That you cannot conceive of it does not make it inconceivable. In fact, scientific theories [1] exist to explain exactly the functional purpose of consciousness.
[1] http://journal.frontiersin.org/article/10.3389/fpsyg.2015.00...
True, but I find it sufficiently difficult to conceive of that I'm not convinced anyone else can. If you claim to be able to, can you explain it to me?
To me, saying experience "is" brain processing is like saying the image on the screen at a cinema "is" projector operation. One may cause the other, but they're still separate things.
> scientific theories [1] exist to explain exactly the functional purpose of consciousness.
But that doesn't explain the mechanism for conciousness to occur, it just explains why it might exist.
It does explain the mechanism actually. The mind builds representations for predictive purposes, it builds a representation of attention because that increases predictive power in achieving goals, a representation of attention is consciousness.
Certainly it's not sufficiently detailed such that you can build one, but that's not really needed to make it conceivable.
You seem to be describing that step as "representation of attention", but I'm not sure what that's supposed to mean.
Certainly it's lacking in sufficient detail to build an artificial consciousness, but it's not lacking in empirical data and testable hypotheses. It's also a perfect example of how subjective experience could be an illusion that exists, and yet still convince us that it's in some sense fundamental.
Hmm, what if both, the physical mechanism and the subjective qualia are simply intertwined in a way, that can not be deduced any further?
Maybe it's a little like the relation between gravitational forces and curved space time. Both are basically the same thing. But if you're used to live in one system, it's hard to imagine how it feels to see things from the other perspective.
Still there may be a lot of value to the complementary theory. Much like the GTR opened up a whole new range of physical applications, a physical theory of consciousness may lead to computer systems that we will have to attribute being conscious the same way as we do with our fellow human beings - just because both will follow the same fundamental laws of consciousness.
Now it's possible neither of those things can actually exist, but the fact that I can imagine them demonstrates the distinction I'm making.
Hmm, really? How? To be honest, I can't. Honestly I think this is just a meaningless mind trick. The more I think about it, the less the notion of a p-zombie really makes sense to me. If a p-zombie existed, and I could never really tell the difference from the outside, this gives rise to many blind-alley-models of the world, for example solipsism: Maybe all others are just p-zombies and maybe I'm the only thing that really exists in the sphere of consciousness (=soul?). I can never know for sure. But if it's true, then there's not really much room for any further discussion.
So I have to assume that everything that behaves like being conscious in fact has a consciousness - even if it isn't even aware of its being conscious.
And the point isn't whether such a thing is physically possible in our universe, merely that being able to conceive of such a thing identifies the distinction we're drawing. There is a notion of experience separate from the physical process that may cause it, because for any such process, we can imagine a world where it does not actually experience anything.