There are many aspects of Theodore Dreiser's An American Tragedy that involve the moral decision versus the immoral decision and God. The main theme that Dreiser maintains throughout the novel is Immorality. Each character in the novel possesses one or more characteristics that show that he or she is partially immoral. When combined, all these elements have a strong message, that there is consequence to straying from God's path.

Clyde Griffiths is the perfect example of how a person is led from God's light. At the beginning of the novel, his character is the son of poor missionary parents. The family spends its' time on street corners, singing church hymns, and reading verses from the Bible. Soon, however, we begin to see the growth of Clyde's free will, and natural curiosity. He begins to explore the world, out of the view of his parents. Soon he realizes the corruption that exists, and falls victim to it, through he does not realize it.

Clyde and his acquaintances explore the possibilities of girls, and drinking alcohol. Eventually, these people steal a car, and Clyde runs away to keep himself from being apprehended by the police. His entire life has been changed because he has made a few bad decisions.

Things turn worse and worse for Clyde as he progresses through the next few months, and he feels exactly the opposite. Clyde receives a job with his uncle's company, and he sees himself as quickly climbing the social ladder as well as feeling he is on his way to success. His desire for social prominence completely overtakes his view of doing the right thing. He leads an illicit relationship with one of his employees, and she becomes pregnant with his child. She is hopelessly in love with Clyde; Clyde is hopelessly in love with his family name and his new circle of friends.

Clyde's oversight of this problem leads to his ultimate downfall. He tries to make Roberta abort the child, and it cannot be done, so Clyde begins thinking of others ways to solve this "problem" he has created. If Clyde had stayed with his parents, and lived a life devoted to God, he would have not succumbed to corruption. He actually murders Roberta because he gives into lust and his desire for Sondra Finchley, who represents the evil that Clyde is so enamoured by. Clyde meets his death, by execution, as a result of his lies and bad choices.

Theodore Dreiser is trying to make the audience realize that morals are more important than the materialistic and unimportant things that people throw their lives into. Every character is An American Tragedy has a problem of some sort. Clyde wants social status, and will stop at nothing to get it. He is the main character of the novel, and therefore the main theme, Immorality, is centered on his life and his actions.

Dreiser wants to show his audience that people make the wrong decisions all the time, without realizing the consequences until it is too late. The entire book, the audience is led to believe that Clyde will manipulate his way to the top. Then, all of a sudden, it is too late, and his life is shattered. Immorality has overcome Clyde Griffiths.