The Conscious Mind: In Search of a Fundamental Theory
by David J. Chalmers
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Materialism is a beautiful and compelling view of the world, but to account for consciousness, we have to go beyond the resources it provides.
Conscious experience is at once the most familiar thing in the world and the most mysterious. There is nothing we know about more directly than consciousness, but it is far from clear how to reconcile it with everything else we know. Why does it exist? What does it do? How could it possibly arise from lumpy gray matter? We know consciousness far more intimately than we know the rest of the world, but we understand the rest of the world far better than we understand consciousness. Consciousness can be startlingly intense. It is the most vivid of phenomena; nothing is more real to us. But it can be frustratingly diaphanous: in talking about conscious experience, it is notoriously difficult to pin down the subject matter. The International Dictionary of Psychology does not even try to give a straightforward characterization: Consciousness: The having of perceptions, thoughts, and feelings; awareness. The term is impossible to define except in terms that are unintelligible without a grasp of what consciousness means. Many fall into the trap of confusing consciousness with self-consciousness—to be conscious it is only necessary to be aware of the external world. Consciousness is a fascinating but elusive phenomenon: it is impossible to specify what it is, what it does, or why it evolved. Nothing worth reading has been written about it. (Sutherland 1989)
Why should there be conscious experience at all? It is central to a subjective viewpoint, but from an objective viewpoint it is utterly unexpected. Taking the objective view, we can tell a story about how fields, waves, and particles in the spatiotemporal manifold interact in subtle ways, leading to the development of complex systems such as brains. In principle, there is no deep philosophical mystery in the fact that these systems can process information in complex ways, react to stimuli with sophisticated behavior, and even exhibit such complex capacities as learning, memory, and language. All this is impressive, but it is not metaphysically baffling. In contrast, the existence of conscious experience seems to be a new feature from this viewpoint. It is not something that one would have predicted from the other features alone. That is, consciousness is surprising. If all we knew about were the facts of physics, and even the facts about dynamics and information processing in complex systems, there would be no compelling reason to postulate the existence of conscious experience. If it were not for our direct evidence in the first-person case, the hypothesis would seem unwarranted; almost mystical, perhaps. Yet we know, directly, that there is conscious experience. The question is, how do we reconcile it with everything else we know?
Some say that consciousness is an "illusion," but I have little idea what this could even mean. It seems to me that we are surer of the existence of conscious experience than we are of anything else in the world.
The subject matter is perhaps best characterized as “the subjective quality of experience.” When we perceive, think, and act, there is a whir of causation and information processing, but this processing does not usually go on in the dark. There is also an internal aspect; there is something it feels like to be a cognitive agent. This internal aspect is conscious experience. Conscious experiences range from vivid color sensations to experiences of the faintest background aromas; from hard-edged pains to the elusive experience of thoughts on the tip of one’s tongue; from mundane sounds and smells to the encompassing grandeur of musical experience; from the triviality of a nagging itch to the weight of a deep existential angst; from the specificity of the taste of peppermint to the generality of one’s experience of selfhood. All these have a distinct experienced quality. All are prominent parts of the inner life of the mind. We can say that a being is conscious if there is something it is like to be that being, to use a phrase made famous by Thomas Nagel.1
Positive arguments for the natural possibility of absent qualia have not been as prevalent as arguments for inverted qualia, but they have been made. The most detailed presentation of these arguments is given by Block (1978).These arguments almost always have the same form. They consist in the exhibition of a realization of our functional organization in some unusual medium, combined with an appeal to intuition. It is pointed out, for example, that the organization of our brain might be simulated by the people of China or even mirrored in the economy of Bolivia. If we got every person in China to simulate a neuron (we would need to multiply the population by ten or one hundred, but no matter), and equipped them with radio links to simulate synaptic connections, then the functional organization would be there. But surely, says the argument, this baroque system would not be conscious!There is a certain intuitive force to this argument. Many people have a strong feeling that a system like this is simply the wrong sort of thing to have a conscious experience. Such a “group mind” would seem to be the stuff of a science-fiction tale, rather than the kind of thing that could really exist. But there is only an intuitive force. This certainly falls far short of a knockdown argument. Many have pointed out that while it may be intuitively implausible that such a system should give rise to experience, it is equally intuitively implausible that a brain should give rise to experience! Whoever would have thought that this hunk of gray matter would be the sort of thing that could produce vivid subjective experiences? And yet it does. Of course this does not show that a nation's population could produce a mind, but it is a strong counter to the intuitive argument that it would not....Once we realize how tightly a specification of functional organization constrains the structure of a system, it becomes less implausible that even the population of China could support conscious experience if organized appropriately. If we take our image of the population, speed it up by a factor of a million or so, and shrink it into an area the size of a head, we are left with something that looks a lot like a brain, except that it has homunculi—tiny people—where a brain would have neurons. On the face of it, there is not much reason to suppose that neurons should do any better a job than homunculi in supporting experience.
It may be that some are unwilling to accept the possibility of conscious thermostats simply because we understand thermostats too well. We know everything about their processing, and there seems no reason to invoke consciousness. But thermostats are really no different from brains here. Even once we understand brain processing perfectly, there will still seem to be no reason to invoke consciousness. The only difference is that right now, what is going on inside a brain is enough of a mystery that one may be tempted to suppose that consciousness is somehow “located” in those brain processes that we do not yet understand. But as I have argued, even coming to understand those processes will not alone bring consciousness into the picture; so here, once again, brains and thermostats are on a par.One might be bothered by the fact that one could build a thermostat oneself, without putting any consciousness in. But of course the same applies to a brain, at least in principle. When we build a brain (in reproduction and development, say), consciousness conies along for free; the same will go for a thermostat. We should not expect to locate consciousness as a physical component of the system! Some may worry about the fact that a thermostat is not alive; but it is hard to see why that should make a principled difference. A disembodied silicon brain of the sort discussed in the last chapter would arguably fail to qualify as alive, but we have seen that it might be conscious. And if the arguments in the last chapter are right, then the fact that a thermostat is not made up of biological components makes no difference, in principle.
