Gatsby is desperately searching for someone who knows Daisy. When he finds out from Jordan Baker that Nick Carraway is Daisy cousin, Gatsby latches on to him in an effort to get Daisy back. Everything he does is for Daisy.
Being free and able to do anything
A third person narrator knows all the characters' feelings and thoughts, an author might choose this perspective to let the reader know everything the characters are feeling and what's going on. This gives a broader perspective on the story and can influence the readers opnion.
“elsewhere derek walcott”
