Why great minds can't grasp consciousness

According to Chalmers, the subjective nature of consciousness prevents it from being explained in terms of simpler components, a method used to great success in other areas of science. He believes that unlike most of the physical world, which can be broken down into individual atoms, or organisms, which can be understood in terms of cells, consciousness is an irreducible aspect of the universe, like space and time and mass.

"Those things in a way didn't need to evolve," said Chalmers. "They were part of the fundamental furniture of the world all along."

Instead of trying to reduce consciousness to something else, Chalmers believes consciousness should simply be taken for granted, the way that space and time and mass are in physics. According to this view, a theory of consciousness would not explain what consciousness is or how it arose; instead, it would try to explain the relationship between consciousness and everything else in the world.

Not everyone is enthusiastic about this idea, however.

'Not very helpful'
"It's not very helpful," said Susan Greenfield, a professor of pharmacology at Oxford University.

"You can't do very much with it," Greenfield points out. "It's the last resort, because what can you possibly do with that idea? You can't prove it or disprove it, and you can't test it. It doesn't offer an explanation, or any enlightenment, or any answers about why people feel the way they feel."

Greenfield's own theory of consciousness is influenced by her experience working with drugs and mental diseases. Unlike some other scientists -- most notably the late Francis Crick, co-discoverer of the structure of DNA, and his colleague David Koch, a professor of computation and neural systems at Caltech -- who believed that different aspects of consciousness like visual awareness are encoded by specific neurons, Greenfield thinks that consciousness involves large groups of nonspecialized neurons scattered throughout the brain.

Important for Greenfield's theory is a distinction between 'consciousness' and 'mind,' terms that she says many of her colleagues use interchangeably, but which she believes are two entirely different concepts.

"You talk about losing your mind or blowing your mind or being out of your mind, but those things don't necessarily entail a loss of consciousness," Greenfield said in a telephone interview. "Similarly, when you lose your consciousness, when you go to sleep at night or when you're anesthetized, you don't really think that you're really going to be losing your mind."

Like the wetness of water
According to Greenfield, the mind is made up of the physical connections between neurons. These connections evolve slowly and are influenced by our past experiences and therefore, everyone's brain is unique.

But whereas the mind is rooted in the physical connections between neurons, Greenfield believes that consciousness is an emergent property of the brain, similar to the 'wetness' of water or the 'transparency' of glass, both of which are properties that are the result of -- that is, they emerge from -- the actions of individual molecules.

For Greenfield, a conscious experience occurs when a stimulus -- either external, like a sensation, or internal, like a thought or a memory -- triggers a chain reaction within the brain. Like in an earthquake, each conscious experience has an epicenter, and ripples from that epicenter travels across the brain, recruiting neurons as they go.

Mind and consciousness are connected in Greenfield's theory because the strength of a conscious experience is determined by the mind and the strength of its existing neuronal connections -- connections forged from past experiences.

Part of the mystery and excitement about consciousness is that scientists don't know what form the final answer will take.

"If I said to you I'd solved the hard problem, you wouldn't be able to guess whether it would be a formula, a model, a sensation, or a drug," said Greenfield. "What would I be giving you?"

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