Personally I do believe that all or almost all actions can be explained by this assertion, however there are a few aspects that are hard to account for. This is mainly because many details of how the brain works are not understood right now. Therefore it is hard to see actions such as thinking, choosing, reasoning, and learning explained simply by chemical processes and electrical impulses. I think it is because we don't completely understand the brain that we find these unaccountable, but I ceratinly do believe they are processes of the brain. These complex functions do occur in the brain, but we just don't know how. How do we store information in our brains, how does memory work? What kind of chemical processes in our brains do we label and know as thinking and reasoning?

Hopefully we will be able to better understand how these processes work and we will be more comfortable making the claim that brain is behavior.

Nice questions. And yes, we'll get to most of them. But why are you so convinced brain is behavior? And why think it would be a good thing if we understand the processes well enough to be persuaded it is so? PG