Tuesday, January 15, 2008

what substance dualists can't accept

Inspired by Malcolm's recent linkage to a Steven Pinker essay, I hereby provide you with a counter-link, if you will, to another Pinker essay titled "The Mystery of Consciousness." The section I reprint below is one that substance dualists generally find hard to swallow, and which they will attempt to dismiss as merely "missing the point" in discussing the so-called "hard problem" of consciousness:


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.

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.

I make some of the above points in my own essay on mind (which I also included in my book), though nowhere near as eloquently or as cogently as Pinker does.

For those who missed it when I published it last time, here's a link to an interview of Steven Pinker by Robert Wright (with thanks again to Sperwer for having alerted me to this very interesting website).

One problem I'd eventually like to address is the dualist's insistence on what is termed "the unity of consciousness," an idea attacked by quite diverse schools of thought ranging from neuroscience to postmodernism to Buddhism.



Anonymous said...

Kevin - I can see pretty clearly why dualists would have difficulty with evidence that mental states are so equisitely responsive to manipulations of "brute matter." Nobody has the foggiest idea of how distinct substances could interact.

But they are correct to observe that clear evidence that mental states are causally influenced by material manipulation "misses the point" of the so-called hard problem of consciousness. Nobody has the foggiest idea of how subjective states of consciousness could be produced by "brute matter."

Kevin Kim said...


Thanks for the comment.

I suspect that what the substance dualists would consider "clear evidence" would have to measure up to an impossibly high standard of proof, as shown by their a priori unwillingness to accept the idea that a rigorous empirical method might produce results.

I see the dualists as irrationally attached to a maniacal version of the mantra that "correlation is not causation." As science continues to provide increasingly persuasive evidence of the intimate correlation between neural activity at the fine level and human action at the gross level, this mantra will appear, I think, increasingly shrill, not to mention untenable.

One thing I've argued before is that progress in the field of artificial intelligence has been predicated on physicalist assumptions; no AI specialist would be taken seriously if s/he were to reveal a substance dualistic bias. As the machines we create continue to evince increasingly complex behaviors, especially behaviors at the pattern-finding and problem-solving levels, it becomes less obvious that we need to posit a whole other substance to explain mental phenomena.

If we're willing to grant that nature has already provided us evidence of simpler forms of mind/consciousness in the guise of non-human animals, the door is open, I think, to the possibilities hinted at in the functionalist view: matter of a sufficiently complex arrangement can manifest consciousness. We can "build upwards" to consciousness, and we can probably do so at a logarithmically faster rate than nature's blind trial and error can.