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Thinking about consciousness is no longer the preserve of philosophers; it is part of science too. Experts from a range of disciplines give their individual views

Old habits die hard, especially habits of thinking, and our "intuitive" ways of thinking about consciousness are infected with leftover Cartesian images, an underestimated legacy of the dualist past. Of course the brain is the seat of consciousness, and all the phenomena that compose our pre-theoretical catalogue of conscious phenomena are ultimately explicable in terms of the activities in our brains and bodies, but the paths of explanation (or "reduction") are not as direct as many materialists have supposed.

My work has two roughly equal components. On the positive side, I have tried to show how to construct a truly non-Cartesian materialist theory of consciousness, in which conscious events are not those that occur in any privileged medium in the brain, but those which triumph in competition with other events, and hence have more persistent influence over subsequent events. This model explains many phenomena that otherwise are baffling, and has even predicted a few strikingly counter-intuitive phenomena that have subsequently been observed. On the negative side, I have tried to show theorists in several disciplines how their presumed-to-be-innocent formulations typically harbour Cartesian presuppositions that still need to be discarded and replaced. For instance, the distinction drawn by David Chalmers between the Easy Problems of consciousness (questions about the mechanics of nerves and brain cells) and the Hard Problem (the problem of phenomenal consciousness or "qualia") is not, I argue, the fruitful insight many have taken it to be, but a symptom of the failure to appreciate that all the work of consciousness, including the "phenomenal" work of appreciation and emotional reaction, must be fragmented and distributed around in the asynchronous activities of many networks extending throughout the body. There are no qualia left to be explained, once these tasks are accounted for, so the Hard Problem is an artefact of false accounting; once all the Easy Problems are solved, consciousness is explained.

Daniel Dennett is director of the Centre for Cognitive Studies, Tufts University.