if mind and brain supervene, no given brain event should be said to cause the subjective event. — J

Thinking more about this, I realize that it's important to emphasize the difference between a single, given brain event -- a firing of neurons that occurs at a particular time -- and the entire physical system we call the brain (and nervous system). I believe it's true that, without my brain, I would not be conscious. And the opposite is, trivially, false: "Without my consciousness, I wouldn't have a brain." This demonstrates a grounding or priority that we don't need to contest because we fear it leads to physicalism.

What happens at time T1 is different. Neurons fire = I picture a purple cow. Why? There is no necessarily correct temporal order. We could say, "The neurons fire and so I picture the cow." Or we could say, "I decide to picture the cow and so the neurons fire." Which causes which? To me, the answer is clearly "Neither one," hence supervenience.

We can reliably, and precisely, induce subjective experiences with chemical, electrical or mechanical effects on the brain. — Mijin

Yes, but the opposite is also the case: We can reliably induce chemical and electrical effects on the brain by subjective experiences.

Yes, but the opposite is also the case: We can reliably induce chemical and electrical effects on the brain by subjective experiences. — J

Sure: both support the position that thoughts, and subjective experience, are based in neurochemistry.
Or put it this way: are there ever subjective experiences that aren't coincident with activation of areas of the brain?

Of course it's the brain. Nobody's questioning that. But that's where, not how. We know that wings make an airplane fly. When we ask how, simply repeating "the wings do it" isn't an answer. Certainly, we can mess with subjective experience by affecting voltage gated calcium channels, serotonin reuptake proteins, and any number of other parts of neurons. But that doesn't even begin to address how those physical things don't only release ions when photons of one particular range of wavelengths hit the retina, but experience redness, and don't only act on themselves in feedback loops, but are aware of their own existence.

Sure: both support the position that thoughts, and subjective experience, are based in neurochemistry. — Mijin

I understand what you mean, but "based in" is tricky. If I have a thought of someone I love, and the brain fires up in all the ways we can now observe, was my thought caused by a yet previous piece of neurochemistry? Couldn't we equally say that the chicken of neurochemistry was preceded by the egg of subjective thought? In other words, if "based in" is supposed to prioritize one level over the other in this way, it doesn't really hold up. But see my previous post. If "based in" merely means that the brain is necessary for subjective experiences to exist, but subjective experiences are not necessary for the brain to exist, then yes, "based in", in that sense, is fine.

Of course it's the brain. Nobody's questioning that. — Patterner

Much pithier than my version! Though in fact there are those who question whether brains are necessary for subjective experience; on this forum many people suggest that a nonbiological entity may achieve consciousness. I find this conceivable but unlikely.

But that's where, not how. — Patterner

Right, simply saying "Subjectivity is neurochemical" is like saying "Consciousness is an emergent property" or "The brain is the seat of the mind." It gives the illusion of understanding something but no actual content.