Consciousness Studies/Nineteenth To Twenty First Century Philosophy
Nineteenth and twentieth century philosophy of consciousness
The nineteenth and twentieth centuries witnessed a confident use of nineteenth century scientific ideas amongst philosophers of mind and a few philosophers such as Whitehead were also coming to terms with modern science.
ER Clay deserves a mention in the catalogue of important nineteenth century philosophers of consciousness for the quotation from his work given in William James' classic text The Principles of Psychology:
The relation of experience to time has not been profoundly studied. Its objects are given as being of the present, but the part of time referred to by the datum is a very different thing from the conterminous of the past and future which philosophy denotes by the name Present. The present to which the datum refers is really a part of the past -- a recent past -- delusively given as being a time that intervenes between the past and the future. Let it be named the specious present, and let the past, that is given as being the past, be known as the obvious past. All the notes of a bar of a song seem to the listener to be contained in the present. All the changes of place of a meteor seem to the beholder to be contained in the present. At the instant of the termination of such series, no part of the time measured by them seems to be a past. Time, then, considered relatively to human apprehension, consists of four parts, viz., the obvious past, the specious present, the real present, and the future. Omitting the specious present, it consists of three . . . nonentities -- the past, which does not exist, the future, which does not exist, and their conterminous, the present; the faculty from which it proceeds lies to us in the fiction of the specious present.
Clay provides an eloquent description of the extended, or specious, present, mentioning both the way that consciousness seems to occupy a duration of time and the way that events within conscious experience have their own durations so that they snap out of existence when they end. This description in itself allows us to see how McTaggart's "A Series" might be constructed from the overlapping extended present's of events.
Clay's use of the pejorative term "specious" for the way that experience has a duration was necessary in the nineteenth century but now we know that it was the nineteenth century idea of physical time that was specious. A neutral term for experience laid out in time might be the "extended present".
Alfred North Whitehead
Many twentieth century philosophers have taken the nineteenth century idea of space and time as the framework within which their descriptions of experience are elaborated. Whitehead was a mathematician and philosopher who understood the limitations of this framework and pointed out that our failure to understand and overcome these limitations was probably at the root of our failure to understand consciousness. He traces the problem to the nineteenth century view of time and space and rails against materialists who elevate nineteenth century scientific doctrine above observational and scientific reality.
He also believed that mind and nature are part of the same phenomena:
What I am essentially protesting against is the bifurcation of nature into two systems of reality, which, in so far as they are real, are real in different senses. One reality would be the entities such as electrons which are the study of speculative physics. This would be the reality which is there for knowledge; although on this theory it is never known. For what is known is the other sort of reality, which is the byplay of the mind. Thus there would be two natures, one is the conjecture and the other is the dream. Another way of phrasing this theory which I am arguing against is to bifurcate nature into two divisions, (31) namely into the nature apprehended in awareness and the nature which is the cause of awareness. The nature which is the fact apprehended in awareness holds within it the greenness of the trees, the song of the birds, the warmth of the sun, the hardness of the chairs, and the feel of the velvet. The nature which is the cause of awareness is the conjectured system of molecules and electrons which so affects the mind as to produce the awareness of apparent nature. The meeting point of these two natures is the mind, the causal nature being influent and the apparent nature being effluent.
He argued that science is about the relations between things:
The understanding which is sought by science is an understanding of relations within nature.
Whitehead was aware of the way that the simultaneity of events is of crucial importance to phenomenal experience:
The general fact is the whole simultaneous occurrence of nature which is now for sense-awareness. This general fact is what I have called the discernible. But in future I will call it a 'duration,' meaning thereby a certain whole of nature which is limited only by the property of being a simultaneity. Further in obedience to the principle of comprising within nature the whole terminus of sense-awareness, simultaneity must not be conceived as an irrelevant mental concept imposed upon nature. Our sense-awareness posits for immediate discernment a certain whole, here called a 'duration'; thus a duration is a definite natural entity. A duration is discriminated as a complex of partial events, and the natural entities which are components of this complex are thereby said to be 'simultaneous with this duration.' Also in a derivative sense they are simultaneous with each other in respect to this duration. Thus simultaneity is a definite natural relation. The word' duration' is perhaps unfortunate in so far as it suggests a mere abstract stretch of time. This is not what I mean. A duration is a concrete slab of nature limited by simultaneity which is an essential factor disclosed in sense-awareness.
Whitehead also stresses the role of the extended, or 'specious', present in sense awareness:
It is important to distinguish simultaneity from instantaneousness. I lay no stress on the mere current usage of the two terms. There are two concepts which I want to distinguish, and one I call simultaneity and the other instantaneousness. I hope that the words are judiciously chosen; but it really does not matter so long as I succeed in explaining my meaning. Simultaneity is the property of a group of natural elements which in some sense are components of a duration. A duration can be all nature present as the immediate fact posited by sense-awareness. A duration retains within itself the passage of nature. There are within it antecedents and consequents which are also durations which may be the complete specious presents of quicker consciousnesses. In other words a duration retains temporal thickness. Any concept of all nature as immediately known is always a concept of some duration though it may be enlarged in its temporal thickness beyond the possible specious present of any being known to us as existing within nature. Thus simultaneity is an ultimate factor in nature, immediate for sense-awareness.
So a set of events that are extended in time constitutes conscious experience. He then defines continuity in terms of overlapping durations:
The continuity of nature arises from extension. Every event extends over other events, and every event is extended over by other events. Thus in the special case of durations which are now the only events directly under consideration, every duration is part of other durations; and every duration has other durations which are parts of it.
That experience exists as whole durations that overlap means that the overlapping durations can be considered to be composed of moments or instants and these can be assigned to a series which we call 'time':
Such an ordered series of moments is what we mean by time defined as a series. Each element of the series exhibits an instantaneous; state of nature, Evidently this serial time is the result of an intellectual process of (65) abstraction.
Processes can occur within a duration of sense awareness so things can change within the extended present of a conscious interval.
Sense-awareness and thought are themselves processes as well as their termini in nature.
So Whitehead's durations of sense awareness both contain processes and are phenomena in their own right. A movement can be both a succession of changes of position and a quality of motion over the whole duration that contains it.
One disturbing feature of his analysis is that he does not mention the way that durations are attached to events; Clay states that the extension in time of an event disappears when the event ceases.
Husserl has been influential in postmodern philosophy. He writes in a slightly obscure style that has been adopted by many European philosophers, an example of this almost post-modern style is given below:
The genuine intentional synthesis is discovered in the synthesis of several acts into one act, such that, in a unique manner of binding one meaning to another, there emerges not merely a whole, an amalgam whose parts are meanings, but rather a single meaning in which these meanings themselves are contained, but in a meaningful way. With this the problems of correlation, too, already announce themselves; and thus, in fact, this work contains the first, though of course very imperfect, beginnings of "phenomenology."" (Husserl 1937).
Husserl seems to be largely a Humean in the sense that he gives precedence to mental experience as the only thing that may be known directly and hence certainly. He regards the components of experience as part of consciousness, so the intention to move, the movement and the sensation of movement are bound or 'bracketed' together into a single meaning.
In my perceptual field I find myself holding sway as ego through my organs and generally through everything belonging to me as an ego in my ego-acts and faculties. However, though the objects of the life-world, if they are to show their very own being, necessarily show themselves as physical bodies, this does not mean that they show themselves only in this way; and [similarly] we, though we are related through the living body to all objects which exist for us, are not related to them solely as a living body. Thus if it is a question of objects in the perceptual field, we are perceptually also in the field; and the same is true, in modification, of every intuitive field, and even of every nonintuitive one, since we are obviously capable of "representing" to ourselves everything which is non-intuitively before us (though we are sometimes temporally limited in this). [Being related] "through the living body" clearly does not mean merely [being related] "as a physical body"; rather, the expression refers to the kinesthetic, to functioning as an ego in this peculiar way, primarily through seeing, hearing, etc.; and of course other modes of the ego belong to this (for example, lifting, carrying, pushing, and the like).
It should be noted that Husserl believes we perform acts of perception and that we should refrain from judgement about where the things in perception are located or their nature. This suspension of judgement is called epoche and derives from ancient Greek skepticism.
Husserl seems to share Locke's view that experience is extended in time. He is obscure about whether he believes consciousness itself is a process that initiates action. He uses a linguistic argument to justify the idea of consciousness as a form of action:
2. Whatever becomes accessible to us through reflection has a noteworthy universal character: that of being consciousness of something, of having something as an object of consciousness, or correlatively, to be aware of it we are speaking here of intentionality. This is the essential character of mental life in the full sense of the word, and is thus simply inseparable from it. It is, for example, inseparable from the perceiving that reflection reveals to us, that it is of this or that; just as the process of remembering is, in itself, remembering or recalling of this or that; just as thinking is thinking of this or that thought, fearing is of something, love is of something; and so on. We can also bring in here the language we use in speaking of appearing or having something appear."(Husserl 1928)
Intentionality is a process and Husserl seems to be suggesting that consciousness is a process:
5. The Purely Mental in Experience of the Self and of Community. The All-Embracing Description of Intentional Processes. (Husserl 1928)
then, not surprisingly, fails to find any processes within it and changes his view of consciousness to that of observation:
... But I <must> immediately add that the universality of the phenomenological epoche as practiced by the phenomenologist from the very beginning the universality in which he or she becomes the mere impartial observer of the totality of his conscious life-process brings about not only a thematic purification of the individual processes of consciousness and thereby discloses its noematic components; (Husserl 1928)
He calls the contents of perception the perceptual noema. Husserl seems to be aware of the problem of the extended present:
How can we account for the fact that a presently occurring experience in one's consciousness called "recollection" makes us conscious of a not-present event and indeed makes us aware of it as past? And how is it that in the "remembered" moment, that sense can be included in an evidential way with the sense: "have earlier perceived"? How are we to understand the fact that a perceptual, that is to say, bodily characterized present can at the same time contain a co-presence with the sense of a perceivability that goes beyond the <immediate> perceivedness? How are we to understand the fact that the actual perceptual present as a totality does not close out the world but rather always carries within itself the sense of an infinite plus ultra <more beyond>?"(Husserl 1928)
But is vague about whether mental time is a continuum or has three components of remembered past, present and some sort of intuition of the future. His rejection of the possibility of describing the mind through the spatio-temporal models of the physical sciences limits his interpretation of mental space and time.
Husserl, E. (1928) The Amsterdam Lectures. PSYCHOLOGICAL AND TRANSCENDENTAL PHENOMENOLOGY AND THE CONFRONTATION WITH HEIDEGGER (1927-1931). edited and translated by Thomas Sheehan and Richard E. Palmer. http://www.stanford.edu/dept/relstud/faculty/sheehan.bak/TSbookcontents.html
Husserl, E. (1937). The Crisis of European Sciences and Transcendental Phenomenology. An Introduction to Phenomenology. (The Crisis of European Sciences and Transcendental Phenomenology (1954) publ. Northwestern University Press, Evanston, 1970. Sections 22 - 25 and 57 - 68, 53 pages in all.) http://www.marxists.org/reference/subject/philosophy/works/ge/husserl.htm
Gilbert Ryle 1900-1976
Gilbert Ryle is famous for his "logical behaviourism". He was Waynflete Professor of metaphysical philosophy at Oxford and amongst his eminent students are Daniel C Dennett and David Armstrong. Dennett wrote the Introduction to the Penguin edition of "Concept of Mind".
The Concept of Mind. First published by Hutchinson 1949. Published by Penguin Classics, Penguin Books, Chippenham, England.
Ryle begins the Concept of Mind by proposing that there is an "official doctrine" of mind due to Descartes:
The official doctrine, which hails chiefly from Descartes, is something like this. With the doubtful exception of idiots and infants in arms every human being has both a body and a mind. Some would prefer to say that every human being is 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.
Human bodies are in space and are subject to the mechanical laws which govern all other bodies in space. ....
But minds are not in space, nor are their operations subject to mechanical laws. The workings of one mind are not witnessable by other observers; its career is private. Only I can take cognisance of the states and processes of my own mind.Chapter 1, p13.
Ryle considers that the "official doctrine" is absurd:
Such in outline is the official theory. I shall speak of it, with deliberate abusiveness, as 'dogma of the ghost in the machine'. Chapter 1, p17.
He considers that the "official theory" is due to a particular mistake that he calls a "category mistake":
I must first indicate what is meant by the phrase 'Category mistake'. This I do in a series of illustrations.
A foreigner visiting Oxford or Cambridge for the first time is shown a number of colleges, libraries, playing fields, museums,scientific departments and administrative offices. He then asks 'But where is the university? I have seen where the members of the Colleges live, where the Registrar works, where the scientists experiment and the rest. But I have not yet seen the university in which reside and work the members of your University.' It has then to be explained to him that the University is not another collateral institution, some ulterior counterpart to the colleges, laboratories and offices which he has seen. The university is just the way in which all that he has already seen is organized. ....
My destructive purpose is to show that a family of radical category mistakes is the origin of the double-life theory. The representation of a person as a ghost mysteriously ensconced in a machine derives from this argument. Because, as is true, a person's thinking, feeling and purposive doing cannot be described solely in the idioms of physics, chemistry and physiology, therefore they must be described in counterpart idioms. As the human body is a complex organised unit, so the human mind must be another complex organized unit, though one made of a different sort of stuff and with a different sort of structure. Or, again, as the human body, like any other parcel of matter, is a field of causes and effects, so the mind must be another field of causes and effects, though not (Heaven be praised) mechanical causes and effects. Chapter 1, p 19-20.
Note that Ryle is still ridiculing the "official theory" in his description of the category mistake given above. Ryle's style frequently makes it difficult to isolate his own proposals from the mockery of the proposals of his imagined rivals.
Ryle continues his attack on the "official doctrine" and considers that the ancient Greeks believed that the theorizing or intelligent part of the person was the mind:
...both philosophers and laymen tend to treat intellectual operations as the core of mental conduct; that is to say, they tend to define all other mental conduct-concepts in terms of concepts of cognition. They suppose that the primary exercise of minds consists in finding the answers to questions and that their other occupations are merely applications of considered truths or even regrettable distractions from their consideration. The Greek idea that immortality is reserved for the theorizing part of the soul was discredited, but not dispelled, by Christianity. Chapter 2. p27
He then attempts to dispel this "intellectualist legend":
The crucial objection to the intellectualist legend is this. The consideration of propositions is itself an operation the execution of which can be more of less intelligent, less or more stupid. But if, for any operation to be intelligently executed, a prior theoretical operation had first to be performed and performed intelligently, it would be a logical impossibility for anyone ever to break into the circle. Let us consider some salient points at which this regress would arise. According to the legend, whenever an agent does anything intelligently, his act is preceded and steered by another internal act of considering a regulative proposition appropriate to his practical problem. But what makes him consider the one maxim which is appropriate rather than any of the thousands which are not? Why does the hero not find himself calling to mind a cooking recipe, or a rule of Formal Logic? Perhaps he does but then his intellectual process is silly and not sensible. Intelligently reflecting how to act is, among other things, considering what is pertinent and disregarding what is inappropriate. Must we then say that for the hero's reflections how to act to be intelligent he must first reflect how best to reflect how to act? The endlessness of this implied regress shows that the application of the criteria of appropriateness does not entail the occurrence of a process of considering this criterion. Chapter 2, p31.
This is the famous "Ryle's Regress".
Ryle considers that when people use the term "in the mind" they actually mean "in their heads":
When people employ the idiom 'in the mind', they are usually expressing over-sophisticatedly what we ordinarily express by the less misleading metaphorical use of 'in the head'. Chapter 2. p 40.
Ryle is utterly against the concept of conscious emulation or simulation of the world:
The statement 'the mind is its own place', as theorists might construe it, is not true, for the mind is not even a metaphorical 'place'. On the contrary, the chessboard, the platform, the scholar's desk, the judge's bench, the lorry-driver's seat, the studio and the football field are among its places. These are where people work and play stupidly or intelligently. 'Mind' is not the name of another place where work is done or games are played; and it is not the name of another tool with which work is done, or another appliance with which games are played. Chapter 2, p50.
Ryle has an implicitly endurantist idea of time in which introspection can only occur as successions of events:
It would be admitted that only people with a special training ever speak of 'introspecting', but in such phrases as 'he caught himself wondering how to do so and so', or 'when I catch myself getting into a panic, I do such and such', the plain man is expressing at least part of what is meant by the word. Now supposing (which it is the negative object of this book to deny), that there did exist events of the postulated ghostly status, there would still be objections to the initially plausible assumption that there also exists a species of perception capable of having any of these events for its proprietory objects.For one thing, the occurrence of such an act of inner perception would require that the observer could attend to two things at the same time. He would, for example, be both resolving to get up early and concomitantly observing his act of resolving; attending to the program of rising betimes and perpetually attending to his attending to this program. Chapter 6, p157-158.
For Ryle things are known after the instant when they occur, he ignores any idea of the specious present:
If retrospection can give us the data we need for some states of mind, there is no reason why it should not do so for all. And this is just what seems to be suggested by the popular phrase 'to catch oneself doing so and so'. We catch, as we pursue and overtake, what is already running away from us. I catch myself daydreaming about a mountain walk after, perhaps very shortly after, I have begun the daydream; or I catch myself humming a particular air only when the first few notes have already been hummed. Retrospection, prompt or delayed, is a genuine process and one which is exempt from the troubles ensuing from the assumption of multiply divided attention; .. Chapter 6, p159.
The basis for much of Ryle's philosophy in Concept of Mind is Aristotle's regress which he interprets in an endurantist fashion as meaning that there can be no internal mind. He considers observing a robin and says:
If sensations are proper objects of observation, then observing them must carry with it the having of sensations of those sensations analogous to the glimpses of the robin without which I could not be watching the robin. And this is clearly absurd. There is nothing answering to the phrases 'a glimpse of a glimpse' or a 'whiff of a pain' or 'the sound of a tweak' or 'the tingle of a tingle', and if there ever was anything to correspond, the series would go on forever. Chapter 8, p197.
Indeed, Ryle's philosophy is entirely the consequences of the acceptance of Aristotle's regress as an absolute constraint, it being assumed that there is no further physical theory available to explain mind or behaviour.
Daniel Clement Dennett (1942 -)
Dennett is well known for his "Multiple Drafts Model" of consciousness. The Multiple Drafts Theory or Model of Consciousness is a theory of consciousness based upon the proposal that the brain acts as an information processor. The Theory is described in depth in the book Consciousness Explained, written by Dennett in 1991. It proposes a form of strong AI.
Dennett describes his theory (CE p117) as operationalist, as Dennett says: "There is no reality of conscious experience independent of the effects of various vehicles of content on subsequent action (and hence, of course, on memory)." (Not to be confused with 'instrumentalism').
Dennett's starting point in the development of the Multiple Drafts theory is a description of the phi illusion. In this experiment two different coloured lights, with an angular separation of a few degrees at the eye, are flashed in succession. If the interval between the flashes is less than a second or so the first light that is flashed appears to move across to the position of the second light. Furthermore the light seems to change colour as it moves across the visual field. A green light will appear to turn red as it seems to move across to the position of a red light. Dennett asks how we could see the light change colour before the second light is observed.
An example of the phi illusion in the format described by Dennett is shown here: phi illusion (use the 'test' option to select the simple phi demonstration).
Dennett explains the change of colour of the light in terms of either Orwellian or Stalinesque hypotheses. In the Orwellian hypothesis the subject develops a narrative about the movement of the lights after the event. In the Stalinesque hypothesis the subject's brain would have a delay in which the movement of the green light towards the red light could be modelled after the sensory information from the red light had been received. He then says that it does not matter which hypothesis applies because: "the Multiple Drafts model goes on to claim that the brain does not bother 'constructing' any representations that go to the trouble of 'filling in' the blanks. That would be a waste of time and (shall we say?) paint. The judgement is already in so we can get on with other tasks!"
It should be pointed out that fMRI studies by Larsen et al. 2006 have shown that the brain does indeed fill in the blanks during the phi illusion and Blankenburg et al. 2006 have shown that the brain fills in the blanks during the cutaneous rabbit illusion so Dennett's primary proposal is now known to be incorrect. The brain uses the Stalinesque paradigm - it models events during a delay.
According to the Multiple Drafts theory there are a variety of sensory inputs from a given event and also a variety of interpretations of these inputs. The sensory inputs arrive in the brain and are interpreted at different times so a given event can give rise to a succession of discriminations. As soon as each discrimination is accomplished it becomes available for eliciting a behaviour. A wide range of behaviours may occur ranging from reactions to the event such as running away to descriptions of the experience of the event etc.
At different times after the event a person is able to relate different stories of what happened depending upon the extent to which the event has been analysed. Dennett compares this with a 'Cartesian Theatre' model of consciousness in which events suddenly appear on some sort of mental screen and then disappear as quickly. He provides numerous examples to show that events are analysed over a period of time rather than instantaneously.
Although Multiple Drafts is described as a model or theory of consciousness that differs from other models, Dennett points out that even Descartes was aware that reactions to an event could occur over a period of time with reflexes occurring first and judgements later. What makes Multiple Drafts different is that Dennett, in different sections of Consciousness Explained, either denies that normal conscious experiences actually occur or describes these as emerging in some unspecified way from the sheer complexity of information processing in the brain. His emergentism is clear when he defends the Multiple Drafts Model from Searle's Chinese room argument by saying of the critics: They just can't imagine how understanding could be a property that emerges from lots of distributed quasi-understanding in a large system (CE p439).
As an example of an apparent denial of conscious experience Dennett denies that there is any internal experience of colour, instead he says that qualia in general are "mechanically accomplished dispositions to react". This view originates in Dennett's belief in the method of heterophenomenology in which narrative is thought to be the most crucial tool for investigating consciousness. However, Dennett does not actually deny conscious experience but he does deny internal conscious experience (see below).
The origin of this operationalist approach can be seen in Dennett's immediately earlier work. 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 infal libility) 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)
This identification of qualia with judgements rather than experience is the key to the Multiple Drafts Model, once accepted there is only a need to explain behaviour rather than personal experience itself.
The origin of this identification of qualia with judgements can be seen in Consciousness Explained p407-408. Dennett considers the experiences of someone looking at the world, and describes his idea of the relationship between conscious experience, mind and representation:
"It seemed to him, according to the text, as if his mind - his visual field - were filled with intricate details of gold-green buds and 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 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"
For Dennett minds have no "plenum", no space with objects in it, the plenum is things outside the mind. Dennett considers mind to be processes. In his imaginary dialogue with 'Otto' in Consciousness Explained Dennett has Otto say "Are you denying then that consciousness is a plenum?" to which he replies "Yes indeed. That's part of what I am denying. Consciousness is gappy and sparse, and doesn't contain half of what people think is there!". (CE p366). Unfortunately Dennett's assertion is difficult to understand because even half a plenum is a plenum, perhaps his remarks given above that 'conscious experience' has a plenum but 'mind' does not, explain his equivocation. This means that Dennett has moved conscious experience into the world outside the body. Unfortunately this still leaves the problem of how this world is turned into the view that we each enjoy (there are no images in the world other than those created by optical instruments such as the eye). Has Dennett shifted the problem of conscious experience from a problem of brain function into a problem of the physics of the world outside the body?
Dennett makes a sharp distinction between information in the world and information in the brain. The information in the world seems to be allowed to be a plenum that can enter conscious experience but ceases to be a plenum in the mind. In contrast, according to Dennett the information in the brain is a "logical space":
"So we do have a way of making sense of the idea of phenomenal space - as a logical space. This is a space into which or in which nothing is literally projected; its properties are simply constituted by the beliefs of the (heterophenomenological) subject."
Although how a "logical space" differs from a real space if it contains several things at an instant is not explained and how this "logical space" appears like phenomenal space at each instant is also not covered.
Dennett also attacks "Cartesian materialism" which he defines very precisely as the idea that there is a Cartesian theatre in the brain:
Lets call the idea of such a centered locus in the brain Cartesian materialism, since its the view you arrive at when you discard Descarte's dualism but fail to discard the imagery of a central (but material) Theater where "it all comes together". The pineal gland would be one candidate for such a Cartesian Theater, but there are others that have been suggested - the anterior cingulate, the reticular formation, various places in the frontal lobes. Cartesian materialism is the view that there is a crucial finish line or boundary somewhere in the brain, marking a place where the order of arrival equals the order of "presentation" in experience because what happens there is what you are conscious of."(CE p107)
It seems that Dennett is unaware of earlier uses of the term "Cartesian materialism" meaning the concept that the mind is in the brain and co-opts the term for his own use. In Consciousness Explained Dennett assumes a model of Cartesian Materialism where some entity is looking at a theatre of events. This is a dynamical interpretation of perception based on the idea that physical events are due to Whiteheadian materialism. As such it is unlike the “theatre” that Aristotle envisaged in his “self aware sense” which has a view but no homunculus to view it. Indeed Dennett(1999) eschews the geometrical physicalism of the last century of physics:
"A curious anachronism found in many but not all of these reactionaries is that to the extent that they hold out any hope at all of solution to the problem (or problems) of consciousness, they speculate that it will come not from biology or cognitive science, but from–of all things!–physics! ....... Not just philosophers and linguists have found this an attractive idea. Many physicists have themselves jumped on the bandwagon, following the lead of Roger Penrose, whose speculations about quantum fluctuations in the microtubules of neurons have attracted considerable attention and enthusiasm in spite of a host of problems. What all these views have in common is the idea that some revolutionary principle of physics could be a rival to the idea that consciousness is going to be explained in terms of “parts which work one upon another,” as in Leibniz’s mill."
(The section of this book on Leibniz shows that he could find nothing resembling human perception in his mill). Dennett(1998) describes consciousness as distributed in time and space: "Consciousness doesn't have to happen at an instant; it is much better to think of it as distributed in both space and time." but, unlike Descartes, Broad or Whitehead uses an early materialist conception of time and process to describe it.
Blankenburg, F., Ruff, C.C., Deichmann, R., Rees, G. and Driver, J. (2006) The cutaneous rabbit illusion affects human primary sensory cortex somatotopically, PLoS Biol 2006;4(3):e69.
Daniel C Dennett. (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
Dennett, D. C., 1998, The Myth of Double Transduction in S. R. Hameroff , A. W. Kaszniak, and A. C. Scott, eds., Toward a Science of Consciousness, II , Cambridge, MA: MIT Press/A Bradford Book, pp97–107.
Daniel C Dennett. (1991). Consciousness Explained. Little, Brown & Co. USA. Available as a Penguin Book.
Dennett, D. and Kinsbourne, M. (1992) Time and the Observer: the Where and When of Consciousness in the Brain. (1992) Behavioral and Brain Sciences, 15, 183-247, 1992. Reprinted in The Philosopher's Annual, Grim, Mar and Williams, eds., vol. XV-1992, 1994, pp. 23–68; Noel Sheehy and Tony Chapman, eds., Cognitive Science, Vol. I, Elgar, 1995, pp. 210–274.http://ase.tufts.edu/cogstud/papers/time&obs.htm
Dennett, D. (1999). "The Zombic Hunch: Extinction of an Intuition?", Royal Institute of Philosophy Millennial Lecture http://ase.tufts.edu/cogstud/papers/zombic.htm
Larsen, A., Madsen, K.H., Lund, T.E., and Bundesen, C. (2006). Images of Illusory Motion in Primary Visual Cortex. Journal of Cognitive Neuroscience. 2006;18:1174-1180.
Ned Block (1942- )
Two types of consciousness
According to Block, "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 feels that it is possible to have phenomenal consciousness and access consciousness independently of each other, but in general they do interact.
There is no generally agreed upon way of categorizing different types of consciousness. Block's distinction between phenomenal consciousness and access consciousness tries to distinguish between conscious states that either do or do not directly involve the control of thought and action.
Phenomenal consciousness. According to Block, phenomenal consciousness results from sensory experiences such as hearing, smelling, tasting, and having pains. Block groups together as phenomenal consciousness the experiences such as sensations, feelings, perceptions, thoughts, wants and emotions. Block excludes from phenomenal consciousness anything having to do with cognition, intentionality, or with "properties definable in a computer program".
Access consciousness. Access consciousness is available for use in reasoning and for direct conscious control of action and speech. For Block, the "reportability" of access consciousness is of great practical importance. Also, access consciousness must be "representational" because only representational content can figure in reasoning. Examples of access consciousness are thoughts, beliefs, and desires.
A potential source of confusion is that some phenomenal consciousness is also representational. The key distinction to keep in mind about representational content that Block would place in the access consciousness category is that the reason it is placed in the access consciousness category is because of its representational aspect. Elements of phenomenal consciousness are assigned to the phenomenal consciousness category because of their phenomenal content.
An immediate point of controversy for Block's attempt to divide consciousness into the subdivisions of phenomenal consciousness and access consciousness is that some people view the mind as resulting (in its entirety) from fundamentally computational processes. This computational view of mind implies that ALL of consciousness is "definable in a computer program", so Block's attempt to describe some consciousness as phenomenal consciousness cannot succeed in identifying a distinct category of conscious states. This viewpoint is highly contentious however, see The problem of machine and digital consciousness for a discussion
As mentioned above, Block feels that phenomenal consciousness and access consciousness normally interact, but it is possible to have access consciousness without phenomenal consciousness. In particular, Block believes that zombies are possible and a robot could exist that is "computationally identical to a person" while having no phenomenal consciousness. Similarly, Block feels that you can have an animal with phenomenal consciousness but no access consciousness.
Block shares Chalmers' belief that we can have conscious experiences that are not possible to produce by any type of computational algorithm and that the source of such experiences is "the hard problem" of consciousness. To functionalists Block's position with respect to consciousness is analogous to that of Vitalists who defined Life as being in a category distinct from all possible physical processes. To those who support phenomenal consciousness the functionalist viewpoint is like believing in a flat earth, flat earthers see the world through biblical cosmology and functionalists view it through nineteenth century science. Biologists refute Vitalism by describing the physical processes that account for Life. Cosmologists refute biblical cosmology by describing modern physics. In order to refute Block's claim about the distinction between phenomenal consciousness and access consciousness, it is up to biologists and artificial consciousness researchers to describe computational algorithms that account for consciousness. In order to refute functionalism philosophers and scientists draw attention to the fact that they are trying to explain an internal state of a conscious observer, something that cannot be explained in terms of the external behaviour of machines.
Why are some neurobiologists and computer scientists sure that Block's division of consciousness is wrong? What is the source of Block's certainty that there are non-computational forms of consciousness? One example of phenomenal consciousness discussed by Block is a loud noise that you do not consciously notice because you are paying attention to something else. Block is sure that you were aware of the noise (phenomenal consciousness) but just not "consciously aware" (access consciousness). Many scientists would say that in this case, you were not "consciously aware" of the noise, but it is almost certain that portions of your unconscious brain activity responded to the noise (you could electrically record activity in the primary auditory cortex that is clearly a response to action potentials arriving from the ears due to sound waves from the noise). This suggests that Block's controversial "non-computational" category of phenomenal consciousness includes brain activity that others would categorize as being unconscious, not conscious. Some unconscious brain activity can begin to contribute to consciousness when the focus of one's conscious awareness shifts. This suggests that some of what Block calls phenomenal consciousness is brain activity that can either take place outside of consciousness or as part of consciousness, depending on other things that might be going on in the brain at the same time. If so, we can ask why the consciously experienced version of this kind of brain activity is computational while the unconscious version is not. On the other hand many authors (Eddington, Broad, Penrose, McFadden, Zeh etc.) would point out that brain activity could be both computational and phenomenal.
Block stresses that he makes use of introspection to distinguish between phenomenal consciousness and access consciousness. Presumably this means that when the loud noise was not noticed, it was not accessed by introspection. Block has thus defined a category of consciousness that is outside of our "conscious awareness" (although he says we are "aware" of it in some other way) and not accessed by introspection. Maybe it is this inaccessibility of some cases of phenomenal consciousness that motivate Block's idea that such forms of consciousness cannot be computational. When experiences are accessible to introspection and available for inclusion in reasoning processes, we can begin to imagine computational algorithms for the generation of the content of those experience. However, it is difficult to imagine how the content could become the same as the form of our experience.
Forms of phenomenal consciousness that are open to introspection
In his 1995 article, Block went on to discuss the more interesting cases such as if upon starting to "pay attention to" the loud noise (see above) that was previously ignored, the experiencer noticed that there had been some earlier experience of the noise, just not of the type that we "pay attention to"; a type of experience that had been just "on the edge" of access consciousness.
In Ned Block's entry for "Consciousness" in the 2004 Oxford Companion to the Mind, he discusses another example that he feels distinguishes between phenomenal consciousness and access consciousness.
- "Liss presented subjects with 4 letters in two circumstances,
- long, e.g. 40 msec, followed by a “mask” known to make stimuli hard to identify
- short, e.g. 9 msec, without a mask.
- Subjects could identify 3 of the 4 letters on average in the short case but said they were weak and fuzzy. In the long case, they could identify only one letter, but said they could see them all and that the letters were sharper, brighter and higher in contrast. This experiment suggests a double dissociation: the short stimuli were phenomenally poor but perceptually and conceptually OK, whereas the long stimuli were phenomenally sharp but perceptually or conceptually poor, as reflected in the low reportability."
This experiment demonstrates a distinction between
- i) reportability of names of the letters
- ii) perceptual sharpness of the image.
Block's definitions of these two types of consciousness leads us to the conclusion that a non-computational process can present us with phenomenal consciousness of the forms of the letters, while we can imagine an additional computational algorithm for extracting the names of the letters from their form (this is why computer programs can perform character recognition). The ability of a computer to perform character recognition does not imply that it has phenomenal consciousness or that it need share our ability to be consciously aware of the forms of letters that it can algorithmically match to their names.
If Block's distinction between phenomenal consciousness and access consciousness is correct, then it has important implications for attempts by neuroscientists to identify the neural correlates of consciousness and for attempts by computer scientists to produce artificial consciousness in man-made devices such as robots. In particular, Block seems to suggest that non-computational mechanisms for producing the subjective experiences of phenomenal consciousness must be found in order to account for the richness of human consciousness or for there to be a way to rationally endow man-made machines with a similarly rich scope of personal experiences of "what it is like to be in conscious states". Other philosophers of consciousness such as John Searle have similarly suggested that there is something fundamental about subjective experience that cannot be captured by conventional computer programs. This has led to proposals by physicists such as Penrose, Stapp, McFadden etc. for non-digital versions of machines with artificial consciousness.
Many advocates of the idea that there is a fundamentally computational basis of mind feel that the phenomenal aspects of consciousness do not lie outside of the bounds of what can be accomplished by computation. Some of the conflict over the importance of the distinction between phenomenal consciousness and access consciousness centers on just what is meant by terms such as "computation", "program" and "algorithm". In practical terms, how can we know if it is within the power of "computation", "program" or "algorithm" to produce human-like consciousness? There is a problem of verification; can we ever really know if we have a correct biological account of the mechanistic basis of conscious experience and how can we ever know if a robot has phenomenal consciousness? Although of course, such misgivings apply both to those who believe that digital consciousness is possible and those who disagree.
Block's justification of access and phenomenal consciousness uses a nineteenth century idea of the world so cannot be easily sustained against attack from functionalists and eliminativists. However he has clearly described a persistent division in the science and philosophy of consciousness that dates from the time of Aristotle. Aristotle considers this division in terms of those who consider that the soul originates movement and those who consider it to be cognitive, Descartes has the res cogitans and res extensa, Kant has the noumenal and phenomenal, Whitehead has the apparent and causative etc. and even Dennett has the reflex and emergent.
- ^ Block, N. (1995). ON A CONFUSION ABOUT A FUNCTION OF CONSCIOUSNESS. Behavioral and Brain Sciences 18 (2): 227-287.
- ^ Block, N. (2004). "Consciousness" (in R. Gregory (ed.) Oxford Companion to the Mind, second edition 2004).
- ^ Liss, P., (1968). “Does backward masking by visual noise stop stimulus processing?” Perception & Psychophysics 4, 328-330.
- ^ For a short account, see the Wikipedia entry for phenomenal and access consciousness. Charles Siewert provides a more detailed analysis in his article "Consciousness and Intentionality" in The Stanford Encyclopedia of the Philosophy of Mind.
- ^ "What is it like to be a bat?" by Thomas Nagel in The Philosophical Review LXXXIII, 4 (1974): 435-50.
- ^ On Certainty by Ludwig Wittgenstein. Publisher: Harper Perennial (1972) ISBN 0061316865.
- ^ Güven Güzeldere described such intuition about the distinctions between phenomenal consciousness and access consciousness as segregationist intuition. See "The many faces of consciousness: a field guide" in THE NATURE OF CONSCIOUSNESS; PHILOSOPHICAL DEBATES Publisher: The MIT Press (1997) ISBN 0262522101.
Francis Crick (1916 - 2004)
Francis Crick (1994) The Astonishing Hypothesis. The Scientific Search for the Soul. Simon & Schuster Ltd. London.
Crick begins this book with a statement about his opinion of the insignificance of human beings:
"The Astonishing Hypothesis is that "You", your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behaviour of a vast assembly of nerve cells and their associated molecules. As Lewis Carroll's Alice might have phrased it: "you're nothing but a pack of neurons". This hypothesis is so alien to the ideas of most people alive today that it can truly be called astonishing."
Crick is not a philosopher so might be forgiven the derogatory "no more than..", as a scientist he realises that the assembly of nerve cells that form a brain is highly complex and difficult to understand.
He suggests that the hypothesis is "so surprising" for three reasons:
"The first is that many people are reluctant to accept what is often called the "reductionist approach" - that a complex system can be explained by the behaviour of its parts and their interactions with each other."
"The second reason why the Astonishing Hypothesis seems so strange is the nature of consciousness. We have, for example, a vivid internal picture of the external world. It might seem a category mistake to believe this is merely another way of talking about the behavior of neurons, but we have just seen that arguments of this type are not always to be trusted."
"The third reason why the Astonishing Hypothesis seems strange springs from our undeniable feeling that Free Will is free. ... I believe that if we solve the problem of awareness (or consciousness), the explanation of Free Will is likely to be easier to solve."
Crick believes that many phenomena in the brain are "emergent" with the vague implication that consciousness may also be emergent. He defines this term in the following way:
"The scientific meaning of emergent, or at least the one I use, assumes that, while the whole may not be the simple sum of the separate parts, its behavior can, at least in principle, be understood from the nature and behavior of its parts plus the knowledge of how all these parts interact."
He wants to avoid the philosophical debates about the nature of consciousness:
"1. Everyone has a rough idea of what is meant by consciousness. It is better to avoid a precise definition of consciousness because of the dangers of premature definition.
"Footnote: If this seems like cheating, try defining for me the word gene. So much is now known about genes that any simple definition is likely to be inadequate. How much more difficult, then, to define a biological term when rather little is known about it."
This is an odd standpoint because any brief review of the ideas of philosophers shows that a good deal is known about phenomenal consciousness. The problem lies in explaining such a bizarre experience, not in defining it.
He then elaborates a further four points covering general features of consciousness and avoiding various types of speculation about consciousness. Excluded are: "what consciousness is for", speculations about consciousness in lower animals and the "self-referential aspect of consciousness"; included are the concept of consciousness in "higher mammals".
As a guide for the scientific investigation of consciousness he puts forward three basic ideas:
""1. Not all the operations of the brain correspond to consciousness.
"2. Consciousness involves some form of memory, probably a very short term one.
"3. Consciousness is closely associated with attention."
The operations of the brain that do correspond to consciousness are the "neural correlates of consciousness" a term that probably predates Crick's work. Crick shows the openness of ideal science when he concludes with:
"The Astonishing Hypothesis may be proved correct. Alternatively some view closer to the religious one may become more plausible. There is always a third possibility: that the facts support a new, alternative way of looking at the mind-brain problem that is significantly different from the rather crude materialistic view many neuroscientists hold today and also from the religious point of view."
David J Chalmers
Review of "The Conscious Mind: In Search of a Fundamental Theory". Oxford University Press. 1996.
Chalmers is perhaps most famous for the "hard problem" of consciousness:
"... I find myself absorbed in an orange sensation, and something is going on. There is something that needs explaining, even after we have explained the process of discrimination: there is the experience."p xii
...."This might be seen as a Great Divide in the study of consciousness. If you hold that an answer to the "easy" problems explains everything that needs to be explained, then you get one sort of theory; if you hold that there is a further "hard" problem then you get another."p xiii
Chalmers describes mind as having "phenomenal" and "psychological" aspects.
"At the root of all this lie two quite distinct concepts of mind. The first is the phenomenal concept of mind. This is the concept of mind as conscious experience, and of a mental state as a consciously experienced mental state. ... The second is the psychological concept of mind. This is the concept of mind as the causal or explanatory basis for behaviour." p11
Chalmers proposes that consciousness can be explained by a form of "Naturalistic Dualism" that is supported by the following argument:
"In particular, the failure of logical supervenience directly implies that materialism is false: there are features of the world over and above the physical features. The basic argument for this goes as follows:
- In our world there are conscious experiences.
- There is a logically possible world physically identical to ours, in which the positive facts about consciousness in our world do not hold.
- Therefore facts about consciousness are further facts about our world, over and above the physical facts.
- So materialism is false."
Chalmers describes his naturalistic dualism:
"The dualism implied here is instead a kind of property dualism: conscious experience involves properties of an individual that are not entailed by the physical properties of that individual. Consciousness is a feature of the world over and above the physical features of the world. This is not to say that it is a separate "substance"; the issue of what it would take to constitute a dualism of substances seems quite unclear to me. All we know is that there are properties of individuals in this world - the phenomenal properties - that are ontologically independent of physical properties." p125
To substantiate his argument he proposes that "zombie" worlds, in which people would behave like us but not be conscious, are logically possible and that worlds that are physically identical to ours, but where conscious experiences are inverted, are logically possible.
Chalmers' argument about the possibility of zombies runs as follows:
A zombie is defined as "...someone or something physically identical to me (or to any other conscious being), but lacking conscious experiences altogether". Chalmers considers that silicon based devices or an entity based on the population of china could lack conscious experience although being able to perform the same functions as a person. He then makes a logical leap to suggest that these examples show that something physically identical to a conscious person could not be conscious:
"But given that it is conceptually coherent that the group-mind set-up or my silicon isomorph could lack conscious experience, it follows that my zombie twin is an equally coherent possibility."p97
In the inverted spectrum argument Chalmers argues that it is logically possible to imagine a world that is physically identical to ours yet where conscious beings experience an inverted spectrum. This assertion is defended on the basis of the elementary science of colour vision.
Unfortunately, without any definite proposal for how conscious experience is realised it seems premature to declare that the zombie and inverted spectrum arguments are correct. Chalmers approaches the problem of the realization of conscious experience when discussing "information".
Chalmers is aware that phenomenal consciousness includes information that is related to information in the physical world:
"A conscious experience is a realization of an information state; a phenomenal judgement is explained by another realization of the same information state. And in a sense, postulating a phenomenal aspect of information is all we need to do to make sure those judgements are truly correct; there really is a qualitative aspect to this information, showing up directly in phenomenology and not just a system of judgements."p 292
Unfortunately he does not explain what a phenomenal "realization of an information state" means. This leads him to consider any information state as potentially capable of conscious experience. He notes that "We find information everywhere, not just in systems that we standardly take to be conscious." and asks whether a thermostat could be conscious. He poses the question "As we move along the scale from fish and slugs through simple neural networks all the way to thermostats, where should consciousness wink out?".
He answers the objection that there may not be any room for consciousness in a thermostat by saying that "If consciousness is not logically supervenient, we should not expect to have to find "room" for consciousness in a system's organization; consciousness is quite distinct from the processing properties of the system". He concludes the thermostat article by declaring that:
"While it could be the case that experience winks in at a particular point, any specific point seems arbitrary, so a theory that avoids having to make this decision gains a certain simplicity."
This set of ideas leads to the possibility of panpsychism:
"If there is experience associated with thermostats, there is probably experience everywhere: wherever there is a causal interaction, there is information, and wherever there is information there is experience." p297
However, Chalmers states that:
"Personally, I am much more confident of naturalistic dualism than I am of panpsychism. The latter issue seems to be very much open. But I hope to have said enough to show that we ought to take the possibility of some sort of panpsychism seriously..." p299
He then postulates that "Phenomenal properties have an intrinsic nature, one that is not exhausted by their location in an information space, and it seems that a purely informational view of the world leaves no room for these intrinsic qualities.". This leads him to suggest that the world is more than just information, that we "need some intrinsic nature in the world, to ground information states". This leads him to propose that:
"So the suggestion is that the information spaces required by physics are themselves grounded in phenomenal and protophenomenal properties. Each instantiation of such an information space is in fact a phenomenal (or protophenomenal) realization. Every time a feature such as mass and charge is realized, there is an intrinsic property, or microphenomenal property for short. We will have a set of basic microphenomenal spaces, one for each fundamental physical property, and it is these spaces that will ground the information spaces that physics requires." p305
So Chalmers takes the proposal of panpsychism, based on the idea that all information spaces might be conscious, to "ground" the information space. Again, any description of how phenomenal consciousness is actually realized in an information space is missing.
Chalmers' explanation of information seems to mystify it, in physics information is arrangements of things, in maths or digital transmission it is usually arrangements of the same thing. For instance 11011 is an arrangement of ones and zeroes along a line - the information has not replaced reality it is simply a way of using reality to represent something else. As Zurek put it: "there is no information without representation". Hence it is difficult to see why microphenomena should be required to instantiate information when the information is already instantiated.
The concept of information as something that can be transmitted from place to place and also as a property of a substance is at the heart of Chalmer's analysis. He states that:
"We have no way to peek inside a dog's brain, for instance, and observe the presence or absence of conscious experience. The status of this problem is controversial, but the mere prima facie existence of the problem is sufficient to defeat an epistemological argument, parallel to those above, for the logical supervenience of consciousness. By contrast there is not even a prima facie problem of other biologies, or other economies. Those facts are straightforwardly publically accessible, precisely because they are fixed by the physical facts." p74
The patterns of things that comprise "biologies" are, according to this, "physical facts". But from the argument about panpsychism above, physical facts are not grounded, they are information that must be instantiated in some way through "microphenomenal" properties. Chalmers seems to be arguing that nothing logically supervenes on the physical because nothing logically supervenes on mind and physical things are mind.
He introduces the idea of organizational invariance as the key feature of a conscious system and declares that a set of beer cans could be conscious:
"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
If two systems have entirely the same fine grained form and function as each other are they not identical systems? Although Chalmer's arguments stress function is it the sleight of hand of arguing for fine grained equivalence of form that makes the argument difficult to gainsay? Is a statement of identity an explanation?
Thomas Nagel is one of the leading defenders of the concept of phenomenal consciousness, in his article What it is like to be a bat he wrote:
"..fundamentally an organism has conscious mental states if and only if there is something that it is to be that organism—something it is like for the organism."
In particular Nagel points out that there are likely to be states within a bat that cannot be imagined by humans:
"But bat sonar, though clearly a form of perception, is not similar in its operation to any sense that we possess, and there is no reason to suppose that it is subjectively like anything we can experience or imagine. This appears to create difficulties for the notion of what it is like to be a bat. We must consider whether any method will permit us to extrapolate to the inner life of the bat from our own case,5 and if not, what alternative methods there may be for understanding the notion."
He considers that reductionism leaves out something essential in our understanding:
"Most of the neobehaviorism of recent philosophical psychology results from the effort to substitute an objective concept of mind for the real thing, in order to have nothing left over which cannot be reduced. If we acknowledge that a physical theory of mind must account for the subjective character of experience, we must admit that no presently available conception gives us a clue how this could be done. The problem is unique. If mental processes are indeed physical processes, then there is something it is like, intrinsically, to undergo certain physical processes. What it is for such a thing to be the case remains a mystery."