Smell, Taste, Temperature, ...?
That's all very well but...
Why study phenomenal consciousness and not other forms of consciousness?Zeman (2001) has given an excellent classification of the meanings of the word consciousness, first distinguishing ‘consciousness’ from ‘self-consciousness’. Within the category of ‘consciousness’ he distinguishes three broad classes, ranging from consciousness as the waking state (as in: “after a lucid interval, the injured soldier lapsed into unconsciousness”), consciousness as experience (as in: “I became conscious of a feeling of dread, and an overpowering smell of burning rubber”) and consciousness as mind (as in: “I am conscious that I may be straining your patience”).
Within the category of ‘self-consciousness’ Zeman distinguishes five classes (proneness to embarrassment, self-detection, self-recognition, awareness of awareness, and self-knowledge). Baars (1997) and Chalmers (1996), among many others have also given very useful classifications of different kinds of consciousness.
But none of all these notions of consciousness interest us here: Why not? Because, though they may represent formidable challenges, there seems a priori nothing to prevent applying the normal scientific method to them.
Thus for example there is a sense in which "being conscious of X" means: being "aware of X" or being ready to make use of X in one's reasoning, planning and judgments, or, as Block calls it having "cognitive access" or "conscious access" to it. This ability to make use of a fact in reasoning, planning and judgment is not something magical, and artificial intelligence programs routinely do just this, albeit perhaps in a restricted way. A functional, scientific explanation of this "Access Consciousness" is feasible, and neural circuitry that implements it can be envisaged.
Furthermore, once we admit that there need be nothing magical about Access Consciousness, we can then explain many of the other forms of consciousness distinguished by Zeman. For example, embarassment might be the particular case of "being conscious of X" where X is: (an agregate of facts such as the fact that I am at this moment making a fool of myself, that I am not sure how to act, that I might be offending someone, etc.). We can also deal with what has been called the "intransitive" (cf. Rosenthal, 1997; Malcolm, 1984) form of consciousness, that is the case of just being "generally conscious": we can just say that this intransitive sense involves the general potential for applicability of the transitive, "conscious of X" sense. Thus, for example, saying that "the soldier lapsed into unconsciousness" means that he was no longer able to be "conscious of" anything around him.
But whereas Access Consciousness poses no logical problem for science, the same is not true for Phenomenal Consciousness.
What do we mean by "accounting for" raw sensory feel?Supposing we were to find a new neural substance called qualiafer, whose different forms had the property of generating different feels. Would this be a step forward?
The answer is no! Discovering a perfect neural correlate of phenomenal consciousness like this would probably be a step backwards. It would immediately give us still more work to do. We would have to explain how qualiafer generated the raw feel rather than no feel at all. And we would have to explain why the particular forms of qualiafer gave the particular differences in feels that are observed: why do feels differ across sensory modalities in the way they do, sometimes being visual, sometimes auditory, for example? And why do feels differ within modalities the way they do, sometimes being red, sometimes green, for example?
If there were some kind of isomorphism between the forms of qualiafer and the differences in the feels produced by these forms, this would be interesting. For example, if there were two forms of qualiafer one which determined the perceived color hue along the Red/Green dimension, and one along the Blue/Yellow dimension, then this might be thought to "account for" the structure of colour space... or would it??
Are we justified in changing the definition of feel?The sensorimotor approach takes an alternative tack as concerns explaining feel. The idea is not to suggest some new mechanism, but rather to suggest that the notion of feel itself has been incorrectly defined. Redefining feel in a somewhat different way allows the infinite regress to be avoided.
Constructing a scientific theory is to some extent a question of choosing something that one can talk about scientifically among the mass of fascinating things one can talk about (like love, art, religion, politics, feelings, emotions, attitudes, and yes, consciousness…). This is not to say that one cannot talk interestingly about love, about politics or religion. It is just that science is a particular way of talking, where we lay down special rules. Not everything that can be talked about, can be talked about in this scientific way. The process of doing science therefore often consists in taking terms used by the man in the street like force, energy, speed, acceleration, magnetism, electricity, capacity, field, etc., and deciding to limit their use to a very special, restricted set of circumstances which have the advantage of being talkable-about in a scientific way. Part of the art of doing science then consists in defining one's terms cleverly so that one can use the rules of science when one uses those terms.
The trouble with the topic of consciousness, is that no one really knows what they mean by consciousness.
In fact, the subject of consciousness has up until very recently been the dominion of philosophers, not of scientists. And the difference between science and philosophy is that in philosophy the problem is not to select the scientifically useful definitions, but to study the ways people use all the different definitions that are actually used. Philosophy can therefore interest itself in politics and love, ethics and aesthetics, where for the moment scientists dare not tread. And with regard to consciousness, philosophers have come up with a wealth of difficult questions and delicate debates that shroud the question of consciousness.
But the task of a scientist is restrictive: it is to choose concepts which can dealt with scientifically, which hold the promise of further scientific investigation and provide opportunities for empirical test. This requires cutting through the tangle of ideas that the philosophers love, and severely restricting and systematizing the senses in which terms are used.
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