How can a third person omniscient point of view advance the plot, develop the main character and shape the theme in "Paul's Case"?
Third person omniscient point of view means that an outside narrator is telling a story and the "views" (i.e., thoughts) of all the characters are able to be heard by the audience. In a limited point of view, only one or a few characters are fully "seen" by the audience. Therefore, omniscient allows us to better understand the motivations of every character, which can better explain the events of the plot and foreshadow what will happen as the plot develops. Also, because the perspective of each character is shown, the author has an easier time using thoughts to promote or underline the theme of the story.
The theme in this story is the danger of the American Dream. This "dream" suggests that all people can have whatever they desire - rags to riches, and so on. However, it is this truism that brings Paul to his downfall. He desires a beautiful and artistic life, and so steals money to go to New York in search of such a life. Understanding his motivations help show that he is not outright criminal, but misled by desires. We see how his belief in the American Dream have led him astray. Having the thoughts of others, though, is what emphasizes that Paul is mistaken. His music teacher thinks that he is "haunted" and that there is something not right about him. Paul's father thinks that Paul can succeed in a more understated way, and shows what can be achieved by not overreaching in dreams.