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Consciousness puzzles scientists and philosophers as much as it baffles the rest of us. Elusive, enigmatic, and difficult to define and probe, consciousness has a peculiar quality that rouses people to insist that somehow it differs from the rest of the physical world and that there is something unique about each person's subjective experience.
Enter Daniel Dennett, a philosopher who directs the Center for Cognitive Studies at Tufts University. In his provocative book, he explores several hot debates over whether consciousness can ever be explained--such as our inability to objectively study subjective experiences or qualia, the impenetrable properties of sensations. Despite our stubborn feelings that consciousness involves something extra--a spirit, soul, miracle or magic--Dennett contends that consciousness is no more than an intriguing but inadequately explained aspect of neural activity.
Consciousness is often celebrated as a mystery, he writes. I think this tradition is not just a mistake, but a serious obstacle to ongoing scientific research that can explain consciousness, just as deeply and completely as it can explain other natural phenomena: metabolism, reproduction, continental drift, light, gravity and so on. Like a persuasive magic show, consciousness fools us into believing that the brain's seamless illusion is real, even though consciousness is a purely biological phenomenon.
To make his point, Dennett works through various thought experiments. One involves imagining a perfect zombie that exactly replicates a person's perceptual and neural processes. Should there be any real difference between the zombie and the conscious person, he wonders? He also attacks the claim that a mechanistic theory of consciousness could not explain such a difference, if it existed. Another thought experiment involves imagining Martian scientists studying human consciousness. In principle, he says, Martians should be able to observe and inspect the mechanisms underlying earthly conscious experiences and, in some sense, grasp what it is like to be human.
In time, Dennett believes people will realize that third-person methods of the natural sciences suffice to investigate consciousness as completely as any phenomenon in nature can be investigated. Like vitalism--the 18thcentury belief that some inexplicable force animates living creatures-- consciousness will ultimately yield to scientific explanation.