Scientific Naturalism and the Argument from Consciousness

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What is Scientific Naturalism?

Scientific naturalism, or strict naturalism, is the view that the spatio-temporal universe of entities postulated by our best current (or ideal) sciences, particularly physics, is all there is (Moreland, 2012, p.284) This world-view aims to provide an event-causal, scientific account of how everything has come to be and a general ontology in which the only entities which exist are those which bear a relevant similarity to those which would characterise a completed form of physics (Moreland, 2012, pp.282-285).

If naturalism is true, all of reality can be accounted for by physics, cosmology, and the processes of evolution. The two core theories of scientific naturalism are the atomic theory of matter and evolutionary theory (Moreland, 2012, p. 285)  These scientific theories use combinatorial modes of explanation. Wholes at each level above the ground level of elementary microphysics are explained by the composition of the separable parts at lower levels. So living organisms are composed of cells; cells are composed of molecules, which in turn are composed of atoms, which are composed of subatomic parts, which are composed of microphysical entities.

Every physical event has physical causes which are sufficient to produce it; therefore, scientific naturalism subscribes to “the causal closure of the physical domain” (Goetz, 2011; Reppert,2003, p.52). Whenever we seek to explain an event or entity we need appeal only to physical laws and physical objects. This entails that we need never appeal to subjective consciousness, thoughts, plans, intentions or desires to explain the properties of any organism. The scientific naturalist can either attempt to reduce mental properties, like “intentions” and “beliefs”, to physical properties ( for example, the neuro-phsyiological states of organisms); or, the scientific naturalist might argue that mental properties supervene on, or are emergent from, physical properties. In this case mental properties would be determined by physical properties.

Arguably, conscious experience presents a problem for scientific naturalism. If we describe every physical fact about an organism we still leave out its conscious state (“what it is like” to be that organism: what it experiences). An “explanatory gap” emerges: physical theories only allow us to predict physical phenomena. Nothing about charge or mass, or any other physical property, explains the emergence of mental properties. There is absolutely nothing about a collection of physical parts that explains the emergence of thought; thoughts and atoms are just too dissimilar.

The Problem Illustrated: The Knowledge Argument

Although versions of the knowledge argument date back as far as 1925[1], in 1974 Thomas Nagel increased interest in the knowledge argument with his paper “What is it like to be a bat?” Nagel (2012) has also recently argued that physicalism cannot fully explain the living world. Physicalism is the doctrine that there is nothing more to the universe than physical facts which can be described in the language of the ideal physical sciences. The knowledge argument seeks to undermine physicalism by pointing out that we cannot deduce, or even reliably predict, truths about phenomenal experience from knowledge of physical facts alone. This is because there are non-physical facts about the experiences of conscious animals.

In “What is it like to be a bat?” (1974) Thomas Nagel pointed out that:

“…bat sonar, though clearly a  form of perception, is not similar in its operation to any sense that we possess, and there is no reason to suppose that it is subjectively like  anything we can experience or imagine. This appears to create difficulties for the notion of what it is like to be a bat.”

No amount of physical information about the bat’s neurology can tell us “what it is like” to live as a bat, (being nocturnal, using echo-location as ones’ primary sense, etc.) because “what it is like” can only be understood from a bat’s point of view. A subjective “point of view” cannot be understood in physical terms because physical terms describe the world in objective third-person terms, equally understandable from many points of view. The animal stands in a particular relationship to its experiences. A complete third person description of the world leaves out these experiences. Therefore, a third person description of the animal is incomplete.

Frank Jackson (1982) developed Nagel’s point. Jackson noted that the problem is not merely that we do not know “what it is like” to be a bat. The problem is not simply that we cannot extrapolate from our own experience to that of a bat’s. There is something about the bat’s experience, a property of it, that we cannot come to know through gathering information about the physical world. We cannot occupy the bats’ “point of view”; however, if we could experience echo-location for a brief moment we would have learned something new: something true about a bats’ experience. There are non-physical as well as physical facts that we need to know to truly comprehend an organism. Jackson illustrates his point in the following thought experiment:

Mary is a brilliant scientist who is, for whatever reason, forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires, let us suppose, all the physical information there is to obtain about what goes on when we see ripe tomatoes, or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just which wavelength combinations from the sky stimulate the retina, and exactly how this produces via the central nervous system the contraction of the vocal chords and expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is blue’.… What will happen when Mary is released from her black and white room or is given a color television monitor? Will she learn anything or not? It seems just obvious that she will learn something about the world and our visual experience of it. But then is it inescapable that her previous knowledge was incomplete. But she had all the physical information. Ergo there is more to have than that, and Physicalism is false. (Jackson, 1982)

Jackson’s argument can be summarised quite neatly (

1. Mary knows all the physical facts about human colour vision before her release

2. There are some facts about human colour vision that Mary does not know before her release.

Therefore, from 2 and 1

3. There are non-physical facts about human colour vision.

Jackson clarifies that:

“clearly the same style of Knowledge argument could be deployed for  taste, hearing, the bodily sensations and generally speaking for the various mental states which are said to have (as it is variously put) raw feels, phenomenal features or qualia. The conclusion in each case is that the qualia are left out of the physicalist story.” (Jackson, 1982)

We can clarify Nagel’s argument in the same way

  1. A neuro-scientist can know all the physical facts about a bat
  2. These facts do not include “what it is like” to occupy the bat’s point of view

Therefore, from A and B

  1. There are non-physical facts about a bat.

What Mary Knows

What does Mary learn when she experiences colour for the first time? Goetz and Taliaferro (2008, p.45-6) claim that Mary learns the intrinsic nature of seeing a colour. Before she left the black and white room she only knew the extrinsic relational properties associated with seeing a colour. They give two reasons for believing that Mary could not learn the nature of experiences like seeing colour or feeling pain from studying physical facts. First, the experiential nature of pain can only be comprehended from a first-person point of view. Physical facts are described from a third-person point of view. Second, physical explanations are given in part-whole, compositional and spatial terms. Consciousness defies explanation in compositional, spatial terms; it is not made up of out of smaller spatial processes. (Goetz and Taliaferro, 2008, p.46)

Indeed, physicalists typically do not attempt to reduce conscious events to physical parts. Instead, they attempt to reductively identify a conscious event with some physical event and this usually takes the form of a functionalist account of consciousness.  Consciousness is reduced to the causal properties of psychological events. Goetz and Taliaferro give the example of a pain; given that a conscious being is not a substantial self, but rather a mental system, a pain can be reduced to (i) a sensor that formed a representation about the being’s environment (ii) a mental representation of damage to a sub-region of that being (iii) a representation of a goal state to end the cause of the damage. However, as Goetz and Taliaferro note:

Notice, however, on this functionalist account of what happens when you experience pain, the ouchiness of pain (its subjective feeling) is never mentioned and has simply disappeared. All that is left is a system of causal inputs provided by or in the form of representations that produce certain casual outputs. In other words, on the functionalist understanding of the experience of pain, that experience is exhaustively characterised in extrinsic, relational terms (inputs and outputs). There is nothing it is like intrinsically to be in pain that is not reducible in a relational analysis to an identity with causes and effects of the pain. It is precisely the inadequacy of the functionalist characterisation of pain that the story of Mary is designed to illustrate. (Goetz and Taliaferro, 2008, p.46)

Philosophers have disagreed over the meaning of the term “fact” (Crane, 2001, p. 94). Some say facts are true propositions, some say they correspond to true propositions, others that they are what make true propositions true (they are “truth-makers).  For the purposes of the “knowledge argument” we need only note that a fact is an object of propositional knowledge. It seems that Mary learned something new about colour experience when she left the black and white room. If so, then all the facts about conscious experience are not physical facts. Given that physicalism entails that all the facts about consciousness are physical facts, the truth of the knowledge argument would mean that physicalism is false.

Daniel Dennett argues that Mary does not really learn anything that she could not have deduced from a knowledge of all the physical facts. He notes that we will come to know many more physical facts about our conscious sensations in the future; our current knowledge is limited and deludes us into thinking that Mary would not already know all there is to know about colour experience in the room. He also points out that if Mary really knows all there is to know about colour from a third person perspective she would be able to avoid being deceived about her colour experiences when she leaves the room.

Suppose that as soon as she leaves the room another neuroscientist showed Mary a piece of blue card, but told Mary “this card is red: you are now experiencing what the colour red looks like”. Mary could tell that person was lying if she had access to the correct equipment. She would know that red emits light at a different wavelength from blue; by measuring the wavelength of the light emitted from the wall she would know it was not red and was in fact blue. Mary would also know, for example, all the salient and specific reactions in the brain and nervous system brought about by light of different wavelengths. She could deduce what colour she was actually experiencing from knowledge of her neurophysiological state.

So Mary can deduce some truths about her phenomenal experience from her knowledge of the physical facts alone. Dennett argues that as our knowledge of physics and biology improves we will eventually be able to deduce every fact about phenomenal experience from the physical facts alone. Perhaps Mary could extrapolate from her experiences of black and white inside the room to imagine what an experience of red or blue would be like.

However, Dennett’s case seems rather weak. Perhaps Mary could identify the colour of a piece of card, or deduce the name of the colour she was experiencing, from knowledge of the physical facts alone. But the identification of colours is not the same as the experience of colours; Mary would not know “what it is like” to experience red in the absence of the requisite experiences. And imagining “what it is like” to play piano like Mozart is a far cry from actually knowing what it is like. Dennett has provided no reason to think that Mary could derive the intrinsic phenomenal character of experiencing colours from the physical facts; one needs to have an actual experience to know what that experience is like (Jacquette, 2009; De Poe, 2013) .

Can Scientific Naturalism Close the Explanatory Gap?

Some physicalists concede that Mary learns something new when she sees colours for the first time;  however they argue that Mary does not gain any new propositional knowledge. Instead, they argue that Mary gains a new ability or “know-how”. Crane (2001, p.94) calls this the “Ability Hypothesis”. On this hypothesis, when Mary experiences the colour red for the first time she learns how to imagine red, remember red and recognise red.

The ability hypothesis not only presupposes that know-how is irreducible to propositional knowledge; it also presupposes that we do not learn any new propositions when we learn a new ability. But as Crane points out, there are plenty of cases of know-how which can be spelled out in terms of propositional knowledge (for example, knowing how to find Albert Hall from Paddington Station). So it is not at all clear that know-how is not reducible to propositional knowledge” (Crane, 2001, p.95).

Furthermore, even if “know-how” cannot be reduced to propositional knowledge, Mary certainly seems to gain new propositional knowledge. “Red looks like this!” is an indicative sentence which, in the correct context, expresses a proposition (Crane, 2001, p.95). If Mary were to be shown a joke banana painted blue, the proposition “red looks like this” would be false. So Mary has learned a new proposition, even if her know-how cannot be reduced to propositional knowledge. Even if there is more to Mary’s new abilities than propositional knowledge there is not less.

In any case, the ability hypothesis does not evade Nagel’s point that a ‘point of view’ cannot be reduced to knowledge of physical facts. The terms “recognise”, “imagine” and “ remember” are, arguably, all mental terms: they do not appear in physics or any of the other hard sciences. Each mental ability is intrinsically connected to a point-of-view, for someone must remember, recognise and imagine. It is not at all clear that the ability hypothesis can answer the knowledge argument; it simply relocates the problem, for now the physicalist must somehow reduce mental abilities to facts about a physical system. But mental abilities depend on a point-of-view; and Nagel has argued that a point-of-view cannot be captured in third person terms.[2]

Perhaps Mary is not thinking about two different properties; perhaps she is merely thinking about the same property in two different ways.  Indeed, some physicalists admit that Mary gains new propositional knowledge but deny that she thereby comes to know a new fact about the world. They claim instead that Mary learns about an old fact in a ‘new way’ (Crane, 2001, p.96). One proposal is that Mary simply now knows about the same facts under a new “mode of presentation”.  It is quite easy to see how the same fact can have different modes of presentation. Ancient astronomers might have been surprised to discover that “the morning star” and “the evening star” were merely different modes of presentation of the planet Venus.

However, the reason we can refer to the same object by two different modes of presentation ( for example, “the morning star”; “the evening star”) is because the different modes of presentation use different properties to fix the referent. So “the morning star” and “the evening star” refer to the different ways that the planet Venus appears depending on when it is viewed. When two objects are identical they have all their properties in common. It is easy to see how “the morning star” and “the evening star” could have all their properties in common. However, we cannot see how a brain state can have all its properties in common with a phenomenal state. And, crucially, when it comes to phenomenal experience the feeling, or the appearance, is the reality. 

Phenomenal Concepts

Perhaps Mary merely gains a new way of thinking about colours  – a new phenomenal concept – when she leaves the black and white room. Such concepts might resemble demonstratives such as “this”, “now” and “here”: they merely pick out their referents without saying anything about them. This lack of content means that they cannot be inferred from the sort of information that Mary possessed in the monochrome room. Phenomenal concepts are essentially subjective and perspectival: they can only be possessed by someone who has undergone the required conscious state.

The qualities picked out by phenomenal concepts are considered to be broadly physical properties (Graham and Horgan, 2000, 65). For example, the phenomenal content of a conscious experience could be construed as the features of the world which our sensory states typically track. And a phenomenal concept is gained when a subject learns to represent this content in a certain way; gaining a phenomenal concept is to gain a new way of labelling or picking out certain features of the world.

So, to take one example, some have argued that Mary gains phenomenal concepts such as “shade of red”, which allow her to distinguish and group red things on the basis of her own experience (Graham and Horgan, 2000, 65-66). So perhaps Mary gains a phenomenal concept which allows her to perceptually classify red things together. This recognitional concept of red can be associated with the property “typically causes such-and-such an experience”; it is a disposition to recognise a certain phenomenal feel. The reference of these recognitional concepts is determined solely by the fact that an individual has been in causal contact with a physical property and is disposed to re-identify it in subsequent experience (Levin, 2007, p.89).

However, whatever Mary is referring to, she is thinking of something very different to a physical state; and this creates problems for scientific naturalism. Let’s focus, following Howard Robinson (2016), on Mary’s real problem when she leaves the black and white room. She is not puzzled by her inability to derive her new conceptual characterizations of red from scientific concepts. What Mary wants to know how “how can this phenomenal experience of red be the same thing that I studied exhaustively in the lab? It does not seem to have any of the same properties with brain states or functional states.”

The phenomenal concept strategy does not come remotely close to answering Mary’s real problem. Why would thinking about a brain states using a different set of concepts create the phenomenal qualities of “red”, “blue”, “pain” (never mind “ecstasy”, “schadenfreude” or “sehnsucht”!)

Furthermore, it seems that Mary is in fact referring to something which is not physical. Some proponents of the phenomenal concept strategy envision phenomenal concepts as “thick”; they represent using modes of presentation. Now, with non-phenomenal concepts there is a difference between the things in the external world which our concepts refer to and the way things appear to us. The natural kind concept water presents what it refers to it by its essential nature- H20. But when we use the concept of water, we do not refer to it by its essential nature, but rather its contingent features – colourless, tasteless, falling from the sky, odourless etc. This grounds the clear distinction between the referent and the mode of presentation.

However, when it comes to phenomenal experiences, there is no distinction between the referent and the mode of presentation; when it comes to phenomenal experience the feeling, or the appearance, is the reality. This means that there is an unusual and noteworthy transparency between the concept and the property (Demircoglu, 2013). “Pain” just is how it feels, seeing “red” just is the visual experience. And it is apparent that brain states and phenomenal experiences do not share all their properties in common.

Thus, even if we consider phenomenal concepts to be “thick”, there is very good reason for Mary to believe that she has encountered a new type of property – a non-physical property. A subject who uses a phenomenal concept directly accesses a property which is radically different from a physical-functional property. That is to say, it is apparent that the phenomenal character of a conscious experience is not a broadly physical property. Brain states and events have a complex physical structure that phenomenal experience lacks. Phenomenal character has a primitive, non-structural quality:

The bluish look of the ocean is intrinsically simple in the following sense: what one directly accesses (what presents itself to one’s awareness) seems to be a smooth, uniform, homogeneous quality, one that is not further dissectible into parts or discernible patterns, as far as the actual phenomenology goes. We have a substantive and determinate conception or grasp of its simple, non-structural qualitative nature (O’Connor, 2011, p.123).

A phenomenal property does not have the structural features of a physical-functional property. When Mary feels pain or sees red for the first time she is thinking of the phenomenal character – the simple, surprising and striking experience – of a new colour or type of sensation. This phenomenal character of “seeing red” or “feeling pain” does not have a complex, mathematically describable structure like a physical state. Mary is directly acquainted with a new type of property when she leaves the black and white room: and it is a non-physical property.

Finally, it is worth noting that this phenomenal concept strategist’s response to the “knowledge” argument helps itself to a number of dualistic notions. Agents are described as representing concepts to themselves in first person introspection; concepts are described as perspectival and subjective. It isn’t at all clear that the physicalist has come remotely close to sweeping non-physical mental properties from his description of the world. When Mary successfully recognises or re-identifies her experiences of the colour red, or when she gains the indexical knowledge “I am now in pain”, she is referring to a rich, significant and surprising experience which is both profound and striking.

The Problem Clarified: Two Types of Property

Mary does not merely learn how to designate old facts in a new way when she leaves the monochrome room. Instead, she gains what Richard Swinburne (Swinburne, 2013) calls an “informative rigid designator”. Swinburne distinguishes between “informative” and “uninformative” rigid designators (Swinburne, 2013, pp.10-14).  A “rigid designator” is a word which in every possible world designates the same object. A “non-rigid designator” is a word which applies to something only as long as it has some non-essential property. “Red” is a rigid designator, always referring to the same colour even if many objects (or none) are painted red. “The colour of my door” is a non-rigid designator.

Not every rigid designator is such that a competent language user knows what is involved in its application to an object. There is a class of rigid designators which pick out things by certain of their superficial properties ; but what makes a substance that substance (or a kind of substance that kind of substance) is the essence underlying those superficial properties. The essence of a substance is a set of necessary and sufficient conditions for a substance to be that kind of substance (or a kind of substance that kind of substance). It is much more accurate to use rigid designators which pick out things by their essence, and not their superficial properties.

If a competent language user knows what is involved in the application of a rigid designator – if they know the set of necessary and sufficient conditions for a thing to be that thing – then that designator is an “informative rigid designator.” To describe the world as accurately and as informatively as possible we must use informative rigid designators like “H20, “red” and “pain”. Any competent language user who knows the meanings of terms like “red” or “pain” knows the necessary and sufficient conditions for their use. They know when and how to apply the terms, and can make simple inferences using them  – for example, we can infer “it is a sensation” and “it is unpleasant” from “it is a pain.”

If a term does not get at the essence of what it designates it is an “uninformative rigid designators”. Early explorers could see a mountain from Tibet which they identified by its shape and called “Everest”. At the same time, other explorers in Nepal could see a mountain with a different shape which they called “Gaurisanker”. However, it soon became apparent that the two mountains were identical – it was the same rocky matter viewed from different perspectives. “Gaurisanker” and “Everest” referred to superficial properties of the same rocky matter (how it appeared from different perspectives).

Two “informative designators” are logically equivalent iff they are associated with logically equivalent sets of necessary and sufficient conditions (Swinburne, 2013, p.12). So, for example, if a shape is trilateral it is also triangular. Being a rectilinear closed figure with three sides entails having three, and only three, angles. Because “having atomic number 84” and “polonium” are both informative rigid designators –we know from science what is involved in the application of those terms  and they are identical in every possible world. So two properties, or events or substances are  identical if their informative rigid designators are logically equivalent (if each entails the other).

Obviously, there are certain things that simply could not be identical. For example, explorers could never discover that the Nile and Everest referred to the same geographical objects.  It is also clear that mental properties and physical properties are not identical. “Reflecting light at such and such a wavelength” does not entail “red” or “blue” – that is, it does not logically entail how that reflected light will appear to observers. Swinburne argues that:

“Since the informative designators of any physical properties are not logically equivalent to those of any mental properties (since there are different criteria for applying the designators), no mental property is identical to a physical property. The criteria for being in pain are not the same as the criteria for having some brain property (e.g. ‘having one’s c-fibres fire’), or behaving in a certain way in response to a bodily stimulus (e.g. crying out when a needle is stuck into you). The criteria for being in pain are how the subject feels, and the criteria for brain and behavioural events are what anyone could perceive” (Swinburne, 2013, pp. 69-70).

Swinburne thus focuses on our ability to directly access our phenomenal events. It is this privileged access (Swinburne, 2013, p.67) to mental events which distinguishes them from physical events. Observers could infer that I was in pain from my behaviour. However  I don’t need to infer that I am in pain by observing my behaviour or brain states; I feel it directly. It is this mental property that I refer to when I say I feel “pain”. I am picking out an experience, describing the property as it appears to me “on the surface”: there is nothing more to this mental event than the way it appears in subjective experience.  I am not picking out a physical event which causes or accompanies that experience. While privileged access is one distinguishing feature of consciousness, O’Connor (2011) outlines another crucial difference between mental properties and the physical properties of the brain. Brain states and events have a complex physical structure that phenomenal awareness lacks. Consciousness, as we experience it, does not have a complex spatial structure; it cannot be broken down into various parts.

Note that there can be no retreat to “functionalism” to account for consciousness. “Functionalists” identify pure mental properties with events that have functions in a person’s life or behavior and which tend to have certain kinds of causes and effects. Swinburne gives a (highly simplified) illustration of a functionalist analysis of pain. To a functionalist:

“… the property of having a pain is the property which events have if they tend to be caused by bodily damage …and tend to cause crying-out or wincing and a desire for bodily damage to cease. And the property to have a desire to do A is the property which events tend to have if they are caused in certain standard ways and tend to produce an intention… “(Swinburne, 2013, p.94).

Swinburne notes what the functionalist account leaves out – what pain actually feels like. But we can only discover the events that tend to cause pain, or that tend to be caused by pain, if we have some prior understanding of what pain is. We must have privileged access to a pure mental event before we can discover and understand the more complex circumstances in which it occurs. Only then can we can give a definition of the causes of mental events like pain.

It is important to appreciate the depth of the problem for anyone who wants to identify mental states with physical states. E. J. Lowe points out that such a claim does not even seem to be intelligible:

“…what is at issue here is the very intelligibility of identifying pain with some physical state…no-one would be remotely satisfied if some Pythagorean philosopher were to tell us that he had discovered a wealth of empirical evidence supporting the thesis that the things that we think of as being material objects really ‘just are’ numbers. We should demand, first, that he explain to us how such an identification even make sense. To many of their opponents, physicalists who propose that mental states really ‘just are’ physical states seem to be in much the same sort of position as this hypothetical Pythagorean philosopher” (Lowe, 2006, pp.35-36).

So the criteria for being a “pain” and for  the occurrence of its underlying brain state are different. We know what the term “pain” refers to without any knowledge of the underlying brain state. “Pain” refers to a specific, simple sensation which we experience directly. The physical events associated with pain are anything but simple. If I describe the complex sequence of neurological events that accompanies that pain, and the specific function that the pain plays in moving my body away from harm, and even the set of physical events that the pain “represents ”, I leave something important out: that simple, specific sensation that makes pain what it is. So mental properties and physical properties are not identical.

Why We Can’t Explain Thought Using Matter

So Mary seems to encounter genuinely new, non-physical properties when she leaves the monochrome room. Interestingly, there seems to be no good physical explanation for the existence of such properties. Gottfried Wilhelm Leibniz, in his Monadology, imagined a “windmill” to illustrate why he could not conceive of matter producing  thought:

“And supposing there were a machine so constructed as to think, feel and have perception, we could conceive of it as enlarged and yet preserving the same proportions, so that we might enter it as into a mill. And this granted, we should only find on visiting it, pieces which push one against another, but never anything by which to explain a perception. This must be sought for, therefore, in the simple substance and not in the composite or in the machine” (quoted in Plantinga, 2006, p12).

The point of Leibniz’s argument seems to be this: a visitor to the windmill, upon entering it, would observe nothing but physical parts and their interactions.  There is nothing in the machinery that would lead us to expect a conscious thought to emerge from it. Regardless of the complexity of the inner workings of this machine or how many physical interactions take place, no matter what effect the machine had on the physical world outside it, we would never expect a non-physical complex thought to emerge. So the interaction of physical parts cannot explain the emergence of consciousness.

Could we argue that mental events somehow “supervene” on physical events? Following David Lewis, we can use the illustration of a dot matrix picture to understand supervenience. All there is to a dot matrix picture is dots at different points of a matrix. Yet, the whole picture can have properties – symmetry, for example – that the individual dots do not. These global properties of the picture can be said to supervene on the dots.

No two pictures could have exactly the same arrangement of dots, yet differ in their global properties: indeed, the global properties can be explained in terms of the micro-properties. The Stanford Encyclopedia of Philosophy entry on “Physicalism”  (Daniel Stoljar 2009, accessed 21/02/14, describes supervenience physicalism as the claim that facts about psychology, history, sociology, biology and the like are nothing more than facts about patterns in the physical properties that make up the world.  No two possible worlds can be the same in their physical properties and differ in their global properties. Supervenience physicalism also claims that mental properties supervene upon physical properties. Mental properties depend upon physical properties and an exact physical replica of our world will exemplify exactly the same mental properties.

Mental properties would supervene on physical properties iff for any mental property ( for example, joy) if a person has that property there is a physical property ( for example, a brain state), such that the person with the mental property has that physical property and whoever else has that physical property has the mental property (Jacquette, 2009, pp.201-202). But it is conceivable that a person might lack the experience of joy even though they have the same brain state as others who experience joy; it is even conceivable non-physical beings exist and experience joy (Zimmerman, 2011, pp.178-180).  That is to say, there are possible worlds which are physically identical to our world which have creatures with very different mental properties. If David Chalmers (1996) is correct, some will have creatures which are physically identical with the creatures in our world  but which have no mental properties at all (so-called “philosophical zombies”).

If a mental property does not entail a particular physical property, and if there is nothing about physical properties that entail particular mental properties, then mental properties do not supervene on physical properties. Now, it is true that there are macro-features of physical systems that supervene upon the causal interactions among the system’s physical elements. Solidity, transparency, liquidity and elasticity are examples. Photosynthesis and digestion are macro-features of organisms that are explicable in terms of the interaction of the micro-features.

The problem is that simply labelling mental properties as “supervenient on” physical properties does not explain the existence of mental properties at all (Goetz and Taliaferro, 2012, pp.72-79).   With physical structures and processes we can predict how the properties of the whole will follow from the properties of the parts: we can explain how the global properties depend upon the micro-properties. So, we could make appropriate predictions about the behaviour of water (even if we had never encountered water) if we had sufficient knowledge of its chemical structure and the underlying physics. However, we could never make predictions about mental states from knowledge of brain states without the first-hand accounts of human agents describing their mental states. Furthermore, digestion and photosynthesis are physically complex events: a thorough knowledge of the various biological structures in the human body and how they interact would be enough to understand digestion. But conscious experience cannot be broken down into compositional, spatial parts; so it is difficult to see how the interaction of spatial parts accounts for something which does not have spatial parts (Goetz and Taliaferro, 2011, p147-149).

So, as Leibniz’s windmill illustrates, nothing about the anatomy of the brain would allow us to predict the emergence of conscious states. Nothing about a brain’s underlying physical properties seems to entail a particular conscious experience. In fact, the underlying physical structure of our bodies does not entail that we should feel anything at all. There is absolutely nothing about the interaction of physical parts that would allow us to predict the existence or character of a conscious experience.

Clarifying Scientific Naturalism’s Problem

Scientific naturalism is the view that “the world consists entirely of physical particles in   fields of force.” (quoted in Moreland, 2008, p.157). According to Goetz and Taliaferro “strict naturalism” is the view that nature is all that exists and nature itself is whatever will be disclosed by the ideal natural sciences, especially physics. “Broad naturalism” works with a broader definition of science, allowing for more than physics,  chemistry and biology and making room for psychology, sociology  and the other “softer sciences”(Goetz and Taliaferro, 2012, pp.7-9 ).

Theories which are paradigms of explanatory success ( for example, the atomic theory of matter) use combinatorial modes of explanation (Moreland, 2008, p.6-8). Complex entities are the arrangement of simpler parts. Wholes at each level above the ground level of elementary microphysics are composed of the separable parts at lower levels. So living organisms are composed of cells; cells are composed of molecules, which in turn are composed of atoms, which are composed of subatomic parts, which are composed of microphysical entities.  Ultimately, the world is composed of physical parts.

Some phenomena are ontologically basic on any worldview: they are not explained in terms of any more basic phenomena (Moreland, 2008, p.28). On naturalism elementary physical entities and the laws which govern them are basic. But Leibniz’s windmill demonstrates that this means the emergence of mental properties is mysterious and inexplicable on naturalism. There is nothing about the physical parts and their interaction that leads us to predict  or that enables us to understand  the existence of consciousness. Furthermore, in Moreland’s terms (Moreland, 2008, pp.28-31) consciousness does not “fit naturally” into the naturalist’s worldview. Consciousness arrives late in evolutionary history (and very late in the history of the universe) and conscious events are not similar to the central, core entities in naturalism’s core ontology.

However, consciousness is basic on theism, because conscious agency characterises God as understood within theism. Theism has the explanatory resources to account for the existence of finite conscious beings in terms of God’s omniscience and omnipotence. Richard Swinburne (2004, pp. 118-121) notes that the existence of finite conscious beings is not surprising on theism because a basic datum of conscious agents is that they are communal beings who desire relationships. Therefore, we would not be surprised if a conscious being desired to bring other conscious beings into existence.

Conclusion: There’s Something Scientifically Inexplicable About Mary….And Bats

It seems that Mary gains something more than new abilities or new concepts; furthermore, Mary cannot gain a new ability or new concepts which would give her knowledge of “what it is like” to be a bat (or any other animal.) Imagining or identifying experiences does not tell us “what it is like” to have that experience. Therefore, the knowledge argument seems to establish that there are non-physical facts which cannot be explained by physical facts. Physical theories can only provide a physical explanation of the appearance of behaviourally complex animal organisms with central nervous systems. But the knowledge argument shows conscious experiences and “points of view” are not reducible to something physical.

Therefore, the existence of conscious organisms is left completely unexplained on physicalism. (Nagel, 2012, p.45)  What has to be explained is not just the organised complexity and increasing adaptiveness of life but the coming into existence of subjective individual points of view. Nagel argues that “This is a type of existence logically distinct from anything describable by the physical sciences alone.” (Nagel, 2012, p.45)  Now, “… since the conscious character of these organisms is one of their most important features” (Nagel, 2012, p.47) any explanation of the coming into existence of such creatures must include an explanation of the appearance of consciousness so there is a significant gap in any physicalist account of biology.

Conscious states and mental states are not identical: unlike physical states we have privileged access to mental states and mental states lack the compositional structure of physical states. Furthermore, there is nothing about complex physical states that would lead us to believe that they  could cause or even be correlated with mental states. The emergence of consciousness is deeply mysterious on naturalism. Indeed, consciousness is so unlike physical states that it does not fit neatly into the naturalist’s worldview – hence the attempt by naturalists like Dennett and Churchland to reduce consciousness to a physical state or to explain it away altogether (Moreland, 2008, pp.157-166). However, the existence of conscious beings is not at all surprising on theism. Therefore, consciousness provides evidence against naturalism and for theism.


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Chalmers, D (2004) “Phenomenal concepts and the Knowledge Argument”, in There’s Something About Mary, Ludlow, P., Nagasawa, Y., and Stoljar, D. (eds.), MIT Press.

Chalmers, D. (2007) “Phenomenal Concepts and the Explanatory Gap,” in T. Alter & S. Walter (eds.)Phenomenal Concepts and Phenomenal Knowledge: New Essays on Consciousness and Physicalism, Oxford: Oxford University Press.

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Nagel, T. (2012) Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False, Kindle: Oxford University Press

Plantinga, A. (2006) “Against Materialism”, Faith and Philosophy 23: 3-32.

Robinson, H (2016) From the Knowledge Argument to Mental Substance: Resurrecting the Mind, Cambridge University Press

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[2] A “point of view” is not analogous to trivial indexical knowledge of the form: “it is this time now”. A “point-of-view” or “what-it-is-like” denotes something which can compare, contrast, make judgments about, and have knowledge of numerous phenomenal states (see Chalmers comparison of Mary and ‘Zombie Mary’ (2007))

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