The most dominant theme of The Grapes of Wrath is that of the oversoul. Although the novel never uses this exact word (it is a term used by Ralph Waldo Emerson, though perhaps not precisely in this manner), the concept is clearly present as early as Chapter 4, when Jim Casy speaks of his realization that "all men got one big soul ever'body's a part of." Because all people are connected in this fundamental way, the distinctions between families, which once seemed so important, are radically diminished. Readers will note how Ma Joad-who, it must be pointed out, begins with an understanding that all people must help each other-must fight to hold on to this understanding as the crucible of her experiences tempts her to abandon it. In the Hooverville, for instance, Ma is at first reluctant to share her stew with hungry children who are not her own; in the end, however, she does share it. The novel's final scene offers the fullest image of "the oversoul," in which Rose of Sharon-who for so long before the delivery of her child was concerned only with her own (legitimate) needs-offers the milk her body made for her own stillborn baby to a man dying of hunger. Her cryptic smile suggests that she has come to the same understanding as had Casy: that all folks are "my own folks." Home is being with our "own folks," broadly-and, so the novel argues, most properly- defined as our fellow human beings.
In Chapter 4, Casy, when confessing his struggles over sex, raises the issue of a dichotomy between flesh and spirit which reappear throughout the novel. It is close to the heart of the new revelation toward which Casy moves as the story continues. Readers will note it again, for instance, when the Jehovites try unsuccessfully to convince Ma that Granma's death is a good rather than an ill; or again, in the Weedpatch camp, when Mrs. Sandry denounces the Saturday night parties as sin. She does not take part in the dancing, and so can consider herself among the few remaining "true believers." Steinbeck seems to reject a division between flesh and spirit. Just as all people must come to know their place in the "oversoul" of the human family, so must people recognize that all life, physical and spiritual, is holy. For this reason, perhaps, Casy tells Uncle John repeatedly that the only "sin" is what people decide is "sin." It may also be the reason John is presented as such a tortured character: Were he able to simply acknowledge his past, both its good and its bad, rather than judge it, he might live more at peace with himself.
Another tension explored in the novel is a dichotomy between words and deeds. We see it first, for example, in Chapter 6. As Muley Graves talks about his inability to leave the land to which he has grown so attached, Casy finds himself drawn to "them folks that's gone out on the road." He feels compelled to help them-but not, he feels, as a preacher, for these "Okies" in exile "need help no preachin' can give 'em." Casy tells Muley-who, somewhat like Casy in Chapter 4, has wondered about the appropriate or inappropriate nature of his speaking-that he must talk even if it feels wrong or dangerous: "Sometimes a sad man can talk the sadness right out through his mouth. Sometimes a killin' man can talk the murder right out of his mouth an' not do no murder." Throughout the novel, readers should bear in mind the question: When is speech "just words" (for example, as it is in the car dealers' "hustling" talk of Chapter 7) and when does speech itself play a redeeming function? For the novel, the answer seems to be that speech is redemptive when it accurately addresses people's experience. For this reason, for instance, all of Casy's "prayers" in the book are not pious petitions of an otherworldly nature, but honest acknowledgments of pains and needs faced in this world. Such frank speech counteracts the harmful speech found in the book-take as one instance the recurrent slang term "Okie"-and empowers people to take action to face their situations, whether that action be striking for just working conditions or simply moving on in search of safety. Honest speech precedes honest action.
The nature of anger is also a central theme in the book. Following the glad reunion of mother and son in Chapter 8, for instance, Ma Joad asks Tom if his time in prison has made him angry-in her words, "poisoned mad." Tom assures her that it has not, but he does show anger when he thinks about "what they done to our house." Ma urges Tom not to fight "'em" alone. She does, however, admit to wondering: "They say there's a hun'erd thousand of us shoved out. If we was all mad the same way, Tommy-they wouldn't hunt nobody down-" Here, Steinbeck has raised the question of the proper role of anger-appropriately enough, considering the book's title (which echoes images of divine judgment in both Jeremiah 25:30 and Revelation 14:19-20, as well as in the first stanza of "The Battle Hymn of the Republic" [Julia Ward Howe, 1861] . What are "the grapes of wrath"? What fruit, sweet or bitter, might anger yield? When Tom says good-bye to Ma in Chapter 28, we seem to learn that anger can, in fact, yield positive fruit when joined to a knowledge of the "oversoul," the one human family, to which we all belong. Tom's anger drives him to fight not only for himself but for all the oppressed. It is righteous anger, motivated by a desire to see all people treated fairly and with dignity-as opposed to the unrighteous anger of land owners who see the migrant workers as threats to their own comfort and prosperity (see also Chapter 29).