"Consciousness" is a multiply ambiguous word, and if our goal is to explain perceptual consciousness we had better be clear about which of the many senses of the word we are endorsing when we sign on to the project. I describe some of the relatively standard distinctions made in the philosophical literature about different meanings of the word "conscious". Then I consider some of the arguments of David Chalmers and of Ned Block that states of "phenomenal consciousness" pose special and intractable problems for the scientific understanding of perception. I argue that many of these problems are introduced by obscurities in the term itself, and propose a distinction between epistemic and non-epistemic senses of the term "phenomenal consciousness". That distinction helps explain why phenomenal consciousness seems so mysterious to so many people. States of "phenomenal consciousness" are not states of one, elemental (and inexplicable) kind; they are a ragtag lot, of differing levels of complexity, corralled under one heading by a regrettable ambiguity in our terminology. Suppose a cruise line offered you a ticket that, like this conference, promised to take you from "neuronal coding to consciousness". Do you have a clear idea of what the destination of that cruise would be? Could you distinguish it from other distinct islands of mental phenomena towards which the pilot might mistakenly steer? And, once you had disembarked, do you know how you would set about determining whether or not you had actually landed on your target?
The fact that these questions are non-experimental, abstract, and intractable has not stopped philosophers from trying to answer them, and in fact those efforts have clarified a number of important distinctions between various senses of the word "consciousness". As these provide various distinct destinations towards which our pilot might steer, I think it might actually be useful to experimenters to have some acquaintance with them. They can help sort out the different itineraries that all advertise themselves under the umbrella term "consciousness," and perhaps help prevent a few travelers from being shanghaied.
My plan of attack is as follows. Recently a number of philosophers have proposed a notion of what they call "phenomenal consciousness", and they have argued that this notion does not map onto any of the current categories available in cognitive science or philosophy. This turns out to be a good way to test the adequacy of those categories: produce some new (or neglected) phenomenon and ask whether it can be adequately characterized in the terms of that taxonomy. Is this slime mold a fungus? Is it a protist? Perhaps neither answer is quite right, and we need to revise our categories. Here phenomenal consciousness is our slime mold, and the question is whether the conventional categories can adequately characterize it. So first I will sketch the now relatively conventional distinctions, and next introduce the putative newcomer: phenomenal consciousness. Then the fun begins.
Presented at the Italian Institute for Philosophical Studies, International School of Biophysics study program "From Neuronal Coding to Consciousness", Ischia (Naples), 12-17 October 1998.In Werner Backhaus, (ed), Neuronal Coding of Perceptual Systems. New Jersey: World Scientific, Series on Biophysics and Biocybernetics, vol 9, 2001, ISBN 981-02-4164-X, pp 405-422.
Austen Clark Department of Philosophy U-54 University of Connecticut Storrs, CT 06269-2054