If Nick is considered the main character, then the culture in the quiet interior of the country has made him a practical, rational man who yearns for adventure and success but who can still see folly and misguided--even destructive--choices. This is amply underscored by the fact that at the end of his experiences with Gatsby, after attending Gatsby's funeral, Nick returns to his homeland in the Middle West, thus leaving the pain of Gatsby’s failed Eastern life behind. As he says:
On the last night, [I] looked at that huge incoherent failure of a house once more.
If Gatsby is considered the main character, as the narrative is about Gatsby and his self-deceiving belief
in the green light, ... that year by year recedes before us,
then the cultures represented by multiple backgrounds and mentors has made him a man who lives by deceptiveness, which he wittingly and unwittingly applies to his dealings with others as well as to his own personal beliefs. Nick summarizes Gatsby's culturally influenced life of deception and self-deception by saying:
his dream must have seemed so close that he could ... grasp it. He did not know that [the future] was already behind him ... borne back ceaselessly into the past.