on [the state of] human nature.

The “close door” button on elevators doesn’t work until after the door fully opens.

(A) Had the “close door” button worked before the elevator door fully opens, then someone would have illicitly prevented another person from entering the elevator.

(B) Had the apple rolled off the table, then it would be on the ground.

Why am I more sure of the truth of (A) than (B) despite the fact that I think the persons that would make (A) true are not necessitated to do what they do in the way that I think the things that would make (B) true are necessitated to do what they do?