|
Basic InformationLatest NewsAHA News: Dr. Dre Recovering From a Brain Aneurysm. What Is That?Can 2 Nutrients Lower Your Risk for Parkinson's?New Clues to How Cancers Originate in the BrainBrain May Age Faster After Spinal Cord InjuryScans Reveal How COVID-19 Can Harm the BrainWhat Loneliness Looks Like in the BrainNeurologists Much Tougher to Find in Rural AmericaCOVID-19 Survival Declines When Brain Affected: StudyAs Testing Costs Rise, Neurology Patients May Skip ScreeningGene Therapy Shows No Long-Term Harm in Animals: StudyCould Gene Therapy Cure Sickle Cell Disease? Two New Studies Raise HopesCocoa Might Give Your Brain a Boost: StudyLockdown Loneliness Could Worsen Parkinson's SymptomsChildhood Lead Exposure Tied to Brain Changes in Middle AgeStaying Social Can Boost Healthy 'Gray Matter' in Aging BrainsDNA Analysis Might Reveal Melanoma RiskGenetics Might Explain Some Cases of Cerebral PalsyDiabetes Drug Metformin May Protect the Aging BrainNew Research Links Another Gene to Alzheimer's RiskYour Sex Affects Your Genes for Body Fat, Cancer, Birth WeightExperimental Drug Shows Promise Against ALSCould Gene Therapy Stem the Damage of Parkinson's?Genetic Research May Help Identify Causes of StillbirthBlood Test Heralds New Era in Alzheimer's DiagnosisMore Clues to the Genes Behind Hearing LossScientists Move Closer to Mapping Entire Human GenomeBlood Test May Reveal Concussion Severity With Accuracy of Spinal TapDeep Brain Stimulation May Slow Parkinson's, Study FindsStroke, Confusion: COVID-19 Often Impacts the Brain, Study ShowsYour Genes May Affect How You'll Heal If WoundedEven Without Concussion, Athletes' Brains Can Change After Head Jolts: StudyHealthDay In-Depth The AI Revolution: For Patients, Promise and Challenges Ahead">HealthDay In-Depth The AI Revolution: For Patients, Promise and Challenges AheadHealthDay In-Depth The AI Revolution: Giving Docs a Diagnostic Assist">HealthDay In-Depth The AI Revolution: Giving Docs a Diagnostic AssistBlood Test Might Predict Worsening MSKeto Diet Might Change Your Gut in More Ways Than OneParkinson's Patient Improving After First-Ever Stem Cell TherapyKey Areas of the Brain Triggered in Recent Heart Attack SurvivorsFirst Good Evidence That Brain Hits 'Replay' While You SleepSome NFL Players May Be Misdiagnosed With Brain Disease: StudyGreenhouse Gases Bad for Your BrainTransplanted Skin Stem Cells Help Blind Mice See LightBrain Plaques Signal Alzheimer's Even Before Other Symptoms Emerge: Study'It's Like You Have a Hand Again': New Prosthetic Gets Closer to the Real ThingLosing a Spouse Could Speed Brain's DeclinePaddles Against Parkinson's: Ping Pong Might Ease SymptomsIn a First, Doctors Use Robotics to Treat Brain AneurysmSkiers Study Suggests Fitness May Stave Off Parkinson'sCRISPR Gene Editing Creates 'Designer' Immune Cells That Fight CancerGene Variant Ups Dementia Risk in Parkinson's Patients: StudyGene Variation May Protect Against Alzheimer's: Study Questions and AnswersLinksBook Reviews |
| |
by Charles P. Siewert Princeton University Press, 1998 Review by Josh Weisberg on Oct 26th 2001 In The Significance of Consciousness, Charles Siewert argues
that "phenomenal consciousness," the subjective feel
or character of conscious experience, is the most significant
aspect of our mental lives, and, what's more, many consciousness
researchers do not adequately account for phenomenal consciousness
in their theories. The book is a complex and sometimes difficult
work of philosophical investigation, and its style is often hard
to penetrate. But Siewert's main points can be succinctly distilled,
and they challenge those investigating the mind to thoroughly
explain the role of phenomenal consciousness in our lives.
The book opens with a defense of what Siewert calls "the
first-person approach to consciousness" (10). Consciousness
is known "from the inside" in a distinctly first-person,
subjective manner. This knowledge is not infallible or beyond
challenge, but, Siewert argues, unless we have good reason to
doubt the deliverances of first-person knowledge, we should respect
it. Siewert charges that many consciousness researchers ignore
this advice in the course of their investigations, and thus deny
or seriously downplay the importance of phenomenal consciousness.
Siewert develops and defends this claim by employing a variety
of thought experiments that isolate phenomenal consciousness,
and arguably show that many theories of consciousness "neglect"
(to use Siewert's favored term) the phenomenon. Siewert positively
describes phenomenal consciousness as what is "shared by
silent speech, other imagery, and sensory experience" (148),
but he also picks out the idea in the negative, as that quality
lacking in the neurological condition known as "blindsight."
Blindsight is a well-documented neurological deficit that can
occur when there is damage to the visual cortex. Subjects claim
they can't see anything in the damaged portion of their visual
field, but they are substantially better than chance at guessing
what is present there. They can identify the form, motion, orientation,
and perhaps the color of test stimuli, but they do not make these
judgments unless prompted to guess by investigators. The condition
suggests that a large amount of visual processing goes on in the
absence of consciousness, and many researchers have focused on
this result to craft their theories.
Siewert proposes that we imagine a blindsight subject who can
use the information gleaned from the blind field without being
prompted to guess, by "self cueing." Next we are to
imagine a subject with badly degraded but conscious blurry vision
who is able to make exactly the same sorts of discriminations
as our imaginary self-cueing blindsighter. Both subjects will
be able to make the same discriminations and arguably will behave
in the same way. But, claims Siewert, one subject, the self-cueing
blindsighter, lacks something. That something is phenomenal consciousness.
Siewert then argues that if a theory must deny the coherence or
possibility of his thought experiment, the theory neglects phenomenal
consciousness. The rejection of the scenario posited by the thought
experiment collapses the distinctly phenomenal aspects of consciousness
into mere behavioral capacities, capacities that arguably can
be exercised without the presence of phenomenal consciousness.
This deflates or neglects what Siewert sees as the most important
aspect of our conscious lives, that aspect that we know in a distinctly
first-personal manner. Siewert claims that theories that identify
consciousness with abilities to perform various perceptual discriminations
or judgments, as well as theories that identify consciousness
with forms of higher-order awareness all must reject the thought
experiment, and so neglect phenomenal consciousness.
Having exposed the alleged neglecters of phenomenal consciousness,
Siewert goes on to stress the significance of phenomenal consciousness
in our lives. He argues that phenomenal consciousness is inherently
"intentional," or about the world, because conscious
subject can be assessed for accuracy or truth in terms of what
their phenomenally conscious states are about. Furthermore, Siewert
argues that in addition to mental imagery, nonimagistic thoughts
have a phenomenal feel and can differ in their phenomenal character.
Siewert ends the book by pointing out that we would sorely miss
phenomenal consciousness if we were deprived of it, so much so
that we might prefer death to the "zombiehood" that
would follow removal of our phenomenal lives.
Siewert's book is thought provoking, but the style of the writing
makes it at times difficult to follow. There are paragraphs that
require reading and rereading by those well-versed in the consciousness
literature, so the work may not prove particularly accessible
to the lay reader. Furthermore, the central thought experiment
designed to show that many theories neglect phenomenal consciousness
is flawed. The additional considerations that are added to the
real blindsight case in order to engage specific theories of consciousness
become progressively more dubious, and in the end the argument
collapses into the claim that we can simply imagine identical
beings, one that is phenomenally consciousness and one that is
not. This is the shopworn "zombie argument," and it
is very controversial whether conceiving of phenomenal zombies
demonstrates anything that threatens empirical investigations
of consciousness. Though Siewert is undoubtedly correct that,
all things being equal, we should respect the deliverances of
our first-person access to our minds, and that we should work
to adequately explain phenomenal consciousness, he has not established
that the theories he attacks have neglected what is significant
about consciousness.
© 2001 Josh Weisberg
Josh Weisberg is
a doctoral student in the philosophy program at the CUNY Graduate
Center
|