solve the One-World Problem and the Now Problem, all we have is a
model of a unified world and a model of the present moment in the
brain. We have a representation of a single world and a representation of
a single moment. Clearly, the appearance of a world is something different.
Imagine you could suddenly apprehend the whole world, your own
body, the book in your hands, and all of your current surroundings as a
“mental model.” Would this still be conscious experience?
Now, try to imagine something even more difficult: The robust sense
of presence you are enjoying right now is itself only a special kind of image.
It is a time representation in your brain—a fiction, not the real
thing. What would happen if you could distance yourself from the current
moment—if the Now-ness of this current moment turned out not
to be the real Now but only an elegant portrait of presence in your
mind? Would you still be conscious? This is not simply an empirical is-sue; it also possesses a distinct philosophical flavor. The pivotal question
is how to get from a world-model and a Now-model to exactly what you
have as you are reading this: the presence of a world.
The answer lies in the transparency of phenomenal representations.
Recall that a representation is transparent if the system using it cannot
recognize it as a representation. A world-model active in the brain is
transparent if the brain has no chance of discovering that it is a model. A
model of the current moment is transparent if the brain has no chance of
discovering that it is simply the result of information-processing currently
going on in itself. Imagine you are watching a movie on TV—2001:
A Space Odyssey, say, and you have just watched the scene in which the
victorious apeman throws his bone-weapon high into the air, at which
point the film jumps into the future, matching the image of the tumbling
bone to that of a spacecraft. Dr. Heywood R. Floyd reaches Moon Base
Clavius in his lunar landing craft, and discusses with the local Soviet scientists
“the potential for culture shock and social disorientation” presented
by the discovery of a monolith on the moon. When they arrive at
the gigantic black monolith, a member of the exploring party reaches out
and strokes its smooth surface, mirroring the awe and curiosity the apemen
exhibited millions of years earlier. The scientists and astronauts
gather around it for a group photo, but suddenly an earsplitting highpitched
tone is picked up by their earphones—a tone emitted by the
monolith as the sun shines down on it. You are completely engaged in the
scene unfolding in front of you, to the point of identifying with the bewildered
spacesuited humans. However, you can distance yourself from the
movie at any time and become aware that there is a separate you sitting
on the couch in the living room and only watching all this. You can also
move up close to the screen and inspect the little pixels, thousands of little
squares of light rapidly blinking on and off, creating a continuous
flowing image as soon as you are a couple of yards away. Not only is this
flowing image made up of individual pixels, but the temporal dynamic is
not really continuous at all—the individual pixels blink on and off according
to a certain rhythm, changing their color in abrupt steps.
You cannot do this distancing with your consciousness. It is a different
kind of medium. If you look at the book in your hands and try to apprehend individual pixels, you can’t see any. The appearance of the
book is dense and impenetrable. Visual attention cannot dissolve the fluidity,
the continuity, of your book experience as it can discover the individual
pixels when you take a closer look at the TV screen. The blinding
speed with which your brain activates the visual model of the book and
integrates it with the tactile sensations in your fingers is simply too fast.
One might argue that this disparity exists because the system creating
the “pixels” is also the one trying to detect them. Of course, in the
continuous flow of information-processing in the brain, nothing like
pixels really exists. Still, could your inability to break the book percept
down into pixels be caused by something other than the speed of integration
in the brain? If your brain worked much more slowly (say, if it
could detect time spans of a year but no briefer), you still wouldn’t be
able to detect those “pixels.” You would still perceive a seamless passage
of time, because the conscious working of our brain is not a single uniform
event but a multilayered chain of events in which different
processes are densely coupled and interacting all the time. The brain
creates what are called higher-order representations. If you attend to
your perception of a visual object (such as this book), then there is at
least one second-order process (i.e., attentional processing) taking a
first-order process—in this case, visual perception—as its object. If the
first-order process—the process creating the seen object, the book in
your hands—integrates its information in a smaller time-window than
the second-order process (namely, the attention you’re directing at this
new inner model), then the integration process on the first-order level
will itself become transparent, in the sense that you cannot consciously
experience it. By necessity, you are now blind to the fundamental construction
process. Transparency is not so much a question of the speed
of information-processing as of the speed of different types of processing
(such as attention and visual perception) relative to each other.
Just as swiftly and effortlessly, the book-model is bound with other
models, such as the models of your hands and of the desk, and seamlessly
integrated into your overall conscious space of experience. Because it has
been optimized over millions of years, this mechanism is so fast and so
reliable that you never notice its existence. It makes your brain invisible to itself. You are in contact only with its content; you never see the representation
as such; therefore, you have the illusion of being directly in
contact with the world. And that is how you become a naïve realist, a
person who thinks she is in touch with an observer-independent reality.
If you talk to neuroscientists as a philosopher, you will be introduced
to new concepts and find some of them extremely useful. One I found
particularly helpful was the notion of metabolic price. If a biological
brain wants to develop a new cognitive capacity, it must pay a price. The
currency in which the price is paid is sugar. Additional energy must be
made available and more glucose must be burned to develop and stabilize
this new capacity. As in nature in general, there is no such thing as a
free lunch. If an animal is to evolve, say, color vision, this new trait must
pay by making new sources of food and sugar available to it. If a biological
organism wants to develop a conscious self or think in concepts or
master a language, then this step into a new level of mental complexity
must be sustainable. It requires additional neural hardware, and that
hardware requires fuel. That fuel is sugar, and the new trait must enable
our animal to find this extra amount of energy in its environment.
Likewise, any good theory of consciousness must reveal how it paid
for itself. (In principle, consciousness could be a by-product of other
traits that paid for themselves, but the fact that it has remained stable
over time suggests that it was adaptive.) A convincing theory must explain
how having a world appear to you enabled you to extract more energy
from your environment than a zombie could. This evolutionary
perspective also helps solve the puzzle of naive realism.
Our ancestors did not need to know that a bear-representation was
currently active in their brains or that they were currently attending to an
internal state representing a slowly approaching wolf. Thus neither image
required them to burn precious sugar. All they needed to know was
“Bear over there!” or “Wolf approaching from the left!” Knowing that all
of this was just a model of the world and of the Now was not necessary
for survival. This additional kind of knowledge would have required the
formation of what philosophers call metarepresentations, or images
about other images, thoughts about thoughts. It would have required
additional hardware in the brain and more fuel. Evolution sometimes produces superfluous new traits by chance, but these luxurious properties
are rarely sustained over long periods of time. Thus, the answer to
the question of why our conscious representations of the world are
transparent—why we are constitutionally unable to recognize them as
representations—and why this proved a viable, stable, strategy for survival
and procreation probably is that the formation of metarepresentations
would not have been cost-efficient: It would have been too
expensive in terms of the additional sugar we would have had to find in
our environment.
A smaller time scale gives another way of understanding why we were
all born as naive realists. Why are we unaware of the tunnel-like nature of
consciousness? As noted, the robust illusion of being directly in touch
with the outside world has to do with the speed of neural informationprocessing
in our brains. Further, subjective experience is not generated
by one process alone but by various interacting functions: multisensory
integration, short-term memory, attention, and so on. My theory says
that, in essence, consciousness is the space of attentional agency: Conscious
information is exactly that set of information currently active in
our brains to which we can deliberately direct our high-level attention.
Low-level attention is automatic and can be triggered by entirely unconscious
events. For a perception to be conscious does not mean you deliberately
access it with the help of your attentional mechanisms. On the
contrary: Most things we’re aware of are on the fringe of our consciousness
and not in its focus. But whatever is available for deliberately directed
attention is what is consciously experienced. Nevertheless, if we
carefully direct our visual attention at an object, we are constitutionally
unable to apprehend the earlier processing stages. “Taking a closer look”
doesn’t help: We are unable to attend to the construction process that
generates the model of the book in our brains. As a matter of fact, attention
often seems to do exactly the opposite: by stabilizing the sensory
object, we make it even more real.
That is why the walls of the tunnel are impenetrable for us: Even if
we believe that something is just an internal construct, we can experience
it only as given and never as constructed. This fact may well be
cognitively available to us (because we may have a correct theory or concept of it), but it is not attentionally or introspectively available,
simply because on the level of subjective experience, we have no point
of reference “outside” the tunnel. Whatever appears to us—however it is mediated—appears as reality.
Nema komentara:
Objavi komentar