So that means you are a computationalist? Fine, but why do you think physicalism may be incoherent?

The distinction seems to hinge on whether physics is computable. I suspect the Church-Turing-Deutsch principle is true and if it is then it is possible to simulate a human mind using a classical computer and that simulation would be conscious. If it is false however then it is possible that consciousness depends on some physical process that cannot be simulated in a computer. That seems to me to be what Pearce is claiming and that is not incoherent. If we live in such a universe however then it is not possible to simulate a human using a classical computer / universal Turing machine and so it is incoherent to claim that you could simulate a human but the simulation would not be conscious because you can't simulate a human.

To me, this reads as an express acknowledgement of the CT thesis (unless quantum gravity turns out to be uncomputable, in which case the CTT is just plain false).

I honestly don't see how you make that connection. It seems clear to me that Pearce is implying that consciousness depends on non-computable physical processes.

A huge look-up table could always "in principle" provide the innards governing any behavioral regularities whatever, and intuition proclaims that we would not consider anything controlled by such a mere look-up table to have psychological states. (If I discovered that you were in fact controlled by such a giant look-up table, I would conclude that you were not a person at all, but an elaborate phony.) But as Alan Turing recognized when he proposed his notoriously behavioristic imitation game, the Turing Test, this "in principle" possibility is not really a possibility at all. A look-up table larger than the visible universe, accessed at speeds trillions of times in excess of the speed of light, is not a serious possibility, and nothing less than that would suffice. What Turing realized is that for real time responsivity in an unrestricted Turing Test, there is only one seriously conceivable architecture: one that creates its responses locally, on the fly, by processes that systematically uncover the meaning of the inputs, given its previous history, etc., etc

-- Daniel Dennett (from here)

The point being that GLUTs are faulty intuition pumps, so we cannot use them to bolster our intuition that "something mechanical that passed the Turing Test might nevertheless not be conscious".

It would take a GLUT as large as the universe just to store all possible replies to questions I might ask of it, but it would flounder on a simple test: if I were to repeat the same question several times, it would give me the same answer each time. You could push me into a less convenient possible world by arguing that the GLUT responds to minute differences in my tone of voice, etc. - but I could also record myself on tape and play the same tape back N times, and the GLUT would expose itself as such, and therefore fail the test, by sphexishly reciting back its stored lines.

There's no way that I can see of going around this, other than to "extend" the GLUT concept to allow for stored states and conditional branches, at which point we recover Turing completeness. To a programmer, the GLUT concept just isn't credible.

The lookup tables are not conscious but the process that produced them was.

If the Church-Turing-Deutsch thesis is true and some kind of Digital Physics is an accurate depiction of reality then a simulation of physics should be indistinguishable from 'actual' physics. Saying subjective experience would not exist in the simulation under such circumstances would be a particularly bizarre form of dualism.