Nephi was given power to perform extraordinary tasks. Among those were feats that would be contrary to known physics. What is important in this impressive ability to manipulate the real world is that he was still powerless to manipulate men’s hearts. Nephi might command a mountain to move, and it would, but he could not command a man to repent and have him do it. Nephi might be able to call a famine to the land, but he could not so much as change the heart of a single person. Agency is so powerful a requirement of our existence that it stands above even the manipulation of the elements.