Earlier quoted context omitted.
Computable doesn't really make sense here IMO, as you say, consciousness is not the illusion, it's the audience, it's the thing receiving the output not just an evaluation of a mathematical function. The better question is why couldn't a consciousness attach itself to (be the audience for) a computation. Since we really don't understand anything significant about it, questions like this are next to impossible to disp…
> it's the thing receiving the output not just an evaluation of a mathematical function. how do you know it's not just an evaluation of a mathematical function?
A mathematical function is a set, possibly infinite, of pairs of abstract elements (commonly defined via sets) where no two pairs share the same first element. Nothing less, nothing more.
Computation is the act of determining the abstract output (second element in the pair) for a given abstract input (first element in the pair).
Nothing in those definitions is capable of expressing the concept of having perceptions (consciousness). That's not an abstract thing.
This isn't to say the concrete thing doing the computation couldn't in principal be conscious, just that it doesn't definitionally make sense for the math itself to be conscious.