On the brain as machine:
[T]he feature [neuroscientists] find least controversial is the one that many people outside the field find the most shocking. 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.
SCIENTISTS HAVE EXORCISED THE GHOST FROM THE MACHINE NOT because they are mechanistic killjoys but because they have amassed evidence that every aspect of consciousness can be tied to the brain. Using functional MRI, cognitive neuroscientists can almost read people's thoughts from the blood flow in their brains. They can tell, for instance, whether a person is thinking about a face or a place or whether a picture the person is looking at is of a bottle or a shoe.
And consciousness can be pushed around by physical manipulations. Electrical stimulation of the brain during surgery can cause a person to have hallucinations that are indistinguishable from reality, such as a song playing in the room or a childhood birthday party. Chemicals that affect the brain, from caffeine and alcohol to Prozac and LSD, can profoundly alter how people think, feel and see. Surgery that severs the corpus callosum, separating the two hemispheres (a treatment for epilepsy), spawns two consciousnesses within the same skull, as if the soul could be cleaved in two with a knife. [Really? I'm a little skeptical of that! --JA]
And when the physiological activity of the brain ceases, as far as anyone can tell the person's consciousness goes out of existence. Attempts to contact the souls of the dead (a pursuit of serious scientists a century ago) turned up only cheap magic tricks, and near death experiences are not the eyewitness reports of a soul parting company from the body but symptoms of oxygen starvation in the eyes and brain. In September, a team of Swiss neuroscientists reported that they could turn out-of-body experiences on and off by stimulating the part of the brain in which vision and bodily sensations converge.
On the illusion of the self:
ANOTHER STARTLING CONCLUSION FROM the science of consciousness is that the intuitive feeling we have that there's an executive "I" that sits in a control room of our brain, scanning the screens of the senses and pushing the buttons of the muscles, is an illusion. Consciousness turns out to consist of a maelstrom of events distributed across the brain. These events compete for attention, and as one process outshouts the others, the brain rationalizes the outcome after the fact and concocts the impression that a single self was in charge all along...
Our authorship of voluntary actions can also be an illusion, the result of noticing a correlation between what we decide and how our bodies move. The psychologist Dan Wegner studied the party game in which a subject is seated in front of a mirror while someone behind him extends his arms under the subject's armpits and moves his arms around, making it look as if the subject is moving his own arms. If the subject hears a tape telling the person behind him how to move (wave, touch the subject's nose and so on), he feels as if he is actually in command of the arms.
The brain's spin doctoring is displayed even more dramatically in neurological conditions in which the healthy parts of the brain explain away the foibles of the damaged parts (which are invisible to the self because they are part of the self). A patient who fails to experience a visceral click of recognition when he sees his wife but who acknowledges that she looks and acts just like her deduces that she is an amazingly well-trained impostor. A patient who believes he is at home and is shown the hospital elevator says without missing a beat, "You wouldn't believe what it cost us to have that installed."
If a man prefers to believe that his wife is an amazingly well-trained impostor rather than admitting they could be wrong, what hope do we have of convincing people to change their minds about politics or religion?
Toward a new morality:
MY OWN VIEW IS THAT [science will kill morality] IS backward: the biology of consciousness offers a sounder basis for morality than the unprovable dogma of an immortal soul. It's not just that an understanding of the physiology of consciousness will reduce human suffering through new treatments for pain and depression. That understanding can also force us to recognize the interests of other beings--the core of morality.
As every student in Philosophy 101 learns, nothing can force me to believe that anyone except me is conscious. This power to deny that other people have feelings is not just an academic exercise but an all-too-common vice, as we see in the long history of human cruelty. Yet once we realize that our own consciousness is a product of our brains and that other people have brains like ours, a denial of other people's sentience becomes ludicrous. "Hath not a Jew eyes?" asked Shylock. Today the question is more pointed: Hath not a Jew--or an Arab, or an African, or a baby, or a dog--a cerebral cortex and a thalamus? The undeniable fact that we are all made of the same neural flesh makes it impossible to deny our common capacity to suffer.
And when you think about it, the doctrine of a life-to-come is not such an uplifting idea after all because it necessarily devalues life on earth. Just remember the most famous people in recent memory who acted in expectation of a reward in the hereafter: the conspirators who hijacked the airliners on 9/11.