Emergentist Monism in the Philosophy of Mind

Philip Clayton

1.1 By way of introduction

Much could be (and has been) said about neuroscience from the perspective of theology; theologians have not been shy about offering their own interpretations of brains, thoughts and spirits. Of course, turnabout is fair play: neuroscientists have also not been shy in commenting on theology, God, free will, and other concepts both human and divine. After all, it is in part an empirical question why a brain with a structure like ours--one that shares our evolutionary history, stores and retrieves information as ours does, and responds like ours to electrochemical stimulation and illness--would produce religious ideas and religious experience as ours does.

As fascinating as such disputes might be, they are not the subject of this paper, at least not directly. For I am not convinced that direct battles between neuroscience and theology (or, for that matter, direct concordances) will stand up to closer analysis until a deeper mediation has been achieved. Instead, the neurosciences raise a question much closer to home than disputes about God: the question of who we are. Progress in neuroscience challenges, or at least is often taken to challenge, cherished notions of what it is to be a human person: self-consciousness, soul, "thinking being," free will. Unless and until we manage to defend a notion of the person that preserves concepts such as these in light of what we now know about the human brain, language about God, and any work such language is supposed to do within the human mental psyche, will appear gratuitous.

This is not to say that theological doctrines cannot be of any assistance.(1) Some theological doctrines could give rise to interesting research programs in the neurosciences and the social sciences. Imagine, for example, how one's notion of personhood would be affected by acceptance of the Christian doctrine of creation, the belief that we are "dust" and yet nonetheless indwelt by the Spirit of God. Divine creation would introduce purpose, for example, and purpose means an arrow of time--the belief that, besides the brute-fact given of the natural world, there is the directing influence of an unconditioned will who is both source and telos of this world. Christian theologians then supplement creation beliefs with content from the biblical texts (and their tradition(s) of interpretation), which are taken to provide an important record of divine communicative intent. When the theologian has this much, she already has huge constraints on her theory of personhood. She has, implicitly, a Christian ethic of "willing the will of God." Moreover, the texts speak of covenant, which implies a set of divine commandments for living--but also mutual agreement and responsibility (hence ethics again). Covenant gives rise to the notion of sin, which Thomas Tracy defines somewhere as "the bias of the will toward an orientation of alienation from God." The idea of sin then gives rise to the idea, and thus the possibility, of reorientation. Possibility is taken to have become actuality through divine initiative or grace.

I include this well-known list to show how detailed is the anthropology (theory of human nature) that theologians bring to the discussion table. It includes, at least for traditional theologians, not only the existence of at least one purely spiritual being--hence the possibility of disembodied agency--but also the notions of will and of freedom, which come in both finite and infinite flavors. With will, so understood, comes consciousness: Christians conceive God as conscious agent, an agent enough like human agents that the predicate "person" can also be attributed, if only in an analogous fashion, to the divine. On this view, humans and God are also moral agents; persons exercise their agency in light of real obligations to other persons (indeed, to the world as a whole) and to God. Finally, these agents are social agents. Religious notions of community emphasize a union among humans in light of the divine presence and the covenant which makes of us "one." The christological expression of community is kerygma, the particular story of Jesus Christ, culminating in the belief in an eschaton or second coming. In short, the Christian parameters for talking about persons stretch from the moment of creation to the consummation of history, and from individual birth through life and death and on to the hope of a final reconciliation.

1.2 Putting the Pieces Together

In this paper I will argue that the perceived tensions between theology and the neurosciences call for renewed reflection on the nature of the person. Formulating a philosophically adequate account of what it is to be a human person provides important guidance on how to relate these two diverse fields. Conversely, attempts at a direct connection (or reduction) of either field to the other threaten to mislead unless one keeps the question of human personhood at the center of attention. In the final pages I then attempt to show that an adequate theory of the person requires an emergentist rather than a physicalist account of the world. Indeed, emergence turns out to be critical for linking personhood and theology proper, since emergence, but not physicalism, allows for specific divine action within the created universe. If one is to conceive a God who influences human thoughts--say, through a self-revelation in Jesus Christ--and yet does so without miraculous interventions that invalidate natural law, then one will need to employ an emergentist framework something like the one developed below.

One feature of this discussion should be clearly acknowledged from the outset: in the nature of the case, physical sciences such as the neurosciences do tend to push one in the direction of physicalism, the view that all things that exist are physical. For it is a basic assumption of good neuroscience, as with the other natural sciences, that only traceable physical causes be employed and that only physical mechanisms be introduced in explanations. "Physical" here has an interesting double meaning: it is a methodological standard (physical means "the sorts of things that physicists can study") as well as an ontological thesis (something is physical if it is built up out of the fundamental particles and energies that we have discovered in the natural world).(2) So the question cannot be, Should we do a different kind of neuroscience, say, one that talks more about souls and their actions? Instead, the guiding question in the dialogue between theology and the neurosciences is, How far can a position go in the direction of the physicalist assumptions that are basic to the empirical study of the brain without denying (or implicitly rejecting) factors necessary for the viability of religious belief?

To start with the obvious: holding a physicalist view of the world that denies the very existence of God---perhaps on the grounds that God is not a physical being, hence (given physicalism) God cannot exist---would leave in place little or nothing of traditional Christian metaphysics. Short of ruling out an existence of God, however, one might find oneself offering interpretations of the human person that fundamentally conflict with belief in God or in divine action---which would constitute virtually as complete a rejection of Christian theology as an outright denial of the existence of God. Or (somewhat less obvious but still crucial) one might be tempted to adopt a theory of knowledge that makes all theological accounts extremely unlikely (or meaningless) as explanations.(3) Finally, there are views and approaches that make the concept of God explanatorily unnecessary, a sort of appendix on the overall body of explanation. Although the last three views are not immediately fatal to Christian belief, they cast this belief deeply into question, opening the door for a well-argued case that "we have no need of that hypothesis."

I suggest that these sorts of tensions, rather than direct disputes over theological claims, actually represent the core of the discussion with the neurosciences. Unfortunately, many of the theological proposals one reads show little awareness of the stakes of the debate. If one holds that theological assertions are mere constructs or "evocative metaphors," then she has already ceded the case; she might as well just admit up front that theology does no explanatory work whatsoever. If theology is to do anything in this discussion, then it must first be shown that there is something about the human person that cannot be captured, directly or derivatively, in neuroscientific terms.

2. The Insufficiency Thesis

The debate about neuroscience, psychology and mind presents one with a confusing clutter of possibilities. And yet in one sense one finds oneself returning again and again to one basic choice. Many neuroscientists, but not all, maintain the Sufficiency Thesis. It is the view that in the future neuroscience will be sufficient to explain all that we know about the human person. By contrast, I will here defend the Insufficiency Thesis. This thesis predicts that neuroscience will not be sufficient to explain all we come to know about the human person.

Note some of the major features of this debate: (a) It is not settled by any current empirical data. (b) It is future-oriented. Indeed, its status is closest to that of a wager. Current scientific results and scientific progress to date are relevant to which side I wager on and how much I am willing to wager (i.e., how strong is my commitment to the one view or the other). But other assumptions--metaphysical assumptions--also play a role in the different predictions of the Sufficiency and Insufficiency theorists. Think, for example, of the stock market: those who invest are willing to wager money on a future state which no one knows for sure. Even when one is a specialist in the vast amount of data that indicate whether one should invest in one or another firm, every investment remains a speculation.

(c) Sufficiency vs. insufficiency is, in this sense, a classic philosophical debate, not itself a scientific debate. In this sense it is more like the debate about universals or free will than like the question of the explanation of thermodynamic phenomena. Finally, (d) the debate bypasses the debate about dualism. Like "positivism," the word "dualism" seems today to be used only as a term of derision, at least in debates with or written for neuroscientists. Dualism is, strictly speaking, a species within the genus substance ontology, that is, it is a theory of being in which the world is divided into two basic types of existing things called substances. As such, it presupposes that a theory of being can and ought to be developed, also a questionable supposition. But the real differences and interesting questions raised by the neurosciences today are not adequately grasped within the framework of (traditional) substance ontology. So defending the Insufficiency Thesis is not the same as advocating dualism.

(e) The Insufficiency Thesis is compatible with believing in the great explanatory power of neuroscience. It need not be an anti-scientific position, and I do not advance it as such. Nothing in the present paper blocks or diminishes the importance of neuroscientific research. It denies only one thing: the final sufficiency of the neurosciences for explaining the human person.(4)

3. Toward a More Productive Debate on Neuroscience and Personhood

3.1 Progress in Neuroscience

One position, which we might call the Arbib Credo(5), states that all data about the human person will eventually be best explained in neuroscientific terms. On this view, theology has no explanatory power of its own; its terms pick out no theological entities or properties in the world but are rather constructs of individuals or societies. Moreover, says the Credo, the neurosciences (among other sources) give us sufficient reason to abandon the traditional explanatory claims of theology. From the outset one should be honest about how strong the tug is in the direction of the Arbib Credo; there is no point in hiding one's head in the sands of a pre-scientific age that denied the dependence of the mental on the physical. Specific types of cognition--perceptions, memories, emotions--do correlate with specific state changes in specific brain regions. In some cases we can predict with a high degree of accuracy what neural processes will accompany which sorts of subjective experiences. Note that knowledge of the connections is increasing in both directions: neuroscience can predict more of the subjective experiences that will follow specific types of brain stimulation, as well as more about the sorts of neural activity (and in what regions) that will precede particular psychological experiences.

The brain sciences have established that, and how, specific types of mental experience correlate with specific brain functions. It is the brain that does the processing when you calculate 73 x 37 or when you feel fear after hearing a threat. In coming years we will learn massively more about what neurological states are necessary for certain mental experiences; we will find more and more such necessary conditions; and we will be able to specify the underlying brain states and processes with greater and greater precision. Gradually, we will be able to cause more and more specific mental or emotional responses by means of carefully controlled stimulation to the brain, and we will be able to model more and more of them on computer-based systems.(6)

As the neurosciences develop, we will be able to give increasingly complete accounts of how perceptions are represented, how they are recalled, and what is happening in the brain when a subject reports that one thought gives rise to another. We'll understand the functions of emotions and why brains that have emotions like ours would confer survival value on an individual. We'll also learn precisely which brain regions or distributed systems are active when a person reports having certain emotional, aesthetic or religious experiences. We'll know why brains such as ours would be prone to aesthetic and religious experiences of these sorts and what kinds of neural stimulations (or lesional damages) tend to increase or suppress such experiences. Some argue--though others dispute--that in the limit case we could learn the precise brain states that would have to occur if a subject is to enjoy particular kinds of mental experience.

Now some readers may find the prospect of such successes in neuroscience greatly exciting; others may find them greatly threatening. Whether a massively successful neuroscience would be a good or bad thing is not the topic of the present paper. Instead, I want to ask: if neuroscience is successful in this way, will we have proven that physicalism is true or (even more absurd) that the conscious self is an illusion? By no means! To move from these sorts of successes to the doctrine of physicalism--be it the falseness of belief in God or other religious truth claims, or the interpretation of the self as "merely metaphorical or constructed"--is, as I shall attempt to show, a category mistake. First let's look at some of the options, and then I shall make a case for a mediating framework that I think is preferable to the two extremes.

3.2 Getting Rid of the Extremes

The sorts of neuroscientific results that I have just summarized (or at least imagined) tend to pull people in one of two directions. Some find here strong evidence that human cognitive behavior will ultimately be fully explained in terms of brain activity (the Sufficiency Thesis). Others find here no threat to their dualist intuitions: thought and emotion are still properties of the so-called "spiritual man," they insist, and spirits or souls are just not the kind of thing that brain science can really tell us anything about. I will argue that neither of these more extreme views does justice to the data we have about the human self. There are serious issues in neuroscience and religion, but they depend on drawing careful distinctions closer to the middle and not on battles fought at the edges.

Let's call the two more extreme positions I've just mentioned strong reductionism and metaphysical dualism. Strong reductionists argue that human thought and mentality is in principle fully explainable by, because wholly caused by, neural firings. To understand why regions of the brain react in the ways they do would be to understand human thought, human emotions, human religious experience. According to so-called identity theorists, thoughts just are the neurological events studied by brain scientists.(7) Metaphysical dualists on the other end of the spectrum argue that there is an ontological entity such as the soul that is forever inaccessible to natural scientific study, even in principle, which is the basis for and possessor of all mental events: ideas, wishes, emotions, intentions, and the like.

Other authors have given good summaries of why dualism is no longer a tenable position; I shall not repeat their arguments here. Is there an equally clear and compelling argument against at least the strongly reductionist programs which dominate much of the literature in the neurosciences? Yes. Bracketing for the moment the causal question, I would argue that there is a difference in kind between physical explanations of thoughts, feelings and emotions on the one hand, and explanations of those ideas in their own terms on the other. Thoughts have a quality which philosophers (following Husserl) call intentionality. The simple definition of intentionality is aboutness; it is the characteristic of referring to something else. The referring relationship is intrinsically different from the causal relationship, where A causes B to occur. Causal relationships are clearly physical; they are the bread and butter of the physical sciences, whereas the reference relationship--which we all employ whenever we speak about something--works according to a vastly different "logic." Brian Cantwell Smith states the difference graphically:

Reference--plain, ordinary, vanilla reference, of the sort out of which even the most trivial conversation is made--is manifestly able to leap amazing gaps in space, time and possibility: backwards to the first 10-23 seconds of the universe, forward to the death of the solar system, sideways into other possible worlds (such as to a world where Apple responded positively to Bill Gates' 1985 offer to license the Mac OS). ... This non-effectiveness [of reference] is in direct and exact contrast to physical causality, which is famously ... proscribed from performing any such fancy long-distance or counter-factual manoeuvres. ... You can refer to the sun, I take it, right now; it doesn't take 8 minutes for your reference to reach its destination!(8)

In reference there is no limitation to the speed of light. The vastly different "logic" of the phenomena of intentions, concepts and references helps explain why there could never be an identity of conceptual relations to the underlying neurological events. Imagine that you could (in principle) know exactly what neurological events occur when Nancey is asked to defined "justice" and makes a verbal response. Still, these events would never be identical to her definition of justice. For some, the analogy between what goes on in your computer's processor, the turning on and off of some 16 million registers, and what goes on in your word processor--say, the message "fatal disk error"--is helpful: knowing everything at the level of the electronics and the charge in every register is not the same as knowing what your software is doing. No amount of electronics data will tell you, for example, that my computer is currently solving a differential equation. (Of course, this analogy may raise further problems of its own because of differences between human and machine intelligence.)

3.3 Continuing Differences between the More Moderate Positions

It's still the case that the two more extreme positions garner most of the popular (and media) attention in debates about mind. Let us take it as shown, however, that these views--strong reductionism, or "the identity thesis," and metaphysical dualism--are not tenable. Do we then find a natural middle position emerging? As nice as that would be, it does not seem to be happening.(9) For one still finds deep divisions between even the more moderate positions. Thinkers such as Jerry Fodor and Hilary Putnam argue that psychology is (more or less) independent of neural considerations; the neurosciences do not play a major constraining role in doing cognitive psychology.(10) (Similar responses are often given by humanistic psychologists.) On the other side, the Churchlands, Andy Clark, William Lycan and others argue that psychology and neuroscience must co-evolve: any genuine progress in psychology will give rise to resultant progress in neuroscience.(11) (Note that "co-evolution" is not a mediating position, since it amounts to the denial of autonomous psychology, or folk psychology, in the sense advocated by Fodor and others.)

Still, at least we're now in the terrain on which any fruitful debate of the deeper questions in neuroscience and religion (e.g., religious experience) must take place. Also, note that we have now managed to formulate a clear disagreement. The one side argues that functionalist neuroscience can eventually provide as much reliable knowledge of human cognition as humans will ever get, whereas the other side denies this premise, maintaining that there are other types of knowledge of human cognition. What arguments can the two sides develop on this topic?

Let us start with the latter position. In recent years, a more moderate version of dualism --at least more moderate than Cartesian dualism--has been developed in the work of neuroscientists like Sir John Eccles and in several publications by Roger Penrose.(12) Penrose does believe that there is something like conscious substance, which is ontologically a different sort of thing than physical phenomena. He also maintains that there is "an essential non-algorithmic ingredient to (conscious) thought processes" (p. 404). But even so he is not primary interested in developing a sharply defined dualist metaphysics à la Descartes. Instead he asks, "What selective advantage does a consciousness confer on those who actually possess it?" (chapter 10). In my view, Eccles and Penrose are saddled with dualist dilemmas that admit of no easy solution. Yet clearly they represent research programs that are more scientifically respectable than classical Cartesian dualism.

On the other side, a more moderate version of the functionalist/neuroscientific position, the "schema theory" as it has been developed by Michael Arbib.(13) Arbib is not a reductionist in the strong sense of the word. Schemas are "the basic functional unit of action, thought and perception, a unit whose functionality is distributed--in the first instance--across the networks of the individual human brain."(14) He has also defined them as a "crystallization of some body of experience within a local situation" or simply as "parallel distributed adaptive computation." A schema can be "an internal structure of process (whether it is a computer program, a neural network, or a set of information-processing relationships within the head of the animal, robot or human)," or it can be "an external pattern of overt behavior." These two basic types of schemas can give rise to a "social schema, a schema which is held by the society en masse."(15)

What is interesting about making the schema concept basic for neuroscience is that it is a logical structure which could be given either a causal/functionalist or an emergentist interpretation. If one looks at schemas solely in a causal fashion, however, as summaries of causal mechanisms, then eventually they must be reduced down to the basic causal units of neural activity, neuronal firings; and this is precisely what Arbib does. Thus he writes in a recent paper that they are "functional units," that is, "composable units of brain function/neural activity."(16)

But note that schema theory is a logical device which could in principle be used in a more holistic fashion. One could speak of schemas as phenomena which emerge only at higher levels, when one abstracts from many of the composite parts. For example, cells are schemas--complex wholes--but they are also existing things in their own right. Likewise, my awareness of an orange, or of a situation of injustice, is a highly abstract phenomenon which includes, but goes beyond, countless observations, neural traces, composites, and other influences. Imagine that we gain massive understanding of the workings of your dog's brain; imagine that our efforts at predicting your canine's behavior succeed beyond our wildest expectations. Would this prove that your dog does not have subjective experiences (qualia) such as fear, concern or affection, or that these qualia do not play any causal role in her actions? Even vastly successful neuroscience thus leaves open the key questions about the mental life. It is these questions, not progress in neuroscience per se, that are of life-and-death concern for those interested in the claims of religion.

So I advocate a kinder, gentler schema theory. We need a study of mental phenomena which allows us to focus on higher-order units as (sometimes) genuine existents, not just composites of the parts of which they are composed. We need a "science" of the person of which neuroscience is one, but only one, contributing part. Such a study of the emergent person is genuinely holistic, however, only if it retains a place for speaking of one higher-order event (e.g., a thought) causing another without insisting that the whole story can be told in terms of neuronal firings. Arbib, in his well-known work in neural modeling, does not give adequate place to this possibility, though I think schema theory leaves room for it. Still, the crucial fact for me is that Arbib and others employ a logical framework which could in principle be read either in a holistic or in an atomistic fashion.

3.4 Closer to a Mediation: Information Biology and Virtual Reality

The last section argued that moderate dualist theories of mind on the one hand, and theories of mind in terms of "composable units of brain function/neural activity" on the other, represent positions that are still too far out along the spectrum of positions on the human person. This is not a straw-man dismissal; both are sophisticated positions, and one can see what features in the contemporary study of mental phenomena would drive the authors to their positions. Nonetheless, I believe the strongest theory of the human person lies in between these views. The question then is, What view of the self starts neither with theological claims as "obviously given" nor with the "obvious ultimacy" of neuroscientific explanations? What would such mediating position look like?

First, it will have to grant what humans know already from their experience in the world: that thoughts are not found apart from the functioning of brains, and that damage to the brain can modify or eliminate subjective experience. At the same time, I have argued, the answer must allow for the emergence of mental phenomena and for mental causation. The resulting view will therefore begin the line of causation at the physical level, in a manner similar to the schema theory of Michael Arbib, but at the same time it must insist that a line of causal influence can also be traced (in the appropriate way) among the highly complex and abstract "schemas" that we call mental phenomena.(17) Any adequate theory of the human person will have to understand the effect of interactions with the surrounding environment upon mentality, while at the same time doing justice to the irreducible subjectivity of experience.

With regard to the former requirement, the field of information biology has begun to grasp the way in which all organisms exchange information with the environment around them. In The Tree of Knowledge: The Biological Roots of Human Understanding, for example, the biophysicist Maturana and the cyberneticist Varela describe the "structural couplings" that arise between an organism and its surroundings.(18) The organism cannot be decoupled from its environment without dying. The feedback loop that exists between environment and organism is more than just an incidental connection between it and its world. Instead, the way in which those links are set up are physically and ontologically constitutive of the organism itself. Certainly a far cry from a dualist position, where the soul is essentially different from (or uncoupled from) its physical world! At the same time, the information that arises out of these links, and the influence that one's understanding subsequently exercises via the body on the world, require a new level of explanatory concepts. Information-processing agents bring the dimension of subjectivity as one element in this biologically mediated two-way interaction with the environment.

The subjective element in this two-way semantic connection is expressed in some recent experiments in 360-dergee virtual reality. For example, in one well-known artwork in this genre, Char Davies' "Osmose," the participant dons a head helmet and a special suit and enters into what seems to be a clearing that surrounds him. He is able to rise in the clearing by breathing in and to lower himself by breathing out; movements are made by gentle leanings from side to side. In the world through which he now "floats" the edges of objects are unclear, and he is able to move through, above, and below the trees and plants at will. This new set of structural couplings between "mind" and "world" can have a profound effect on participants.(19)

What occurs when one is in a 360-degree surround-sound virtual world? It seems clear that the experience gives to subjects a new sense of being embodied--they actually are embodied in a different way, thanks to the computer interface. This is why some describe the experience, even months later, as being "within me." New mental experiences arise out of one's being given new structural couplings with the world, altering one's mental experience as a result. (Similar mental transformation can arise out of the physical changes associated with drug experimentation, brain disease, or amputation--certainly more brutal forms of cognitive alternation!)

But the lesson to be drawn from these transformations is not the functionalist/neuroscientific one that some brain scientists would have us accept. For the transformation, though physically dependent, is a mental transformation, one whose explanation involves (among other things) psychological concepts. One's particular experience will rely on one's particular set of structural couplings with the world--and, in the case of brain damage, it may be altered by damage to receptors and processing regions--but it is also (irreducibly) about the new mental state that is caused. Equally importantly, these states in turn give rise to a new manner of being embodied in the world and to a new manner of acting causally upon the physical world.

This is a key insight; let me generalize it. The causal line seems to move "up" from the physical inputs and the environment to the mental level, then along the line of mental causation--the influence of one thought on another--and then "down" again to influence other physical actions, to make new records and synaptic connections within the brain, to produce new verbal behaviors, and so forth. This view is monist, not dualist: there is only one physical system, and no energy is introduced into that system by some spiritual substance external to it. At the same time, it seems, subsequent states of the entire system cannot be specified without reference to the causal influence exercised by the higher-level phenomena.

In a famous thought experiment by the Harvard philosopher Hilary Putnam,(20) the reader is asked to imagine a "brain in a vat," a brain that has been removed from its body by a team of scientists and kept alive in a vat. The imaginary scientists have re-established all of the myriad links that the brain had to its body, replacing them with computer inputs which exactly simulate the body and the environment that the person had experienced before the removal of his brain.

The thought experiment may suggest more than Putnam intended, however. Its practical difficulty, verging on inconceivability, underscores how the mental life is highly, even extremely, dependent on our structural couplings with the physical world. The brain possesses an incredibly large number of receptors for information from other parts of the body, and interrelates them with an amazing 1016 synaptic connections. Our mental experience is conditioned far beyond our ability to imagine by this incredibly fine-grained input from the world and by the complex way in which the brain processes it. And yet there is a subjective experience of that world which is different from those physical inputs and which in turn helps cause the variety of the outputs which constitute our action in the world. (Obviously the brain in the vat would have to be given not only massive inputs, but also the impression that it is acting within the world if it is not to "know" that it has been so rudely imprisoned!) The language of mental impressions, intended references, and mental causes is an irreducible part of the full story, just as in a virtual reality chamber the full story includes not only the new physical inputs to the brain, but also the irreducibly mental dimension of the experience--the transformed mental "place" that arises out of this new virtual-physical surrounding.

4. Emergentist Non-Reductionism

4.1 Toward a Theory of the Person

The study of the human person therefore involves not only all the knowledge we can glean about the brain and its workings, but also study of the emergent level of thought, described and explained not only in terms of its physical inputs and nature, but also in terms intrinsic to itself. My first task has been to argue for the existence of both levels, and to understand the way in which the mental emerges out of the physical. The second task is to begin to integrate these two levels. What is the best framework for doing this? I suggest beginning with the notion of the human person as psycho-somatic unity. Humans are both body and mind, and both in an interconnected manner. How does this work?

It is not difficult to describe what is normally connoted by the word "person." A person is one who is able to enter into human social interaction: praising your tennis partner, planning your dinner party for next Friday, carrying out your intention to graduate from college by next May--and being aware of (at least some) other humans as moral agents who have value and rights equal to your own. These are concepts of personhood that are basic to research in the social sciences (psychology, sociology, and cultural anthropology); they are reflected in the literature of various cultures around the world, as well as in multiple religious traditions. Of course, there are many questions that still leave us unsure: when does personhood start? Does it demand a metaphysical basis, such as the introduction of the soul or person-substance? Does it develop and end gradually? Can it be effaced within a human being? Is it a legal or social fiction, or a metaphysical reality? Such broader philosophical questions are crucial to the complete definition of personhood and hence part of the discussion that neuroscientists and theologians must have if they are to find any common ground at all.

Personhood is therefore a level of analysis that has no complete translation into a state of the body or brain--no matter how complete our neuroscience might be. Of course, it presupposes such states; yet personhood represents an explanatory level that is distinct from explanations at the level of our "hardware." As Brian Cantwell Smith writes:

First, you and I do not exist in [physical explanations]--qua people. We may be material, divine, social, embodied, whatever--but we don't figure as people in any physicist's equation. What we are--or rather what our lives are, in this picture--is a group of roughly aligned not-terribly-well delineated very slightly wiggling four-dimensional worms or noodles: massively longer temporally than spatially. We care tremendously about these noodles. But physics does not: it does nothing to identify them, either as personal, or as unitary, or as distinct from the boundless number of other worms that could be inscribed on the physical plenum ...(21)

The languages of physics and of personhood only partly overlap; one cannot do justice to the one using only the tools of the other. To give a purely physics-based account of the person is like saying that, because a club or church cannot survive without being financially viable (e.g., receiving income from some source), it just is the economic unit which economists describe in terms of income and expenditures. The confusion, one might say, is a confusion of necessary and sufficient conditions. A living body and a functioning brain are necessary conditions for personhood, yet the wide discrepancy in the "logic" of the vocabularies suggests that they are not sufficient conditions. Personhood is not fully translatable into "lower-level" terms; persons experience causal and phenomenological properties (qualia) that are uniquely personal.

4.2 Separating the Questions of Science and Ontology

But is this answer permanent or temporary? What if, some time in the future, neuroscience succeeds beyond our wildest imaginings? What if we are some day able to model human behaviors precisely in complex computational machines? Won't we have shown that personhood is best understood as (something like) a sufficiently complex software system running on the right sort of hardware?

I don't think so. The debate between physicalist and nonphysicalist views of the person, after all, is not only about science; it is also about what actually or really or finally exists. We must ask: are the properties measured by natural scientists--and recall that we have defined physicalism in terms of the methods of physics--the only sorts of properties that this particular object in the world has? In debating the issue it is important to distinguish the ontology of the phenomena (i.e., of the world as we experience it) from the ontology of the best explanation of the phenomena. A cultural anthropologist, for example, might note that the subjects of her study report discussions with the spirits of animals and give explanations of her arrival in their village which conflict with the world as she experiences it (e.g., she is the spirit of one of their ancestors). In describing their beliefs, she suspends judgement on their truth, attempting to be as accurate as possible in re-presenting the world as they see it. In her explanations, however, she will feel free--indeed, it is required of her--to offer explanations which use an ontology (an account of what really exists in the world) that may diverge widely from their own.

The key question under debate, then, is the question of how much of subjective experience or "folk psychology" is irreducible, that is, how much of it actually belongs in a correct explanation of human experience. Some views countenance an explanatory ontology that consists of brains and other physical organs and their states alone. At the opposite end, other ontologies argue that only minds exist, or that both minds and bodies represent primitive substances, defined as radically different sorts of things. Still other thinkers (e.g., social behaviorists) hold that both brains and their social contexts exist, that is, both brains and whatever things whose existence we are committed to by an account of social contexts. The view to be defended here, emergentist supervenience, holds that brains, social context, and mental properties exist; which means (if I am right) that the correct explanatory ontology has to introduce at least three levels of "really existing properties." More robust ontologies are of course available, such as those involving the real existence of ethical predicates, religious predicates, and various religious beings or dimensions. But nothing in emergentist supervenience immediately commits one to other types of properties than the mental.

4.3 Emergentist Supervenience

The philosophical notion of supervenience is especially attractive as a bridge framework when discussing neuroscience and the person. Simply put, supervenience grants the dependence of mental phenomena on physical phenomena while at the same time denying the reducibility of the mental to the physical. Note that supervenience is about properties or groups of phenomena, and not about relations between substances (and the ontology that supports them).

The early uses of the concept of supervenience described the way in which ethical judgments are dependent upon certain physical states and yet not reducible to them. The notion made its major entrance into the mind/body debate in the early article "Mental Causation" by Donald Davidson. Davidson writes,

Although the position I describe denies there are psychophysical laws, it is consistent with the view that mental characteristics are in some sense dependent, or supervenient, on physical characteristics. Such supervenience might be taken to mean that there cannot be two events alike in all physical respects but differing in some mental respects, or that an object cannot alter in some mental respects without altering in some physical respects. Dependence or supervenience of this kind does not entail reductibility through law or definition: if it did, we could reduce moral properties to descriptive, and this there is good reason to believe cannot be done.(22)

In the accounts examined so far, there is a direct dependence relationship between the mental and the physical. We might call those views strong supervenience in which the mental is determined by the physical, so that there is no room for "play" in their relationship. Bruntrup writes of the strong supervenience relation, "Micro-properties determine completely the macro-properties (micro-determinism). ... If mental properties are macro-properties in this sense, they are causally inefficacious qua mental properties."(23)

There is a certain inherent tension in strong supervenience, however. As Jaegwon Kim, one of its best known (former) advocates, admits, "nonreductive materialism is not a stable position. There are pressures of various sorts that push it either in the direction of an outright eliminativism or in the direction of an explicit form of dualism."(24) One of the reasons for this instability emerges from the central emphasis of this chapter: strong supervenience stands in apparent tension with the view of the person defended in these pages.(25) Strong supervenience does not reduce mental phenomena to their physical causes, but it also does not allow them to do anything either. Mental phenomena become mere epiphenomena; their reality is bought at the cost of their causal impotence.

So the question becomes, Can any framework that is consistent with what we know today about the brain, and with what we may reasonably be expected to come to know, also be consistent with a real causal influence of mental phenomena? Not only folk psychology, the common-sense way of speaking of human persons, depends on a successful theory of mental causation, but also the viability of (at least) traditional theological claims does as well. Strong supervenience theories might suggest how religious beliefs and experiences could arise. But however much the function of religious beliefs might be incorporated, their truth could not be.(26) There would be no place for religious insights to alter behavior, and definitely no role for any influence of a disembodied divine force on the world. The supervenience concept seemed to offer the sort of framework necessary for drawing the links between the brain sciences and the mental life, but strong supervenience conflicts both with folk psychology and with theology. Is it possible, then, to formulate a "weaker" version of the dependence relationship? Suppose we define "weak supervenience" as denying the reducibility of the mental to the physical and asserting the dependence of mental phenomena on physical phenomena. But in this case we will define "dependence" as a dependence of origination and not as a full explanatory determination of the mental by the physical. Could this view incorporate neuroscientific results within an adequate theory of the person?

This is this view I have in mind when I defend an emergentist theory of supervenience and thus of the person. The background for emergentist supervenience comes from the British Emergentists in the 1920s and '30s. As Jaegwon Kim notes, the early emergentists held "that the supervenient, or emergent, qualities necessarily manifest themselves when, and only when, appropriate conditions obtain at the more basic level; and some emergentists took great pains to emphasize that the phenomenon of emergence is consistent with determinism. But in spite of that, the emergents are not reducible, or reductively explainable, in terms of their 'basal' conditions."(27) Lloyd Morgan thus appeared to use "supervenient" as an occasional stylistic variant of "emergent."(28)

In a recent article, O'Connor has defined property emergence in a more careful manner:

Property P is an emergent property of a (meriologically-complex) object O iff:

(1) P supervenes on properties of the parts of O;

(2) P is not had by any of the object's parts;

(3) P is distinct from any structural property of O.

But after those three conditions we come to the big break in the philosophy of mind, the question that Kim calls "arguably the central issue in the metaphysics of mind"(29): the question of mental causation. O'Connor formulates it this way in his final premise:

(4) P has direct ("downward") determinative influence on the pattern of behavior involving O's parts.(30)

Note that emergent properties of this sort are genuinely novel. As Bruntrup writes, "Even if all the physical facts have been fixed, the emergence of consciousness is not implied with nomological necessity. ... The existence of emergent properties could not be predicted by even a perfect knowledge of the underlying physical facts alone."(31)

A property is thus emergent only if laws cannot be formulated at the lower level that predict its occurrence, say as a boundary condition of other, well-established laws at that level. If for example we can relate the levels with the same precision with which we can formulate the necessary physical conditions for the existence of conductivity or elasticity, then we do not have emergentist supervenience. A set of phenomena is designated as emergentist only when an exhaustive description of the underlying physical state of affairs, although necessary, is not sufficient for explaining the emergent properties. Thus an emergent condition might be implied in Leslie Brothers' explanation of human social behavior in terms of "the representation of the generalized other" and the irreducible nature of first-person language (especially if she asserts that these categories of mental phenomena are not necessary for understanding animal social behavior).(32) One would also need to use the language of emergence if qualia (human subjective experiences, e.g. seeing red or thinking of the national debt) are, at least in part, self-explaining.

I believe that emergentist supervenience offers the philosophically most adequate framework for conceptualizing mental properties in human persons. Does emergentist supervenience also offer a view of the person that is more compatible with theology than strong supervenience as defined above? If true, would it represent, from the standpoint of theology, a better bridge principle? Clearly the answer is yes. Presumably theologians would have many more things to say about emergent properties and their source and ultimate purpose. They might also attempt to offer theologically based explanations of why the biological world could or would give rise to such emergent properties. Two caveats, however: when speaking in this way, theologians do not speak as scientists, and the status of such language vis-à-vis any presently possible empirical verification should be made fully clear. Also, there is nothing in emergentist supervenience that requires a theological interpretation; it is not a form of natural theology. Emergentism is, in my view, a necessary condition for a theological interpretation of the human person, but it is emphatically not a sufficient condition for a theological anthropology.

Coming from the viewpoint of science, one might worry that such a position closes off research and hence progress in neuroscience. Does it introduce a constraint on the work of empirical scientists? I would argue not. Emergentists may have an equally vivid interest in knowing more about actual brain functions and in seeing neural explanations extended as far as possible. It is just that they wager that the "as far as possible" does not extend as far as an exhaustive explanation of the mental--unless part of that explanation is given in irreducibly mental terms! Talk about the subjective experience of being in love or the sense of self-awareness is irreducibly mental; such phenomena exercise a type of causal influence of their own.(33)

5. Persons and Explanatory Levels

By exploring a family of positions that eschew both dualism and strong reductionism, this paper has focused on that range of positions that seek to do justice both to neuroscience and to the human experience of personhood. Following contemporary usage, I have characterized these as the family of supervenience theories. We discovered that the same tension arises within this family as was present in the old dualism versus reductionism debate. One either does or does not accept the Sufficiency Thesis, the view that the causal explanations of human behavior will ultimately be given in neuroscientific terms.

On the view I have defended, mental phenomena are still dependent on the physical. But the nature of this relationship supports the ontological hypothesis that mentality represents an emergent level. That is, although they are dependent on the physical, mental properties are different in kind from the properties that one observes at lower levels and exercise a type of causal influence unique to this new emergent level.

5.1 Minimalist Emergence

Much is at stake in the present debate. If one wishes to avoid talk of self-consciousness (say, in the causal sense used by the German Idealists), or God-talk, or an opening for any other such religiously-tinged predicates, then one must insist that the mental be understood fully in terms of the physical world. By contrast, if one finds in the mental some sign of a new type of phenomenon within the world, then one has thereby introduced at least the possibility that there is something inherently mental or spiritual within the one world that we find around us. Clearly this possibility would represent an opening to theology that is of great significance to both sides. If one wishes to avoid such openings, then one must be sure at every cost that the mental is not interpreted in an emergentist sense. Conversely, it seems that those with theological interests--and with some motivation to integrate these interests with their understanding of science--will need to develop a theory of humans and their mental life that is either emergentist or establishes the same sort of minimal opening that emergentism defends. These are the stakes that make the present discussion of such overwhelming importance. It is perhaps not too much to say that this debate about the human person expresses the crux of the battle between physicalist naturalism and its opponents today.

It is also a debate with no easy resolution, as we have seen. "Opening" means possibility, not proof; no one is talking of conclusive demonstrations here. One could easily accept emergentist supervenience and deny the truth of theism or religious belief in all its forms.(34) Still, even in this incredibly circumscribed form, emergentist supervenience presents one with what philosophers call a "forced choice." If one holds that all mental phenomena are only expressions of physical causes or are themselves, at root, physical events, then one has (at least tacitly) advanced a theory of the human person that is pervasively physical. It then becomes extremely unclear (to put it gently) why, from the perspective of one's own theory of the human person, a God would have to be introduced at all (except perhaps as a useful fiction). If a theologian espouses physicalism, she may be forging an alliance with the majority worldview within the neurosciences, but she may also be giving up any interesting rapprochement between theology and the sciences of the person just as she approaches that debate's most decisive issue. By contrast, to introduce a soul-substance at this crucial juncture would be to abandon the debate altogether, for that move, almost by definition, leaves no common ground with natural science. Here I have argued not that supernatural souls exist but rather that human action reflects a type of mental causation that is something more than physical. This claim, minimalist as it is, may just be the necessary condition for a theology that is anything more than metaphorical. Theologians stand before their Rubicon and must either cross or not cross.

My strategy has been to map out a crossing where the river is most narrow (why add any unnecessary distance when the crossing itself is already difficult enough?). This helps explain why I have broken with dualist thinking and moved as far as possible in the direction of the natural sciences by arguing that:

* mental predicates represent a type of property, not a new form of substance;

* mental causation does not involve the addition of new energy into physical systems;

* mental processing does not occur without concurrent physical activity. Indeed, changes in brain structure and function (brain disease, lesions) have important and predictable effects on mental functioning;

* one's overall ontology should be monist. There is only one natural order, although it includes many different types of things. Mental causation is not supernatural; it is natural. It is thus amenable in principle to naturalist explanation, though these explanations may well not be "nomological" or law-like. I have not pleaded for supernatural interventions, nor have I construed mental functioning in any way analogous to the classic supernaturalist notion of intervention from outside. To put it bluntly: though there may be divine action on analogy with the action of embodied persons with the world, I have left no place for miracles in the sense of a countervening of natural law.(35)

I imagine, one final time, the objection, "Well, you have wagered against neuroscience, have you not?" The critic might object that I have introduced, if not a "God of the gaps," then at least a "mental causation of the gaps." Isn't the more scientific response to expect that law-like explanations will eventually be possible "all the way down"--until all phenomena in the natural world have been explained from the bottom up? Doesn't "wagering" as I have amount to betting against science, and thus blocking the road for scientists? Indeed, isn't the success of science heretofore good reason to conclude that bets on my side are backward-looking, obscurantist, and in general inhibitors to further scientific progress?

No. These well-worn objections tell against dualist positions, but they beg the question at dispute between supervenience theorists. The reason it is absurd to postulate occult forces in the physical world (or "vitalist" forces in the biological world) is that we have learned that these realms operate in a fully law-like manner based on predictive successes in the relevant sciences. What is really at stake in the present debate is the question whether human persons are analogous --whether they can be exhaustively predicted and explained in a "bottom-up" manner. I have argued that we have good evidence to think not. Indeed, the hierarchy of the sciences itself offers evidence of principles which are increasingly divergent from "bottom-up" physicalist explanation.(36) An emergentist view of the person is thus not an argument against science but rather consistent with the pattern that we find emerging in the natural hierarchy of the sciences.

6. Emergentist Monism(37)

One might ask, "What does it all mean? What kind of ontological position do these emergent properties entail? Is it monism or property dualism or panpsychism? And where does this all leave theology?"

The ontological view that I defend might be called emergentist monism.(38) Monism asserts that only one kind of thing exists. There are not two substances in the world with essentially different natures, such as the res cogitans and res extensa (thinking and extended substance) propounded by Descartes and the Cartesians. But unlike dual-aspect monism, which argues that the mental and the physical are two different ways to characterize the one "stuff," emergentist monism conceives the relationship between them as temporal and hierarchical.

In one sense, monism is a necessary assumption for those who wish to do science. For instance, we can (and must) assume that the total physical energy of the universe as a whole is conserved. No action that you perform, no thought that you think, can add to the total energy of the system without invalidating calculations based on physical laws. Incidentally, this is the problem with dualism, and with direct interventions into the world by a God who breaks natural laws: if a spiritual cause gives rise to a physical effect, you have brought about physical change without a physical cause or the expenditure of physical energy, and this breaks the natural order in a way that would make science impossible. There could be no scientific study of a world where cups spontaneously fly across the room and objects released from your hand could go either up or down according to spiritual forces. Science does not need full determinism (see the next paragraph). But it does need the world to reflect at least patterns of probability over time.

Note that monism is not only in the interests of science; one can also give a theological arguments in defense of monism. Theologically, it amounts to the assertion that the world is one, that it constitutes a distinct order. Theologians speak of the universe as a whole as finite, in order to specify its single ontological status and to contrast it with a Creator whose nature is essentially infinite. Herein lies the theological importance of the phrase, "the unity of nature": in comparison to the Creator, all things in the universe share a common nature. Theologians have also argued that creatures can only exercise freedom within an ordered world that has an integrity and lawlike structure of its own.

I don't care if you want to think of this monism as a sort of materialism, but only if you mean by that that the "things" in the world--rocks and computers and persons--are all made out of some material or other. What's crucial is that you develop theories which do justice to the specific qualities that we actually find associated with the various "things" in the world. For example, after Newton we thought that physics presupposed at least the possibility of a fully determinate, and determined, account of the world. But when we found out that microphysical or quantum events simply don't work this way, we developed an essentially stochastic or probability-based science to deal with them. Likewise, when scientists began to research chaotic "systems," or systems far from thermodynamic equilibrium, they discovered that they were essentially unpredictable (for finite agents). But science did not end; instead, a fascinating new science of chaotic systems has been developed. An equally complex story would have to be told about the convertability of matter and energy.

Now we come to a very complex object in the world: humans. With some 1016 neural connections, the brain is the most complex interconnected system we are aware of in the universe. This object has some very strange properties which we call "mental" properties--properties such as being afraid of a stock market crash, or wishing for universal peace, or believing in divine revelation. On the one hand, to suppose that these features will be fully understood in terms of physics as we now know it is the height of absurdity. Let me say this even more plainly: there is no need, and no justification, for taking a physicalist approach to the human person--if by that one means that the actions of persons must be explained through a series of inter-translatable explanatory sciences reaching down (finally) to physics, or, more simply, that all causes are (ultimately) physical causes. On the other hand, for both scientific and theological reasons, I do not therefore advocate introducing an occult entity, such as Descartes' soul substance, in order to explain the person. To say that the human person is a psycho-somatic unity is to resist both positions. It is instead to say that the person is an entity within the world, a very complexly organized collection of matter, which has complex properties that need to be understood by a science appropriate to its own level of complexity.

As we have seen, an emergentist position rejects causal reductionism, since it accepts mental causes. It therefore rejects explanatory (theoretical, epistemological) reductionism, insofar as mental properties need to be explained using a theoretical structure appropriate to them. At first blush, emergentist monism may seem like a version of ontological or metaphysical reductionism, since it breaks with dualism and refuses to postulate non-physical entities such as souls. But emergentism must finally declare itself opposed to reductionism even with respect to ontological (metaphysical) questions. For its central assertion is that the history of the universe is one of development and process. The one order exists at each stage in its history, but what it is that exists is not identical through time. Genuinely new properties emerge which are not reducible to what came before, although they are continuous with it.

What emerges in the human case is a particular psycho-somatic unity, an organism that can do things both mentally and physically. Although mental functions supervene upon a physiological basis, the two sets of attributes are interconnected and exhibit causal influences in both directions. We therefore need a science or mode of study that begins (as a science should) with a theoretical structure adequate to this level of complexity. To defend an emergentist account of the self is not to turn science into metaphysics. Instead, I have here made a plea for acknowledging that the one natural world is vastly more complicated and more subtle than physical analysis can ever grasp. You can wager that the real things that exist in the world are physical processes within organisms, and that everything else--intentions, free will, ideas like justice or the divine--are "constructs," complicated manifestations of neural processes. But I'm wagering on the other side. I wager that no level of explanation "lower" than the conscious self--and that means no ontology without mental causes--will finally do an adequate job of accounting for the human person.

7. Where Divine Action and the Philosophy of Mind Meet

In these final few pages we should pause to consider what is at stake theologically when one accepts or rejects emergentist monism in the philosophy of mind. The stage has been set by my defense of a particular theory of what constitutes human action. The argument's burden was to show that human action is not adequately accounted for by a physicalist account that happens to produce the sorts of qualities we call mental. Rather, I argued that the best hypothesis views the natural world as evolving multiple levels, each of which is as real as those that preceded it.

The question then becomes: how is God's action in the world is to be understood? In God and Contemporary Science I argued against two particular models of divine action. The first involves a model of miraculous interventions, "miracles" in the strong sense. It is unwise, I argued, to commit oneself to a view of divine action that negates natural science; yet influxes of divinely produced energy into the natural world would certainly do so. The conservation of energy is a necessary assumption for physics; only if one imagines a closed system with one set total amount of energy can one perform the computations physics entails. The second view may not have God adding to the total amount of energy, but it places God outside the world and makes any divine influence a total mystery. Now one can of course eschew the task of a philosophical theology of divine action, or give up on the project when it gets hard. But is it possible to accept the task and make some progress toward an answer?

7.1 Physicalist vs. emergentist panentheism(39)

If one has reasons not to conceive God as located mysteriously outside the world, and yet still preserves the notion of God as conscious agent (in opposition, say, to pantheism), then one is working with a framework not unlike the theological position called panentheism. Panentheism is usually defined as the view that the world is contained in some sense within God, although God is also more than the world. I have argued elsewhere for the theological advantages of panentheism(40) and will not bore you by repeating those arguments here.

Panentheism immediately helps with at least one kind of divine action: the regular or lawlike functioning of the world. If the world is in some sense within God, then physical interactions that operate according to natural law are in some sense also divine actions. We might call them autonomic, since they occur with a regularity analogous to the autonomic functioning of physical bodies (though we must imagine that an omniscient being, unlike a human being, would have an awareness and a sense of its own causal agency even at this level). Panentheism thus helps with traditional assertions such as the doctrine of the conservation of the world, since we can understand God's role of continually willing it in existence as a form of divine autonomic action. There is, on this account, no external causal influence of a purely spiritual being; the physical regularities just are divine regularities (one thinks of Spinoza's famous identification, deus siva natura, "God, that is, nature"). If human action and what we call "the mental life" is really a complicated form of physical causality within the world, then it too might fall under this heading.

But the tradition has spoken also of another form of divine action: God's direct conscious influence on specific parts of the world. Let's call this not autonomic but focal divine action: God's bringing about focally intended results in the world. Here it becomes crucial to distinguish two forms of panentheism corresponding to the two positions in the philosophy of mind discussed in this paper: non-reductive physicalism and emergentist monism. Both positions make it difficult to affirm direct physical miracles in the world. Yet only emergentist monism can offer a plausible account of God's influence on and communication with the human conscious life.

Neither position, once again, helps with physical miracles.(41) Non-reductive physicalism admits only physical things (this is what "physicalism" means!), although physical things can have some rather surprising qualities, such as thoughts and wishes. Still, if all things are (ultimately) physical, all causal influences are (ultimately) physical. This means that there is no analogy within the world for speaking of a disembodied agency (say, one consisting of mental predicates) influencing physical states. Emergentist monism might seem better off in this regard, since it allows for mental causation. But recall that on this view the mental predicates are attributes of the one natural being; they are not reified into substances in their own right. The only position in the philosophy of mind that would allow for physical miracles is dualism. For if human action consists in a disembodied soul moving a physical body, then there would be no problem in principle for a disembodied divine being to cause parts of the physical world to act differently than they otherwise would. (This is why theologians have been so retiscent to admit the weaknesses of dualist theories of the person.)

If we must do without physical miracles, so be it. Much of modern theology has sought to rethink Christianity within the context of this limitation, not always unsuccessfully. But would we still have Christian theism without any way to speak of God's influence on and communication with human minds? Certainly preserving a role for such influence would be a theological desideratum of the highest order. How do the two positions under discussion fare on this subject? Non-reductive physicalism knows no top-down causation, either mental-to-mental or mental-to-physical; for physicalists, all higher-order phenomena such as intentions are constructed out of a substrate that is ultimately physical. The only way for God to influence the human mental life would be to alter this physical substrate. Thus it is that Nancey Murphy, a leading non-reductive physicalist, has supported divine action at the lowest physical level. If God could act at the level of quantum indeterminacy, God would not break any natural laws; and perhaps chaos effects could then "amplify" what God does at the quantum level so that it had perceivable effects on human thoughts and emotions.(42)

But we have already seen the difficulty that such accounts face: there is no analogy on this account for a mental agency changing things within the physical world, be it at the quantum level or otherwise. Of course, one can simply assert that a disembodied mental substance exists and causes changes within physical systems; but then one is advocating precisely the kind of mind/body dualism that one worked so hard to avoid within the philosophy of mind.

A very different route is open to the emergentist monist, however. The core assertion of this view is that the natural world is hierarchically structured; that each level, when it reaches sufficient complexity, gives rise to a new level. Higher levels may depend on the lower for their existence (corpses don't have mental experiences, as far as we know), but they can also exercise a causal influence of their own on these lower levels. Within such a theory, the influence of divine mental content on human mental content is not without analogy, for mental-mental causation is a standard feature of the natural world. This may not be the physical miracle-working God of pre-modern Christian theism. But it does allow for a God who, for instance, initiates a new order of reality and communicates the experience of forgiveness--divine actions that are central to the christology and doctrine of the resurrection for theologians such as Edward Schillebeeckx.(43)

7.2 Toward an emergentist theory of causation

I have presupposed that an account of divine action must do justice to what humans have come to know about the structure and evolution of the cosmos and of ourselves within it. The question is, How should we conceive divine action on cosmic or human nature given the lawlikeness of the physical world, the increasing complexity of the biological world, and the conscious agency that we have found to be indispensable within the sphere of human action? Just as important, if the history of the cosmos does reveal a gradual "becoming conscious" of the spiritual nature of the universe and its Creator, in what sense was that spiritual dimension present and efficacious from the start? Does God only emerge gradually along with the creation (but then it's not God's creation!); or is there some sense in which God is present and active in the world in different ways during the different periods and at the different levels of cosmic evolution?

If the emergentist account of personhood developed above is correct, then the one natural world exhibits different kinds of properties at different levels, and different kinds of causation are at work at the various levels. There may be a very large number of such levels, with subtle gradations between them, but we must be able to distinguish at least three of them. (If I could identify only two, then the suspicion would be raised that emergentism is really crypto-dualism: there are only mental and physical properties or causes, and the two are utterly different.) I must therefore pause to sketch a constructive account of the evolutionary process of emergence that created the stratified reality that is, I submit, the key to an understanding of divine action today.(44)

(a) Physics. It is easy to formulate several unsatisfactory ways of interpreting the suggestion that God affects the physical world: on the one side, supposing that God is constantly performing physical miracles by communicating divine purposes to rocks and plants and animals that directly cause them to behave in ways they otherwise wouldn't; on the other, supposing that talk of divine messages is purely otiose, merely adding a religiose rhetoric to what can be fully explained in natural terms. Recent work in the religion-science discussion, much of it stemming from the projects of our own CTNS under the direction of Bob Russell, suggests a more adequate approach: specific features of the physical world are compatible with, and even best explained by, the creation of that world by God. For example, lawlikeness and regularity reflect the enduring character of God. The Big Bang cosmology that is now dominant is fully consistent with the creation of the universe by a conscious intelligence. And the Anthropic Principle, which shows that many variables are "fine-tuned" for the production of intelligent life in a way that would be a priori extremely unlikely, suggests a structuring of the universe for the evolution of consciousness. Note that none of these features depends on an intervention of God into the physical order; yet each does reflect the sort of universe one would expect if the physical world is an expression of a divine being who pervades but is also greater than the entire physical order.

It is not as though the natural world reveals only classical Newtonian causality at the one end and mental causes at the other. Such a picture lends itself too easily to a dualist ontology, with all its attendant problems. Consider instead the vast variety of causal influences that one encounters as one moves up the ladder of complexity that cosmic, and subsequently biological, evolution has created.(45) Many equate scientific causality with efficient causality, using the collision of two billiard balls as the paradigm example. But already the phenomena of thermodynamics suggest a rather more complicated sort of causality. The transfer of heat is a causal process, yet without the clear causal agents and simple equations of Newtonian mechanics. Likewise, in the physics of chaos "strange attractors" are held to exercise a causal influence, producing patterns in what are genuinely chaotic systems, though again the kind of causality in question is far removed from Newtonian efficient causation.

(b) Biology. We have seen how some biologists wish to perceive in the actions of persons nothing but the effects of neural firings. This insistence on finding causal patterns only in the lowest level of a more complex emergent reality has been called causal reductionism. It is of course found in other parts of biology than neuroscience. The fascination with (and rich funding for) research in genetics, for example, reflects the expectation that the ultimate explanation for the behavior of living beings will be found by locating causality only at the bottom. On this view, organismic behavior is traced back to cell functioning and then via proteins to the DNA code, which involves chemical compounds that point back through physical chemistry to fundamental physics.

If reductionism in neuroscience points in one direction, the theory of emergent levels defended in this paper points in another. It suggests that one look not only for "bottom-up" causes but also for causal influences that work in a "top-down" manner. As systemic features influence the behavior of particles in a physical system (as in the Bénard phenomenon), so also higher-order units influence the behavior of the parts in biological systems as well. Work on cell functioning, called "epigenesis" in the recent literature, has revealed the causal influence of the cell in triggering particular components of the DNA chain.(46) In these studies the cell itself acts as the broader environment, determining which parts of the DNA code are activated. A feedback loop of the sort revealed in these studies tells against unidirectional (i.e., only bottom-up) accounts of cell functioning. If one follows the lead of epigenesis, a similar account can be given of the emergence of broad evolutionary patterns, such as the gradual increase in complexity in complicated ecosystems.

It is this "top-down" account of evolutionary biology that justifies talk of purposiveness (or: purpose-likeness) in the biological realm even in the absence of explicit purpose. As natural entities begin to behave in more complex and patterned ways, the theologian may speak of organized forms of divine action that are not merely autonomic--i.e., explicable as mechanical results of God's autonomic agency--but that nevertheless stop short of focal purpose. Arguably, these emerging patterns represent the central feature of the biological realm. Here again we find an increase in complexity: life forms absorb physical energy and use it to build complicated structures such as eyes, organs and DNA strands; they also transform physical energy into the complicated patterns of behavior that they manifest. Although the second law of thermodynamics always wins in the end--the net result is an increase of entropy in the universe--the principles of life move, at least temporarily, in the opposite direction, producing brief eddies in the overall flow toward thermodynamic equilibrium.

This fact is theologically significant because both the individual organisms and the process as a whole work in a manner that appears purposive--even though, again, biological evolution does not require or directly assume purpose as an explanatory category. One is reminded of Kant's account of natural beauty as involving "purposiveness without purpose." Each organism strives "naturally" to keep itself in existence.(47) The parts of an organism (or organ or cell or ecosystem) work together for its survival. Growth, nurturance and reproduction function so that the chances of the organism's survival, and therefore of the survival of the gene pool from which it stems, are maximized.

Biology cannot explicitly introduce purpose into the process, since its ontology does not include any entities (short of the higher primates, as we've seen) of which it makes biological sense to postulate actual purpose or goals. But this does not prevent a theological interpretation of biology from doing so. Just as we can speak of fundamental features of the physical world as reflecting the divine character, without however imagining that God is actually intervening in the physical realm specifically in order to determine these features, so also can we speak of the central features of the biological realm as reflecting the divine character and influence without claiming that kidneys or amoebas themselves possess the goals of functioning in this or that particular way. Actual purpose, after all, can only be predicated of purposive beings; purpose in a colony of bacteria is a fiction (the colony behaves as if it really desired to nourish itself and grow). But if the world remains within God, then it is possible to speak of the divine purposes and goals being expressed even at the stage at which there are no other actually conscious agents.

(c) Psychology. The emergentist view of reality that I have advocated here shows why one should expect to find different types of causal influences at the various levels. The culminating level--at least insofar as it is scientifically accessible to us-- involves the indispensability of mental causes for making sense of the human mental life:

The fact that mentality has emerged, on the emergentist view, must make a genuinely new causal difference to the world. So the following summarizes the heart of the emergentist doctrine on mental causation: mentality must contribute genuinely new causal powers to the world--that is, it must have causal powers not had by any physical-biological properties, not even by those from which it has emerged.(48)

Eventually, as we have seen throughout this paper, there emerges a level at which entities within the created universe become capable of acting according to explicit purposes. Persons exhibit mental properties and exercise a type of influence that Richard Taylor has labeled "agent causation."(49) Agent causation is characterized by intentionality and by the presence of causal influence without the transfer of physical energy. Here there are conscious persons who can be affected by and affect other conscious beings, in a manner that is fully consistent with, though it also goes beyond, the laws of physics. Agent causation thus stakes out a position between physical reductionism on the one hand (there are no non-physical causes) and an unacceptable dualism that requires an influx of energy into the world due to the actions of mental agents.

8. Conclusion

We have seen that functionalist explanations play a role in the biological sciences (from cell structures through neural systems to ecosystem studies) that is different from the structure of explanation in fundamental physics, just as intentional explanations play a role in explaining human behavior not called for at lower levels. These emerging orders of explanation may also involve an increasing role for top-down explanations. Thus, for example, DNA embodies in its very structure the top-down action of the environment on the molecular biology of the human body. In intentional explanations it is even more clear that the goal for which the agent acts, or the broader context within which she understands her actions, influences the particular behaviors or thoughts.

On this view, entities evolving within the created universe progressively exhibit new ways of functioning that could not have been predicted from the point of view of "lower" stages of development and that therefore lend themselves to theological explanation. What sort of theological explanation, exactly? Given the various scientific and theological reasons I have already ennumerated, it must not be interventionist or occasionalist. It isn't as if God introduces a new form of energy into the physical universe or directly wills the motions of created entities. In what sense, then, can God be said to exert a causal influence on such entities? Their behavior is an expression or manifestation of the divine character or intentionality.

If this account is carried through consistently, human thoughts and intentions become in one sense expressions of divine agency (after all, on this account everything else is!). And yet, like every other form of activity within the created universe, human thought is also conditioned by the autonomic or natural-law level of divine activity, as well as by the quasi-intentional level of biological drive and process; hence it is not simply a direct, unmediated expression of God's own focal thoughts and purposes. In this respect, human thoughts are removed from any simple identity with the divine will by their location in a context determined by the various "lower" expressions of divine agency. To this one may wish to add an account of human freedom, which, along with the influence of physical laws and biological drives, would become another factor distinguishing human thoughts and intentions from any pure or simple identity with focal divine thoughts and intentions. Human minds in this sense could be seen as relatively isolated pockets of divine thought and purpose--isolated, again, by the conditions of natural law and biological drive, and perhaps also by their own free agency. The final step is then to suppose that God as it were reconnects with these isolated pockets of divine intentionality by addressing them via the sphere of human/divine interaction we call the realm of spirit.

There is no intrinsic reason why a divine agent could not affect and be affected by these persons, also in a manner consistent with the laws of physics--at least not as long as one retains an understanding of God's relation with the world such that these beings are not "outside" of God but always already within the divine presence. Negatively, to say that complex phenomena like life or mind lend themselves to theological explanation is to say that they cannot be given a reductive explanation in terms of lower levels of "natural" functioning. But it isn't as if God gets into the picture for the very first time when one of these higher levels emerges from the merely physical level. From a panentheistic perspective, the energies at work at the physical level are already divine energies. The fact that they function without anything we can identify as a focal purpose is what leads us to speak of them as manifesting God's "autonomic agency." For the emergentist, however, the regular or, as it were, habitual operation of divine action need not exclude specific or "focal" divine intentions.


1. I am grateful to Mark Richardson for discussions of the following theological constraints on the theory of personhood.

2. To say that physics is committed to materialism, the view that all things that exist are composed out of matter (or basic material particles such as atoms) would be to assert that physicists are committed to a particular metaphysical thesis; but this is to place metaphysics prior to the actual methods and results of science, which is a move I reject. What is interesting about physicalism is that it focuses one on the actual results of physics: one is committed to the sorts of entities that our best physics commits us to (or: the sorts of entities that physics could, in principle, come to know). Given this definition, to resist physicalism is to resist the claim that all adequate explanations will ultimately be given in terms of (or "reduced to") physical laws and entities.

3. See Philip Clayton, "Inference to the Best Explanation," Zygon (1997): 100-110.

4. For that matter, why should anyone want to claim "final sufficiency" for some science and its results? The very concept of final sufficiency seems theologically tinged--certainly an embarrassing result for an anti-theological naturalist!

5. In deference to Michael Arbib, who has presented one of the most sophisticated alternatives to a theological position.

6. I recall reading recently in the popular press that Air Traffic Control already has an awareness meter that allows supervisors to monitor when an air traffic controller is losing conscious attention ("dozing off'). Perhaps it would be useful for professors to employ awareness meters for those students who tend to doze off during lectures!

7. See D. M. Armstrong, A Materialist Theory of the Mind, rev. ed. (New York : Routledge, 1993); Patricia S. Churchland and Terrence J. Sejnowski, The Computational Brain (Cambridge, MA: MIT Press, 1992); Churchland, Neurophilosophy: Toward a Unified Science of the Mind-Brain (Cambridge: MIT Press, 1986).

8. Brian Cantwell Smith, "God, approximately," unpublished paper, p. 8. This paper provides a brief summary of the broader argument in Smith's On the Origin of Objects (Cambridge, MA: MIT Press, 1996). Michael Arbib argued correctly in a criticism of an earlier draft that leaping gaps in space and time and other "long-distance manoeuvres" is not in itself sufficient to show that reference is non-physical. But if one considers the full range of what reference involves, I think it is clear that it's more closely associated with the logic of the mental than with the logic of physical-causal explanations.

9. Those who have listened in on these debates in the past know that argumentation usually takes place by members of one moderate and viable research program accusing their opponents of actually holding one of the extreme positions just cited. Clearly, such comments generate more heat than light.

10. See Jerry Fodor, The Elm and the Expert: Mentalese and its Semantics (Cambridge, MA: MIT Press, 1994); Fodor and Ernest Lepore, Holism: A Shopper's Guide (Oxford: Blackwell, 1992); Fodor, A Theory of Content and Other Essays (MIT Press, 1990).

11. See Paul Churchland, The Engine of Reason, the Seat of the Soul: A Philosophical Journey into the Brain (Cambridge, MA: MIT Press, 1995); Andy Clark, Associative Engines: Connectionism, Concepts, and Representational Change (Cambridge, MA: MIT Press, 1993); Clark, Being There: Putting Brain, Body, and World Together Again (Cambridge: MIT Press, 1997); William Lycan, Consciousness and Experience (Cambridge: MIT Press, 1996).

12. See e.g. Roger Penrose, The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics (New York: Penguin Books, 1989); Sir John Eccles, Evolution of the Brain: Creation of the Self (New York: Routledge, 1989); Eccles, How the Self Controls its Brain (New York: Springer-Verlag, 1994).

13. See Michael Arbib, "Schema Theory," in S. Shapiro, ed., The Encyclopedia of Artificial Intelligence (New York: Wiley, 1992), pp. 1427-43; Arbib, E. Jeffrey Conklin and Jane C. Hill, From Schema Theory to Language (New York : Oxford University Press, 1987).

14. Michael Arbib, "Computing the Self and the Horrors of Humanity," unpublished paper, p.6.

15. See Arbib, "Crusoe's Brain: Of Solitude and Society," unpublished manuscript, pp. 20-22.

16. Arbib, "Crusoe's Brain: Of Solitude and Society," manuscript, p. 4.

17. I admit that one can speak of causal influences among ideas, and of ideas on the brain, only in a sense that diverges from the standard use of the term "causality" in science. Here (as in the perplexing "non-locality" results in quantum physics) 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, and of the whole on its parts--yet without falling back into the four-fold causality of medieval metaphysics (formal, final, efficient and material) and the pre- or anti-scientific mindset that it fostered.

18. Humberto Maturana and Francisco Varela, The Tree of Knowledge: The Biological Roots of Human Understanding, rev. ed., trans. by Robert Paolucci (New York: Random House, 1992).

19. Some persons emerge from 15 minutes in this virtual world deeply touched, and (by their reports) sometimes profoundly transformed. Some report that they later experience being embodied in the non-virtual world in a different way, and a few have said, "I am no longer afraid of dying."

20. See Hilary Putnam, Reason, Truth, and History (New York: Cambridge University Press, 1981).

21. Brian Cantwell Smith, "God, approximately," unpublished paper, p. 3.

22. Donald Davidson, "Mental Events," p. 214, cited in Jaegwon Kim, Supervenience and Mind: Selected Philosophical Essays (Cambrdige: Cambridge Univ. Press, 1993), pp. 138f.

23. Godehard Bruntrup, "The Causal Efficacy of Emergent Mental Properties," unpublished paper, p. 3.

24. See Jaegwon Kim, "The Myth of Nonreductive Materialism," in Richard Warner and Tadeusz Szubka, eds., The Mind-Body Problem (Oxford: Blackwell, 1994), pp. 242-260.

25. Of course, it could be true nonetheless; conflict with a specific theory of the person (or with theology, for that matter) is not ipso facto a criterion of falsity. Also, remember that the battle between the Sufficiency Thesis and the Insufficiency Thesis involves a wager on what progress in scientific understanding humans will achieve in the future. We do not yet know what miraculous advances the neurosciences may make and which of the phenomena that currently appear irreducible to us will later be accounted for in terms of underlying physical processes.

26. The same is true also of Davidson's theory of "mental events." His view is "psychophysical anomalism," according to which there are no laws that connect the mental with the physical. Yet there are other difficulties with Davidson's view. Mental causation is asserted, but the mechanics of it are left unexplained. (Other views also may leave the actual causal connection between the mental and the physical unexplained; doing so does not automatically rule out a position. It should only be clear that Davidson does not have an advantage over other positions in this respect.) Davidson has also not adequately specified the nature of the monism--the fundamental ontological similarity between the mental and the physical--which his position presupposes.

27. Jaegwon Kim, Supervenience and Mind, p. 138.

28. So Kim, p. 134.

29. Kim, p. xv.

30. See O'Connor, "Emergent Properties," American Philosophical Quarterly (1994): 97f.

31. Bruntrup, p. 11. Note that in this article Bruntrup does not accept the position that I am defending.

32. Other arguments proceed from the fact that qualia appear to be self-explaining.

33. Indeed, wouldn't it be a strange thing for a neuroscientist to find herself in the position of denying with passionate subjective conviction that there is any such thing as a force of subjective conviction?

34. Indeed, as I show in the final chapter of God and Contemporary Science (Edinburgh: Univ. of Edinburgh Press; Grand Rapids: Eerdmans, 1998), emergentist supervenience stands in a certain tension with traditional theological belief, which asserts a dependence of the physical on the spiritual. Either the dependence of the mental on the physical that I have defended must be corrected from another source, or it will require significance revisions in traditional Christian belief.

35. The details of what divine action would look like in this context are spelled out in the work cited in the previous note.

36. I cannot review the entire argument here. It is powerfully laid out in Arthur Peacocke, Theology for a Scientific Age: Being and Becoming--Natural, Divine, and Human, enlarged ed. (Minneapolis: Fortress, 1993).

37. In a subsequent paper I have offered a fuller defense of emergent qualities within an overarching monistic framework. See "Emergent Properties as Bridge Principle in Recent Philosophy of Science," forthcoming.

38. Emergentist monism is a position that I have developed in conjunction with Arthur Peacocke, and I am grateful to him for scientific support for the position that I would not have been able to provide. Both of us develop the position in two separate chapters of the forthcoming CTNS/Vatican volume on theology and the neurosciences.

39. This concluding section stems out of a lengthy correspondence and a series of discussions with Steven Knapp, former member of PCTS and currently Provost of Johns Hopkins University. Many of the ideas, and some of the formulations, are as much his as mine. The final version of this text will appear in a co-authored piece on "Christology and the Presumption of Naturalism," in preparation for submission to Religious Studies.

40. See Clayton, God and Contemporary Science (note 34 above); "In Defense of Christian Panentheism," Dialog (Summer 1998); "Moltmann and the Question of Christian Panentheism," under consideration at the Scottish Journal of Theology.

41. The theological desiderata for a theory of divine intervention are not too difficult to list. In some way God must be the ultimate source of the natural world, yet the natural world also needs its own integrity and order. On the one hand, if the doctrine of providence is to be retained, God must be able to guide the course of affairs within the world in some way. On the other, if we suppose that there is no obstacle at all to God's manipulation of physical events and human decisions, the problem of evil may become insurmountable, for there are innumerable events and decisions that a benevolent God would presumably prevent if free to do so. Furthermore, both the integrity of the natural order and the significance of human action are called into question if natural laws can be suspended at will and the created order is continually subject to divine preemption.

42. See Nancey Murphy, "Divine Action in the Natural Order: Buridan's Ass and Schrodingers's Cat," in Robert J. Russell, Nancey Murphy and Arthur Peacocke, eds., Chaos and Complexity: Scientific Perspectives on Divine Action (Vatican City State: Vatican Observatory Publications, 1995), pp. 325-357.

43. See Edward Schillebeeckx, Jesus: An Experiment in Christology, trans. Hubert Hoskins (New York: Crossroad, 1981); Christ: The Experience of Jesus as Lord, trans. John Bowden (New York: Crossroad, 1981); Schillebeeckx and Bas van Iersel, eds., Jesus Christ and Human Freedom (New York: Herder and Herder, 1974).

44. Clearly one can meet this dual constraint only by taking process extremely seriously. Time will not be extrinsic to the God-world relation; rather, the process of divine self-revelation and influence (and ultimately these two factors must be identical) will develop along with the universe to which God is relating. At the earlier stages little or nothing of the self-conscious, personal character of the divine may be visible; in the middle stages some anticipations of that character should be detectable; and in the later stages parts of the natural order (or: the natural order as a whole) should take a form that reflects the personal agency that created and sustains it.

45. Arthur Peacocke makes a similar point in Theology for a Scientific Age: Being and Becoming--Natural, Divine, and Human, enlarged ed. (Minneapolis: Fortress, 1993).

46. See Brian Goodwin and Peter Saunders, eds., Theoretical Biology: Epigenetic and Evolutionary Order from Complex Systems (Edinburgh: Edinburgh University Press, 1989); Vincenzo E.A. Russo, Robert A. Martienssen, Arthur D. Riggs, eds., Epigenetic Mechanisms of Gene Regulation (Plainview, N.Y. : Cold Spring Harbor Laboratory Press, 1996); Derek J. Chadwick and Gail Cardew, eds., Epigenetics (New York : J. Wiley, 1998). See also Harry Rubin, "'Spontaneous' transformation as aberrant epigenesis," Differentiation 52 (1993): 123-37; Richard Strohman, "Epigenesis: The Missing Beat in Biotechnology?" Bio/Technology 12 (1994): 156-64.

47. Cf. Spinoza's conatus in Ethics III,8.

48. Jaegwon Kim, p. 135.

49. See Richard Taylor's early manifesto in Sidney Hook, ed. Determinism and Freedom in the Age of Modern Science (New York Univ. Press, 1958), as well as his classic Action and Purpose (New York: Humanities Press, 1973). Taylor further developed certain suggestions of Roderick Chisholm; see e.g. Chisholm's piece in the same collection. The role of agent causation emerges also in the discussions in Keith Lehrer, ed. Freedom and Determinism (New York: Random House, 1966) and G.H. von Wright, Causality and Determinism (New York: Columbia Univ. Press, 1974).