<quote> Stathis Papaioannou wrote:
; you might even be able to "read" the brain, scanning for neuronal activity and deducing correctly that the subject sees a red flash. However, it is impossible to know what it feels like to see a red flash unless you have the actual experience yourself.
So I maintain that there is this extra bit of information -subjective experience or qualia - that you do not automatically have even if you know everything about the brain to an arbitrary level of precision. Moreover, it cannot be derived even in theory from the laws of physics - even though, of course, it is totally dependent on the laws of physics, like everything else in the Universe.
I'll grant you that the subjective experience of "red" etc cannot be derived from a theory of physics.
However, by Occam's Razor we can say that the qualia that other people experience are the same as those that we experience.
The reasoning is as follows:
The theorem that the qualia are the same is justifiable on the simple theory that near-identical physical brain structure and function
(amongst humans) leads to near-identical perception of the qualia of consciousness.
What simple theory which is consistent with the rest of our scientific knowledge would justify that the qualia are significantly
different? Right now, in the absence of such a qualia-difference-explaining theory, and with a plausible and simple and
non-revolutionary and reasonable theory of qualia-sameness, a scientific-thinking default assumption should be qualia-sameness.
I never meant to suggest that other people's subjective experiences are different to our own (although it is certainly logically possible, in the same way that solipsism is logically possible). What I am saying is that there is this extra piece of information needed - the nature of the subjective experience - if we are to claim complete understanding of the brain and mind. Furthermore, this extra piece of information differs from all the other kinds of empirical data scientists collect and analyse in that it cannot be understood unless the person trying to understand it has experienced something like it himself. Thus, a man blind from birth may be a world expert on the neurophysiology of human vision but know nothing about what it feels like to see. If you are correct and there is nothing to know beyond the neurophysiology, you would have to say that there is either no such thing as "what it feels like to see", or that he doesn't understand it yet because he doesn't yet know enough neurophysiology!
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