Important Characters in The Grapes of Wrath
No discussion of The Grapes of Wrath would be complete without the quixotic Jim Casy. Even if he didn't have the same initials as the most famous martyr of all time (Jesus Christ), he exemplifies the idea of sacrifice. However, Jim Casy had already left the church behind, claiming that the true holiness was to be found out in the world, among people.
Like Christ, Jim Casy speaks out against injustice -- in this case, organizing laborers to fight the terrible conditions that fruit-pickers faced in California during the Dust Bowl era. When he first meets Tom Joad, Casy has not yet found the specific focus of his mission on earth. By the end of the story, Casy has devoted himself to bettering the lives of working people in California, and he sacrifices his own life for this purpose. Casy's death changes Tom Joad from slacker to activist.
One of the main rhetorical arguments of The Grapes of Wrath has to do with the cruelty with which employers and landowners in California treated the poor victims of the Dust Bowl in Oklahoma. The establishment of Jim Casy as a Christ figure squarely on the side of the workers shows Steinbeck's sympathy with the plight of people who couldn't work their way back to dignity, even though there was plenty of food and sustenance to share.
When the novel begins, Tom is just returning from a four-year stint in prison for manslaughter. This may indicate that he will not be of much importance to advance the themes of the novel, but by the end he becomes the most dynamic of the Grapes of Wrath characters. At the beginning of the story, his philosophy is purely carpe diem but the lessons he learns from Jim Casy gives him a longer-term view of his actions. As the family travels west, Tom learns more and more from Casy, who teaches him that the only way to have a powerful effect on the world is to join with others in one's efforts.
As the Joads travel west, the need to cooperate and coexist in order to survive becomes more and more apparent. The death of Jim Casy galvanizes Tom once and for all, turning him into a fiery advocate of social justice. While killing the police officer may not be the most appropriate avenue for powerful action, the killing is clearly revenge, not cold-blooded, and Tom's passion for the working poor becomes obvious as one of Steinbeck's themes in the novel.
Ma and Pa Joad
These two characters begin the novel as the center of the family; as the trip to California takes its toll, Ma becomes more and more the locus of strength, while Pa becomes weaker. Even when Granma dies during the family's trip across the desert, Ma keeps this knowledge to herself so that the rest of the family can make the trip safely. When Pa starts to lose his confidence, Ma becomes more and more decisive, and every choice she makes is designed to hold the family together. The theme of sacrifice, expressed eloquently by the death of Jim Casy, also appears in the many choices Ma makes for the sake of family unity and togetherness.
While Pa wants to lead his family and serve as the provider, he detaches more and more from those around him when he has a hard time finding work, and by the time the Joads leave the camp at Weedpatch, Ma takes him to task for forgetting to be the provider. By the time the story comes to a close, Pa is just another one of Ma's children. Adversity has definitely not built Pa's character.
Rose of Sharon
Throughout the novel, Rose of Sharon is the closest to a symbol among the characters. While Jim Casy may be a Christ figure, Rose of Sharon is definitely an allusion to the Virgin Mary. Throughout the book, Rose of Sharon is happy to keep to herself, showing the world a smile as strong and opaque as any wall. At the end of the story, when she has lost her own child but still has milk to nurse the emaciated man, that sacrifice becomes a "Pieta" for the modern era -- the mystery of religious belief replaced by the power of grace and giving.