Journal of Consciousness Studies
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Faster than Thought

Holism, Homogeneity and Temporal Coding

Thomas Metzinger, Fachbereich 5.1 Philosophie, Universitat des Saarlandes, Postfach 151150, 66041 Saarbrucken, FRG <T.METZINGER@RZ.UNI-SB.DE>



In this speculative paper I would like to show how important the integration of mental content is for a theory of phenomenal consciousness. I will draw the reader's attention to two manifestations of this problem which already play a role in the empirical sciences concerned with consciousness: The binding problem and the superposition problem. In doing so I hope to be able to leave the well-trodden paths of the debate over consciousness. My main concern is to gain a fresh access to the familiar theoretical difficulties associated with the concept of 'consciousness'.

My discussion has three parts. The first part is an attempt to define the explananda with which I am concerned. This will be done by adopting the style of a deliberately naive phenomenological descent and examining two interesting properties of the phenomenon of consciousness 'itself', from the first-person stance. The second part shifts back to a third-person perspective and considers a promising approach in neurobiology. This approach could point towards a naturalistic account of these properties of the phenomenon in the realm of empirical research into consciousness. In the third and concluding section I rise step by step towards the genuinely philosophical level of the discussion in the style of a speculative semantic ascent. In doing so I will make several assumptions concerning the genesis of phenomenal consciousness. These assumptions will serve as a testing ground for a new model: I will offer some ideas about how models originating in brain research might be helpful in developing a clearer conceptual analysis of the explananda. As a first step, I will now attempt to isolate these explananda.

I. Holism and Homogeneity: Higher-Order Phenomenal Properties

The space of consciousness is the space of subjective experience. Since this is the space in which the world and we ourselves appear to ourselves on an experiential level, I will also call it the phenomenal space. Many people believe that our phenomenal space is also a representational space: In this space we represent a part of the world and of ourselves to ourselves. The phenomenal representata, i.e. the vehicles of representation bearing subjective content, I will henceforth call 'mental models', without trying to explicate this concept further at this point.[1] Our conscious space - this is the basic idea - consists of mental models which are often embedded in each other. The largest of the mental models active in this space is our conscious 'model of reality' or 'model of the world'. This phenomenal model of the world contains all the other conscious mental models and its content is identical with the overall content of our conscious space. As I mentioned above, our conscious space is the space of experience. But since we are beings who almost constantly fail to recognize our mental models as models,[2] our phenomenal space is characterized by an all-embracing naive realism, which we are incapable of transcending in standard situations. In this way, the totality of mental contents which fill this space form a structure that can be described from the external perspective of science as a self-referentially opaque phenomenal model of the world. From the internal perspective of the system activating this model, however, this structure is quite simply subjectively experienced reality: the only reality existing for this system. One of the main challenges for any naturalistic theory of mind is that of providing us with a clear account of this transition: How does a model become this reality?

What we really need is a mathematical model describing the phenomenal ontology of the human brain - i.e. that which exists according to conscious experience - in a precise and empirically plausible manner. Philosophical analysis can then, for instance, explain the relation of the phenomenal properties described by this model to folk psychology and investigate the modality of the relation between the phenomenal properties thus described and the physical properties upon which they are based.[3] My aim in this paper, however, is much more modest. I shall concentrate on two particularly interesting phenomenal properties. Our phenomenal space and the respective phenomenal model of reality active within it possess two properties which I believe to be of crucial importance for any theory of consciousness which takes the first-person perspective seriously. In the style of an uncritical phenomenological turn 'towards the things themselves', I shall first describe both these properties from the first-person perspective as properties of reality itself, pretending that we have direct and epistemologically unproblematic access to these properties through the evidence of subjective perception and the traditional descriptive systems of folk psychology. My statements, however, refer exclusively to human beings in ordinary waking states: The intended class of systems is formed by human organisms in 'non-pathological waking states'.[4] Thus I will steer clear of any fundamental discussion of the question of what the philosophical problem of consciousness consists in at all - rather, I shall now finally shift to the first-person perspective and confine myself to the following two aspects of the problem.

I am one person living in one world: For the majority of us this seems to be an obvious and indubitable truth, since for most of us this is one of those intuitions concerning our own consciousness and reality in general, which we almost never state explicitly or even less call into doubt. The reason for this is that most of us can hardly imagine any alternative situations. We have never experienced phenomenal states in which we were many different persons at the same time or in which we simultaneously existed in different parallel worlds. Only professional philosophers or patients with severe neurological disorders, people who have experimented with major doses of hallucinogens or those suffering from multiple personality disorder are sometimes capable of developing a more vivid idea of what it would be like, if the numerical identity of the phenomenal world or the unity of self-consciousness were suspended. In standard situations we are simply unable to carry out the corresponding mental simulations.[5] For this reason our phenomenal world and the phenomenal self do not only appear as numerically identical to us, but even appear as indivisible - a fact which was already exploited by Descartes in section 36 of his Sixth Meditation in order to construct an - albeit unconvincing - argument for the ontological distinction of mind and body. I think that there is a highest-order phenomenal property corresponding to this classical concept of 'indivisibility':[6] The property of wholeness. The wholeness of our reality (and of ourselves in it) can easily be discovered by all of us from our own experience. This wholeness is much more than a simple unity in the sense of the concept of numerical identity mentioned above: I am not able voluntarily to split or dissolve my global experiential space - this reality - or my own experienced identity - myself. On the other hand, the contents of my experience characteristically display a high selectivity: The surrounding world, which in conscious perception seems to be immediately given, is always presegmented, for example into a variety of objects which may even overlap with or cover each other. By directing my attention to a wide variety of areas of my world I am even able to detach the most different figures from a background and then perceive or imagine them as separate units in subjective experience. That is, although I am not able to dissolve the highest-order wholeness of reality or of myself simply by a reversible act of will, I am perfectly able to perceive or even actively generate lower-order phenomenal wholes within the space which is held together by this highest-order property.

Perhaps this holistic character of reality, which is stronger than mere numerical identity and which cannot be transcended experientially, could be described as phenomenal coherence: Our conscious experience of reality is held together internally by a principle or a mechanism, which itself is subjectively inaccessible. This coherence of my reality has nothing to do with the concept of coherence in physics or logic. Rather, it is responsible for a succinct phenomenal holism, which we ought to take into account on the conceptual level. Although a world made out of discrete, building block-like elements could well be a unity, it could never be a whole. But my world is not a toy world composed of little building blocks: it is also a living reality whose parts interact in a quasi-organic way (in the sense of the German concept Erleben). This concretely experienced unity of a diversity is accompanied by a multitude of dynamic part/whole relations. Thus, the additional phenomenological aspect of holism or wholeness which goes beyond mere unity results from the fact that the parts constituting the phenomenal model of reality are not elements, but parts of this reality. For this reason, if we want to understand the holistic character of our phenomenal world, we will have to take its multi-levelled mereological structure as the starting point of our investigation.

Another aspect is important in order to understand what else can be meant by 'wholeness'. Although this aspect is not at the centre of my discussion, we will repeatedly encounter it whenever we ask ourselves how a model can turn into a reality which is phenomenally present.[7] This second aspect consists in the fact that the experiential contents appearing in our conscious space are joined together into a holistic entity of the highest order, something we might call a global Gestalt, by spatial neighbouring relations and especially by temporal identity within an experienced present, i.e. by subjective simultaneity, by being given within a single psychological moment. This global Gestalt quality is necessary for the whole to become a reality: The whole is always given to us in a single psychological moment, that is to say in the experienced present of a subjective Now. The phenomenal presence of the whole springs from this 'now', i.e. from the temporal identity of a diversity of experiential contents. What does this mean? It means that the holistic diversity of phenomenal contents becomes a coherent reality because there is an elementary 'window of presence'. One thing cannot be doubted from the first-person perspective: I always experience the wholeness of reality now. This yields a first phenomenological concept of conscious experience: Conscious experience is the phenomenal presence of an all-embracing whole.

At this stage I would like to introduce a concept to which I will later return: subjectively experienced reality is a 'phenomenal Holon', an experientially present whole in the sense defined above. It always emerges in the context of a subjective present and is internally characterized by part/whole relationships. We are thus dealing with a variant of the classical philosophical question concerning the unity of consciousness: What, from an external theoretical perspective, appears as the issue of the unity and indivisibility of consciousness, turns out to be 'the wholeness and presence of reality' under a simple phenomenological description. In this version, the problem of the unity of consciousness consists in offering a conceptually convincing analysis of the fact that from the perspective of the first person, this reality is a phenomenal Holon. This fact is my first explanandum.

My second explanandum is the homogeneity of elementary phenomenal properties. We are now moving from the highest to the lowest level: We are no longer concerned with a higher-order phenomenal property of the overall space of consciousness, but with a higher-order phenomenal property of the smallest constitutive parts of this space. I am, of course, alluding to qualia. Simple sensations of sensory consciousness instantiate first-order phenomenal properties: for example the subjectively experienced quality of turquoise in the visual experience of a tropical lagoon, or the olfactory quality of sandalwood in a conscious experience of smell. Such qualities themselves possess a fascinating, but philosophically problematic higher-order property, because they are homogeneous. This theoretical problem also has its - albeit younger - precursor in the form of the grain problem. [8] Let us look back to the classical example of Wilfrid Sellars, the pink ice cube:

For Sellars, the essential question of the grain problem was whether it could, in principle, be possible within the conceptual framework of neurophysiology to define states which in their intrinsic character show a sufficient similarity to sensations. Only states of this kind, Sellars thought, could render a reductive solution of the mind-body problem (in the sense of early identity theory) plausible.

Returning to the first-person perspective, 1 would like to illustrate the subjectively non-transcendable homogeneity of phenomenal qualities by using an example from the art world. Like Sellars' argument, the example dates from the beginning of the second half of this century. In the Fifties, the artist Yves Klein studied the power of pure colour more intensely than anyone else. His monochrome blue paintings are famous and have in subsequent years exerted a strong influence on the international avant-garde movement. In his crusade for the spiritual power of pure colouredness, Yves Klein even tried to turn his favourite colour - ultramarine - into his own identity and his official trade-mark. He went so far as to have the pure ultramarine blue which he developed patented under the name of International Klein Blue (I.K.B.) on 19 May 1960.[9] Indeed, he himself soon became known under the name Yves Klein le monochrome.

When one looks at one of his monochromes and disregards the grainy texture of the surface, one experiences a pure and simple quality, namely a pure and intense ultramarine. In the general introduction to this volume, I used the Pantone Blue 72 of the cover as a first example of a phenomenal property. International Klein Blue belongs to the same phenomenal type, but it possesses considerably more subjective power and depth. This subjective quality of colouredness is once more homogeneous in the sense indicated by Sellars. For Yves Klein, the fascination of this homogeneity lay in the subjective aspects of presence, immateriality and the intensive concretization of a dimensionless spatiality.[10] For philosophers, however, the homogeneity of phenomenal properties is so particularly fascinating because it generates conceptual predicates which may defy definition. Can a colour predicate like International Klein Blue have a successor predicate within the scientific world view, for instance in a scientific theory of phenomenal consciousness, or is International Klein Blue a primitive predicate? For Sellars a 'primitive' predicate refers to properties which are ascribed to things that are made up exclusively of things which in turn possess this property. For some non-dualistic philosophers this would mean that single molecules of Rhodopas, vinylchloride, ethyl alcohol, ethyl acetate (out of which the substance I.K.B. is made) themselves possess the colour of International Klein Blue. Other non-dualistic philosophers would see themselves driven to the conclusion that a certain number of the nerve cells firing in our visual cortex while we are looking at one of Yves Klein's monochrome pictures, are in fact International Klein Blue. Of course this assumption is absurd in both cases.

A solution to this problem - a naturalization of my second explanandum - seems to be of central importance for any theory of sensory consciousness. The problem can be conceptually generalized in different ways, for instance - as Sellars thought - by moving from the homogeneity of monochrome colours to the more abstract property of colouredness in general. The homogeneity of elementary sensations, however - as they can be given to us as International Klein Blue, the tone of a cello or the smell of sandalwood - is a pre-reflexive and to a large extent non-discursive characteristic of our subjective experience: The homogeneity of phenomenal properties seems to be impenetrable to cognitive operations and, for this reason, it is very hard to express adequately on a verbal level. What Sellars called ultimate homogeneity seems to be a paradigmatic example of the ineffability of the subjective quality of experience. For this reason, I will try to offer a metaphorical description of the property in question by borrowing from physics and mathematics.

What does it mean to say that International Klein Blue is homogeneous? The primary phenomenal property is characterized by a kind of 'field quality', generating a subjective continuum in a certain subregion of our conscious space.[11] If, for instance, we visually experience objects which possess the property of International Klein Blue, the following statement seems to be always true: There is always a finite region within phenomenal space, in which no changes take place with regard to the quality in question.[12] I believe that it is precisely for this reason that we experience subjective qualities as immediately given. Let us now turn to the second metaphor. Perhaps it is also possible to refer to this property of phenomenal properties as their subjective 'density': It seems as if, for any two points (no matter how close they are to one another) within the respective region of my experiential space, there always exists a third point which lies between them. The mathematical analogy of this flowing density is the continuum of real numbers. At least intuitively it remains utterly obscure how this density of phenomenal properties could be open to a mechanistic strategy of explanation, i.e. how we could analyse them as the results of myriads of causally intertwined singular events on the neural level. It is, I maintain, exactly for this reason that subjective qualities such as International Klein Blue appear as intrinsic and non-relational:[13] If they were really identical with a dancing pattern of micro-events in our brain, they would have to possess something like a graininess, their subjective 'surface' should not be so infinitely smooth. Michael Lockwood has illustratively called this effect 'glossing over' . [14]

Before I switch back to the external perspective of empirical science, 1 must draw the reader's attention to two important points. First, the two higher-order phenomenal properties which I have just described, provide -a s past debates in the philosophy of mind have shown - excellent starting points for anti-reductionist or anti-naturalist arguments, because holism and homogeneity are at the root of many Cartesian intuitions. They should be of great interest to all those philosophers who feel attracted to property dualism. I suggest in particular that it may not be the first-order phenomenal properties which make qualia appear irreducible to many people, but rather the higher-order property of the phenomenal field-quality, viz. density or ultra-smoothness: The real problem is not International Klein Blue, but the homogeneity of International Klein Blue. Not the subjective blue itself, but its structureless density resists analysis. On the other hand the concept of a 'non-homogeneous' phenomenal property clearly is an incoherent concept: We would then be thinking of a set of phenomenal properties or of non-phenomenal properties altogether. Therefore 'inverted non-homogeneous qualia' are logically impossible, because the connection between simple phenomenal content and their experiential homogeneity is a very strong one. I am not concerned with analysing existing approaches any further here, however. Instead I will attempt to gain fresh access to the basic problem.

Secondly, the property of wholeness does not appear merely on a single phenomenological level of description. It is not only my conscious space which is characterized by the higher-order property of wholeness: The phenomenal self and the phenomenal objects, which constitute the situation in which the phenomenal self is embedded through its relational profile, possess the same characteristic, each in their own way. They too are phenomenally coherent. And within each single psychological moment, within each single subjective 'window of presence' all these holistic entities become simultaneously phenomenally present. These observations must be reflected in our phenomenological concept of 'conscious experience'. They also permit us to give a more precise explication of the provisional concept of a 'phenomenal Holon' introduced at the beginning. There are three things one can say. First, a phenomenal Holon is a subjectively experienced whole, a Gestalt experienced as numerically identical and indivisible from the first-person perspective. Secondly, every phenomenal Holon possesses an aspect which endows it with presence. The properties blending together into the whole possess a temporal identity because I always experience them now. From the first-person perspective, not only reality as a whole, but also objects and the phenomenal self are subjectively present and real in this sense. It may be this presentational aspect that makes the experience of duration possible at all.[15] And thirdly, through directed attention every phenomenal Holon can be embedded in a higher-order phenomenal Holon and in this way be episodically integrated into a higher-order structure, which again passes on the properties of wholeness and presence to the newly emerging unit of conscious experience. However, this last criterion is not fulfilled for the largest and highest-order phenomenal Holon - for my reality.

If our aim is a theory of conscious experience which takes seriously the internal perspective, I think that holism and homogeneity will have to be at the heart of this theory. The classical phenomenological strategy, however, no longer presents a viable path. The evidence of inner perception still assumed by Brentano has been rendered untenable by the progress of scientific psychology operating from the empirical point of view. Research on split-brain patients or hypnotized subjects, the study of disconnection-syndromes and anosognosias have vividly demonstrated not only the modularity of the brain, but also the modularity of consciousness.[16] On the other hand, this development now confronts us urgently with the question of the integration of conscious mental content. In this situation it is at least open to doubt whether the higher-order phenomenal properties I have discussed could ever be turned into explananda for an objective phenomenology? At first glance it is hard to see how they could be integrated into the conceptual framework of theories of the neuro- and cognitive sciences in an intuitively convincing manner, yielding naturalistic theories which we could nevertheless accept as theories about ourselves. Let us keep this question in mind as we shift to the third-person perspective.

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