Monist vs. Dualist Experiment?

[genkaus]

I get it. I just don't agree that the analogy holds. In the case of 9/11, there is no sufficient explanation for the video planes crashing into buildings and causing a fire than an "actual" plane crashing into an "actual" fire (quotes because in this argument, solipsism and idealism always linger in the background). Yes, it's possible that neither the planes, nor the buildings, nor New York exist, in which case it would be a pretty fantastic conspiracy, but that's not because of their PROPERTIES as I perceive them. It's a different kind of agnosticism.

Actually, it is exactly the same kind of agnosticism.

Either, there were no planes and no towers and the whole thing is a fantastic conspiracy to deceive you or there were plane that hit the towers and the videos and news-reports are evidence for the event.

Similarly, either nobody has any capacity for subjective experience, except you and all of them saying that they do and acting in that way is a fantastic conspiracy to deceive you - or they do have qualia and their behavior and statement are evidence of it.

In the case of qualia, you have a secondary property which is not necessary to explain behavior. The brain itself is a sufficient explanation: "Data comes in, brain processes it, and behavior comes out." Our reason for believing in qualia therefore is not behavior-- it is the direct experience of our own qualia as a brute fact.

You ignore the fact that subjective experience is an essential part of "brain processing it". Without the subjective experience or qualia being included in the processing, the behavioral output cannot be sufficiently explained. Qualia is necessary to explain behavior.

I do not have my own interior plane or my own interior fire which I necessarily extend by philosophical pragmatism to 9/11

You do - in a manner of speaking. You have personal experience of existing planes and of existing buildings and that is what you extend by "philosophical pragmatism" to 9/11. If, instead, I told you that a spaceship flew into a crystal spire and showed you videos and news-reports to that effect, you would not believe that.

The difference is that nobody is equating planes with invisible secondary properties which I must ALSO assume.

Aren't you the one who keeps insisting that qualia is a brute fact. Which means they are not invisible secondary properties that you have to assume.

In a physical monism, the brain is sufficient to explain behaviors, which are really just the physical motions of the body.

And the capacity for subjective experience is a part of that explanation.

The only assumption I need to make is that the brain, and its relationship to the body, are real (no solipsism, no Matrix, etc.). Whether qualia exist is irrelevant, since whether or not I accept the qualia of others, their brains and behaviors are the same-- there's still no mystery which demands the extra inference.

I agree - there is no mystery that demands extra inference. The existence of qualia is required to explain how and why some behavior occurs and if its existence can be explained by brain function, there is no need to invoke anything extra like a "soul" or "atomic quale".