You are using the term 'irrational' equivocally. You are also using 'post hoc ergo propter hoc'. Whether the universe is irrational (is not the product of mind) has no bearing on the rationality (the ability to reason) of the human (or any other animal's) mind.
I think I am not using the term "irrational" in an equivocal way. Rationality is taken for granted, but my point is that it cannot be accounted for if it is nothing but the product of brute physical forces of either chance or mechanical necessity. How is rationality derived from irrational force? Is rationality a physical thing? If it is not does it really exist? If it does not exist then why should it be taken for granted? It is not 'post hoc ergo propter hoc' to point out that the 'oughts' and 'ought-nots' of reason, truth, morality, etc. cannot be derived merely from an 'is'.
Let me try an example. I believe rationality cannot be accounted for by mere matter in motion. You believe it can be. Suppose our respective "thoughts" are really nothing but the product of brain chemistry, so to speak - some thing that was triggered by some prior physical force, and so on, turtles all the way down. Which of this chemistry is "wrong", yours or mine? How can any of this very complex chemistry be "wrong"? Or "right" for that matter?
From your #406 ---And yet "things" in the brain indisputably DO move, change states, etc, when we speak. And indisputably the ability to speak (or reason, or remember, etc) can be affected, even eliminated, by damage to physical structure in the brain. Indisputably simulating certain structures in the brain can cause involuntary memories, thoughts, speech, and etc.
No one disputes these things. The problem is, how do you account for rationality?
Even to ask the question, "...why in the heck is it rational to say 'all these physical things happen in detailed coordination with an independent substance called 'mind'", you have to presuppose the very thing you deny (that independent substance called 'mind') in order for the question even to make sense. What cannot be accounted for is the notion that that physical matter and forces (brain chemistry) ARE rational.
It is the physicalist IDENTIFICATION of reason with, or as nothing but, matter/force that renders knowledge itself unintelligible. What if one asks if the question itself is rational or irrational? On the physicalist view, it's like asking if electricity is rational or not - the question doesn't even make sense without presupposing MIND. So what property of matter gives rise to rationality and irrationality - to MIND? You believe in logic and reason but can you justify them on purely physical grounds? (Pun intended:^)
Cordially,