Destroying the zombic hunch

Review of Sweet Dreams: Philosophical Obstacles to a Science of Consciousness
by Daniel C. Dennett, Cambridge, MA and London, MIT Press, 2005
ISBN 0-262-04225-8

(Note this is the unedited version submitted to Nature)

Has the devil lost his horns? Dan Dennett has been demonised because of his tough materialist stance on consciousness, but now he updates his theory and, I think, presents a softer version.

Sweet Dreams: Philosophical Obstacles to a Science of Consciousness is a collection of essays and lectures written between 1999 and 2005 in which Dennett tries to freeze time and present a “best” version of his evolving ideas. There are problems with this, especially in the chunks which are somewhat disconcertingly repeated from one chapter to the next, but the overall picture gives a good idea of where Dennett’s thinking has been going.

He describes his task as being to explain away qualia-based intuitive objections to materialism, and this he does using some of his favourite examples. One is the ever-popular philosopher’s zombie; an imaginary creature who looks, acts and speaks like a normal person but has no subjective experiences – or qualia. It’s easy to imagine a zombie – or at least to think you are imagining one – says Dennett, and he calls this “falling for the Zombic Hunch”, which traps people into believing that consciousness is separate from brain function. Dennett has tried to murder the zombie before, explaining how people fail to follow the rules when they think they are imagining one, but now with the concept of the Zombic Hunch he explores the damage done by this false intuition. But don’t worry, he says, if you are patient and open minded it will pass, or mutate into a less virulent form. Just as we still feel as though the Earth stands still, in the future people may still feel the Zombic Hunch but they won’t believe it. They will know that mechanistic theories of consciousness do the whole job, and we don’t need the concept of qualia.

Demystifying consciousness is Dennett’s forte, and probably the main reason for his status as the devil – after all, people like their mysteries. Some even think that if consciousness is explained they will be diminished as people, being turned into “mere things.” They don’t like the idea that there is no one at home inside their head; no audience watching the magic show of conscious experiences from the safety of the Cartesian theatre. Dennett contrasts theorists to whom it is obvious that a theory which leaves out the subject cannot explain consciousness, with those to whom it is obvious that the subject has to vanish. The first type must be wrong, he says; “A good theory of consciousness should make a conscious mind look like an abandoned factory.”

All these ideas will be familiar to lovers, and haters, of Dennett, as will his attacks on Mary the colour-scientist, the idea of first-person science, and his defence of heterophenomenology, although he adds some new twists and, as ever, delights with his quirky turns of phrase. I laughed out loud at his example of a folk theorem as ludicrous as some of the ones people claim are “just obvious” – “If you burp, sneeze, and fart all at the same time, you die.” But let’s have some evidence, he says.

What may be less familiar is Dennett’s updating of his theory of consciousness, from the original “Multiple Drafts” theory, through the delightfully named “Fantasy Echo”, to his latest ideas of “Fame in the Brain” or “Cerebral Celebrity”.

In a paper originally published as an overview for the special 2001 issue of Cognition, he joins in the “gathering consensus” favouring global workspace (GW) theory. Originally proposed by Bernard Baars in 1988, this theory is explicitly based on a theatre metaphor in which the contents of consciousness are illuminated by a spotlight of attention, shining on the stage of working memory. The idea is that many specialist brain systems contribute information to the GW; its contents are then broadcast to the rest of the system and this global availability is experienced as a conscious state.

Doesn’t this go against everything Dennett has been fighting for? He tries to explain why not like this: Consciousness, like fame, is not an intrinsic property of brain processes but is more like political influence or clout; conscious events are the ones that have widespread effects in the brain. So we mustn’t think that becoming famous in the brain magically ignites the glow of conscious qualia or lets pictures into the Cartesian Theatre to be watched by the conscious subject; the effects are enough. Fame in the brain does not lead to consciousness; it is consciousness.

Clearly many GW theorists don’t see it this way, and Dennett describes them as “surrendering just when victory is at hand.” The critical point hinges on what he calls the Hard Question “And then what happens?” (not to be confused with Chalmers’ Hard Problem, which he thinks is illusory). If you think that something has to happen next, like “entering consciousness” or “becoming conscious” then you are still wallowing in mystery.

But if the devil stuck with his original Multiple Drafts theory he would surely have gone further. One of its most startling claims is that “there are no fixed facts about consciousness independent of particular probes” (Dennett 1991 p ). I took this to mean something like this: at any time there are multiple versions of representations in the brain, none of which is conscious or unconscious. Only when the system is probed – for example by asking a question or requiring an action – does one of the drafts have consequences which cause us to say, after the fact, that it was conscious. In other words there are no conscious and unconscious streams; nothing ever “enters consciousness”; there is no “crucial finish line or boundary somewhere in the brain, marking a place where the order of arrival equals the order of “presentation” in experience” (Dennett 1991 p 107).

Yet the GW theorists do believe in conscious and unconscious streams, in contents becoming conscious, and in looking for the neural correlates of the “movie in the brain”. I think they still need the old devil.