This novel has as one of its principle themes the deep connection that exists betwen people and the land that sustains them and provides their livelihood. Part of the inhumanity of the situation that the Joad family faces is the way in which they are forced to leave the land that has been there home for so long and become rootless, itinerant individuals trying to make a living through whatever means are open to them. Note the following quote from Casy about the importance of the land:
"Fella gets use' to a place, it's hard to go," said Casy. "Fella gets use' to a way of thinkin' it's hard to leave."
Steinbeck uses this novel as an explicit criticism of the way in which modern industrial society produces situations of inequality where people are forced to become rootless wanderers and where the deep, abiding link between man and land is taken away. The way in which the land is depicted as being swallowed up to satisfy the hunger of "the Bank" in this novel makes a sharp criticism of capitalist society and the way that it is focused on insatiable growth:
If a bank or finance company owned the land, the owner man said, The Bank--or the Company--needs--wants--insists--must have--as though the Bank or the Company were a monster, with thought and feeling, which had ensnared them
In the face of such hunger, the suffering of individuals goes unheard and untold.