>So far as I can see, your argument that physicalism entails substance independence works equally well for the substance independence of wetness:

I have no problem with this if the terms are properly understood. Wetness as a relational property can obtain in a sufficiently precise simulation. Wetness as a metaphysical property can't obtain in a simulation because the term includes suppositions of ontological grounding that interactions of electrical signals don't satisfy (why my head can't get wet from simulated water). If we note this distinction then there is no issue or reductio.

Let me ask you this: if you take it that there is some difference-making physical property of matter for consciousness that doesn't manifest as a kind of physical interaction studied by physics, then what is the nature of that property? Physics tells us that physical properties are defined by their interactions. So if we rule out the standard kind of influence that physical properties have, then whatever is left is necessarily unobservable. This is plainly non-physical influence if you take physics seriously.

>That is not operationalization in the usual sense, since it isn’t possible to observe which quales are or aren’t seeming to someone.

It's not measurable in practice, but it might be in principle if physicalism or materialism is true (i.e. influence should be measurable).

>That depends on how you cache out the formula “it seems that [quale]”. If it’s an attribution of a propositional attitude, then it certainly could be mistaken.

Right, attributing such a statement externally could be mistaken. But we do know that such a self-report, if genuine, necessarily is correct. And so in the context of analyzing consciousness, we can assume genuine reports of phenomenal properties and so attribution isn't an issue.

> "John is in pain" unambiguously means that John is undergoing a particular sensation, not that he is exhibiting a particular kind of behavior.

The issue is less about ambiguity (I know I used that word), and more about bias. If we want to avoid bias in our specification of the problem, we need to use theory-neutral language. "John is experiencing pain" isn't theory-neutral, as it assumes John and pain are distinct things rather than pain being a state or property of John.

Some random thoughts on the subject (feel free to skip):

With my "it seems that [quale]" formulation and the idea that genuine self-reports of that nature cannot be mistaken, some interesting questions arise. In Chalmers' zombie argument, a zombie would give utterances of this sort exactly like we do. But on what basis can we say that their reports are not genuine without begging the question against physicalism? On the other hand, if we say their reports are not genuine, neither are ours! Actual phenomenal properties by assumption play no causal role in our behavioral reports of phenomenal properties and so the utterances are not genuine. When we think "I seems that [quale]" we are correct, but every time we create a physical artifact to that effect, we are wrong. What a strange state of affairs non-physicalism is.

Under what conditions are we justified in believing phenomenal reports are genuine? If I were to evolve or train an artificial neural network that, without any explicit training, started to make such phenomenal reports, are we justified in believing it genuine?