F. Scott Fitzgerald's classic novel, The Great Gatsby is narrated by a young man from Minnesota, Nick Carraway. After growing up in the midwest, Carraway was sent to Yale for college, went overseas during World War I, returned to New York afterward and began training in the bond business. Carraway presents himself as being above the shallow money-focused world of Jay Gatsby and his cousin, Daisy Buchanan. Telling the novel in the first person, Carraway doesn't seem to have any self-esteem problems, presenting himself as a good listener to whom people like to talk, and allowing him to be "in the loop" about all the important gossip pertaining to Gatsby, Daisy, and others of that circle. He also claims to be open and tolerant, explaining that he did not return to the midwest after the war because he had really evolved far beyond that narrow minded way of life.
Nick Carraway tells this story in retrospect, looking back at it, after Gatsby's murder, after he comes back from the East. Nick functions as a participant, first-person narrator. Because he is a minor character in the story, he is both involved in Jay Gatsby's world (and draws the reader into it), yet he maintains a somewhat objective point of view (POV) and tone throughout most of the novel.
Before this story begins, Nick (like Gatsby) has just returned from The Great War, and he shares Gatsby's ambitions to live the American Dream. Unlike Gatsby, however, he "wanted the world to be in uniform and at a sort of moral attention forever" (chapter 1, pg 2). In the same breath, Nick acknowledges that Gatsby is exempted from his scorn for moral disorder because "there was something gorgeous about him, some heightened sensitivity to the promises of life"(chapter 1, pg 2).
Therefore, immediately in chapter one, Nick is established as a minor character with two conflicting desires. On one hand, he has an interest in maintaining a sense of moral order in the world. This corresponds with his objective POV and tone as the narrator. He's neutral, nonjudgmental. On the other hand, the very first thing he reveals to the reader is his father's advice to him: "Whenever you feel like criticizing anyone . . . just remember that all the people in this world haven't had the advantages that you've had" (Chapter 1, pg 1).
As a character himself, Nick is conflicted. He wants to maintain a moral order and yet remain nonjudgmental of the moral disorder around him (the riotous parties, drinking, fighting, cheating, criminal activity, debauchery). This conflict in Nick's own character creates an interesting tension as the novel progresses.
In contrast to Gatsby's life of riotous parties and criminal activity, Nick is the character who stands for moral order. He attempts, at the end, once he becomes disgusted with the callousness and debauchery of the characters in the world around him, he attempts to restore order, to do the right thing (invites Gatsby's "friends" to his funeral, etc.)
Is Nick a reliable narrator? Can we trust his POV?
We can to a large extent. Nick says his cardinal virtue is honesty. We have no reason to question this or distrust him. And yet, we have to consider the various and limited sources of information Fitzgerald provides about the character of Gatsby himself in this novel. We have Nick's memory of events (memory is fallible, Nick is a minor character in Gatsby's life); there is also a childhood schedule in the copy of "Hopalong Cassidy" Gatsby's father brings to the funeral (a testament to the type of child Gatsby was); consider Gatsby's own account of his past (his encounter with Dan Cody); consider what his party guests claim and speculate about him (also consider how little they know about him); and think about what Jordan says, what she tells Nick about how Gatsby and Daisy met.
How reliable is Nick's account? ... Happy analyzing!