The weakest position for a naturalist, who at least accepts emergent mental properties and events, is one according to which all the naturalist must adequately do to explain the mental is to establish contingent correlations between physical and mental states and leave it at that. The most prominent attempt to flesh out this approach is the biological naturalism of John Searle.
Searle’s position Contingent correlation
Searle actually acknowledges that such correlations are not enough for an adequate account of the mental, which should also include the transformation of correlations into causal relations by showing that the manipulation of the physical state alters the mental state and by providing a mechanism as to how this works.1 But for three reasons I believe it is appropriate to take him as an example of a contingent correlation position. First, he takes such correlations to be adequate to justify the superiority of biological naturalism, so they are sufficient conditions for a naturalist account of consciousness.2 Second, he explicitly claims that a causal explanation of consciousness may be in principle beyond our abilities to obtain. Moreover, even if this is the case, his biological naturalism remains standing.3 Third, he argues against the need for a naturalist to meet some necessitation requirement according to which one can show that the relevant mental state must occur given a certain physical state.4 That leaves us with correlations for which the establishment of counterfactual covariance would be nice but not necessary for biological naturalism to be adequate.
Biological naturalism
Searle has some pretty harsh things to say about the last fifty years or so of work in the philosophy of mind.5 Specifically, he says that the field has contained numerous assertions that are obviously false and absurd and has cycled neurotically through various positions precisely because of the dominance of strong physicalism as the only live option for a naturalist. Searle’s statement of the reason for this neurotic behavior is revealing:
How is it that so many philosophers and cognitive scientists can say so many things that, to me at least, seem obviously false? ... I believe one of the unstated assumptions behind the current batch of views is that they represent the only scientifically acceptable alternatives to the antiscientism that went with traditional dualism, the belief in the immortality of the soul, spiritualism, and so on. Acceptance of the current views is motivated not so much by an independent conviction of their truth as by a terror of what are apparently the only alternatives. That is, the choice we are tacitly presented with is between a ‘‘scientific’’ approach, as represented by one or another of the current versions of ‘‘materialism,’’ and an ‘‘unscientific’’ approach, as represented by Car-tesianism or some other traditional religious conception of the mind.6
In other words, philosophy of mind has been dominated by scientific naturalism for fifty years and scientific naturalists have advanced different versions of strong physicalism, however implausible they may be in light of what is obviously known by us about consciousness, because strong phy-sicalism was seen as a crucial implication of taking the naturalistic turn. For these naturalists, if one abandons strong physicalism one has rejected a scientific naturalist approach to the mind/body problem and opened himself up to the intrusion of religious concepts and arguments about the mental.
Searle offers his analysis of the mind as a naturalistic account because, he says, no one in the modern world can deny ‘‘the obvious facts of physics - for example, that the world is made up entirely of physical particles in fields of force.’’7 An acceptance of naturalism is constituted by an acknowledgment of the atomic theory of matter and evolutionary biology both of which allow for micro-to-micro or micro-to-macro causal explanations, but not macro-to-micro ones.8 According to Searle, dualism in any form is widely rejected because it is correctly considered inconsistent with the scientific worldview.9 He also claims that because people educated in the contemporary scientific worldview know how the world works, the existence of God is no longer a serious candidate for truth.10 But a commitment to naturalism and a concomitant rejection of dualism have blinded people to the point that they feel compelled to reject what is obvious to experience, namely, the obvious nature of consciousness and intentionality.
Searle’s own solution to the mind/body problem is biological naturalism: consciousness, intentionality, and mental states in general, are emergent biological states and processes that supervene upon a suitably structured, functioning brain. Brain processes cause mental processes which are not reducible to the former. Consciousness is just an ordinary, i.e. physical feature of the brain and, as such, is merely an ordinary feature of the natural world.11 Despite the frequent assertions by a number of philosophers that Searle is a property dualist, he denies the charge and seems puzzled by it.12 However, in my view, Searle is indeed a property dualist and an epi-phenomenalist one at that, though he also denies the latter charge as well.13 To show this, let us consider the charge of property dualism first. Searle’s characterization of neurophysiological and mental states are exactly those of the property dualist who insists that mental and physical properties are to be characterized in a certain way and that they are two, different types of properties. In light of Searle’s descriptions of the mental and physical, it is obvious why most philosophers charge him with property dualism and the burden of proof is on him to show why he is not.
Searle’s response to this problem is twofold.14 First, he seems to think that a property dualist must accept the entire Cartesian metaphysics. Second, he says that dualists accept a false dichotomistic vocabulary in which something is either physical or mental but cannot be both. So biological naturalism is to be distinguished from property dualism in that the former does not include the entire Cartesian apparatus and it rejects this dichotomistic vocabulary. Now if this is how Searle distinguishes biological naturalism from property dualism, then his response is inadequate. For one thing, it is absurd to claim that one must accept the entire Cartesian metaphysics to be a property dualist. Thomas Aquinas was a certain sort of property (and substance) dualist, but obviously, he did not accept the Cartesian apparatus.15 Swinburne defends Cartesian property and substance dualism without accepting Descartes’ entire metaphysical scheme.16 Moreover, Searle’s own view has a dichotomistic vocabulary in which he distinguishes normal physical (e.g. neurophysiological) properties from emergent biological “physical’’ (i.e. mental) properties. So he has simply replaced one dualism with another one.
Perhaps there is a different and deeper distinction between (at least) Cartesian property dualism and biological naturalism for Searle. For the property dualist mental and physical properties are so different that it is inconceivable that one could emerge from the other by natural processes. However, for the biological naturalist, biological physical properties are normal physical properties in this sense: they are like solidity, liquidity, or the properties of digestion or other higher-level properties that can emerge by means of natural processes. I don’t wish to comment further on this claim here except to say that Searle’s employment of it to distinguish biological naturalism from property dualism amounts to nothing more than a mere assertion combined with a few undeveloped examples (e.g. liquidity) that are supposed to be good analogies to emergent mental states. But this assertion is simply question begging in light of AC and, as I will show later, it amounts to an abandonment of naturalism. At the very least, one should stop and ask why, if Searle’s solution to the mind/body problem is at once obvious and not at all problematic for naturalists, a field of philosophy dominated by naturalists for fifty years has missed this obvious solution?
Searle’s response to this question involves a specification of why it is that emergent mental states have no deep implications. We will look at this issue shortly, but for now, I want to show that Searle’s biological naturalism implies an epiphenomenalist view of emergent mental states in spite of his denial that this is so. Searle’s position is epiphenomenalist for at least three reasons. First, Searle takes scientific naturalism to imply that there is no macro-to-micro causation and, as we have seen, on this point, most naturalists would agree: Jaegwon Kim says ‘‘a physicalist must, it seems, accept some form of the principle that the physical domain is causally closed - that if a physical phenomenon is causally explainable, it must have an explanation within the physical domain.’17 He goes on to say that ‘‘Causal powers and reality go hand in hand. To render mental events causally impotent is as good as banishing them from our ontology.’’18 For these reasons, Kim claims that a naturalist should be a strong and not a supervenient physicalist because the latter implies a problematic epiphe-nomenal view of the mental. David Papineau has endorsed the same point.19
Second, Searle distinguishes two types of emergent features. Emergent;! features are caused by micro-level entities and do not exercise independent causality. Emergent2 features are caused by micro-level entities and are capable of exercising independent causality once they exist. Searle rejects the existence of emergent2 features because, among other things, they would violate the transitivity of causality. Since he holds that conscious states are emergent1, it is hard to see how those states could have causal efficacy.
Third, Searle holds to the causal reduction of the mental. In causal reduction, the existence and ‘‘powers’ of the emergent but causally reduced entity are explained by the causal powers of the reducing, base entities. It is hard to see how he could hold this and avoid epiphenomenalism. I conclude then, that despite protests to the contrary, Searle's biological naturalism is a certain type of epiphenomenal property dualism. According to the typology of chapter one, Searle accepts emergence2a.
Why are there no deep metaphysical implications that follow from Searle's biological naturalism? Why is it that biological naturalism does not represent a rejection of scientific naturalism which, in turn, opens the door for religious concepts about and arguments from the mental? Searle's answer to this question is developed in three steps. First, he cites several examples of emergence (e.g. liquidity) that he takes to be unproblematic for a naturalist and argues by analogy that the emergent properties of consciousness are likewise unproblematic.
Step two is a formulation of two reasons why, appearances to the contrary notwithstanding, consciousness is not a problem for naturalists. First, Searle says that naturalists are troubled by the existence of irreducible mental entities because they are misled into thinking that the following is a coherent question that needs an answer: ‘‘How do unconscious bits of matter produce consciousness?’’20 Many ‘‘find it difficult, if not impossible to accept the idea that the real world, the world described by physics and chemistry and biology, contains an ineliminably subjective element. How could such a thing be? How can we possibly get a coherent world picture if the world contains these mysterious conscious entities?’’21
For Searle, the question of how matter produces consciousness is simply a question about how the brain works to produce mental states even though individual neurons in the brain are not conscious. This question is easily answered in terms of specific though largely unknown neurobiological features of the brain. However, Searle thinks that many are misled into thinking this question is about something deeper and more puzzling. Setting consciousness aside, in all other cases of entities arranged in a part/ whole hierarchy of systems, we could picture or image how emergent features arise because these systems and all their features are objective phenomena. Our problem is that we try to image how consciousness could arise from a system of unconscious bits of matter in the same way, but this is not possible because consciousness itself is not imageable and we cannot get at it through a visual metaphor.22 Once we give up trying to imagine consciousness, any deep puzzlement about the emergence of consciousness, given naturalism, evaporates and the only question left is one about how the brain produces mental states.
There is another reason Searle offers as to why the emergence of consciousness has no deep metaphysical significance.23 In standard cases of reduction, e.g. heat and color, an ontological reduction (color is nothing but a wavelength) is based on a causal reduction (color is caused by a wavelength). In these cases we can distinguish the appearance of heat and color from the reality, place the former in consciousness, leave the latter in the objective world, and go on to define the phenomenon itself in terms of its causes. We can do this because our interests are in the reality and not the appearance. The ontological reduction of heat to its causes leaves the appearance of heat the same. However, when it comes to mental states like pain, even though an ontological reduction cannot be found, there is a similar causal pattern, e.g. pain is caused by particular brain states.
So why do we regard heat as ontologically reducible but not pain? In the case of heat, we are interested in the physical causes and not the subjective appearances, but with pain, the subjective appearance itself interests us. If we wanted to, we could reduce pain to particular physical processes and go on to talk about pain appearances analogous to the heat case. However, in the case of consciousness, the reality is the appearance. Since the point of a reduction is to distinguish and separate reality from appearance in order to focus on underlying causes by definitionally identifying the reality with those causes, the point of a reduction for consciousness is missing, since it is the appearance itself that is the reality of interest. Therefore, the irreducibility of consciousness has no deep metaphysical consequences and is simply a result of the pattern of reduction that expresses our pragmatic interests.
In step three, Searle claims that an adequate scientific explanation of mental emergence is a set of very detailed, even law-like correlations between specific mental and physical states.24
Searle vs. Nagel on causal necessitation
Searle rejects an argument by Thomas Nagel, which denies that mere correlations amount to a scientific explanation. In terms of AC, Nagel would accept premise (6) (the explanation is not a natural scientific one) and deny that Searle’s correlations count as scientific explanations. Searle rejects (6) and believes such correlations count as adequate scientific explanations. Nagel claims that in other cases of emergence like liquidity, a scientific explanation does not just tell us what happens, it explains why liquidity must emerge when a collection of water molecules gather under certain circumstances. In this case, scientific explanation offers physical causal necessity: given certain states of affairs, it is causally necessary that liquidity emerge and it is inconceivable that it not supervene. But, argues Nagel, no such necessity and no answer to a why question is given by a mere correlation between mental states and physical states in the brain.
Searle’s response to Nagel is threefold.25 First, he says that some explanations in science do not exhibit the type of causal necessity Nagel requires, e.g. the inverse square law is an account of gravity that does not show why bodies have to have gravitational attraction. This response is question-begging against Nagel because the inverse square law is merely a description of what happens and not an explanation of why it happens. Interestingly, Newton himself took the inverse square law to be a mere description of how gravity works but explained the nature of gravity itself (due to his views about action at a distance, the nature of spirit, and the mechanical nature of corpuscularian causation by contact) in terms of the activity of the Spirit of God. The point is not that Newton was right, but that he distinguished a description of gravity from an explanation of what it is and his explanation cannot be rebutted by citing the inverse square law. Rather, one needs a better explanatory model of gravity. Therefore, Searle’s own example actually works against him.
Moreover, even if we grant that covering law explanations are, in fact, explanations in some sense, they are clearly different from explanations that offer a model of why things must take place given the model and its mechanisms. Since the argument from consciousness assumes the correlations and offers an answer to the why question, Searle’s solution here is not really a rival explanation, but merely a claim that such correlations are basic, brute facts that just need to be listed. In light of what we have already seen, there are at least two further difficulties with Searle’s claim.
First, given AC and the nature of theory adjudication among rivals, it is question-begging and ad hoc for Searle to assert that these correlations are basic. For the correlations themselves, along with the entities and properties they relate are natural and bear a relevant similarity to other entities, properties, and relations in theism (e.g. God as spirit who can create and causally interact with matter), but are unnatural given the naturalist epistemology, Grand Story, and ontology. As we saw in chapter one, selfreflective naturalists understand this. Thus, Terence Horgan says that ‘‘in any metaphysical framework that deserves labels like ‘materialism’, ‘naturalism’, or ‘physicalism’, supervenience facts must be explainable rather than being sui generis.’26 And to restate Armstrong’s admission:
I suppose that if the principles involved [in analyzing the single allembracing spatio-temporal system which is reality] were completely different from the current principles of physics, in particular if they involved appeal to mental entities, such as purposes, we might then count the analysis as a falsification of Naturalism. But the Naturalist need make no more concession than this27
Horgan and Armstrong say this precisely because mental entities, the supervenience relation, or a causal correlation between mental and physical entities, simply are not natural given a consistent naturalist paradigm. Nor can they be located in Jackson’s sense in the Grand Story. Their reality constitutes a falsification of naturalism for Horgan and Armstrong and, given AC, they provide evidence for theism. It is question-begging and ad hoc simply to adjust naturalism, as does Searle, given the presence of AC as a rival explanation.
Naturalists have long criticized Cartesian dualism because the causal relation it posits is so bizarre and its relata so disparate that the relation is virtually unintelligible. Many Cartesian dualists are theists and have sought to rebut this claim by appealing to the alleged clarity of divine miraculous activity in the natural world as a counter example. However, the dialectical situation worsens if the Cartesian is a naturalist for she must now try to render interaction intelligible solely in light of the resources of the Grand Story, and that cannot be done if the interaction relation is taken to be a natural entity at home in the naturalist ontology. It clearly does not bear a relevant similarity to other entities in that ontology. However, this problem is not a function of the ontological category of the relata. Specifically, it is not a problem that arises for naturalism only if the relata are in the category of individual. It applies equally to the category of property. This is why this problem is sometimes called ‘‘Descartes’ Revenge.’’ Thus, Searle’s employment of a supervenience relation—causal or otherwise—between the brain and consciousness is a serious difficulty for his biological naturalism, one he does not adequately address.
Second, Swinburne’s version of AC notes that a correlation can be either an accidental generalization or a genuine law (which exhibits at least physical necessity). We can distinguish these two in that laws are (but accidental correlations are not) non-circular correlations that fit naturally into theories that 1) are ontologically simple, 2) have broad explanatory power, and 3) fit with background knowledge from other, closely related scientific theories about the world. By ‘‘fit,’’ Swinburne means the degree of naturalness of the correlation and entities correlated in light of both the broader theory of which the correlation is a part and background knowledge. Now Searle admits that mental phenomena are unique compared to all other entities because they ‘‘have a special feature not possessed by other natural phenomena, namely, subjectivity.”28 Unfortunately, it is precisely this radical uniqueness that makes mental phenomena unnatural for a naturalist worldview. It also prevents Searle from distinguishing an accidental correlation from a genuine law of nature regarding mental and physical correlations.
So much, then, for Searle’s first response to Nagel. His second response is that the apparent necessity of some scientific causal explanations may just be a function of our finding some explanation so convincing that we cannot conceive of certain phenomena behaving differently. Medievals may have thought modern explanations of the emergence of liquidity mysterious and causally contingent. Similarly, our belief that specific mind/brain correlations are causally contingent may simply be due to our ignorance of the brain.
It is hard to see what is supposed to follow from Searle’s point here. Just because one can be mistaken in using conceivability as a test for causal necessity, it does not follow that conceivability is never a good test for it. Only a case-by-case study can, in principle, decide the appropriateness of its employment. Now when it comes to things like liquidity or solidity, Nagel is right. Precisely because of what we know about matter, we cannot conceive of certain states of affairs existing and these properties being absent. That Medievals would not be so convinced is beside the point since they were ignorant of the relevant atomic theory. If they possessed the correct theory, their intuitions would be as are ours. However, when it comes to the mental and physical, they are such different entities, and the mental is so unnatural given the rest of the naturalist ontology, that there is no clearly conceivable necessity about their connection. Moreover, this judgment is based, not on what we do not know about the two types of states, but on what we do know.
Moreover, a more detailed correlation in the future will not change the situation one bit. There is no non-circular or non-ad-hoc way to formulate such a correlation and we will merely be left with a more detailed dictionary of correlations that will leave intact the same type of problem of causal necessity true of less detailed correlations. Our current lack of belief in such a causal necessity is not due to ignorance of more and more details of the very thing that lacks the necessity in the first place. Rather, it is based on a clear understanding of the nature of the mental and physical, an understanding that Searle himself accepts.
This is why it will not do for naturalists to claim that they are not committed to anything ultimately or utterly brute (like the divine will), just to their being something unexplained at any given time but which can be explained through deeper investigation. No scientific advance in our knowledge of the details of mental/physical correlations will render either the existence of mental entities or their regular correlation with physical ones anything other than utterly brute for the naturalist.
But Searle had another line of defense against Nagel: Even if we grant Nagel’s point about the lack of causal necessity in the mental/physical case, nothing follows from this. Why? Because in the water and liquidity case, we can picture the relation between the two in such a way that causal necessity is easily a part of that picture. But since we cannot picture consciousness, we are not able to imagine the same sort of causal necessity. Yet that does not mean it is not there.
Here Searle simply applies his earlier point that, given naturalism, our puzzlement about the emergence of consciousness from unconscious bits of matter is due to our attempt to picture consciousness. Now it seems to me that this point is just false and egregiously so. I, for one, have no temptation to try to picture consciousness. In addition, other naturalists have put their finger on the real difficulty about the emergence of consciousness. D. M. Armstrong states that
It is not a particularly difficult notion that, when the nervous system reaches a certain level of complexity, it should develop new properties. Nor would there be anything particularly difficult in the notion that when the nervous system reaches a certain level of complexity it should affect something that was already in existence in a new way. But it is a quite different matter to hold that the nervous system should have the power to create something else [mental entities], of a quite different nature from itself, and create it out of no materials.29
Along similar lines, Paul Churchland says,
The important point about the standard evolutionary story is that the human species and all of its features are the wholly physical outcome of a purely physical process. ... If this is the correct account of our origins, then there seems neither need, nor room, to fit any nonphysical substances or properties into our theoretical account of ourselves. We are creatures of matter. And we should learn to live with that fact.30
Churchland identifies two reasons the naturalist should opt for strong physicalism—there is neither need nor room for anything else. Regarding need, I take it he means that everything we need in order to explain the origin and workings of human beings can be supplied by physicalist causal explanations. Regarding room, entities do not come into existence ex nihilo nor do radically different kinds of entities emerge from purely physical components placed in some sort of complex arrangement. This is what Nagel was getting at when he rejected radical emergence. What comes from the physical by means of physical processes will also be physical.
Searle is simply wrong about the problem being the imageability of consciousness. The problem here for naturalism is ontological, not epistemological as most naturalists have seen. What is curious about Searle’s reduction of an ontological problem to an epistemological one is that his entire work on biological naturalism is replete with criticisms of other naturalists for doing this very thing in other areas of the philosophy of mind. Could it be that Searle’s own misidentification of the ontological problem here is ‘‘neurotic’’ in just the sense that he applies to his naturalist colleagues: if one takes the emergence of consciousness as an ontological problem, then biological naturalism will, in fact, give cause for introducing religious concepts and explanations for the mental as expressed in AC?
Searle vs. McGinn on causal necessitation
Searle has one final line of defense against those who place a necessitation requirement on an adequate naturalist explanation for ‘‘emergent’’ properties. Searle seeks to rebut an argument by Colin McGinn to the effect that such a necessitation requirement is both essential for and unavailable to a strictly naturalist account of consciousness.31 We will investigate the details of McGinn’s position in chapter five, but for present purposes, Searle focuses on the following aspects of McGinn’s position: Consciousness is a kind of ‘‘stuff’’ that is known by introspection, things known by introspection are non-spatial, an adequate solution to the mind/body problem requires understanding the ‘‘link’’ between matter and consciousness, but given our noetic limitations, it is in principle beyond our ability to know that link and, therefore, there is no naturalist account of consciousness. Searle rebuts McGinn because (1) consciousness is a property not a stuff; (2) introspection is a confused notion and should be abandoned; given (1) and (2), there is no reason to deny that consciousness is spatial; and moreover (3) there is no link between consciousness and the brain anymore than there is a link between liquidity and H2O.
Setting aside until chapter five the issue of whether or not Searle has adequately rebutted McGinn’s particular formulation of this argument, the more important point is whether Searle has rebutted this form of argument if it is stated in more plausible dualist terms. This is a fair approach to Searle’s rebuttal because he explicitly takes McGinn’s premises to represent broad Cartesian-style commitments (except for McGinn’s claim that the link is in principle unknowable) and his own rebuttal to be successful against Cartesian dualism in general. Given this broader context, I believe Searle’s rebuttal fails. Consider premise (1). I do not know of a single property dualist (Cartesian or otherwise) who would take mental properties to be a sort of stuff that, for example, should be referred to by mass terms. Even with respect to mental substances, a framework of stuff is not usually employed. To be sure, some Cartesian dualists may believe in soul-stuff, but most substance dualists, including me, employ a substance/attri-bute ontology to characterize a mental substance as an individuated mental essence; they do not use a separable part/whole framework or the notion of stuff.32 Therefore, Searle is guilty of arguing against a strawman in (1).
What about (2)? Searle’s argument against introspection is as follows:33
1I If the standard model is true, then there is a distinction (presumably, not a distinction of reason) between the thing seen and the seeing of it. 2I The standard model is true.
3I Therefore, there is a distinction between the thing seen and the seeing of it.
4I If introspection occurs, then there is no distinction between the thing seen and the seeing of it.
5I Therefore, introspection does not occur.
There are at least two problems with this argument and they involve (2I) and (4I). Let us begin with (4I). Searle gives no good reason to accept it and, in fact, there are sufficient reasons to reject it. Let us assume, as is standardly granted, that in introspection we have a second-order mental state directed upon a first-order mental state. For example, in introspection the self—whatever it is—is directly aware of a sensation of red or a feeling of pain by directing a second-order mental state onto a first-order one. This is a perfectly intelligible account of introspection and it provides the distinction required to reject (4I).
If someone rejects this model of introspection, then one can still rebut Searle’s argument by rejecting (2I). That is, one can grant (1I) for the sake of argument and deny that it applies to introspection because it begs the question. After all, why apply the standard model to introspective acts? Recall that in chapter two I claimed that at least a certain range of mental states relevant to introspection is self-presenting properties. According to a standard characterization of them, a self-presenting property presents to a subject the intentional object of that property (e.g. an apple’s surface) and the self-presenting property itself (being-an-appearing-of-red). Such properties present other things to a subject intermediately by means of them, and they present themselves to a subject directly simply in virtue of the fact that he has them. Introspective awareness of being-an-appearing-of-red could be understood as the exemplification of a self-presenting property.
In this case, introspection provides a counter example to the standard model. And while Searle does not mention the self, I see no reason why one cannot be directly aware of oneself. On a certain understanding of intentionality according to which it is a monadic property, when one is aware of oneself (as opposed to a mental state one has), in direct selfawareness, one simply directs one’s intentionality onto oneself and the subject and object of awareness stand in the identity relation to each other. Nothing Searle says comes close to undermining such an understanding of self-awareness.
Searle similarly attacks a spatial metaphor associated with “privileged access’’ that he alleges to go proxy for introspection:34 When I spatially enter something, there is a distinction among me, the act of entering, and the thing entered. No such distinction obtains in alleged acts of ‘‘private access’’ and, thus, ‘‘private access’’ should be rejected. The appropriate rebuttal analogously follows the lines of response given to the argument against introspection.
This brings us to (3). As we shall see below, liquidity is a bad analogy with conscious properties. Liquidity may be understood as the property of flowing freely, which, in turn, may be characterized in terms of friction, flexibility of bonding angles, degree of spatial compactness, and so forth. In short, liquidity is a structural property and, as such, liquidity constitutively supervenes ‘‘upon’’ a collection of water molecules. There is no causal relation here. Liquidity just is a feature of non-rigid motion constituted by a subvenient base. Thus, it is plausible to deny a ‘‘link’’ between liquidity and a swarm of water molecules. But Searle is clear that conscious properties are simple, sui generis emergent properties, and as such, are causally supervenient on the brain. In this case, there is indeed a causal ‘‘link’’ between the brain and consciousness and Searle’s analogy employed in (3) is a failure, even in terms of his own views.
I conclude, therefore, that Searle has not succeeded in undermining Nagel: premise (6) of AC (the explanation is not a natural scientific one) is correct and Searle’s correlations are not examples of scientific explanation, which count against (6). But what about premise (3) (there is an explanation for these correlations)? Why is it not reasonable to take mental entities and their regular correlations with physical entities to be utterly brute natural facts for which there is no explanation? The answer is provided by the arguments just mentioned about why Searle’s correlations are not really scientific explanations. Mental entities are not natural or at home in the naturalist epistemology, etiology, and ontology. Given theism and AC as a rival explanatory paradigm, and given the fact that mental entities and correlations are natural for theism, it is question-begging and ad hoc simply to announce that these entities and correlations are natural entities.
Searle could reply that biological naturalism is not question-begging because we already have reason to believe that naturalism is superior to theism prior to our study of the nature of the mental. The only support Searle gives for this claim, apart from a few sociological musings about what it means to be a modern person, is that it is an obvious fact of physics that the world consists entirely of physical particles moving in fields of force. It should be clear, however, that this claim is itself question-begging and clearly false. When there is a statement in a physics text about the world in its entirety, it is important to note that this is not a statement of physics. It is a philosophical assertion that does not express any obvious fact of physics. Moreover, it is a question-begging assertion by naturalists prior to a consideration of the evidence and arguments for theism, including AC. If Searle denies this, then he should inform advocates of AC of exactly what obvious fact of physics they deny in their employment of the argument.
Most naturalists have seen this and have opted for strong physicalism in order to avoid abandoning naturalism and legitimizing the introduction of religious concepts and explanations into the picture. It may be ‘‘neurotic’’ to deny consciousness, as Searle points out. But it is far from ‘‘neurotic’’ to be driven to do so in terms of a prior commitment to naturalism, and AC makes clear why this is the case.
Mackie on Locke and thinking matter
But perhaps there is a naturalist rejoinder at this point in the form of a tu quoque against theists and AC. J. L. Mackie advanced just such an argu-ment.35 According to Mackie, theists like John Locke admitted that God could superadd consciousness to systems of matter fitly disposed and, therefore, as a result of Divine intervention, matter may give rise to consciousness after all. Thus, Locke leaves open the possibility that a mere material being might be conscious given theism. Mackie then asks this question: ‘‘But if some material structures could be conscious, how can we know a priori that material structures cannot of themselves give rise to consciousness?’’36 He concludes that this Lockean admission opens the door for the naturalist to assert the emergence of consciousness from fitly disposed matter as a brute fact.
In my view, Mackie’s argument carries no force against AC because a main part of AC consists in the recognition that mental/physical correlations exist, they are not explicable within the constraints of scientific naturalism, and they require a personal theistic explanation if they are to be explained at all. In this sense, the idea that, in one way or another, God could “superadd’’ thinking or other mental states to matter is required for AC to go through.37
However, as I have tried to show, it does not follow from this ‘‘Lockean admission' that it is a brute, naturalistic fact that material structures of themselves can give rise to consciousness or that adequate naturalistic explanations can be given for this. Indeed, Locke himself constructed detailed arguments to show that mental states like thinkings are not within the natural powers of matter nor could they arise from material structures without an original Mind to create and attach those mental states to matter.38 Locke’s view that God could superadd thinking to a material substance just as easily as to a spiritual substance was a conclusion he drew from the omnipotence of God along with the claim that ‘‘thinking matter’’ is not a contradiction and, thus, possible for God to bring about.
I am not defending Locke’s way of arguing that God could superadd thinking to matter. In fact, I do not think it is correct as he formulated it but, clearly, Locke would not have believed that Mackie’s naturalistic conclusion could justifiably be drawn from his own (Locke’s) admission of the possibility of Divine omnipotence adding a faculty of thought to a material structure.
Mackie cannot simply assert that material structures have the power to give rise to consciousness and also claim to be operating with a naturalistic depiction of matter. According to David Papineau, matter with emergent mental potentiality is not the sort of matter countenanced by naturalists. This is why, when Papineau attempts to characterize the physical in terms of a future ideal physics, he places clear boundaries on the types of changes allowed by naturalism for developments in physical theory. According to Papineau, the naturalist will admit that future physics may change some features of what we believe about matter, but in light of a naturalist commitment and the past few hundred years of development in physics, future physics will not need to be supplemented by psychological or mental categories.39
Given theism, we cannot say a priori just what capacities or states God will correlate with specific physical states. But given naturalism, and the commitment to the role of physics in naturalism, along with a view of the physical that is required by physics, we can say that mental potentiality is just not part of matter. Thus, it is question-begging and ad hoc against AC for Mackie to adjust naturalism to allow that material structures of themselves can give rise to consciousness.