> lweiger at umich.edu wrote:
>
>> It might well be that _all_ mental states depend on brain chemistry.
>
>
> And how do you know that brain chemistry doesn't depend on mental
> states? Repeated stresses/insults/disappointments/injuries could
> change the biochemistry, no?
Well, since stresses, insults, and injuries are also applicable to _physical_ changes to the brain, yeah, of course.
But lweiger's error was, frankly, making only a tentative claim; I regard it as axiomatic that mental states depend upon physical states of the brain. (Otherwise, we'd have to put up with speculation about souls, spirits, and other mystical bullshit.)
The core assumption here is that, since consciousness is an expression of the brain, for every mental "state" there is a physical analogue. Our understanding of those physical underpinnings is imperfect, of course. And as Doug points out, the causality works both ways; disturbances in the physical state of the brain can cause changes in mental states, and changes in one's mental state (through events in one's life, social interactiona, etc.) are expressed in changes in the physical state of the brain. There are also predispositions among individuals that develop with an interaction of genes and environment.