In The Great Gatsby, there are a variety of symbols that Fitzgerald uses to demonstrate Gatsby's dreams, social decay, and the eyes of God.voices.yahoo.com
Gatsby's hopes and dreams are symbolized by the green light on the dock of the Buchanans.
The green light is also associated with the American Dream, since in the process of trying to get Daisy, Gatsby becomes rich.
The Valley of Ashes represents the moral decay that had taken place in the American society due to avarice and the desire to become rich. The Valley of Ashes signifies the moral decomposition of society created by the pursuit of wealth.
Theme of the book: Compassion and Forgiveness
The characters in The Great Gatsby all show a unique combination of a willingness to forgive and a stubbornness not to.
The social setting is among wealthy, educated people, those with a good deal of leisure time and little concern about people who are not in their social milieu. Nobody’s concerned about politics or spiritual matters – but everybody cares about how they are perceived socially. The social climate demands respectability; it asks people to conform to certain standards. This is one reason why Tom’s flaunting of his mistress is an issue. Organized crime enters the picture through the backdoor with Jay Gatsby. Everybody suspects him, but everybody is willing to partake in his lavish parties anyway.