The mystery of consciousness
(TIME Jan 19, 2007)
The young woman had survived the car crash, after a fashion. In the five months since parts of her brain had been crushed, she could open her eyes but didn’t respond to sights, sounds or jabs. In the jargon of neurology, she was judged to be in a persistent vegetative state. In crueler everyday language, she was a vegetable.
So picture the astonishment of British and Belgian scientists as they scanned her brain using a kind of MRI that detects blood flow to active parts of the brain. When they recited sentences, the parts involved in language lit up. When they asked her to imagine visiting the rooms of her house, the parts involved in navigating space and recognizing places ramped up. And when they asked her to imagine playing tennis, the regions that trigger motion joined in. Indeed, her scans were barely different from those of healthy volunteers. The woman, it appears, had glimmerings of consciousness.
It shouldn’t be surprising that research on consciousness is alternately exhilarating and disturbing. No other topic is like it. As René Descartes noted, our own consciousness is the most indubitable thing there is. For each of us, consciousness is life itself, the reason Woody Allen said, “I don’t want to achieve immortality through my work. I want to achieve it by not dying.”
WHAT REMAINS IS NOT ONE PROBLEM ABOUT CONSCIOUSNESS BUT two, which the philosopher David Chalmers has dubbed the Easy Problem and the Hard Problem. Calling the first one easy is an injoke: it is easy in the sense that curing cancer or sending someone to Mars is easy. That is, scientists more or less know what to look for, and with enough brainpower and funding, they would probably crack it in this century.
The Easy Problem, then, is to distinguish conscious from unconscious mental computation, identify its correlates in the brain and explain why it evolved.
The Hard Problem, on the other hand, is why it feels like something to have a conscious process going on in one’s head. Not only does a green thing look different from a red thing, remind us of other green things and inspire us to say, “That’s green” (the Easy Problem), but it also actually looks green: it produces an experience of sheer greenness that isn’t reducible to anything else. As Louis Armstrong said in response to a request to define jazz, “When you got to ask what it is, you never get to know.”
The Hard Problem is explaining how subjective experience arises from neural computation. The problem is hard because no one knows what a solution might look like or even whether it is a genuine scientific problem in the first place. And not surprisingly, everyone agrees that the hard problem (if it is a problem) remains a mystery.
Francis Crick called it “the astonishing hypothesis”—the idea that our thoughts, sensations, joys and aches consist entirely of physiological activity in the tissues of the brain. Consciousness does not reside in an ethereal soul that uses the brain like a PDA; consciousness is the activity of the brain.
