The problem of spaceEdit
The problem of Relationalism and Substantivalism has been discussed earlier. In this section the concept of space will be explored in more depth.
Space is apparent to us all. It is the existence of many simultaneous things at an instant. If we see a ship and hear a dog barking on our left there is space. If we look at a checkerboard there is space. This occurrence of space in phenomenal experience is similar to the measurement of space in the world: things that are simultaneously at the ends of a metre rule are a metre apart; if there is more than one object at a given instant the objects are separated by space.
Physicists have found that the mathematics of vector spaces describes much of the arrangement of things in the world. In a vector space the independent directions for arranging things are called dimensions. At any instant physical space has three clearly observable dimensions.
It has been known for millennia that the three dimensions observable at an instant are interrelated by Pythagoras' Theorem:
Pythagoras' theorem on a plane shows that the length of any displacement is related to the sum of the squares of the displacements in the independent directions (x and y):
Pythagoras' theorem in three dimensions is:
The advances in geometry in the nineteenth century showed that Pythagoras' theorem was a special case of a metric, an equation that describes displacements in terms of the dimensions available. In the twentieth century it was realised that time was another independent direction for arranging things that was interrelated to the other three dimensions. The world is now described as a four dimensional manifold.
The illustration below shows how different numbers of dimensions affect the arrangement of things.
It is sometimes suggested that our idea of space is due to some sort of memory that is read out sequentially. This is unlikely because, at any instant a one dimensional form cannot be made to overlie a two dimensional form and a two dimensional form cannot overlie a three dimensional form etc. One dimensional forms are not congruent with two dimensional forms. This means that a one dimensional form such as virtual memory cannot, at any instant, overlie two dimensional forms such as occur in phenomenal experience and hence experience does not supervene on the idea of virtual memory (See section on functionalism as a one dimensional Turing Machine).
Curiously the idea of mental space is often denied. McGinn(1995) gives such a denial:
We perceive, by our various sense organs, a variety of material objects laid out in space, taking up certain volumes and separated by certain distances. We thus conceive of these perceptual objects as spatial entities; perception informs us directly of their spatiality. But conscious subjects and their mental states are not in this way perceptual objects. We do not see or hear or smell or touch them, and a fortiori do not perceive them as spatially individuated.(2) This holds both for the first- and third-person perspectives. Since we do not observe our own states of consciousness, nor those of others, we do not apprehend these states as spatial. McGinn(1995).
This denial is strange because it begins by describing phenomenal experience as clearly spatial and then proceeds to argue that there is some other thing, the "mental state", which is non-spatial. This seems to contradict our everday life where our experience is our experience, there is no other experience. The issue is whether this experience is things in themselves (Direct Realism) or some other form in the brain (Indirect Realism). The illustration below shows how space occurs in phenomenal experience; it sidesteps the issue of the location of the contents of phenomenal consciousness.
McGinn (1995) gives a description of how phenomenal experience cannot be overlaid by a 3D model of events in the brain:
"Consider a visual experience, E, as of a yellow flash. Associated with E in the cortex is a complex of neural structures and events, N, which does admit of spatial description. N occurs, say, an inch from the back of the head; it extends over some specific area of the cortex; it has some kind of configuration or contour; it is composed of spatial parts that aggregate into a structured whole; it exists in three spatial dimensions; it excludes other neural complexes from its spatial location. N is a regular denizen of space, as much as any other physical entity. But E seems not to have any of these spatial characteristics: it is not located at any specific place; it takes up no particular volume of space; it has no shape; it is not made up of spatially distributed parts; it has no spatial dimensionality; it is not solid. Even to ask for its spatial properties is to commit some sort of category mistake, analogous to asking for the spatial properties of numbers. E seems not to be the kind of thing that falls under spatial predicates. It falls under temporal predicates... McGinn(1995)
He concludes that a 3D form can only be rearranged into the form of the things in experience over a succession of instants ("It falls under temporal predicates"). This is highly suggestive of phenomenal experience having more than three dimensions in the same way as an ordinary physical thing or field has more than three dimensions.
The problem of qualiaEdit
A quality of an object such as its colour, roughness, temperature etc. is known as a quale, the plural of quale is qualia. Qualia are the contents of phenomenal consciousness. The term "qualia" is sometimes extended to all mental aspects of an object such as roundness, size and even relative position.
The physics of qualiaEdit
According to physicalism qualia must be things in the universe. But what are "things in the universe" and which of these are qualia?
If we wish to explain phenomenal experience we must first decide whether experience is a measurement or things themselves. Measurement begins with a quantum mechanical interaction between an instrument and a set of particles, this then creates a signal which is a change in the state of the instrument. The signal can be a flow of charge or a chemical change etc. In the Direct Realist case the signal would be the change at the interface between the bulk of a material (a crude measuring device) and a set of QM particles, in the Indirect Realist case it would be some signal in the brain derived from the initial signal. In either case phenomenal consciousness would be some form of a set of signals themselves. Intriguingly, these final signals that are the content of consciousness would be subject to quantum uncertainty.
The signals that form phenomenal consciousness would differ from those that mediate the transfer of information from QM phenomena to measuring instruments.
The signals in measuring events arise as a result of interactions between QM phenomena and a measuring apparatus composed of relatively large structures. These structures (called the environment) produce signals at definite locations. This chain of fixing positions is known as decoherence (see Zurek (2003) or Bacciagaluppi (2004) for a review). This means that measuring events fix the positions of signals and these represent the positions of QM events. (Some physical particles such as photons are subject to little decoherence during propagation, even in water (cf: Anglin & Zurek (1996)).)
So signals in measuring devices usually have highly restrained positions. Now consider the final signals, the one's in phenomenal consciousness. To an observer of the brain they should be, very nearly, in their classical positions within the brain unless they consist of photons or are subject to some special effect such as has been proposed for microtubules. The brain acts as a measuring device causing decoherence. But despite this even signals composed of sodium ions, which should decohere rapidly in water, have a tiny, but finite, probability of remaining in a coherent state.
If your conscious experience is the signals and not the fabric of the brain are you the set of signals that interacts with the brain fabric almost immediately, the set that interacts after a minute or the set that almost never interacts? To an outside observer you must be the main chance, the rapidly interacting signals, but to the signals themselves all possibilities exist. Which one are you? Certainly any interaction between the signals and the mutually observed world must involve decoherence but the external observer would find it difficult to determine whether a particular interaction was due to signals that had interacted immediately or ones that were delayed (or delayed in an alternate QM reality). This problem is part of the preferred basis problem that will be discussed later.
Zurek (2003)assumes that phenomenal experience is identical to measurements. The observer is then both the signal and the apparatus that encloses the signal. He summarises the resultant idea of the completely determined observer who is fully integrated into the measured world:
The ‘higher functions’ of observers - e.g., consciousness, etc. - may be at present poorly understood, but it is safe to assume that they reflect physical processes in the information processing hardware of the brain. Hence, mental processes are in effect objective, as they leave an indelible imprint on the environment: The observer has no chance of perceiving either his memory, or any other macroscopic part of the Universe in some arbitrary superposition. " Zurek (2003)
Notice the phrase "perceiving .. his memory" - as neuroscientists we must ask "how"? By more measurements? There are no more measurements when things are arranged in phenomenal consciousness, the information has nowhere else to go. However, according to the empiricist philosophers the arrangements of the signals in phenomenal consciousness do extend through time in a definite order at any instant. Is it this order that determines the positions of signals in the brain or is it the brain that determines this order?
Physicalism leads us to an idea of the content of consciousness as an arrangement of quantum fields like the content of the brain or the content of the world. The arrangement of the quantum fields at an instant in experience is probably related to the arrangement of measured events at a succession of instants in the world.
The philosophy of qualiaEdit
The term "qualia" was introduced by C.I. Lewis in 1929:
This given element in a single experience of an object is what will be meant by "a presentation." Such a presentation is, obviously, an event and historically unique. But for most of the purposes of analyzing knowledge one presentation of a half-dollar held at right angles to the line of vision, etc., will be as good as another. If, then, I speak of " the presentation" of this or that, it will be on the supposition that the reader can provide his own illustration. No identification of the event itself with the repeatable content of it is intended.
In any presentation, this content is either a specific quale (such as the immediacy of redness or loudness) or something analyzable into a complex of such. The presentation as an event is, of course, unique, but the qualia which make it up are not. They are recognizable from one to another experience.(CI Lewis, Mind and the World Order, 1941 edition Chapter 2)
Tye (2003) gives the following definition of qualia:
"Experiences vary widely. For example, I run my fingers over sandpaper, smell a skunk, feel a sharp pain in my finger, seem to see bright purple, become extremely angry. In each of these cases, I am the subject of a mental state with a very distinctive subjective character. There is something it is like for me to undergo each state, some phenomenology that it has. Philosophers often use the term 'qualia' to refer to the introspectively accessible properties of experiences that characterize what it is like to have them. In this standard, broad sense of the term, it is very difficult to deny that there are qualia." Tye(2003).
In philosophy objects are considered to have perceived features such as shape and colour, weight and texture which are called sensible qualities. Sensible qualities are divided into intrinsic, or primary, qualities that are properties of the object itself and extrinsic, or secondary, qualities which are related to the sensations produced in the observer. Shape is generally considered to be a primary quality whereas colour is often considered to be a secondary quality. It is generally considered that secondary qualities correspond to qualia (Smith 1990, Shoemaker 1990) and the two terms are often used synonymously. Although secondary qualities may be qualia, the term "qualia" may include things other than perceptions such as pain etc. that are, arguably, not secondary qualities. Primary qualities might also give rise to experience that is distinct from, say, the shape of an object itself.
Although "qualia" is a recent term, the philosophical debate about the nature of secondary qualities, such as colours, and the nature of conscious experience itself has been around for millennia.
It seems that the visual system gives rise to experience even in the absence of previous visual stimulation. For example, when someone recovers from blindness they have an experience that contains shapes and colours even though these have little meaning:
"When he first saw, he was so far from making any judgement of distances, that he thought all object whatever touched his eyes.... he knew not the shape of anything, nor any one thing from another, however different in shape and magnitude.. We thought he soon knew what pictures represented, which were shewed to him, but we found afterwards we were mistaken; for about two months after he was couched, he discovered at once they represented solid bodiess, when to that time he considered them only as party-coloured panes, or surfaces diversified with variety of paint." William Cheselden (1728)
Qualia are the components of experience, whatever the mode of input to that experience. Strawson (1994) includes content such as accompanies suddenly remembering or thinking of something as examples of qualia.
There is thought to be an explanatory gap associated with qualia (Levine 1983), as an example it is hard to imagine how the experience called pain could be a set of impulses in the brain.
Some philosophers have attempted to bridge this gap by invoking Direct Realism, proposing that our experience is in some way 'transparent' so that we experience the world or the injured limb directly (i.e.: there is an assumption that things flow within phenomenal experience into a centre point and we see right through this flow!). Strange though it may seem, this idea has led to a deduction that phenomenal experience is a set of things and qualities are these things, not deductions about or experiences of these things. As Tye (2003) puts it:
These observations suggest that qualia, conceived of as the immediately 'felt' qualities of experiences of which we are cognizant when we attend to them introspectively, do not really exist. The qualities of which we are aware are not qualities of experiences at all, but rather qualities that, if they are qualities of anything, are qualities of things in the world (as in the case of perceptual experiences) or of regions of our bodies (as in the case of bodily sensations). This is not to say that experiences do not have qualia. The point is that qualia are not qualities of experiences.
However, the outstanding issue for Tye's analysis is where in the world the thing that is called a quale exists - on a thing in the world beyond the body, on the retina, in the cortex, in the thalamus? Tye seems to be suggesting that "in the world" can only be beyond the retina but given that a television can have a colour and a retina can have a colour why should we insist that the colour in conscious experience is always of the thing being represented via the DVD or videotape?
As was seen in the previous section, only signals are available in the classical world of conscious observation. The "reality" of the things that generate signals is not available. So whether experience is a signal at the position of what we call an "oak tree" or a signal in the eye due to photons reflected from the tree or a signal in the brain the same sort of phenomena would apply. Qualia would be a field of signals, not processes based on these signals.
Some philosophers hold that qualia are a field of signals derived from the original signals that are next to the quantum phenomena that compose an object. In other words they propose that qualia are not the first signals in the chain from whatever composes an object to the observer. These philosophers are known as Representationalists and the emphasis on secondary signals allows a contribution from the brain etc. to the field of signals that is conscious experience. Modern representationalists such as Tye (1995), Lehar(2003) and Dretske(2003) emphasise the idea that qualia are actual things that represent objects rather than concepts or experiences of things. As Dretske puts it:
"..the features that define what it is like to have an experience are properties that the objects we experience (not our experience of them) have.(Dretske 2003).
Lehar(2003) uses modern language to express the empiricist notion that the signals that comprise qualia are more likely to be in our brains than elsewhere, according to Lehar the objects we experience must be informational replicas in our heads:
"The central message of Gestalt theory therefore is that the primary function of perceptual processing is the generation of a miniature, virtual-reality replica of the external world inside our head, and that the world we see around us is not the real external world, but is exactly that miniature internal replica (Lehar 2003)."
Direct Realists and Representationalists share the same view that qualia are an actual, physical field of things somewhere in the world. Some functionalists and eliminativists take a different view, believing that qualia do not exist except as judgements of properties that are used in interactions (i.e.: as disembodied information - see the section on Direct Realism).
Lewis, C.I. (1929) Mind and the World-Order. http://www.ditext.com/lewis/mwo2.html Smith, A.D. (1990) Of Primary and Secondary Qualities, Philosophical Review 99 (1990).