I dont understand how (F) can be true, unless you're accepting of something that is simply divine and magical that we 'know' without needing to have evidence... Which seems like shaky ground to base anything off of.
Also, I'm not sure I see the issue with consciousness not existing. Since, as detailed, we can't observe/measure it, and have (at least as laid out above) there's no reason to believe it exists.
Maybe I've missed something.
Well, the reference there to Descartes, I think, is a call to a sort of "foundational epistemology." For Descartes, his "radical doubt" leads to the "bottom" being something like:
dubito, ergo cogito, ergo sum ("I doubt, therefore I think, therefore I am"). So, what does it mean then, to "know?"
On one hand, I agree, if we can't "observe/measure" it, we could rightly question, does it exist? So, if we can't directly observe thinking, and then if I doubt that thinking exists, there seems to still be a problem. That problem, of course, is that in order to doubt, well, doubt seems to be a thought, and then if there is a thought, seemingly something is thinking. In any case, there seems to be no "way out" from a skeptical point of view, that thinking seems to be occurring. Of course though, this does not actually answer what thinking is, rather only speaks to it as being something (seemingly) experientially "real."
Even if consciousness is a delusion, that is, not what it "seems" experientially, it does still seem to be. Unless we suppose that consciousness, thinking, is actually nothing, then we are really no better off in "knowing" what it is we are then experiencing as consciousness. Is thinking then an experience of nothing? Even so, thinking is still then an experience and so not nothing.
Of course though, I think the author here is likely making something of a "mistake" to be casting in lots with Descartes here (in the grand scheme of things). Because, despite the above, all he gets is a sort of phenomenology. All Descartes can really speak then of, is that experience is all that can be known. Be that, experience of thinking. In the end, everything is a sort of "something" born of the Substance called Experience.
So, in the end, what this is saying, I think, is that we can't doubt away consciousness, we can't (yet) prove or disprove consciousness, therefor, we can't prove or disprove panpsychism. Since we "have" experience, we don't doubt consciousness (generally), but since we can't quantize "experience" or "consciousness" we can't say what rightly has it or does not, since we can't observe it in the the first (experianiental) case.
TL;DR: Descartes says we can't doubt away consciousness, therefor we can't doubt away panpsychism.
(I think, I'm not sure I didn't just vomit out a word salad though.)