The circuits that light up do so stochastically as a function of inputs. If you clamp these, you get neural activation that is not mysterious, even if unknowable by you (or anyone). That's the heart of the problem with the "unknowable" critique. 

Well, sure, but I was trying to refer to the impossibility of prediction by anyone. 

I'm realizing prediction is not the right word. *Determined by* is more what I mean, but it is clunkier. 

A computer will have certain circuits light up because of certain inputs. Neural circuits in a human brain may light up because of certain inputs...or they might not. 

Sure, I may not be able to perceive the true logical structure of human brains, but I may choose to reason about them anyway, or I may not. I'm not sure this is true of a computer. 

Scoresby

AskSN

Is the brain a biological computer?

k00b

Just because you personally can't predict it doesn't mean the logical structure for predictability is not in place. 