Hi everyone, I've just signed up and am excited to have found this forum. There's so much to discuss. I've read just about every post in this thread. Some of what I've written below I started to form before I got to the end but I don't think there's too much overlap with what's already been said.
raw_thought wrote: ↑
Tue Mar 07, 2017 1:52 pm
The visualized triangle is not a part of the brain. It is nowhere in the brain. To say ( to repeat myself ) that the triangle is embedded in the brain in a non-triangular form is like saying that holding a CD of Mozart is identical to hearing the music.
raw_thought wrote: ↑
Tue Mar 07, 2017 6:57 pm
3. It is obviously not physical as there is nothing physical that is in a triangular shape in the brain that is created by visualizing a triangle. Any scientist will tell you that you do not cause your neurons to fire in a triangular shape ( or that you create a subatomic particle that is triangular ) when you visualize a triangle.
It wouldn't be relevant for anything in the brain to be physically arranged in a triangular shape (except perhaps nerves on the retina) because neurons generally speaking don't care how they are laid out in space relative to one another. What matters is how the neurons are connected to one another. You can jumble up a bundle of wires without changing the function of the circuit they form.
It's clear to me that there is a strong representation of visual fields in the brain. I use the plural because it seems possible (though may be difficult) to view a real scene at the same time as vividly imagining an image of an object without the two images overlapping. There seems to be at least one separate sort of "mind's eye" for imagining images rather than them appearing sharply in the normal visual field (which would probably be dangerous and place a species at a disadvantage. Trajk Logik has already touched on this difference). Now in the original point you raised, the explanatory gap was a question of how can something in one of these visual fields have a physical existence.
As the brain depends upon electrical and chemical signals, it has to translate information about the environment into terms of these. A triangular pattern of light on the surface of a retina is not of direct use to the brain and so cannot be thought about nor remembered. The translation into patterns of neural activity clearly brings the information closer
to what the mind can experience. We're intuitively so used to thinking of "real" things in terms of the shapes and sounds and objective measurements outside of our bodies in the external universe that we tend to expect that something has to exist in such forms to be real. And that obsession with only objective measurements being real is probably a key motive in the beliefs of most eliminativist physicalists. But to the mind, the patterns of information in the brain are the native language of what is real. Again, when we think about this objectively it seems very strange because we get caught up thinking about fleshy brains and masses of neurons and Leibniz's mills and how far removed they seem to be from any image of a triangle. But it's the information itself that I believe is where the triangle exists. The qualia seem to be some kind of manifestation of that information and, for me, that is where the explanatory gap lies, between the information and the qualia. Is the information itself physical? I'd opt for calling it metaphysical.
I'll grant you it does seem strange how vividly and directly the 2 dimensional nature (plus some stereoscopic depth information and color) of the visual field appears to us. And even as someone with dualist leanings, I have to ask exactly how much
of that visual field is physical. I mentioned above why a physically triangular shape somewhere inside the brain wouldn't be appropriate to give a triangular experience, but it's worth noting that there are ways that neurons can gain some concept of relative position, shape and size. A good way to understand that is to look at how it is done with computer memory. An image to be displayed on the screen is held in memory but ordinarily, until it is displayed on the screen, information on the relative positions and shapes of objects drawn on it might not explicitly exist anywhere. However, computer software can be loaded into the computer's memory that can manipulate and compare memory addresses. By subtracting one memory address from another, effectively a sort of distance between those two memory locations is obtained and stored. This could be used to find the distance between two points on a triangle on the screen. A similar sort of process could find a sort of distance metric between two points on a triangle encoded by neurons that represent a visual field in someone's brain. Other algorithms, like the Hough Transform, can form a representation of the shape. When these mental representations are derived from the visual field and held in other neurons they could trigger further qualia giving impressions of shape, color, size and depth.
The really strange bit for me, stranger even than qualia, is why our experience of the universe seems to be exactly centered on the qualia of one particular brain and not another one nor several of them. Fundamentally physics makes no distinction between one human body and another. It's all just one pile of interacting particles. These are questions involving indexicality and personal identity and continuity of consciousness but I have a lot of reading to do on these and they deserve their own forum thread. To me though, this represents an even bigger explanatory gap and an even bigger problem for the eliminativist - unless they're content with embracing solipsism.