> But according to solipsism you can't be sure my brain actually exists at all, right?
Right but my belief is I live in a universe with regular processes depending on regular arrangements. It seems like a relatively weak axiom to hold and precludes the version of solipsism you mention.
> They're both made of the same protons and electrons, right?
They have different arrangements. A MOSFET is just a block of polysilicon sitting on top of another layer of silicon which has been doped to contain some arsenic or boron atoms (+ some other details). I can put some legos together which correspond conceptually to this, but they will have functional differences. The actual substrate is what causes the mosfet to have the function of a transistor. Of course the neurons in the brain are far more complex and have different physical properties.
To me trying to explain how protons and electrons put together results in consciousness feels the same as the pre-Newtonians trying to explain gravity with their mechanical philosophy. The only thing I know is my brain is conscious, and your brain is physically similar to mine. Substrate non-independence is actually the weaker of the two assumptions in a sense because it makes a positive statement about fewer systems.
> That feels like a reach for a theory that wants to find a certain conclusion.
The problem with this kind of thinking is one can impugn the beliefs of either side with underhanded motives. Maybe people self-identify as being moral and ethical and elevating the talking computer gives them status in their circle. Maybe the personhood for AI researcher has a big ego and wants their work to be extremely important today.
I honestly do not find it plausible that we cannot build a consciousness-free intelligent computer system. A computer system can be made out of marbles, or pulleys, or pen and paper. All of these are having an experience if you put the symbols or objects in the right order? It just seems absurd to me.
> Right. But that's circular, isn't it? Consciousness is what I feel like consciousness is.
A priori why must real concepts be reducible in the way you want? Gravity is the thing that makes stuff fall, actually it’s the curvature tensor of the spacetime metric? What is the spacetime metric actually? Maybe something in string theory? Eventually you get to irreducible primitives that simply correspond to something we observe. Why isn’t consciousness just this with fewer steps?