Problems with Physicalism
Thomas Nagel – What is it like to be a bat?
Perhaps the most fundamental and commonly used notion of “conscious” is captured
by Thomas Nagel’s famous “what it is like” sense (Nagel 1974). When I am in a
conscious mental state, there is “something it is like” for me to be in that state from
the subjective or first-person point of view. When I am, for example, smelling a rose
or having a conscious visual experience, there is something it “seems” or “feels” like
from my perspective. There is something it is like to be a conscious creature whereas
there is nothing it is like to be, for example, a table or tree. An organism, such as a
bat, is conscious if it is able to experience the outer world through its (echo-locatory)
senses.
Nagel then asks the question: can we discover what it is like to be a bat?
He first looks to our imagination:
‘Our own experience provides the basic material for our imagination, whose range is
therefore limited. It will not help to try to imagine that one has webbing on one's
arms, which enables one to fly around at dusk and dawn catching insects in one's
mouth; that one has very poor vision, and perceives the surrounding world by a
system of reflected high-frequency sound signals; and that one spends he day hanging
upside down by one's feet in an attic. In so far as I can imagine this (which is not very
far), it tells me only what it would be like for me to behave as a bat behaves. But that
is not the question. I want to know what it is like for a bat to be a bat. Yet if I try to
imagine this, I am restricted to the resources of my own mind, and those resources are
inadequate to the task’ (Nagel (1974) p324).
Then he looks to science:
It seems that no amount of objective data will provide us with this knowledge, given
that we do not share its type of point of view (the point of view of a creature able to
fly and echolocate). Learning all we can about the brain mechanisms, biochemistry,
evolutionary history, psychophysics, and so forth, of a bat still leaves us unable to
discover (or even imagine) what it’s like for the bat to hunt by echolocation on a dark
night. But it is still plausible that there are facts about what it’s like to be a bat, facts
about how things seem from the bat’s perspective. And even though we may have
good reason to believe that consciousness is a physical phenomenon (due to
considerations of mental causation, the success of materialist science, and so on), we
are left in the dark about the bat’s conscious experience. This is the hard problem of
consciousness.
Frank Jackson – Knowledge Argument
‘Mary is a brilliant scientist who is, for whatever reason, forced to investigate the
world from a black and white room via a black and white television monitor. She
specializes in the neurophysiology of vision and acquires, let us suppose, all the
physical information there is to obtain about what goes on when we see ripe tomatoes,
or the sky, and use terms like ‘red’, ‘blue’, and so on. She discovers, for example, just
which wavelength combinations from the sky stimulate the retina, and exactly how
this produces via the central nervous system the contraction of the vocal chords and
expulsion of air from the lungs that results in the uttering of the sentence ‘The sky is
blue’... What will happen when Mary is released from her black and white room or is
given a color television monitor? Will she learn anything or not? It seems just
obvious that she will learn something about the world and our visual experience of it.
But then it is inescapable that her previous knowledge was incomplete. But she
had all the physical information. Ergo there is more to have than that, and
Physicalism is false’ (Jackson (1982) Epiphenomenal Qualia).
David Chalmers – The Conceivability Argument
‘The most obvious way (although not the only way) to investigate the logical
supervenience of consciousness is to consider the logical possibility of a zombie:
someone or some-thing physically identical to me (or to any other conscious being),
but lacking conscious experiences altogether. So let us consider my zombie twin. This
creature is molecule-for-molecule identical tome, and indeed identical in all the lowlevel properties postulated by a completed physics, but he lacks conscious experience
entirely. To fix ideas, we can imagine that right now I am gazing out the window,
experiencing some nice green sensations from seeing the trees outside, having
pleasant taste experiences through munching on a chocolate bar, and feeling a dull
aching sensation in my right shoulder. What is going on in my zombie twin? He is
physically identical to me, and we may as well suppose that he is embedded in an
identical environment. He will certainly be identical to me functionally: he will be
processing the same sort of information, reacting in a similar way to inputs, with his
internal configurations being modified appropriately and with in-distinguishable
behavior resulting. It is just that none of this functioning will be accompanied by any
real conscious experience. There will be no phenomenal feel. There is nothing it is
like to be a zombie. This sort of zombie is quite unlike the zombies found in
Hollywood movies, which tend to have significant functional impairments. I am
concerned with phenomenal zombies, which are physically and functionally identical,
but which lack experience.
Zombies as I have described them are a strange idea, and it is unlikely that they are
empirically possible. In practice, it is likely that any replica of me would be
conscious. But the question is not whether it is plausible that zombies could exist in
our world; the question is whether the notion of a zombie is coherent. On the face of
it, the notion seems entirely intelligible. If this is correct, the conclusion is
established’ (Chalmers (1996) The Conscious Mind).