Once we understand all the physical facts (including e.g. the physical causes of people talking about qualia) there are no other facts to understand.
It's the last bit here that's controversial. Why are there no other facts to understand past the physical ones? What's the argument for that?
Here's what I mean: Say that whenever I see that something is red, a certain neural network is activated, call it the R-network. Once we discover that seeing red is, physically, the activation of the R-network, should we then say that there are two facts ('I saw a red thing' and 'My R-network was activated') or only one fact ('My R-network was activated')? We might readily admit that seeing red is reducible to the activation of the R-network, but that alone doesn't mean that the fact 'I saw a red thing' is not a fact.
Every time I see a red thing, I see a thing. So, are "I see a red thing" and "I see a thing" two separate facts? If so, then I cannot imagine what value there is in counting facts. On that account simply listing all the facts that derive from a given observation ("I see a thing that isn't blue" "I see a thing that isn't yellow" "I see a thing that isn't orange" etc. etc. etc.) would take a lifetime. It might be useful to Taboo "fact".
[Cross-posted.]
1. Defining the problem: The inverted spectrum
A. Attempted solutions to the inverted spectrum.
B. The “substitution bias” of solving the “easy problem of consciousness” instead of the “hard problem.”
2. The false intuition of direct awareness
A. Our sense that the existence of raw experience is self-evident doesn’t show that it is true.
B. Experience can’t reveal the error in the intuition that raw experience exists.
C. We can’t capture the ineffable core of raw experience with language because there’s really nothing there.
D. We believe raw experience exists without detecting it.
3. The conceptual economy of qualia nihilism pays off in philosophical progress
4. Relying on the brute force of an intuition is rationally specious.
Against these considerations, the only argument for retaining raw experience in our ontology is the sheer strength of everyone’s belief in its existence. How much weight should we attach to a strong belief whose validity we can't check? None. Beliefs ordinarily earn a presumption of truth from the absence of empirical challenge, but when empirical challenge is impossible in principle, the belief deserves no confidence.