If any of you have a moderate astigmatism, you may have observed this - if
not, you'll have to take my word for it.
If I close my weak eye*, I find that after a few seconds, the image from
the strong eye, even though it is closed, tries to creep into my visual
field. It is not difficult at this point to 'look through' the eye that is
closed (seeing phosphenes or just darkness). Reversing the test, with my
weak eye closed, there is no creeping effect and it is not really possible
for me to look through the eye that is closed.
In a universe of functionalism or comp, I would expect that this would
never happen, as my brain should always prioritize the information made
available by any eye that is open over that of an eye which is closed. The
fact that closing the weak eye instead does not produce the creeping image
effect demonstrates that there is no functional purpose which could be
served by favoring the strong eye when it is the one which is closed.
In some people astigmatism progresses until the develop a wandering eye.
The physicalist can claim victory over the functionalist here in that the
atrophy of nerve connections to the weak eye and the relative hypertrophy
of the nerve connections to the strong eye clearly dominate the functional
considerations of the visual mechanism. The creeping image effect also is
not immediate, so that it is not the case that the hardware is incapable of
maintaining clear vision through the weak eye, it is obviously the inertia
of purely physical-perceptual processes which is dragging the function down.
Between the physical and the perceptual, which one is driving? It would
seem that physics would win here, because the creeping image is not the
more aesthetically rich image - however, this is not a case where the
aesthetics are determined only from the top down. Remember that both eyes
are exposed to the same light. The retinas receive the same total number of
photons. The strong eye develops more robust connections to it not because
it has more light, but because the shape of the eye is such that the cells
(sub-personal agents) of the retina are able to make more sense out of the
better focused light.
There are not more signals being generated, but clearer signals which carry
farther up the ladder from sub-personal optical detection to personal
visual sensation. The nerve growth follows the coherence of visual
consciousness, not a just a photological nutrient supply. The eye becomes
stronger because the brain population is prioritizing higher sensitivity,
not because neurons are being pushed around by blind ionic concentration
gradients. That sensory priority is the cause of the neurological
investment in that eye's sensitivity, so that it is perceptual inertia
which drives the creeping image effect not just biological morphology.
*which is my left eye. Curious if any of you left brainy types have an
astigmatism in the right eye.
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