Altruism in The Grapes of Wrath

One of the themes in this story is the cruelty and greed of the banks and big companies. In contrast the migrants, who have nothing to share, help each other out. They understand that their survival depends on their collective good will and altruism to each other. Steinbeck pits these two forces, greed and altruism, against each other in the book. Despite the greed of big companies the migrants inspire a sort of "pay it forward" ethic that even rubs of on non-migrants in the story.