities.

If this is the case, Murphy cannot avoid the Thomistic argument that a lower-nature by itself cannot produce a higher one. By affirming natures and their limitations, she must accept the implications of this view. Given her strong commitment to the idea that God acts without violating a being's nature, I cannot see how religious experience, moral awareness, and higher-level cognitive functions emerge from a physical substrate. Those natures in the lower-levels, say, brain chemicals, are limited in their causal capacities. God does not override their natures, imposing God's will on them to bring about mental events. Instead, God works within their created natures. These natures simply lack the causal powers to give rise to qualitatively more perfect mental events like religious experiences. To bring this about, we need an influx of being exceeding their capacities. Therefore, we are left with the mystery of how consciousness emerges solely from a physical base. This is a major lacuna in Murphy's research program. She promises to explain the traditional faculties of the soul physicalistically, but relies on merely correlating mental and neurological events without ever explaining their causal relation. At this point, it is worth recalling Aristotle's idea that wisdom involves the knowledge of causes.⁸⁷ If Aristotle is correct, as I believe he is, Murphy offers us very little wisdom about the mind and body.

Why do we need a metaphysic of causality? Metaphysics and science

Readers may wonder what import my criticisms of Murphy have for the contemporary dialogue between religion and science.⁸⁸ I am first suggesting that Murphy and other thinkers in this dialogue should pay far more attention to the metaphysical issues than they currently do. Despite its repeated claims to be postmodern, non-reductive physicalism is like many modern philosophical movements that neglect systematic metaphysics. It reflects very little on the nature of existence, causality, substance, event, participation, and other concerns of classical Christian and Buddhist metaphysics. For example, Murphy insightfully criticizes modern epistemological foundationalism, but fails to recognize that the recent debate about it is a parochial one. Some twentieth-century thinkers wrote about the issues in this debate long before they became popular in Anglo-American philosophy. Before "postmodernity" emerged on the philosophical scene, Thomists like Etienne Gilson, Jacques Maritain, and Joseph de Finance offered penetrating critiques of what thinkers today call Cartesian foundationalism. Edmund Husserl, Max Scheler, and other phenomenologists debated and refuted scientific foundationalism.⁸⁹ Some of these thinkers rejected the modern focus on epistemology altogether, arguing that modernity's fatal error was to insist on epistemology before metaphysics.⁹⁰ In contrast, Murphy uncritically shares with the moderns the need to do epistemology first.

I believe that without a systematic, historically informed metaphysic, we enter religion and science debates with ill-defined concepts that obscure, rather than clarify philosophical issues. Like Murphy, we can simply assume that the conceptual tools of our day (in this case, Anglo-American philosophy) are adequate; or, we can develop a metaphysic that critically retrieves from the past, using it to engage scientific developments self-consciously. In this essay, I have adopted the latter stance, suggesting that the Thomistic tradition offers a systematic metaphysic worth embracing. It has developed in dialogue with revealed texts and the history of theology, and it provides a careful analysis of existence, change, the divine nature, knowledge, and other key metaphysical and epistemological concepts. On each of these topics, modern Thomists have responded to criticism, demonstrating how many modern philosophers simply misunderstand or distort Thomistic thought.

How we employ Thomism in the religion/science dialogue will vary according the case under consideration. To describe how Thomism fits into the contemporary religion and science debates, I would adopt what Nicholas Wolterstorff calls the model of "overlap but disequilibrium."⁹¹ Speaking about the relationship between religion and science, Wolterstorff says that we ought to expect both overlap and conflict between these two types of inquiry, leading to adjustments on both sides. Applying this idea to metaphysics, I think we can say that scientific advances may require that we alter our metaphysics, but also that a systematic metaphysic may challenge scientific claims about reality. We cannot ascertain a priori when we will have overlap or disequilibrium, or know when metaphysics or science will carry much of the burden in the dialogue. For example, quantum mechanics challenges Thomistic understandings of substance, forcing Thomists to think clearly about whether substance exists at the sub-atomic level. We begin with a clear account of substance, but then acknowledge scientific challenges that stretch or challenge it.⁹² In this case, only a rich dialogue between Thomism and science will decide whether sub-atomic particles are substances. The Thomistic account of substance may look significantly different than it would without this encounter with quantum mechanics. Alternatively, it may conflict with quantum mechanics, forcing us to decide whether to go with the scientific or metaphysical account.

On the question of causality, I think metaphysics must complete a scientific understanding of it. As Murphy notes, the practice of science assumes no uniform metaphysic of causality. What scientists generally require, although not in all cases, is causality as predictability and regularity. Instead of a productive idea of a cause, they have "substituted what is more easily discoverable and subject to validation by rigorous scientific methods; a regular sequence of events, such that given event A, event B can be predicted from it according to some law, whether deterministic or statistical."⁹³ For scientific practice, scientists may require no more than this idea of predictability. However, as a philosophical matter, this idea is incomplete, because it ignores the productive feature of a cause. To complete it, we need a metaphysical understanding of causality, and Thomistic philosophy offer a comprehensive one that has withstood considerable philosophical challenge. Armed with it, we can then return to scientific practice, asking if scientific developments challenge it. For example, some philosophers of science make extravagant claims about how quantum mechanics completely undermines Aristotlean/Thomistic accounts of causality. Confronting such arguments, a metaphysician involved in religion/science debates must accept their challenge. Without an adequate metaphysic, however, he or she has nothing to work with, bringing only confusion to the dialogue with physicists. On the matter of causality, this is exactly what I think Murphy offers, a series of claims with little or no philosophical justification.

Conclusion

Non-reductive physicalism is a philosophically unstable position that cannot withstand careful scrutiny.⁹⁴ Admirably, Murphy rejects reductionism, retaining a commitment to the mental as irreducible and causally efficacious. She also eliminates any doctrine of the soul, arguing that the mental emerges from the physical. However, she offers no causal explanation for how our mental life emerges from physical processes. Too often, she simply cites contemporary research in neuroscience, cognitive science, and evolutionary theory, proffering it as evidence for emergence. By themselves, however, correlations between physical and mental states cannot illuminate how complex properties like rationality and the capacity to love materialize out of neurological activity. Without a causal account, emergence is a highly implausible thesis, a metaphysical sleight of hand in which at one point we have physical properties, and at another point we have mental properties. As I have suggested several times in this essay, this is a metaphysical, not a scientific issue. Murphy rarely reflects on the nature of causality, and when she does, she fails to commit herself to a particular understanding of it. Yet, she embraces the idea of natures, making it central to how she construes divine action. By taking this step, she commits herself to a theory of causality with important philosophical implications. One of these implications is that natures are limited in their causal powers, and by themselves cannot produce qualitatively superior natures.

Like many strands of modern and postmodern philosophy, non-reductive physicalism has a superficial understanding of causality. It speaks often of downward and bottoms-up causation, but ignores movements in the history of philosophy centrally concerned with causality. Too often, it uncritically celebrates developments in modern science, ignoring deep criticisms of physicalism in Buddhism, Christianity, and philosophical traditions. Consequently, it lacks a critical distance from contemporary philosophy, falsely assuming that it provides adequate tools for thinking through metaphysical issues. By drawing on Thomism's rich account of causality, I have challenged this presupposition, arguing that non-reductive physicalism has a metaphysically defective understanding of causality. By superficially engaging Thomism, non-reductive physicalists manage to evade important criticisms of their work. It is time they recognize its challenge, and abandon their philosophically parochial framework.⁹⁵

Endnotes

1 Nancey Murphy, "Preface," in Whatever Happened to the Soul? Scientific and Theological Portraits of Human Nature, eds Warren S. Brown, Nancey Murphy, and H. Newton Maloney (Minneapolis, MN: Fortress Press, 1998), xiii.

2 Nancey Murphy, op. cit, 129.

3 Ibid., 129

4 Ibid., 129

5 Paul Churchland is one of the most famous of the eliminative materialists. For one example of his work, see Paul M. Churchland, The Engine of Reason, The Seat of the Soul: A Philosophical Journey into the Brain (Boston, Massachusetts: MIT Press, 1996).

6 Murphy, op. cit., 130.

7 Ibid., 131.

8 Ibid., 131.

9 Ibid., 132.

10 Ibid., 134.

11 Ibid., 135.

12 Ibid., 137.

13 For a more technical presentation of supervenience, see Murphy's appendix to her article, "Supervenience and the Nonreducibility of Ethics to Biology," in Evolutionary and Molecular Biology: Scientific Perspectives on Divine Action, eds Robert John Russell, William R. Stoeger, S.J. and Francisco J. Ayla (Vatican City State: Vatican Observatory Publications, 1998), 487-489.

14 Discussing his intellectual trajectory, Kim writes, "I myself did at one point think—that the answer is yes, that what might be called supervenient physicalism is a possible position to take on the mind-body problem. There has been a controversy concerning whether supervenience, in the sense of strong supervenience, is indeed consistent with the irreducibility of the supervenient properties to their subvenient base. But the discussion of this question has been inconclusive, and I now believe that the debate was framed in terms of a seriously flawed notion of reduction (see chapter 4). Here we will focus on the question whether or not mind-body supervenience as such can be thought of as an account of the mind-body relation," Jaegwon Kim, Mind in a Physical World: An Essay on the Mind-Body Problem and Mental Causation (Representation and Mind) (Cambridge, Massachusetts: MIT Press, 2000), 12.

15 Kim, Mind in a Physical World, 12.

16 Ibid., 13.

17 Ibid., 14. Charles Taliaferro makes a similar point, arguing that "talk of supervenience linking the two [mental and physical properties] seems more of a way to label the conceptual difficulty of construing this hybrid than it does to explain it," Charles Taliaferro, Consciousness and the Mind of God (Cambridge: Cambridge University Press, 1994), 165. John R. Searle also sees little value in supervenience, see John R. Searle, The Rediscovery of the Mind (Cambridge, Massachusetts, MIT Press, 1992), 126.

18 Philip Clayton, "Shaping the Field of Theology and Science: A Critique of Nancey Murphy, Zygon: Journal of Religion & Science, Volume 34, Issue 4 (December, 1999).

19 W. Norris Clarke, S.J., The One and the Many: A Contemporary Thomistic Metaphysics (Notre Dame, Indiana: The University of Notre Dame Press, 2001), chapter three. Joseph de Finance, S.J., Etre et Agir dans la Philosophie de Saint Thomas (Rome, Italy: Libraire Editrice de L'Universite Gregorienne, 1960). Joseph de Finance's book is a neglected classic, a wonderful account of how being is dynamic and self-communicating.

20 Paul J. Griffiths, On Being Mindless: Buddhist Meditation and the Mind-Body Problem (La Salle, Illinois: Open Court, 1986), 85. For translated sources from Yogacara Buddhism and excellent critical essays, see Mathew T. Kapstein, Reason's Traces: Identity and Interpretation in Indian and Tibetan Buddhist Thought (Boston, Massachusetts: Wisdom Publications, 2001).

21 Griffiths, On Being Mindless, 86-88.

22 Murphy, "Supervenience and the Nonreducibility of Ethics to Biology," 473.

23 In discussing this question of laws and causality, Murphy draws on Donald Davidson's work. For Davidson's discussion of causality, see Donald Davidson, Essays on Actions and Events (Oxford, England: Oxford University Press, 1980), Essays 1 and 7. In this essay, I will not evaluate Murphy's account of downward causation. However, I think it is inadequate, for she fails to explain exactly what acts causally. Do emergent properties exert causality, or is it a larger whole that acts? For an excellent discussion of this issue, see Michael J. Dodds, O. P. "Top Down, Bottom Up or Inside Out? Retrieving Aristotelian Causality in Contemporary Science," Jacques Maritain Thomistic Institute, 25 July 1997. This article is available at http://www.nd.edu/Departments/Maritain/ndjmc.htm . Dodds maintains that we cannot defend downward without affirming formal causality, and I agree with him entirely. Interestingly, Philip Clayton recognizes the need for some kind of formal causality, arguing, "we need nothing less than a new theory of causality. This theory must supplement the so-called efficient causality on which modern science has been based with a way of speaking of the "causal" influence of form or structure, of function, of information, or of the whole on its parts—without falling into the four-fold causality of medieval metaphysics (formal, final, efficient, and material) and the pre-or antiscientific mindset that it fostered." Philip Clayton, "Neuroscience, the Person, and God: An Emergentist Account," Zygon: Journal of Religion and Science, 35:3 (September 2000), 649 n. 13. What I find odd in this passage is how Clayton seems almost allergic to any attempt to retrieve Aristotelian causality, falsely associating it with an "anti-scientific mindset."

24 Murphy, "Preface," 1.

25 Ibid., 13.

26 Ibid., 13.

27 Murphy explores Thomas in several essays. For one treatment, see Nancey Murphy, Religion and Science: God, Evolution, and the Soul. Proceedings of the Goshen Conference on Religion and Science (Goshen, Indiana: Pandora Press, 2002), 17-21.

28 Murphy, op. tit, 16.

29 Ibid., 18.

30 Murphy, Religion and Science, 20.

31 Murphy, "Supervenience and the Nonreducibility of Ethics to Biology," 472. For a good technical definition of emergence, see Clayton, "Neuroscience, the Person, and God," 634-635.

32 Ibid.

33 William Hasker, The Emergent Self (Ithaca, NY: Cornell University Press, 1999), 59.

34 Ibid., 61.

35 Clayton, "Neuroscience, the Person, and God: An Emergentist Account," 617. Clayton rejects physicalism, arguing that it undermines our understanding of God who is spirit acting in the natural world.

36 Taliaferro, Consciousness and the Mind of God, chapter 2.

37 Searle, The Rediscovery of the Mind (Cambridge, Massachusetts: MIT Press, 1992), 19.

38 Hasker argues that "all physical causation and physical explanation must be mechanistic," a useful definition of the physical, see Hasker, The Emergent Self, 59.

39 Murphy, "Non-reductive Physicalism: Philosophical Issues," 139.

40 St. Thomas Aquinas, Questions on the Soul, Question Ten. Translated by James Robb (Milwaukee, Wisconsin: Marquette University Press, 1984), 139. In this question, Thomas asks if the soul exists in the whole of the body, and answers that it does. Of course, he was entirely unaware of the deep interactions between the soul and the brain, which reveal just how much the soul depends on the body for acquiring important information. However, I see no difficulties in incorporating contemporary developments in neuroscience into his metaphysical framework.

41 Murphy, "Non-reductive Physicalism: Philosophical Issues," 139.

42 Ibid., 139.

43 Ibid., 139. In developing her ideas about a research program, Murphy draws heavily on Imre Lakatos's work. For an extended discussion of Lakatos, see Nancey Murphy, Theology in the Age of Scientific Reasoning (Ithaca, NY: Cornell University Press, 1990), chapter 3.

44 Murphy, "Non-reductive Physicalism: Philosophical Issues," 140.

45 Murphy, Religion and Science, 21.

46 Norris Clarke, S.J., The One and the Many: A Contemporary Thomistic Metaphysics (Notre Dame, Indiana: Notre Dame Press, 2001).

47 Searle makes just such an appeal, arguing that our scientific worldview requires us to accept that mental properties emerge from physical ones. Sadly, however, he fails to support this appeal to authority, denigrating religious thinkers who raise questions about emergence by saying that they "have not heard the news yet or are in the grip of faith," and "must separate their minds into separate compartments in order to believe such things," Searle, The Rediscovery of the Mind, 90-91. My goal in this essay is not to defend an account of the soul, but I want to be clear that I affirm evolutionary theories, but reject the idea that soul emerges from matter. I agree with Pope John Paul II, who argues that God creates the individual human soul at some point in evolutionary history, see "Truth Cannot Contradict Truth, Address of Pope John Paul II to the Pontifical Academy of Sciences" (22 October 1996). This address is available at http://www.vatican.va/holy_father/john_paul_ii/ . Murphy criticizes this "creationist" view, but I find her arguments entirely unpersuasive, see Murphy, Religion and Science, 16-17. For a good response to them, see Clarke, The One and the Many, chapter fifteen. Brian Leftow argues that Thomas is an emergentist who uses the idea of active potencies in form and matter, see "Souls Dipped in Dust," in Soul, Body, and Survival: Essays on the Metaphysics of Human Persons (Ithaca, New York: Cornell University Press, 2001), 120-139.

48 Clarke, The One and the Many, 194.

49 Murphy, "Preface," 11.

50 Murphy, Religion and Science, 15.

51 Murphy, "Divine Action in the Natural Order: Buridan's Ass and Schrodinger's Cat," 336.

52 Ibid., 337.

53 For one discussion of this history, see Michael J. Dodds, "Science, Causality and Divine Action: Classical Principles for Contemporary Challenges," CTNS Bulletin 21 (Winter 2001)3-12.

54 St Thomas Aquinas, The Summa Theologica of S. Thomas Aquinas, I-II, 112, Ic. (Second and Revised Edition). Literally translated by Fathers of the English Dominican Province. This edition is available online at http://www.newadvent.org/summa/

55 Aquinas, The Summa Theologica, III, 79, 2, 3. I owe this and the references to follow to Francis X. Meehan's excellent study of efficient causality in Aristotle and Thomas, see Francis X. Meehan, Efficient Causality in Aristotle and St. Thomas (Washington, DC: The Catholic University of America Press, 1940). This dissertation is one of the most sustained English-language treatments of causality in Thomas, but sadly, it has never been published. I thank W. Norris Clarke, S. J. for alerting me to its existence. For an excellent discussion of causality in Thomas, see Cornelio Fabro's work, particularly Cornelio Fabro, C. P. S. "La Difesa Critica del Principio di Causa," in La Rivista di Filosofia Neo-scholastica, XXVIII (1936), 102-142, and "L'origine Psicologica della nozione di Causa, La Rivista di Filosofia Neo-scholastica, XXXIX (Vita e Pensiero, Milan, Italy, 1937), 207-245.

56 Clarke, The One and the Many, 210.

57 Thomas Aquinas, Commentary on the Metaphysics of Aristotle, trans, John P. Rowan (Chicago, IL: Henry Regnery Company), Book V, 751.

58 For an account of Aristotle and Thomas' division of causality into four kinds of causes, see Meehan, Efficient Causality in Aristotle and St Thomas, 176-198, and Clarke, The One and the Many, chapters 12 -13.

59 Clarke, The One and the Many, 210. Naturally, this definition requires that we define and discuss action. For good discussion of the meaning of action, see Meehan, Efficient Causality in Aristotle and St Thomas, 187-188, 201-239, Clarke, The One and the Many, chapter 3, and Joseph de Finance, S.J., Etre et agir dans la philosophie de S. Thomas, (Rome: Universita Gregoriana, 1960).

60 W. Norris Clarke, S. J., "The Immediate Creation of the Soul by God: Some Contemporary Challenges." Father Clarke presented this unpublished paper at the 2001 meeting of the American Catholic Philosophical Association. I thank him for providing me with a copy. For one of Thomas' most sustained discussions of natures, see Thomas Aquinas, On Being and Essence: A Translation and Interpretation (Notre Dame, Indiana: University of Notre Dame Press, 1965). For an excellent discussion of substance as active, see W. Norris Clarke, S. J., "To Be is to Be Substance-in-relation," in Explorations in Metaphysics: Being, God, Person (Notre Dame, Indiana: University of Notre Dame Press, 1994), chapter 6. Clarke rejects the charge that a substance is static and inert, arguing that this idea originates with Descartes, Hume, and Locke. He maintains that the Thomistic idea of substance includes the idea of self-communicating action in relation to others.

61 R. Harre and E.H. Madden, Causal Powers: A Theory of Natural Necessity (Totowa, New Jersey: Rowman and Littlefield, 1975), 13.