A -> B -> A -> B

You: "Why do you view the brain as a muscle? Can't we attemp to understand staff like that via research?"

Him: "Because the normal human brain is what it is because it does not see all the possible aspects of anything. And that's because it is willing to focus all of his willpower on this".

What to answer?

a. What does it mean to focus all of your willpower on something?

b. Says who that focusing all your willpower into this will make you fully understand reality?

c. Says who that it's even possible to focus all your willpower on one thing?