Consciousness: a philosophical tour
DOI:10.1093/acprof:oso/9780198524144.003.0001
Abstract and Keywords
The main concern of this chapter is to provide an overview of the main philosophical positions on consciousness. Ontology is the study of the way things are or the study of the nature of things. The focus of this chapter is on the ontological questions of consciousness: what is its nature and how does it fit into the overall fabric of the universe? The author examines how the concepts of consciousness and mind, and consciousness and intelligence, are not equivalent. Different philosophical positions on the problem of consciousness are presented in the chapter. It explores the Cartesian and epiphenomenalist’s view of the conscious mind and demonstrates how the Cartesian tradition inflates its importance while the latter deflates its significance. In addition, parallelism, new mysterianism, and constructive naturalism’s position on consciousness are illustrated as well.
Keywords: philosophical positions, consciousness, Ontology, Cartesian tradition, epiphenomenalist’s view, parallelism, new mysterianism, constructive naturalism
Introduction
The aim of this chapter is to provide an overview of the main philosophical positions on consciousness. The main focus will be on the ontological question. Ontology is the study of the way things are, the study of the nature of things. With respect to consciousness the ontological questions are what is its nature and how does it fit into the overall fabric of the universe. Answers to questions such as these are philosophical, but they do not come only from philosophers. Philosophy is continuous with science in two senses. Philosophical questions about the nature of things have been best addressed by thinkers, both philosophers and scientists, who pay attention to what the most relevant sciences say about the phenomena in question. Furthermore, scientific theories inevitably assume certain broad philosophical positions. Some world-class neuroscientists in the twentieth century have thought that the mind is the brain and thus that neuroscience holds the key to understanding mental life, while others have embraced dualism, the view that the conscious mind is a phenomenon of an altogether different kind than that countenanced by brain science.
Naturalism and non-naturalism
The most fundamental ontological question is this: why is there something rather than nothing? This almost everyone will admit is a perplexing question. Once we admit that there is something rather than nothing, even if we cannot explain why, other, potentially more tractable, questions arise: given that there is something rather than nothing, what is it that there is? What in the most general terms comprises reality? Why is some of the stuff that exists alive, and why is some of the live stuff conscious? These are among the basic ontological questions.
Naturalism is the view that what there is, and all there is, is natural, or physical, or material stuff. This, of course, is more of a motto or slogan than an analysis, since it is silent about what counts as natural, or physical, or material. The standard move here is to say that what is natural is whatever the physical sciences end up telling us exists, whatever the physical sciences end up being ontologically committed to as they proceed in the project of understanding the nature of things. For such reasons, naturalism is also sometimes called physicalism or materialism.
(p.4) Non-naturalism comes in several versions. The version relevant for present purposes says that in addition to the material world there is an immaterial world. Physical science will suffice to teach us about the nature of the material world. But metaphysics (that which goes beyond physics) will be required to explain the nature of the immaterial world.
With respect to the nature of persons, the naturalist says that we are material beings living in a material world. The mind is the brain; mental events are brain events. The non-naturalist says that persons have an immaterial part, typically their souls or minds. The mind is not the brain, mental events are not brain events. Again, these are slogans. But they serve to capture the spirit of the position.
Consciousness and mind
Some philosophers equate the concept of mind with the concept of consciousness. Others, mostly contemporary thinkers, think that consciousness is one among many faculties of mind or, more plausibly, that the set of mental events is larger than and includes the set of conscious mental events.
According to the first view, a mind is necessarily a conscious mind. All mental events necessarily have the property of being conscious. It is fair to credit Descartes, the great seventeenth century philosopher, mathematician, and scientist, with the view that mental events are necessarily conscious and thus that there are no non-conscious mental events. ‘As to the fact that there can be nothing in the mind, in so far as it is a thinking thing, of which it is not aware, this seems to me to be self-evident.’ (Descartes 1993, p. 171 (fourth set of replies to Arnaud).)
John Locke, despite being engaged in a controversy with the Cartesians over innate knowledge, nonetheless agreed with Descartes and his followers that all mental events were conscious. In 1690 Locke wrote: ‘thinking consists in being conscious that one thinks’, and ‘the idea of thinking in the absence of consciousness is as unintelligible as the idea of a body which is extended without having parts’ (Locke 1959, Book 2, Chapter 1, p. 138).
According to the second view, there are non-conscious mental events. Freud canonized this idea. Indeed, until the time of Freud there was no widely shared theoretical framework in which to reject the Cartesian idea of equating the mind with whatever lay within the scope of one’s consciousness. But the basic insight that mental events need not necessarily be conscious is available in the writings of Leibniz. Leibniz, in a series of responses to Locke written between 1703 and 1705, anticipated some important developments in psychology two centuries ahead of their time, especially those with regard to the nature and role of the unconscious:
[T]here are a thousand indications which lead us to think that there are at every moment numberless perceptions in us, but without apperception and without reflection…. In a word, insensible [unconscious] perceptions are of as great use in psychology as insensible corpuscles are in physics, and it is equally as unreasonable to reject the one as the other under the pretext that they are beyond the reach of our senses. (Leibniz 1951, pp. 374–8.)
(p.5) Now we have not only the dynamic unconscious of Freud but also the information-processing unconscious of cognitive psychology and even the neurobiological unconscious. If one thinks that any of these systems exists, are mental, and are non-conscious, then the concept of mind includes as a subset the conscious mind but is not equivalent to it. In this way questions about mind and consciousness come apart. The relationship of the conscious mind and the body may require a different analysis than the relationship of the non-conscious mind and the body. And the relationship between non-conscious mental events and conscious mental events may require yet a third analysis.
Some distinguished contemporary philosophers reject the picture of mental activity as including both conscious and non-conscious events. John Searle (1992) and Galen Strawson (1994) argue that all mental events are conscious (or potentially conscious). According to both Searle and Strawson it is a misleading linguistic courtesy to extend the tribute of ‘mental’ to non-conscious information-processing states or to neural events that lack the property of being conscious.
Consciousness and intelligence
So far we have seen that according to many but not all contemporary philosophers, the concepts of ‘mind’ and ‘consciousness’ are not equivalent. The same is true for the concepts of ‘consciousness’ and ‘intelligence’. Without defining either term—‘consciousness’ or ‘intelligence’—we can see some reasons for keeping the problem of the nature of consciousness separate from the problem of the nature of intelligence. This is true even though the normal use of our conscious minds may be to guide our actions rationally and intelligently. The reason is this: there are computational systems that display signs of intelligence—they play world-class chess and prove theorems in mathematics, for example. No one thinks that such systems are conscious. But they display flexible, novel, unpredictable behaviour just as humans faced by similar problems do.
Alan Turing, in a famous paper written in 1950, suggested interpreting the question: ‘can machines think?’ as equivalent to the question ‘can a machine successfully mimic human behaviour?’ (Turing 1964). If it can, we should say it thinks, that it is intelligent.
Is such a machine a conscious thinking thing? The answer has only become obvious recently, and the answer is ‘no’. The question of consciousness was dropped by the wayside by the Turing test, the test designed to answer the question: can a machine think? Turing’s insight, one might say, was to see that intelligent systems and conscious systems—smart or dumb—need not be equated.
To get a grip on Turing’s insight one might imagine someone observing a world-class chess-playing computer asking the questions: how can it play so well?; how can a computer be so smart?; how can a mere machine display such intelligence? The answer would come from within a naturalistic ontology: the complex interplay between the software and hardware explains the intelligent behaviour displayed by the computer.
(p.6) Complex adaptive systems such as computers, missiles, and robots perform all sorts of functions similar to those humans perform. Intelligence, reasoning according to the canons of deductive logic and probability theory, performing chemical assays, even ‘visual’ discrimination of objects and locomotion are capacities that most people can understand in naturalistic terms. What has historically been found puzzling is how conscious intelligence, conscious reasoning, conscious perception, consciously deciding to walk from home to the office can be explained in natural terms.
In 1898, physicist John Tyndall wrote: ‘The passage from physics of the brain to the corresponding facts of consciousness is unthinkable.’ (Tyndall 1898, p. 420.)
The difficulty of conceptualizing how physical brains can give rise to experience, how certain features of the objective world can give rise to subjectivity is the problem of ‘the explanatory gap’ (Levine 1983).
In his famous paper ‘What is it like to be a bat?’ (1974), Thomas Nagel writes that ‘Consciousness is what makes the mind–body problem really intractable…. Without consciousness the mind-body problem would be much less interesting. With consciousness it seems hopeless’ (Nagel 1979, pp. 165–6).
One interpretation of Nagel’s remark is this: if the mind-body problem is simply the problem of how physical systems such as ants, bats, and humans can intelligently get around, behave socially, and the like, then the resources of physics, neuroscience, and evolutionary biology can make visible the shape of a naturalistic solution. When consciousness, subjectivity, experience, qualia are added to the mix, confidence in the explanatory power of naturalism can easily wane. As Colin McGinn puts it: ‘How can technicolour phenomenology arise from the soggy grey matter of brains?’ (McGinn 1989).
The point is that problems of intelligence or rationality can, in principle, be prised apart from questions of conscious experience. David Chalmers calls the problems associated with intelligent information processing and action guidance ‘the easy problems’ in the sense that we can picture how the natural sciences can solve them. Consciousness is ‘the hard problem’.
[E]ven when we have explained the performance of all the cognitive and behavioural functions in the vicinity of experience—perceptual discrimination, categorization, internal access, verbal report—there may still remain a further unanswered question: Why is the performance of these functions accompanied by experience? […] This further question is the key question in the problem of consciousness. Why doesn’t all this information-processing go on ‘in the dark’, free of any inner feel? (Chalmers 1995, p. 203.)
The official doctrine of the ghost in the machine
In the opening chapter of The concept of mind, entitled ‘Descartes’ Myth’, Gilbert Ryle writes:
There is a doctrine about the nature and place of minds which is so prevalent among theorists and even among laymen that it deserves to be described as the official theory…[T]he official (p.7) doctrine, which hails chiefly from Descartes, is something like this…every human being has both a body and a mind…His body and his mind are ordinarily harnessed together, but after the death of the body his mind may continue to exist and function. (Ryle 1949, p. 11.)
This is the doctrine of ‘the ghost in the machine’. My non-physical mind is harnessed to my body during my lifetime, but being non-physical it is of a different ontological kind than my body and can exist without it.
What could be at the basis of this powerful intuition that mind and body are ontologically different? For Descartes the intuition expressed a self-evident truth. Bodies are extended in space. Atoms, rocks, tables and chairs, and human bodies are extended in space. These are paradigm case physical objects. Thoughts are, or so it seemed to Descartes, unextended—paradigm case non-physical objects. Thoughts still seem this way to most people. Whether they are this way is a different question.
The official doctrine, despite its intuitive appeal, has some problems. How a non-physical mind which occupies no space can be ‘in’ anything is left unsolved, as is the problem of how the world can get information to the mind and how the mind can move the body. Descartes located the point of commerce between mind and body, between the ghost and the machine, in the pineal gland. But this tells us only where immaterial and material forces meet, it tells us nothing about how causation in either direction is possible (see Popper and Eccles (1977) for a recent attempt to spell out the details of a dualistic theory).
Parallelism and worries about interaction
The official doctrine of the ghost in the machine remains the most popular version of non-naturalism. Philosophers, among them Descartes’ contemporaries and their followers, saw that the interaction problem among different ontological kinds was a big problem:
One strategy was to take the theological background theory available to all the modern philosophers working on the mind-body problem and have God more involved in making the mind-body relation intelligible. This Cartesian picture assumes an ontological continuum with God as pure mind, pure res cogitans, rocks as pure matter, pure res extensa, and humans, while embodied, as mixtures of thinking stuff and extended stuff. Once an omniscient God is part of the background, the Cartesian can say that God somehow solves the interaction problem. We may not understand how God solves the problem, but he, being God, does solve the problem.
Some other ontological non-naturalists or dualists seem to have thought that there were better ways for God to solve the mind-body problem than by allowing interaction among different ontological kinds. Leibniz’ and Malebranche’s different kinds of parallelism were similar ways of retaining dualism without the interaction problem, but at no small cost.
According to Leibniz, God (possibly at the creation of the universe) set a pre-established harmony between mind(s) and body(ies). When I decide to move my arm it moves, but not because my decision causes my arm to move but because God has (p.8) willed that minds and bodies stay in synchrony. Malebranche’s view (1638–1715) differed only in having God involved on each and every occasion in which a mental act and a bodily event needed to co-occur. While both views solve the interaction problem by denying that there is any interaction, they cause trouble for the concept of free will. According to Descartes, writing in 1649, one advantage of the official doctrine is the place it leaves for free will: ‘But the will is so free in its nature, that it can never be constrained…And the whole action of the soul consists in this, that solely because it desires something, it causes a little gland to which it is closely united to move in a way requisite to produce the effect which relates to this desire.’ (Descartes 1968, p. 350.)
The Leibnizean has trouble with free will since he has us picture a world in which God sets all the clocks at creation. Malebranche’s view has resources to avoid this problem (although these are not discussed by him). Since God is at all times involved in every life, he can wait until I make a decision and then (being God) simultaneously get my body to fall into line.
Without getting into unnecessary intricacies we can get a feel for parallelism from this quotation:
If we knew thoroughly the nervous system of Shakespeare, and as thoroughly all his environing conditions, we should be able to show why at a certain period of his life his hand came to trace on certain sheets of paper those crabbed little marks which we for shortness’ sake call the manuscript of Hamlet. We should understand…all this without in the slightest degree acknowledging the existence of thoughts in Shakespeare’s mind. [B]ut, on the other hand, nothing in all this could prevent us from giving an equally complete account of…Shakespeare’s spiritual history, an account in which gleam of thought and emotion should find its place. The mind history would run alongside the body-history of each man, and each point in the one would correspond to, but not react upon, a point in the other. (James 1976, p. 136–7 quoting Clifford.)
Three points about parallelism. First, it might seem like a solution to the interaction problem, but it isn’t since it still requires God, either at creation (Leibniz) or on each occasion (Malebranche), to get body and mind to be or appear to be coordinated. This is no less byzantine than Descartes’ solution which just has God figure out how to make different ontological kinds interact.
Second, and on a different trajectory, the position contains an important insight which has contemporary relevance. Even today, philosophers, psychologists, neuro-scientists, and laypeople will remind us that what we always and only seem to have when it comes to the consciousness-brain problem are correlations. A positron emission tomography (PET) scan shows Shakespeare’s brain lighting up and he claims that he is thinking about writing a play called ‘Hamlet’. What are we to say? That the lighted area is the thought of writing the play or that it is correlated with the thought (and the subsequent taking of pen in hand). The move from correlations to identities is a live ontological and methodological issue in contemporary mind science. We will return to this issue shortly.
Third, parallelism is instructive when thinking about reductionism or, more generally, the issue of levels of explanation. One might think that both stories, the (p.9) mental story of Shakespeare’s life and the bodily story of his life—or just take the Hamlet segment of both stories—are equally explanatory. But this is not obvious: the bodily story explains all his bodily movements but it does not explain the production of the meaningful play we call ‘Hamlet’, and this despite the fact that it does explain how certain marks on paper came to be. Nor, on the other side, does the mental story explain the bodily movements even though it explains the ideas behind the play.
Many contemporary naturalists, known as identity theorists, have taken the correlations identified by dualists of the parallelist persuasion and suggested that what we really have are identities. That is, Shakespeare’s thoughts and intentions about the play are in fact identical to a certain set of events taking place in his nervous system. Just as water is H2o and just as salt is NaCl, so too Shakespeare’s plan to write Hamlet is some set {n1, n2…nn} of neural events. From a logical point of view, when we have strict identities we have synonyms, and synonyms can replace synonyms without any loss of meaning. Thus we should be able to tell the mental story of Shakespeare’s writing of Hamlet in terms of the neural states which constitute the activity, which are, as it were, the very activity. This is reduction. But again, many baulk, since something seems to get lost in the reductive translation, namely, the meaningful, intentional properties of the activity.
Epiphenomenalism: Darwin, Freud, and cognitive science
If the Cartesian tradition inflates the importance of the conscious mind, the epiphenomenalist deflates its importance. Epiphenomenalism says that conscious events are ‘mere’ side-effects of the locus of the really interesting action. Epiphenomenalism comes in both a non-naturalist and naturalist version. The non-naturalist thinks that the conscious side-effects of bodily processes are non-physical; but they needn’t worry those who are trying to develop a science of human behaviour since these non-physical side-effects do no significant causal work. The epiphenomenalist who is also a naturalist says that the side-effects are physical but causally inconsequential. William James quotes Thomas Huxley’s startling version of epiphenomenalism.
The consciousness of brutes would appear to be related to the mechanism of their body simply as a collateral product of its working, and to be completely without any power of modifying that working, as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery. Their volition, if they have any, is an emotion indicative of physical changes, not a cause of such changes…. The soul stands to the body as the bell of a clock to the works, and consciousness answers to the sound which the bell gives out when it is struck…to the best of my judgment, the argumentation which applies to brutes holds equally good of men…. We are conscious automata. (James 1976, p. 135.)
Why would anyone think that consciousness was a mere epiphenomenon, a side-effect of what the system is really doing? Part of the reason comes from evolutionary considerations. Nature abounds with creatures that are reproductively successful but are not conscious. The social insects are fantastically fit as measured by the criteria (p.10) of evolutionary biology, but most philosophers and scientists do not attribute consciousness to the social insects. If consciousness is not necessary for reproductive success, then perhaps it is just an accidental and unnecessary appendage in creatures like us that are conscious.
Although James called epiphenomenalism ‘an unwarrantable impertinence’, claiming that ‘[i]t is inconceivable that consciousness should have nothing to do with a business which it so faithfully attends’ (James 1976, pp. 140–1), epiphenomenalism has been taken more seriously in the twentieth century than at any previous time. One reason for the enhanced status of epiphenomenalism comes from the rejection of the Cartesian equation of mind with consciousness. Psychoanalysis, cognitive information-processing psychology, and neuroscience all attribute significant causal power to non-conscious mental events. This convergence of opinion about the causal efficacy of the non-conscious mind has reduced confidence in the causal powers of consciousness. Consciousness seems as if it runs the show, but then again conscious mental states are the only mental states that seem any way at all. This could easily have led us to overestimate dramatically the causal role of consciousness.
This issue of the causal role of conscious mental events in the overall economy of mental life remains very much a live issue.
Contemporary non-naturalists and agnostics
All the traditional views discussed so far continue to have advocates within the philosophical and scientific communities. Despite what many see as the ascendency of naturalistic or scientific views over more traditional theological views, non-naturalism continues to have articulate advocates. Some contemporary non-naturalists think, just as Descartes did, that consciousness can be made intelligible only if it is understood as a power of a non-physical substance or as composed of non-physical properties (Popper and Eccles 1977). Others think that we need to invoke a supernatural cause to explain why phenomenal qualia, the sensation of red or the scent of a rose, are correlated with specific types of brain states (Adams 1987; Swinburne 1984). Still others think that consciousness is miraculous. Like transubstantiation and the Trinity, it is not for us to fathom.
Thomas Nagel, more than anyone else, has articulated a certain uneasiness with both major ontological options. Call his position principled agnosticism (Nagel 1979, 1986). Naturalism is a position we do not understand, because we do not understand (at least at present) how the relation of consciousness and the brain can be made intelligible in naturalistic terms. We do not understand what it would mean to give an objective account of subjectivity. Since one should not believe a theory one does not even understand, agnosticism is the best policy.
One could add a further consideration in favour of agnosticism to which we alluded at the start. Namely, naturalism follows the lead of the physical sciences in (p.11) determining what counts as natural. But the more science develops, the wilder and woollier the natural world seems. The science of Descartes’ time took extension in space as definitive of matter. But today we countenance electrons as part of the material world and our best theories ask us to think of electrons as point-particles without extension. Developments such as these make the boundary between what is natural and what is non-natural increasingly obscure. Again, on the principle that one should not commit oneself to a position one does not understand, agnosticism is a position one might take for reasons of intellectual integrity.
New mysterianism
A somewhat different position is anticonstructive naturalism, noumenal naturalism, or new mysterianism (McGinn 1991). This is the view mat naturalism is true. There are, in fact, properties of the brain that account naturalistically for consciousness. But we cannot grasp these properties or explain how consciousness depends on them. Consciousness is terminally mysterious to our minds but possibly not to minds of greater intelligence. It is terminally mysterious not because it is a non-natural phenomenon, and not because it is a miracle, but because an understanding of its nature is ‘cognitively closed’ to us. The problem of consciousness is a case where we know how to ask the question but lack the mental powers to find the answer.
To get a feel for this position imagine that the most intelligent creatures in the universe are the social insects. They cannot do science. Nonetheless, the laws of gravity, electromagnetism, relativity theory, quantum physics, and so on, hold in the world they live in. They are simply incapable of asking the questions that would lead them to discover the answers about the world that the world, as it were, exemplifies.
According to McGinn we are in a slightly better position: we can ask certain questions about how consciousness works, what it is, and so on. The social insects cannot even ask the questions. But, for this reason, our situation is considerably more frustrating. Since one doesn’t miss what one doesn’t want, the social insects are not frustrated by not understanding the nature of things. They have no desire to know. We can ask the questions and we want the answers, but at least with respect to the problem of consciousness we are simply not up to the task of answering the questions we ask—or so the new mysterians say.
Non-naturalists have their own reasons for thinking that the problem of consciousness will not yield to science. Anticonstructive naturalism, or new mysterianism, is the surprising view that consciousness, despite being a natural phenomenon, will never be understood. Whether its causal role is significant or not, it will not be understand. The ‘old mysterians’ were dualists who thought that consciousness cannot be understood scientifically because it operates according to non-natural principles and possesses non-natural properties. Consciousness might be understood in other ways, for example, by way of an elaborate metaphysical view about the nature of non-physical things and the ways in which they can interact with physical (p.12) things, or by invoking supernatural phenomena (for some sophisticated contemporary defences of supeinaturalism, see Swinburne 1984 and Adams 1987). Because it is somewhat counterintuitive it needs to be repeated that unlike the old mysterianism or contemporary supernaturalism, new mysterianism is a naturalistic position. Mind and consciousness exist, and they operate in accordance with natural principles and possess natural properties. But new mysterianism is a postmodern position designed to drive a railroad spike through the heart of scientism, the view that science will eventually explain whatever is natural.
Colin McGinn thinks that naturalism must be true. There is no other credible way to think about the relation of consciousness and the brain than as a natural relation. Nonetheless, he thinks, we will never be able to set out a credible constructive theory of that relation.
McGinn (1989, p. 349) writes, ‘We have been trying for a long time to solve the mind-body problem. It has stubbornly resisted our best efforts. The mystery persists. I think the time has come to admit candidly that we cannot resolve the mystery’. McGinn (1989, p. 350) thinks that ‘we know that brains are the de facto causal basis of consciousness’, but ‘we are cut off by our very cognitive constitution from achieving a conception of that natural property of the brain (or of consciousness) that accounts for the psychophysical link’.
Although the doctrine is mischievous, coming from a naturalist, it is a coherent position. There are limitative results in physics and mathematics, for example Heisenberg’s Uncertainty Principle and Gödel’s Incompleteness Theorem, that tell us of in-principle impossibilities faced by the physicist and mathematician. It is conceivable that just as we cannot know the position and momentum of an electron at one and the same time, or just as we can know that a certain sentence in arithmetic is true though it is in principle impossible for us to prove it within arithmetic, so we can know that consciousness is a natural phenomenon though it is in principle closed to us to know what sort of natural phenomenon it is.
It is important to see that new mysterianism is different from principled agnosticism. The agnostic thinks that we do not understand what form a naturalistic solution to the consciousness-brain problem would take, so we ought not to confidently claim that naturalism is true. What makes the principled agnostic position agnostic is that naturalism, materialism, and physicalism are not embraced because they are too poorly understood as ontological positions to commit oneself to; but neither is non-naturalism embraced nor is physicalism declared to be false. Nagel (1979, p. 176) writes: ‘It would be a mistake to conclude that physicalism is false…. It would be truer to say physicalism is a position we cannot understand because we do not at present have any conception of how it might be true’.
In his book The view from nowhere, Nagel (1986, p. 47) puts it this way: ‘We have at present no conception of how a single event or thing could have both physical and phenomenological aspects, or how if it did they might be related’. Because we do not understand what form a constructive naturalistic solution to the problem of consciousness would take, we cannot assign credibility to the claim that physicalism is true or to the claim that it is false. Intellectual honesty requires that we be agnostics.
(p.13) Constructive naturalism
Finally, there is constructive naturalism. Against the anticonstructivist and principled agnostic, the constructive naturalist thinks that there is reason for optimism about our ability to understand that relation between consciousness and the brain—reason for hopefulness that we can make intelligible the existence of consciousness in the natural world. Constructive naturalists resist principled agnosticism because they think that the concept of ‘the natural’ can be filled out in a coherent way, and they resist anticonstructivist naturalism because they do not see the cognitive closure or epistemic impossibility that the new mysterian sees. After all, the main argument for the impossibility of solving the consciousness-brain problem comes from the failure to do so thus far. There is nothing like a formal Gödel-like result which proves that certain obstacles to knowledge in the domain of consciousness exist.
Recent work by David Chalmers (1996), Patricia S. Churchland (1986), Paul M. Churchland (1989, 1995), Daniel Dennett (1991), Fred Dretske (1995), Owen Flanagan (1991, 1992), Valerie Hardcastle (1995), William Lycan (1996), John Searle (1992), Galen Strawson (1994), and Michael Tye (1995) is in the constructive naturalist mode. All these philosophers take conscious experience seriously as a phenomenon or set of phenomena to be explained. And they all are optimistic that philosophy and science can build a credible theory of the nature and function of consciousness. There are many disagreements among these philosophers about a wide variety of issues. Where the views converge is on the ontological commitment to naturalism and optimism that consciousness can at least in principle be understood within such a framework.
The following three principles are not shared by all constructive naturalists but they provide a sense of the sort of commitments that might engender confidence that the problem of consciousness can be made to yield.
1. Principle of supervenience
- (a) There exist emergent properties such as liquidity or solidity. Consciousness is in all likelihood an emergent property of complex states of the nervous system.
- (b) A microlevel change need not produce a macrolevel change; for example, two H2o molecules do not produce liquidity.
- (c) But if there is a macrolevel change—if it gets wet in this vicinity—then there is (must have been) a microlevel change, that is, a sufficient number of H2o molecules must have accumulated.
- (d) Emergent, macrolevel properties, can causally interact with other emergent, macrolevel events or processes, as well as with (often because of) interactions with microlevel events and processes. So too can emergent conscious events and processes causally interact with conscious and non-conscious mental events (understood now as emergent neural events).
(p.14) 2. Principle of organismic integrity
That consciousness exists is amazing. But ‘given that consciousness exists at all, there is no mystery in its being connected with what it is connected with’ (Dewey 1922, p. 62). The basic idea behind this principle is to soothe, and then remove, certain troublesome intuitions about subjectivity. Given that emergent properties are possible, and that consciousness is probably such a property, then there should be no surprise in the fact that each person has their own and only their own experiences. It is because of the design of the nervous system. We are uniquely hooked up to ourselves. Given that mere are experiences at all, it makes perfect evolutionary and physiological sense that I have my experiences and that you have yours.
3. Principle of biological naturalism
Consciousness…is a biological feature of human and certain animal brains. It is caused by neurobiological processes and is as much a part of the natural biological order as any other biological features such as photosynthesis, digestion, or mitosis. (Searle 1992, p. 90.)
Stated this way, the principle does not deny that consciousness could conceivably occur in systems with alternative biologies (non-carbon based ones, for example) or even in robots made of inorganic parts. It simply proposes that if you want to understand consciousness, study the systems that exist in our vicinity that are known to be conscious.
Conclusion
The aim of this chapter has been to provide an overview of the main ontological positions concerning the nature of consciousness, to provide a quick tour of the main live philosophical positions on the problem of consciousness. Although almost all philosophers and mind scientists are committed to one of the broad ontological positions discussed here, it would be premature to say that anyone knows which picture is ‘the right one’. It is possible that the best ontological position has not yet been thought of. Happily, the area of consciousness research is at present engaging more good minds than at any point in human history. There is reason to be hopeful that philosophy and science will illuminate each other and take us in the direction of getting a better hold on the nature and function of consciousness. Time will tell.
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