The irony of this discussion is that efforts to put the functions of the brain into a coherent theory can be used to support a purely deterministic explanation for things; yet that deterministic explanation is simply not very useful for trying to explain human behavior. Let's say for the sake of argument that you could predict someone's future actions exactly with 100% knowledge of their past actions. The problem is, getting that 100% knowledge is effectively impossible. That means that the deterministic explanation is just not that useful, no matter how accurate it might be.
Which of these statements can you assert with a high degree of certainty?
If I cut of John's head, he will die.
If I show John video of someone he loves about being bloodily murdered, he will feel horror.
John will disrobe in a doctor's office but not in an elementary school.
If I tell John, "That woman's top just fell off", he'll immediately look.
If I tell John that there is an invisible man in the sky who will throw him into a lake of fire forever if he eats prawns, he will not eat the prawns.
On the surface, these statements seem to be arranged in descending order of certainty. But then you get to the last one and it is unclear where that should statement should rank. Then it becomes clear that ranking these statements is based upon a series of assumptions about the nature of John, John's past, and what forces are acting on John. Is John human (could be a name for my robot). If he is, is he a sociopath? On drugs? Being threatened with a gun to his daughter's head?
But it is still useful. The usefulness is already understood in the notion that you can
predict someone's future actions. The limitations are real, you are correct; in real life,being unable to determine 100% of a person's past is incredibly daunting, and even if we did we'd need exacting information about their environment as well as their physical state. At the same time can be allowed for and mitigated. After all, the same limitations are present in every endeavor. We don't know 100% of anything, except those things we've made up
Yet even with those limitations we have developed disciplines that seek to express cause and effect because it is vital to our survival; if this
, then that
. And we apply it to everything, and then when it comes to ourselves, we say "Whoa! Whoa! That's not right! I'm SPECIAL!"
Interestingly enough, we do the same thing when it comes to death. Also, when it comes to estimating our abilities in things that we haven't actually tried
. It seems to be a human thing, and it may even be a necessary human thing, to have so little self-awareness that things that apply to [everything else in our observed existence] don't actually apply to us.
Don't get me wrong. There is apparently a degree of unpredictability in the universe. As I understand how decay works (and if I don't people will correct me), you can't tell exactly
when a particular atom of a radioactive element will decay, only that half of the atoms in a particular element will have decayed by a certain time. Human behavior covers a much larger range of options beyond "decay" and not decay", and is subject to a large variety of forces, including the forces that come from being able to manipulate its environment.
This lends a huge degree of uncertainty to complex issues, but like Newton's laws are sufficient to describe the way we interact with the observable universe on a day to day level, studies of human behavior can explain and predict on a certain scale. For the variables and unknowns, one can feel free to insert "free will" in the same way that one inserts "god" until we have better understanding of human behavior.
God and free will appear to be our go-to bookmarks for things we don't want to acknowledge about place in the universe.