The title of the novel is a clear reference to the Biblical stories of both Adam and Eve and Cain and Abel. Adam and Eve, the original man and woman on earth, commit the original sin by eating the fruit of the tree of life or knowledge, which has been forbidden to them by the Lord. As punishment, Adam and Eve are sent to a less perfect world outside of the Garden of Eden. They are, however, allowed to have children. After their expulsion from Eden, Eve gives birth to Cain and Abel. The brothers are, therefore, born east of Eden, in a land where Cain commits the first sin of murder. When he becomes jealous of Abel, he kills his brother.
Caleb and Aaron are Cain and Abel figures. Although Cal does not literally murder his brother, he indirectly causes his death. Cal takes Aaron to meet their mother at the house of prostitution that she owns and runs. Aaron is so upset about learning the truth that he joins the military and goes to war, where he is shot and killed. Cal blames himself for his brother’s death. Unlike Cain, who seemed to have little remorse, Cal has a conscience and feels terribly guilty. He is so miserable about what he has done and caused that he goes to Adam and confesses his sin. As a result, Adam blesses his son and confirms the fact that he has the freedom to choose goodness over evil. Caleb can reach the Promised Land. He does not have to wander for the rest of his life, like Cain. He can accept forgiveness and love, lead a normal life, and become the hope for future.