Continuing the abstracting begun yesterday, this is Chapter One of Metzinger's "The Ego Tunnel" - The appearance of a world.
Consciousness is the appearance of a world. Mammals, birds, and probably octopi have appropriate brain structures (for color vision, for example) and a primitive transparent PSM. “Higher -order” levels of the PSM in humans may be only a couple of thousand years old, higher levels attending to lower ones.
Human beings in other historical epochs - during the Vedic period of ancient India, say, or during the European Middle Ages, when God was still perceived as a real and constant presence - likely knew kinds of subjective experience almost inaccessible to us today. Theories change social practice, and practice eventually changes brains, the way we perceive the world.
The conscious brain is a biological machine - a reality engine - that purports to tell us what exists and what doesn’t. It is unsettling to discover that there are no colors out there in front of your eyes...they are models created by your brain...The world is not inhabited by colored objects at all..there is just an ocean of electromagnetic radiation, a wild and raging mixture of different wavelengths. Most of them are invisible to you and can never become part of your conscious model of reality. ...the visual system is your brain is drilling a tunnel through this inconceivably rich physical environment and in the process is painting the tunnel walls in various shades of color. Phenomenal color. Appearance. For your conscious eyes only...cognitive neuroscience has shown that the process of conscious experience is just an idiosyncratic path through a physical reality so unimaginably complex and rich in information that it will always be hard to grasp just how reduced our subjective experience is.
Shadows do not have an independent existence. And the book you are holding right now...is just a shadow, a low-dimensional projection of a higher-dimensional object ‘out there’...What is the fire that causes the projection of flickering shadows of consciousness, dancing as activation patterns on the walls of your neural cave? The fire is neural dynamics.”
The idea is that the content of consciousness is the content of a simulated world in our brains, and the sense of “being there” is itself a simulation...the conscious experience of knowing, acting, and being connected is an exclusively internal affair.
Any convincing theory of consciousness will have to explain why this does not seem so to us.