I think the best way to reach an understanding of a new concept is repetition.
Mechanism is one thing. Agency is another.
Let this ring back and forth in your mind for a while. Then, remember that explanation of agency is never meant to provide explanation of mechanism. This is where atheists most often become confused.
As for the underlying assumption of whether or not God exists, you and I can only choose between the two. There are no other possibilities.
What scientific disciplines use it? It doesn't seem to make much sense as you describe it.
As for the underlying assumption of whether or not God exists, you and I can only choose between the two.
I don't need to choose either. I can freely look at the evidence and see that all of the evidence supports the latter.
I have chosen to believe this.