Consciousness Studies/The Conflict2
This part of this section is about the where and when of the experience called consciousness. Is it in the world, in the brain or are the world and brain within it?
- 1 Phenomenal consciousness and access consciousness
- 2 Direct Realism and Direct Perception
- 3 Indirect Realism
- 4 Dualism
- 5 Idealism
- 6 Panpsychism
- 7 References
Phenomenal consciousness and access consciousnessEdit
Block(1995) drew attention to the way that there appear to be two types of consciousness: phenomenal consciousness and access consciousness:
Phenomenal consciousness is experience; the phenomenally conscious aspect of a state is what it is like to be in that state. The mark of access-consciousness, by contrast, is availability for use in reasoning and rationally guiding speech and action. (Block 1995).
See the section on Ned Block's ideas for a deeper coverage of his approach to access and phenomenal consciousness.
Block uses Nagel's famous (1974) paper, "What is it like to be a bat?" as an exemplary description of phenomenal consciousness. Excellent descriptions have also been proffered by the empiricist philosophers who gave lengthy descriptions of consciousness as partly experience itself. Although Block has formalised the idea of phenomenal and access consciousness similar ideas have also been put forward by many philosophers including Kant and Whitehead.
Access consciousness has two interpretations, in the first, used by Block, it applies to the functions that appear to operate on phenomenal consciousness. In the second, used by the behaviourists and eliminativists, it is some property of the functions of the brain that can be called 'consciousness'.
This division between phenomenal and functional aspects of consciousness is useful because it emphasises the idea of phenomenal consciousness as observation rather than action. Some philosophers such as Huxley in 1874, have taken the view that because phenomenal consciousness appears to have no function it is of no importance or cannot exist. James (1879) introduced the term "epiphenomenalism" to summarise the idea that consciousness has no function.
The idea that phenomenal consciousness cannot exist is a type of Eliminativism (also known as Eliminative Materialism). Eliminativism owes much to the work of Sellars(1956) and Feyerbend (1963). Dennett (1978) applied Eliminativism to phenomenal consciousness and denies that pain is real. Others such as Rey(1997) have also applied eliminativism to phenomenal consciousness.
Dennett (1988) redefines consciousness in terms of access consciousness alone, he argues that "Everything real has properties, and since I don't deny the reality of conscious experience, I grant that conscious experience has properties". Having related all consciousness to properties he then declares that these properties are actually judgements of properties. He considers judgements of the properties of consciousness to be identical to the properties themselves. He writes:
"The infallibilist line on qualia treats them as properties of one's experience one cannot in principle misdiscover, and this is a mysterious doctrine (at least as mysterious as papal infallibility) unless we shift the emphasis a little and treat qualia as logical constructs out of subjects' qualia-judgments: a subject's experience has the quale F if and only if the subject judges his experience to have quale F. "
Having identified "properties" with "judgement of properties" he can then show that the judgements are insubstantial, hence the properties are insubstantial and hence the qualia are insubstantial or even non-existent. Dennett concludes that qualia can be rejected as non-existent:
"So when we look one last time at our original characterization of qualia, as ineffable, intrinsic, private, directly apprehensible properties of experience, we find that there is nothing to fill the bill. In their place are relatively or practically ineffable public properties we can refer to indirectly via reference to our private property-detectors-- private only in the sense of idiosyncratic. And insofar as we wish to cling to our subjective authority about the occurrence within us of states of certain types or with certain properties, we can have some authority--not infallibility or incorrigibility, but something better than sheer guessing--but only if we restrict ourselves to relational, extrinsic properties like the power of certain internal states of ours to provoke acts of apparent re- identification. So contrary to what seems obvious at first blush, there simply are no qualia at all. " (Dennett 1988)
Dennett's asserts that "a subject's experience has the quale F if and only if the subject judges his experience to have quale F". This is a statement of the belief that qualia are the same as processes such as judgements. Processes such as judgements are flows of data where one state examines a previous state in a succession over time and embody what Whitehead called the "materialist" concept of time. Dennett does not consider how a scientific concept of time might affect his argument.
Dennett's argument has been persuasive and there are now many philosophers and neuroscientists who believe that the problem of phenomenal consciousness does not exist. This means that, to them, what we call 'consciousness' can only be a property of the functions performed by the brain and body. According to these philosophers only access consciousness exists.
Those who support the idea of phenomenal consciousness also tend to frame it in terms of nineteenth century theory where one state examines a previous state in a succession over time, for instance Edelman(1993) places the past in memories at an instant and time within experience is explained as continuing modelling processes:
"Primary consciousness is the state of being mentally aware of things in the world--of having mental images in the present. But it is not accompanied by any sense of a person with a past and a future.... In contrast, higher-order consciousness involves the recognition by a thinking subject of his or her own acts or affections. It embodies a model of the personal, and of the past and the future as well as the present. It exhibits direct awareness--the noninferential or immediate awareness of mental episodes without the involvement of sense organs or receptors. It is what we humans have in addition to primary consciousness. We are conscious of being conscious."
Block(2004) also suggests this flow from state to state in his idea of "Reflexivity" where our idea of familiarity with an object is due to one state being analysed by another:
"Thus in the “conscious” case, the subject must have a state that is about the subject’s own perceptual experience (looking familiar) and thus conscious in what might be termed a “reflexive” sense. An experience is conscious in this sense just in case it is the object of another of the subject’s states; for example, one has a thought to the effect that one has that experience. The reflexive sense of 'consciousness' contrasts with phenomenality, which perhaps attaches to some states which are not the objects of other mental states. Reflexive consciousness might better be called ‘awareness’ than ‘consciousness’. Reflexivity is phenomenality plus something else (reflection) and that opens up the possibility in principle for phenomenality without reflection. For example, it is at least conceptually possible for there to be two people in pain, one of whom is introspecting the pain the other not. (Perhaps infants or animals can have pain but don’t introspect it.) The first is reflexively conscious of the pain, but both have phenomenally conscious states, since pain is by its very nature a phenomenally conscious state. "
Both Block and Edelman allow phenomenal consciousness, our experience, as an unexplained phenomenon. Block, Edelman and also Dennett's ideas of consciousness are shown in the illustration below:
This model differs from the empirical reports of phenomenal consciousness that were considered earlier. According to the empirical reports the present moment in our experience is extended so the succession of outputs or stages of access consciousness could constitute the contents of phenomenal consciousness. In other words phenomenal consciousness is composed of periods of access consciousness. This is how it seems to the empiricist and in our own experience but how such a state could be explained in terms of brain activity is highly problematical. Given that nineteenth century ideas cannot explain such a state a scientific explanation will be required.
The idea that phenomenal consciousness misrepresents or "misdiscovers" itself (Dennett 1988) deserves further discussion. According to materialism the present instant has no duration so can only be known in succeeding instants as a report or memory and this could be wrong. Whitehead considered that this viewpoint originates in an archaic view of science, particularly the concept of time in science:
"The eighteenth and nineteenth centuries accepted as their natural philosophy a certain circle of concepts which were as rigid and definite as those of the philosophy of the middle ages, and were accepted with as little critical research. I will call this natural philosophy 'materialism.' Not only were men of science materialists, but also adherents of all schools of philosophy. The idealists only differed from the philosophic materialists on question of the alignment of nature in reference to mind. But no one had any doubt that the philosophy of nature considered in itself was of the type which I have called materialism. It is the philosophy which I have already examined in my two lectures of this course preceding the present one. It can be summarised as the belief that nature is an aggregate of material and that this material exists in some sense at each successive member of a one-dimensional series of extensionless instants of time. Furthermore the mutual relations of the material entities at each instant formed these entities into a spatial configuration in an unbounded space. It would seem that space---on this theory-would be as instantaneous as the instants, and that some explanation is required of the relations between the successive instantaneous spaces. The materialistic theory is however silent on this point; and the succession of instantaneous spaces is tacitly combined into one persistent space. This theory is a purely intellectual rendering of experience which has had the luck to get itself formulated at the dawn of scientific thought. It has dominated the language and the imagination of science since science flourished in Alexandria, with the result that it is now hardly possible to speak without appearing to assume its immediate obviousness." (Whitehead 1920).
Direct Realism and Direct PerceptionEdit
Direct Realism proposes that phenomenal experience is directly objects in the world without any intervening representation. It is motivated by the belief that the Problem of Regression, the Subject-Object Paradox and the recursion form of the Homunculus arguments show that phenomenal consciousness cannot occur in the brain alone. Direct Realists reason that if phenomenal consciousness cannot be things in the brain then it must be something outside the brain.
There are two principle types of Direct Realism: Natural Dualism and Behaviourism (both Radical and Analytical). Some behaviourists use the term “Direct Perception” rather than Direct Realism and consider that only the invariant parts of perception are direct (see for instance Michaels and Carello 1981). Thomas Reid is generally regarded as the founder of Direct Realism. In his Natural Dualism he proposed that the soul is in direct contact with the contents of experience and these contents are things in the world beyond the body. The Direct Realism of Reid is summarised in the statement of his famous disciple Sir William Hamilton: "In the simplest act of perception I am conscious of myself as the perceiving subject and of an external reality as the object perceived". Reid's Natural Dualism has now been largely replaced by radical and analytical behaviourism which eschew the idea of a soul and propose that phenomenal consciousness, if it exists at all, is a behavioural reflex.
The modern justification of Direct Realism mainly consists of arguments against Indirect Realism or Representationalism. Philosophers such as Austin (1962) and Le Morvan (2004) have summarised the Direct Realism debate and have identified the following arguments in favour of Indirect Realism and given rebuttals to each of them:
1. The Causal Argument: perception involves a succession of causal events such as the reflection of photons, bleaching of retinal pigments etc. so perception must involve the end of this causal chain. The Direct Realist response is that, although there may be a causal chain in sensation this does not inevitably imply that the end of the chain is the content of phenomenal experience.
2. The Time Lag Argument: it takes time for light to travel from an object to the senses, time for chemical changes in the retina etc... The Direct Realist response is that direct perception may be referred back in time.
3. The Partial Character of Perception Argument: we only perceive the surface of objects, and then only a part of the surface. As the whole object would be perceived directly perception must be indirect. The Direct Realist response is that direct perception could occur even if only parts of an object were perceived.
4. The Perceptual Relativity Argument: things appear to be different shapes depending upon the point of view. The Direct Realist response is that if perception can occur backwards in time it should have no problem occurring back down a line of sight. However, Le Morvan's argument does not seem to encompass the geometrical nature of phenomenal experience, seeking to explain geometry in terms of movement.
5. The Argument from Perceptual Illusion: A stick may appear bent when projecting from the surface of water. Direct Realists apply the argument used in (4) to this problem. The bent stick illusion is a physical event in the world beyond the eye rather than a normal optical illusion such as the Muller-Lyer illusion etc., see (6) for a discussion of optical illusions.
6. The Argument from Hallucination: Hallucinations are not in the world beyond the body. This is highly problematical for Direct Realists especially when phenomena such as lucid dreams, dreams and visual imaginations are included along with hallucinations. Direct Realists classify these phenomena as not being perceptions or deny that they actually exist as phenomena. Indirect Realists would maintain that all of perception is a reconstruction and use optical illusions such as the Muller-Lyer, Ames Room etc. to justify this contention so the Direct Realist approach to hallucination, dreams etc. might seem like an unwillingness to accept Indirect Realism rather than an argument.
7. The Dubitability Argument (cf: Indubitability argument): we cannot doubt current phenomenal experience but we can doubt the world beyond the body therefore phenomenal experience is not the world beyond the body. Direct Realists fall back on Presentism or functional Presentism to defeat this argument. If phenomenal experience is instantaneous and made anew at each instant then anything can be doubted.
The points above have summarised the Direct Realist stance on visual perception. Other sensory modalities have also been considered in the Direct Realism debate.
Fowler (1986) considered that sounds were attached to objects in the world. This idea is strange because sounds only seem to be closely attached to objects in the world when these objects are seen as well as heard. For example, when a subject is blindfolded it is found that there can be a large error in locating the position of a sound in the world, this is especially true for low frequency sounds. The Direct Realist approach has difficulty explaining the transition from sounds with an indefinite location when a subject is blindfolded to sounds that are bound to visual events when the blindfold is removed. It also runs into problems explaining how the sound of speech from a single loudspeaker can become bound to lip movements on a cinema screen. If the binding does not occur in the brain then where does it occur?
Pain is particularly problematic for Direct Realism because, unlike colour vision where 'red' is inferred to be a property of electrons or light, pain is an inner experience that is not a property of tissue damage. Tissue damage has properties such as bleeding, wheal formation etc. but pain seems to be phenomenal experience in the brain and 'phantom pain' can occur without tissue damage (see Aydede (2001), Tye (2004) and Chapman, and Nakamura (1999) for further analysis). On closer inspection other sensations also appear to be inner experiences rather than direct sensations. For instance, the red crosses of different hues in the illustration below are all due to the same physical wavelengths of light. In this case the range of hues in experience is unrelated to the actual physical red on the page or screen.
Another problem for Direct Realism is that it does not overcome the problems that it is supposed to solve. The argument for Direct Realism begins with the idea that there are severe problems with representationalism (the idea that phenomenal experience is in the brain) and that direct perception is an alternative that does not have these problems. However on closer inspection Direct Realism suffers from almost same problems as representationalism. If phenomenal experience is the world itself then Ryle's regress applies to the world itself and this can only be avoided by assuming that phenomenal experience is a subset of the world (i.e.: a representation) that receives input from other parts of the world that are not part of phenomenal experience.
It is also commonly assumed that Direct Realism avoids the recursion argument because it is believed that the separation of the observer from the things that are observed is simply due to the geometry of the world. If such simple geometry is possible between the eye and the world then it should also be possible in the brain and a similar geometrical explanation could be invoked to avoid recursion in representations.
These points are shown in the illustration below:
Scientists have a further problem with Direct Realism. The illustration below demonstrates that our scientific knowledge of the world differs markedly from our phenomenal experience.
It is difficult to see how the form and content of phenomenal experience could supervene directly on the world beyond the body. The world inferred from measurements beyond the body seems to be a nebulous set of quantum phenomena that are arranged as probability fields in three dimensions at any instant. The objects in this real world are mostly space. The world of phenomenal experience on the other hand contains objects that are one-sided, and are like a 2 dimensional field of vectors directed simultaneously at an observation point which is apparently separate from them. Phenomenal experience is not three dimensional, the rear of objects is not available within it at any instant. Visual phenomenal experience seems to be a geometrical relationship between an abstract observation point and the reflection properties of the part of the world external to the body. It is a form that crudely overlies the angular separations in inferred reality, providing approximate directional data. It is not like things in themselves beyond the body, not even in type, being a set of directional vectors. (See the module on the neuroscience of perception for a discussion of depth perception).
If the form and content of visual phenomenal experience are abstractions separated according to the angular positions of things in the world beyond the body then theories which propose that phenomenal experience is the world itself are problematical. It should be noted that things arranged according to angular positions can appear to overlie any group of similar things along a radius from the centre point.
If Direct Realists admit that things are as they appear to be, observed according to angular positions at a 'point eye', then any representation of things on the inside of a sphere of any radius would appear similar. The geometry of the 'point eye' is problematical whether the view contains the world itself or a representation of the world; it cannot be the movements of lumps of matter or energy and the point observation cannot be due to lumps all landing at a point. In other words the 'view' is inconsistent with nineteenth century materialism and will require a scientific explanation.
Radical and Analytical Behaviourism tackle the problem of the difference between the world inferred from measurements beyond the body and the phenomenal world by denying phenomenal consciousness and maintaining that access and reflex consciousness are all that exists or is necessary. Radical Behaviourism is an offshoot of psychological behaviourism and was established as a philosophical adjunct to Marxism by Vygotsky and popularised by Burrhus Frederic Skinner (see Skinner 1953). There is another movement in psychological behaviourism which is similar to Radical Behaviourism called Ecological Psychology (see Gibson 1966, 1979 and also Michaels and Carello 1981). Analytical Behaviourism is a philosophical movement established by Gilbert Ryle (see Ryle 1949).
The core of Analytical and Radical Behaviourism is the assumption that consciousness exists for a durationless instant so that the Dubitability Argument and the Regression and Recursion Arguments can be applied (Ryle 1949, Skinner 1971 and see the sections on Ryle's Regress and the Subject-Object Paradox above). As a result the Direct Realist is able to insinuate that subjects only think that they have had a particular experience (cf: Dennett 1991a). It is intriguing that Eliminativists also maintain that experience is the world itself, for instance an insight into Dennett's idea of the mind is to be found on pages 407-408 of Consciousness Explained:
"It seemed to him, according to the text, as if his mind - his visual field - were filled with intricate details of gold-green buds an wiggling branches, but although this is how it seemed this was an illusion. No such "plenum" ever came into his mind; the plenum remained out in the world where it is didn't have to be represented, but could just be. When we marvel, in those moments of heightened self-consciousness, at the glorious richness of our conscious experience, the richness we marvel at is actually the richness of the world outside, in all its ravishing detail. It does not "enter" our conscious minds, but is simply available"
This is a clear description of Direct Realism (although Dennett does not describe himself as a direct realist).
Radical Behaviourism is sometimes described as the dictum that the only psychological events that are of importance are those that occur outside the head. The absurdity of this has led to jokes:
Q: What does one behaviorist say to another when they meet on the street?
A: You're fine. How am I?
Q: What does one behaviorist say to another after sex?
A: That was great for you. How was it for me?
However Vygotsky, Skinner and other Radical Behaviourists hold that inner behaviour is possible so that events within the brain can result in reward or punishment. Vygotsky (1925) describes this approach:
"Consciousness is wholly reduced to the transmitting mechanisms of reflexes operating according to general laws, i.e., no processes other than reactions can be admitted into the organism. The way is also paved for the solution of the problem of self-awareness and self-observation. Inner perception and introspection are possible only thanks to the existence of a proprioceptive field and secondary reflexes, which are connected with it. This is always the echo of a reaction."
Hence Radical Behaviourists are able to make the claim that what are believed to be representations with phenomenal content are processes. Even events such as pain can then be explained as reflexes involving organs within the skin. However, by opening the possibility that such reflexes could occur at any sense organ, including the eye, this makes Radical Behaviourism a mixed Direct Realist/Indirect Realist philosophy with consciousness as a process, not a separate thing such as phenomenal consciousness (see the section on representationalism and intentionality below).
But this raises a serious issue for science: can the phenomenal consciousness that seems to contain our observations really be argued out of existence on the basis of a theory? As Gregory (1988) put it: “ ‘If you can’t explain it – deny it’ is one strategy for dealing with embarrassing questions such as ‘what is consciousness?’ ”. But is this the right strategy?
Direct Realism fails to overcome the problems of regression and recursion inherent in representations. It proposes that phenomenal consciousness is identical to the physical world beyond the body but must then use a plethora of arguments to explain why this is evidently not so. When confronted with these problems its proponents resort to the argument that everything can be doubted and can misrepresent itself. Yet it is still widely believed.
It should be noted that Direct Realism is espoused in Religious Natural Dualism, some forms of Augustinian theology, nineteenth century materialism and its offspring such as Marxism, post-modernism, post-Marxism, and various sociological movements. It is also necessary for some forms of Strong AI to occur. Perhaps this explains why few ideas have attracted as much attention and defence as Direct Realism.
It is interesting to compare the Direct Realist and Indirect Realist interpretations of something as simple as a cartoon on television (such as the image below). According to Indirect Realism the cartoon would be a moving representation constructed in the brain using data from the senses. This leads to the prediction of brain mechanisms for modelling motions, combining colours, binding sound and vision etc., many of which have been verified. Can you demonstrate how the theory of Direct Realism could explain the phenomenal experience that contains the cartoon and produce a list of the predictions made by the theory?
In science a theory should be of predictive value, for instance, information theory describes how the state of a thing can be impressed on a carrier so that a signal can be transmitted from one place to another. This theory predicts what will happen when the signal arrives at its destination and how the state of the source can be inferred from the events at the destination, the total amount of information that can be transmitted etc. At the destination it is the form of the signal that is directly known by interaction and measurement, the form of the source is inferred. Direct Realism is a direct challenge to this information theory but does it deliver a more powerful predictive description of phenomenal consciousness or is experience always dependent on what happens to the information flow between things in the world and somewhere in the brain? Does direct realism have a physical theory?
Ultimately it appears as if Direct Realism is about various understandings of Information Theory. For example, Austin (1962) discusses what we see when we see a church camouflaged as a barn and comments that: "We see, of course, a church that now looks like a barn.". Do we see a church or a barn? Scientific information theory is clear about this, the church is an entity composed of selected information from the quantum state of its constituents, the optical image of a camouflaged church is an arrangement of photons emanating from a screen on which it is projected, the retina has an arrangement of chemical and electrical events based on an optical image and conscious visual experience correlates with the arrangement of things on the retina. The fact that conscious experience also correlates with classifications of the retinal image as a barn or a church suggests that conscious experience is an arrangement of things in the brain based on both the retinal arrangement and the contents of a relational database.
Austin's arguments have been mythologised as a final demonstration that "sense data" theories are false. However, as will be seen below, sense data theories merely claim that there is a succession of information states between an information state outside the body and that reported as conscious experience i.e.: subjects report that a church is camouflaged when it is camouflaged.
Indirect realism proposes that phenomenal consciousness exists and is a set of signals or sense data, usually in the brain. This was proposed by philosophers from Aristotle to Locke and was probably the most widespread idea of conscious experience until the eighteenth century.
The idea of sense data is discussed in depth by Russell (1912). Russell's original definition is given below:
"Let us give the name of 'sense-data' to the things that are immediately known in sensation: such things as colours, sounds, smells, hardnesses, roughnesses, and so on. We shall give the name 'sensation' to the experience of being immediately aware of these things. Thus, whenever we see a colour, we have a sensation of the colour, but the colour itself is a sense-datum, not a sensation. The colour is that of which we are immediately aware, and the awareness itself is the sensation. It is plain that if we are to know anything about the table, it must be by means of the sense-data -- brown colour, oblong shape, smoothness, etc. -- which we associate with the table; but, for the reasons which have been given, we cannot say that the table is the sense-data, or even that the sense-data are directly properties of the table."
Russell's definition is a materialist concept in which experience is always of something because the durationless instant of the present has always gone. As such it differs from some empiricist ideas where experience is not confined to the durationless instant.
Science is Indirect Realist because it holds that the scientist can only make measurements of events in the world. These measurements give rise to signals as a result of interaction with the event. According to decoherence theory the signals are a state that is a mixture of the state of the measuring instrument and the state of the thing being measured. For example, the eyes are measuring instruments that are sensitive to photons, photons are signals containing a state that is based on the state of electrons in a surface and the state of electrons is based on the state of the surface etc. Scientific inference allows some aspects of the state of the surface to be inferred from the state of the photons.
In modern Indirect Realism there is an attempt to distinguish the phenomenal content of conscious experience from the processing involved in accessing this phenomenal content. According to these theories phenomenal experience is an arrangement of signals that are the content of the experience. This arrangement forms a representation of things in the world so this form of indirect realism is known as Representationalism. Tye (2003) describes types of representationalist theory:
"Representationalism, as I have presented it so far, is an identity thesis with respect to qualia: qualia are supposedly one and the same as certain representational contents."
Tye also describes variants of this idea of representationalism:
"Sometimes it is held instead that qualia are one and the same as certain representational properties of experiences; and sometimes it is is argued that these representational properties are themselves irreducible (Siewert 1998). There is also a weaker version of representationalism, according to which it is metaphysically necessary that experiences exactly alike with respect to their representational contents are exactly alike with respect to their qualia. Obviously, this supervenience thesis leaves open the further question as to the essential nature of qualia." (Tye 2003).
In a scientific sense Direct Realists believe that phenomenal experience is the signals that occur next to things in the world beyond the body (which they call "things in themselves") and Indirect Realists usually believe that phenomenal experience is signals in the brain. It can be seen from the pattern of signal flow that the signals travelling into the brain preserve the spatial relationships of the original signals and encode the properties in the original signals. This means that the original signals next to the QM sources and the signals in the brain are equivalent provided the latter are oriented appropriately relative to signals from the body. Either set of signals could transmit or contain the same information. Both Direct and Indirect Realism cannot, at present, explain the physics of how a viewing point occurs in experience i.e.: how we seem to see through an apparent space to the signals that are the contents of experience. So the choice between Direct Realism and Indirect Realism reduces to whether there is only one set of signals or a chain of signals between the world and phenomenal experience.
The philosophical arguments for Indirect Realism are listed below:
1. Variable perspective: when we see things the view changes so what we see must be a different set of signals depending on the view rather than a constant object.
2. Illusions: we can see through fingers and see a variety of colours where measurements tell us one exists. Direct Realists quote the "bent stick illusion", which is not really an illusion at all, being a physical event.
3. Hallucinations: two people can have phenomenal experience containing a table. The first may be viewing a real table whereas the second may be hallucinating a table. If the tables are the same (phenomenally) then experience is indirect.
4. Double vision: press the side of one eye, two images appear (cf Hume 1739) yet there are not two things in the world.
5. Time gap arguments: according to materialism the past has gone. The things being seen no longer exist in the state that relates to the state in experience. In the extreme case, some stars in the night sky no longer exist but are still in experience so experience must be a derived signal.
6. Secondary qualities such as pain, colour and smell do not exist as physical things in the source of signals and are likely to be properties of signals in the brain.
Indirect Realism has received strong support from recent discoveries in neuroscience, for example, it is now clear that both the colour and motion in phenomenal experience are added by cortical processes. In Cerebral Achromatopsia patients have suffered trauma to area V4 of the cerebral cortex and report seeing the world in greyscale with no colour vision and in Congenital Achromatopsia people do not even understand the meaning of 'colour'. In an astonishing ailment called Akinetopsia patients perceive movement as a succession of stationary images (Rizzo et al. 1995). Akinetopsia is usually associated with damage to cortical area V5. Moutoussis and Zeki (1997) have demonstrated that the addition of colour occurs more rapidly than the addition of motion. The section on the Neuroscience of Consciousness describes these discoveries and many other aspects of the creation of phenomenal experience in the brain.
Unfortunately knowledge of the whereabouts of the signals that are the content of conscious experience does not resolve the problem of phenomenal consciousness. Whether these signals are next to objects in the world or at the end of a chain of signals in the brain there still remains the problem of how they become arranged in the form of experience. If such a thing occurs at all.
Intentionality and representationEdit
There is a materialist interpretation of representationalism in which representations are redefined as intentional states:
"One way of explaining what is meant by ‘intentionality’ in the (more obscure) philosophical sense is this: it is that aspect of mental states or events that consists in their being of or about things (as pertains to the questions, ‘What are you thinking of?’ and ‘What are you thinking about?’). Intentionality is the aboutness or directedness of mind (or states of mind) to things, objects, states of affairs, events. So if you are thinking about San Francisco, or about the increased cost of living there, or about your meeting someone there at Union Square—your mind, your thinking, is directed toward San Francisco, or the increased cost of living, or the meeting in Union Square. To think at all is to think of or about something in this sense. This ‘directedness’ conception of intentionality plays a prominent role in the influential philosophical writings of Franz Brentano and those whose views developed in response to his (to be discussed further in Section 3)."(Siewert 2003)
This definition allows "representation" to be redefined as a data stream rather than a set of things arranged in some mental or neural state that represents things in space. Husserl thought this approach would allow a description of consciousness that "carefully abstains from affirming the existence of anything in spatio-temporal reality" (Siewert 2003) although it could be argued that a data stream such as any description can never escape the constraints of representation in time at some place.
Unfortunately the concept of "intentionality" has become so diverse that it could be applied to almost any aspect of the description of consciousness. An interesting example of this is given by Loar (2001) where "intentionality" is considered to overlap "representing" and "conceiving":
"A person's thoughts represent things to her -- conceive things -- in many ways: perceptually, memory-wise, descriptively, by naming, by analogy, by intuitive sorting, theoretically, abstractly, implicitly and explicitly. These various manners of conceiving have something in common: they have intentional properties, and they have them essentially.
The usage of the term "intentional state" has become so broad that it now means little more than a state that is about another state.
Siewert, C. (2003). Consciousness and Intentionality. The Stanford Encyclopedia of Philosophy. http://plato.stanford.edu/entries/consciousness-intentionality/
Also see Loar, B. (2001) “Phenomenal Intentionality as the Basis of Mental Content”, in Reflections and Replies, ed. M. Hahn and B. Ramsberg, MIT. http://www.nyu.edu/gsas/dept/philo/courses/concepts/loar.html Williford, K. (2002) The intentionality of consciousness and the consciousness of intentionality. Intentionality: Past and Future, edited by Gábor Forrai and George Kampis, Amsterdam/New York: Rodopi. http://web.stcloudstate.edu/kwwilliford/Intentionality%20of%20Consciousness.pdf
Byrne, A. (2001). Intentionalism Defended. Philosophical Review 110 (April 2001):199-240. http://stripe.colorado.edu/~leeds/byrne.pdf
The term "Cartesian materialism" once meant the idea that the mind is in the brain (see for instance Block 1995). The term had largely fallen out of use in philosophy until revived by Daniel Dennett (1991) in the book Consciousness Explained. Dennett uses a very particular definition of the term in his discussions and also uses a particular definition of the word "mind". See the section on Daniel Dennett for Dennett's critique. Philosophers who adhere to the idea that the mind is in the brain tend to call themselves "indirect realists" or "representationalists" where the substrate of conscious experience is in the brain and would deny that Dennett's critique applies to their proposals. Dennett's critique makes the materialist assumption that if there is a representation in the brain then a further flow of material out of this representation would be required for the representation to become part of mind.
Identity theories of mindEdit
The idea that mental states are brain states is known as the identity theory of mind. There are two sorts of identity theory, in type identity theory it is held that mental states are identical to brain states whereas in token identity theory it is held that mental states correlate with brain states.
Type identity theory was attacked by Putnam in "The Nature of Mental States" where he pointed out that if mental states are functions then type identity theory would presuppose that animals that had the same mental states would need to have identical brain structures. He suggested that this is unlikely, it being more probable that animals have functional systems that perform similar overall functions but which are not identical. In other words, if it is assumed that conscious experience is a set of functions then token identity theory is more probable than type identity theory.
Putnam's critique does not preclude identity theories of mind that involve "passive ideas" (i.e.: states that are not classical functions).
Most identity theories of mind would be representational, the physical states representing the world in some way. All identity theories of mind involve Cartesian materialism in the sense of the mental states being brain states. According to identity theories the mind is in the brain.
Putnam, H. (1967) The nature of mental states. In The Nature of Mind, edited by Rosenthal, pp. 197–203. Originally published as "Psychological predicates in Art, Mind, and Religion", edited by Capitan and Merill, pp. 37–48.
Prior to considering the arguments surrounding dualism it is important to have a clear idea of "information" because many of these arguments have parallels with the difference between information as a set of states that can be transmitted and the substrate on which this information is expressed or from which the information is derived. See Elementary information and information systems theory.
Descartes, a philosopher, analysed his experience and developed an empirical description of how it is arranged. He described mental images and perceptions as extended in space and with a duration. He called these extended things ideas (Cartesian ideas) and proposed that they are patterns in the brain. Descartes thought the pineal gland was the most likely location for these ideas because it is one of the few single organs in the brain. He also proposed that there is a rational soul that directly contacts these ideas:
"Now among these figures, it is not those imprinted on the external sense organs, or on the internal surface of the brain, which should be taken to be ideas - but only those which are traced in the spirits on the surface of gland H (where the seat of the imagination and the 'common sense' is located). That is to say, it is only the latter figures which should be taken to be the forms or images which the rational soul united to this machine will consider directly when it imagines some object or perceives it by the senses." Descartes (1664)
See section on Descartes for more information and references.
Descartes considered that the soul was a physical point, an unextended entity that acts like a mind's eye. He called this unextended place the res cogitans and concluded that it was a substance that differed from that of material things:
".. I thence concluded that I was a substance whose whole essence or nature consists only in thinking, and which, that it may exist, has need of no place, nor is dependent on any material thing; so that " I," that is to say, the mind by which I am what I am, is wholly distinct from the body, and is even more easily known than the latter, and is such, that although the latter were not, it would still continue to be all that it is."Descartes (1637)
This unextended substance that is not material gives the word "substance" a new meaning. It has been attacked as a concept by Locke, Hume, Berkely and many other philosophers. The concept of there being two substances, that which composes the physical world and that which composes the soul, is the origin of the word Dualism but dualism, as a concept, has been extended beyond this original meaning. Cartesian dualism is a type of substance dualism.
Cartesian dualism is an attempt to explain our experience. According to Descartes something supernatural would be needed for an unextended viewing point to exist.
Reid's Natural Dualism also has a point soul looking at things but proposes that the things in question are forms in the world rather than in the brain.
Another sort of dualism has arisen out of a particular interpretation of the regress and homunculus arguments. These arguments show that phenomenal experience is not due entirely to flows from place to place (i.e.: it is not due to classical processes and functions). Property dualism asserts that when matter is organized in the appropriate way (i.e. in the way that living human bodies are organized), mental properties emerge.
As Goldman (1993) pointed out, qualitative experience does not seem to be needed in a functional description of a system:
"For any functional description of a system that is in pain (or has an itch), it seems as if we can imagine another system with the same functional description but lacking the qualitative property of painfulness (or itchiness)."
Certainly a functional system that merely reports the words "I am in pain" when it is dropped on the floor does not require any qualitative property of painfulness. The absent qualia arguments suggest that even in a large system there would be no need for qualitative properties for the performance of any classical function.
Chalmers (1993) commenting on Goldman's point, said that this implies that zombies might exist, functional replicas of humans but without qualia. He then denied that a complete functional replica of a human could exist without also including qualia:
"It seems to me that the only way to avoid this conclusion is to deny that Zombie Dave is a conceptual possibility; and the only principled way to deny that Zombie Dave is a conceptual possibility is to allow that functional organization is conceptually constitutive of qualitative content." Chalmers (1993).
In other words he identifies qualia with function. According to Chalmers (1996) qualia are a particular type of function:
"I claim that conscious experience arises from fine-grained functional organization. More specifically, I will argue for a principle of organizational invariance, holding that given any system that has conscious experiences, then any system that has the same fine-grained functional organization will have qualitatively identical experiences. According to this principle, consciousness is an organizational invariant: a property that remains constant over all functional isomorphs of a given system. Whether the organization is realized in silicon chips, in the population of China, or in beer cans and ping-pong balls does not matter. As long as the functional organisation is right, conscious experience will be determined." p249
Chalmers' idea of functional organisation has within it a sometimes vague implication that the functional units must have a particular form; for instance, in the development of his argument, he refers to “fine grained” replacement of organic functional units with inorganic units.
Chalmers is actually making two major points, firstly that qualia occur during the motion of things (functions), secondly that qualia are independent of any particular substrate.** For the first point to be consistent with materialism the qualia must have no effect on the function, they must be epiphenomenal. Epiphenomenal qualia would not be forbidden by the regress and homunculus arguments and would be akin to Berkeley's "passive ideas".
Whether or not epiphenomenal qualia are physical depends upon the definition of the word "physical". If physical functions cause qualia but qualia cannot affect functions then the qualia are "physical" in the sense of being caused by physical events but might be regarded as non-physical in the sense of being isolated from further physical events. In philosophical terms they violate the principle of Causal Closure. However, there are other definitions of physicalism based on arguments such as Methodological Naturalism which hold that anything that can be investigated using the methods of natural science is a physical thing (see Stoljar 2001). Thus, although epiphenomenal qualia may not conform to materialism they may be encompassed by physicalism; as events that are related to material events they are awaiting a physical theory of how they emerge from a given function.
The reader might consider whether phenomenal consciousness is indeed epiphenomenal. Empirical reports describe it as something that is different from the world beyond the body (see direct realism) - could we generate empirical reports of an epiphenomenon?
The term property dualism describes how physical events might give rise to a set of properties that cannot be predicted from the fine structure of the physical system. The "dualism" is present because one set of events is related to two sets of properties, one of which is not related by materialism to the set of events. In the case of the proposal about consciousness outlined above an extra assumption, beyond materialism, would be needed to explain qualia. Property dualism might be defined as a theory that there could be a theory of consciousness but that this requires some new assumption.
As far as the "when and where" of consciousness are concerned, property dualism states that it is somewhere in the processes performed by the organism and the parts of the organism.
** In terms of information processing, Chalmers is proposing that qualia are the enactment of a particular information processing structure.
- Block, N. (2006). Max Black's objection to mind-body identity. Oxford Review of Metaphysics No.3. http://philrsss.anu.edu.au/BlockFest/MaxBlack.rtf
- Chalmers, D.J. (1993) Commentary on "The Psychology of Folk Psychology". Behavioral and Brain Sciences 16:35-36, 1993
- Chalmers, D.J. (1996) "The Conscious Mind: In Search of a Fundamental Theory". Oxford University Press. 1996.
- Goldman, A.I., (1993). The Psychology of Folk Psychology. Behavioral and Brain Sciences 16: 15-28 (1993). http://www.ecs.soton.ac.uk/~harnad/Papers/Py104/goldman.psyc.html
Predicate dualism is the view espoused by most non-reductive physicalists, such as Donald Davidson(1980) and Jerry Fodor(1968), who maintain that while there is only one ontological category of substances and properties of substances (usually physical), the predicates that we use to describe mental events cannot be redescribed in terms of (or reduced to) physical predicates of natural languages. If we characterize predicate monism as the view subscribed to by eliminative materialists, who maintain that such intentional predicates as believe, desire, think, feel, etc., will eventually be eliminated from both the language of science and from ordinary language because the entities to which they refer do not exist, then predicate dualism is most easily defined as the negation of this position. Predicate dualists believe that so-called "folk psychology", with all of its propositional attitude ascriptions, is an ineliminable part of the enterprise of describing, explaining and understanding human mental states and behavior.
Davidson, for example, subscribes to Anomalous Monism, according to which there can be no strict psycho-physical laws which connect mental and physical events under their descriptions as mental and physical events. However, all mental events also have physical descriptions. It is in terms of the latter that such events can be connected in law-like relations with other physical events. Mental predicates are irreducibly different in character (rational, holistic and necessary) from physical predicates (contingent, atomic and causal).
(Section based on Wikipedia article)
- Davidson, D (1980). Essays on Actions and Events. Oxford University Press. ISBN 0-19-924627-0
- Fodor,J. (1968) Psychological Explanation, Random House. ISBN 0-07-021412-3.
The interaction between mind and brain in dualismEdit
Interactionism is the view that mental states, such as beliefs and desires, causally interact with physical states. This is a position which is very appealing to common-sense intuitions, notwithstanding the fact that it is very difficult to establish its validity or correctness by way of logical argumentation or empirical proof. It is appealing to common-sense because we are surrounded by such everyday occurrences as a child's touching a hot stove (physical event) which causes him to feel pain (mental event) and then yell and scream (physical event) which causes his parents to experience a sensation of fear and protectiveness (mental event) and so on.
According to epiphenomenalism, all mental events are caused by a physical event and have no physical consequences. So, a mental event of deciding to pick up a rock (call it "M") is caused by the firing of specific neurons in the brain (call it "P"), however when the arm and hand move to pick up a rock (call it "E") this is only caused by P. The physical causes are in principle reducible to fundamental physics, and therefore mental causes are eliminated using this reductionist explanation. If P causes M and E, there is no overdetermination in the explanation for E.
Psycho-physical parallelism is a very unusual view about the interaction between mental and physical events which was most prominently, and perhaps only truly, advocated by Gottfried Wilhelm von Leibniz. Like Malebranche and others before him, Leibniz recognized the weaknesses of Descartes' account of causal interaction taking place in a physical location in the brain. Malebranche decided that such a material basis of interaction between material and immaterial was impossible and therefore formulated his doctrine of occasionalism, stating that the interactions were really caused by the intervention of God on each individual occasion. Leibniz idea is that God has created a pre-established harmony such that it only seems as if physical and mental events cause, and are caused by, one another. In reality, mental causes only have mental effects and physical causes only have physical effects. Hence the term parallelism is used to describe this view.
Occasionalism argues that bodily events are the occasion of an act by the Creator causing a corresponding mental event, and vice versa. Any such view requires a theological structure as a premise.
- Robinson, Howard, "Dualism", The Stanford Encyclopedia of Philosophy (Fall 2003 Edition), Edward N. Zalta (ed.), http://plato.stanford.edu/archives/fall2003/entries/dualism/
- Robinson, H. (2003) "Dualism", in S. Stich and T. Warfield (eds) The Blackwell Guide to Philosophy of Mind, Blackwell, Oxford, 85-101.
- Amoroso, R.L. (2010) "The complementarity of Mind and Body: Realizing the Dream of Descartes, Einstein and Eccles", New York: Nova Science Publishers,
According to Idealism only the mental truly exists.
The form and content of personal conscious experience might be related to the structure of the world and brain in several ways. It could be a solipsism or be the mind of God.
This is a stub and needs expansion.
According to Panpsychism everything in the world may be conscious; consciousness is a fundamental entity like energy. Conscious experience is then due to an interaction of conscious entities, personal conscious experience being centred on the individual. In some interpretations, such as monadism, Panpsychism and Idealism can overlap because the universe is conceived as being composed of an infinity of point consciousnesses that each contain information about the whole universe.
The form and content of personal conscious experience might be related to the structure of the world and brain in many ways.
This is a stub and needs expansion.
Seager W. & Allen-Hermanson (2001). ‘Panpsychism.’ Online document: Stanford Encyclopedia of Philosophy, [online], http://plato.stanford.edu/entries/panpsychism/, [accessed 10/2005]
- Chalmers, D.J. (1996). The Conscious Mind. Oxford University Press.
The problem of regression
- Ryle, G. (1949) The Concept of Mind. The University of Chicago Press, 1949.
The homunculus argument
- Gregory, R.L. (1990) Eye and Brain: The Psychology of Seeing, Oxford University Press Inc. New York.
- Gregory, T.L. (1987). The Oxford Companion to Mind. Oxford University Press.
- James, W. (1904)Does 'Consciousness' Exist? Journal of Philosophy, Psychology, and Scientific Methods, 1, 477-491.
- Hegel, G.W.F. PHILOSOPHY OF MIND: SECTION I. MIND SUBJECTIVE B. PHENOMENOLOGY OF MIND CONSCIOUSNESS Part Three of the Encyclopaedia of the Philosophical Sciences
- Velmans, M. (1996) Consciousness and the "Casual Paradox". Behavioral and Brain Sciences, 19 (3): 538-542.
- Bermudez, J.L. (1999) The Paradox of Self-Consciousness (representation and Mind) Psycoloquy: 10,#35
- Bierman, D.J. (2004) Non Conscious Processes Preceding Intuitive decisions http://m0134.fmg.uva.nl/~djb/publications/2004/Intuition_bialsymp2004.pdf
- Damasio, A.R. (1994). Descartes' error: Emotion, reason and the human brain. New York: Grosset/Putnam Book.
- Kant, I. Critique of Pure Reason http://www.arts.cuhk.edu.hk/Philosophy/Kant/cpr/
Phenomenal consciousness and access consciousness
Block, N. (1995) On a confusion about a function of consciousness. Behavioral and Brain Sciences 18 (2): 227-287. http://www.bbsonline.org/documents/a/00/00/04/31/bbs00000431-00/bbs.block.html
Block, N. (2004). The Encyclopedia of Cognitive Science. http://www.nyu.edu/gsas/dept/philo/faculty/block/papers/ecs.pdf
Dennett, D. (1978). Why You Can't Make a Computer that Feels Pain, in: Brainstorms. Cambridge, MA: MIT Press: 190-229.
Dennett, D. (1988). Quining Qualia. in A. Marcel and E. Bisiach, eds, Consciousness in Modern Science, Oxford University Press 1988. Reprinted in W. Lycan, ed., Mind and Cognition: A Reader, MIT Press, 1990, A. Goldman, ed. Readings in Philosophy and Cognitive Science, MIT Press, 1993. http://ase.tufts.edu/cogstud/papers/quinqual.htm
Edelman, G.M. (1993). Bright Air, Brilliant Fire: On the Matter of the Mind. New York:
Feyerabend, P. (1963). Mental Events and the Brain, Journal of Philosophy 40:295-6.
Huxley, T. H. (1874). On the Hypothesis that Animals are Automata, and its History, The Fortnightly Review, n.s.16:555-580. Reprinted in Method and Results: Essays by Thomas H. Huxley (New York: D. Appleton and Company, 1898).
Nagel, T. (1974). What is it like to be a bat? The Philosophical Review LXXXIII, 4 (October 1974): 435-50. http://web.archive.org/19990218140703/members.aol.com/NeoNoetics/Nagel_Bat.html
Rey, Georges, (1997). Contemporary Philosophy of Mind.Blackwell: Oxford
Sellars W. (1956). Empiricism and the Philosophy of Mind, In: Feigl H and Scriven M (eds) The Foundations of Science and the Concepts of Psychology and Psychoanalysis: Minnesota Studies in the Philosophy of Science, Vol. 1. Minneapolis: University of Minnesota Press: 253-329
Whitehead, A.N. (1920). The Concept of Nature. Chapter 3: Time. http://spartan.ac.brocku.ca/~lward/Whitehead/Whitehead_1920/White1_03.html
- Austin, J.L. (1962) Sense and Sensibilia, ed. by Geoffrey J. Warnock (Oxford, 1962)
- Aydede, M. (2001) Naturalism, introspection, and direct realism about pain. Consciousness and Emotion, Vol. 2, No. 1, 2001, pp. 29–73.
- Chapman, C.R., and Y. Nakamura (1999). A Passion of the Soul: An Introduction to Pain for Consciousness Researchers. Consciousness and Cognition, 8: 391-422.
- Dennett, D. (1991a). Consciousness Explained. Boston: Little, Brown
- Dennett, D. (1991b). Lovely and suspect qualities. Commentary on David Rosenthal, "The Independence of Consciousness and Sensory Quality" in E. Villanueva, ed., Consciousness, (SOFIA Conference, Buenos Aires), Atascadero, CA: Ridgeview 1991. http://ase.tufts.edu/cogstud/papers/lovely&s.htm
- Fowler C A (1986): “An event approach to the study of speech perception from a direct-realist perspective”, J of Phonetics 14(1):3-28.
- Gibson, J. J. (1966) The Senses Considered as Perceptual Systems. Houghton Mifflin Company,Boston.
- Gibson, J. J. (1979) Ecological Approach to Visual Perception.: Lawrence Erlbaum Associates Publishers, Hillsdate.
- Gregory, R.L. 1988. Consciousness in science and philosophy: conscience and con-science. Chapter 12 in Consciousness in Contemporary Science. (Editors: Marcel, A.J. and Bisiach, E.). Oxford Science Publications.
- Le Morvan, Pierre (2004). Arguments against direct realism and how to counter them. The American Philosophical Quarterly, 41(3), 221-234.] (pdf) http://www.tcnj.edu/~lemorvan/DR_web.pdf
- Michaels, C. F. and Carello, C. (1981). Direct Perception. Century Psychology Series. Prentice-Hall. ISBN 01312147912 Invalid ISBN. 1981. Download this book at http://ione.psy.uconn.edu/~psy254/MC.pdf
- Oliveira, André L. G. and Oliveira, Luis F. (2002) Toward an ecological conception of timbre. In Proceedings Auditory Perception Cognition and Action Meeting 2002, Kansas City. http://cogprints.org/2713/
- Skinner, B. F. Science and Human Behavior . New York: Macmillan, 1953.
- Skinner, B. F. 1971. Beyond Freedom and Dignity. New York: Knopf.
- Skinner, B. F. 1948. Walden Two. New York: Macmillan.
- Tye, M. (2004). ANOTHER LOOK AT REPRESENTATIONALISM ABOUT PAIN. Consciousness and Emotion 2004, special issue on pain, edited by Murat Aydede (with replies by M. Aydede, N. Block, B. Maund, and P. Noordhof http://sun.soci.niu.edu/~phildept/MT/RepresentationalismAndPain.pdf
- Vygotsky, L.S.(1925) Consciousness as a problem in the psychology of behavior. Undiscovered Vygotsky: Etudes on the pre-history of cultural-historical psychology (European Studies in the History of Science and Ideas. Vol. 8), pp. 251–281. Peter Lang Publishing. http://www.marxists.org/archive/vygotsky/works/1925/consciousness.htm
- Ziff, Paul. "About Behaviourism." Analysis 18 (1958): 132-136. Quoted by Larry Hauser in the Internet Encyclopedia of Philosophy. http://www.utm.edu/research/iep/b/behavior.htm#B. F. Skinner: Radical Behaviorism
- Moutoussis, K. and Zeki, S. (1997). A direct demonstration of perceptual asynchrony in vision. Proceedings of the Royal Society of London, Series B: Biological Sciences, 264, 393 - 399.
- Rizzo, M., Nawrot, M. & Zihl, J. (1995). Motion and shape perception in cerebral akinetopsia.Brain, 118. 1105-1127. http://nawrot.psych.ndsu.nodak.edu/Publications/Nawrot.pdf/RizzoNawrotZihl.1995.pdf
- Russell, B. (1912). Problems of Philosophy. Home University Library. http://www.ditext.com/russell/rus1.html
- Tye, M. (2003) Qualia. Stanford Encyclopedia of Philosophy. http://plato.stanford.edu/entries/qualia/#Repqualia
- Hume, D. (1739). A Treatise of Human Nature. http://www.class.uidaho.edu/mickelsen/ToC/hume%20treatise%20ToC.htm
- Firth, R. (1949) Sense Data and the Percept Theory, Mind, 58 (1949); 59 (1950). (Describes early reasons for rejecting Indirect Realism) http://www.ditext.com/firth/spt.html
- Grush, R. (2000). Self, world and space: The meaning and mechanisms of ego- and allocentric spatial representation. Brain and Mind 1(1):59-92.