Called a "naturalistic epic," The Grapes of Wrath chronicles the collision of the displaced from the Dust Bowl against the economic force of capitalism in the form of the banks that have expelled them from the land and the corporate owners of large farms who control wages and pricing against the smaller farmers and pickers. It is this conflict between the Haves and the Have Nots that drives the novel and moves readers from sympathy to a certain moral outrage at the exploitation of the lower classes such as the Okies, the Mexicans, and the Native Americans as described in the intercalary chapter, Chapter Nineteen. Indeed, the capitalist is viewed as an uncaring, insensitive, materialistic automaton, whose greed has wrought the Great Depression.
But, in its carefully woven narrative, there is something that transcends this chronicle of class struggle: There is the struggle for the dignity of man. This essential need is acknowledged in the characters of Ma Joad and Tom Joad. For, it is they who extend themselves beyond the moment, holding tenaciously to their beliefs in family, community, and the dignity of man in their willingness to sacrifice themselves for their beliefs. For instance, in Chapter Twenty, Ma tells Tom,
"You got to have patience....us people will go on livin' when all them people is gone. Why, Tom, we're the people that live. They ain't gonna wipe us out. Why, were the people--we go on....we keep a-comin'. Don't you fret none, Tom. a different time's comin'."
Tom does have the faith. He joins with Casy in his altruistic efforts to help men organize and have strength in numbers. For Ma and Tom, theirs is the struggle of all humanity, the struggle to end their hungers, physical and spiritual.