In his essay, The Oversoul, the great 19th century American, Ralph Waldo Emerson writes of the qualities of man's soul, one of which is that it is connected to that of other men:
...that Over-soul, within which every man's particular being is contained and made one with all other; that common heart.
This same transcendental unity is what the former preacher Jim Casy intuitively acknowledges in Chapter 4 as he says,"Maybe all men got one big soul everybody's a part of." Later in Chapter 26, Tom finds Casy again, who has been in jail. He tells Tom how the men there organized and made demands that were met. Tom concludes that "It's need that makes the trouble." Unfortunately, as they talk, a vigilante finds them and kills Jim Casy, crushing his head with a pick axe. Tom reacts by wrenching the club free and using it on the man, killing him, in turn. Suddenly, Tom feels a glancing blow, so he flees. He stays in the camp while the rest of the family picks until Ruthie inadvertently refers to her brother to another girl. Consequently, Tom has to hide until Ma advises him that he must go away.
In Chapter 28, Tom recalls to Ma things that Jim Casy has said about just having a piece of a big soul. Further, he tells Ma that he wonders why people cannot all live and rule themselves as in that government camp where they have stayed earlier on their journey. This thought connects to Casy's remarks about his time in jail, and Tom decides to take up Casy's fight. He tells his mother not to worry about him because
"....I'll be ever'where--wherever you loo. Wherever they's a fight so hungry people can eat, I'll be there. Wherever they's a cop beatin' up a guy, I'll be there. If Casy knowed, why, I'll be in the way guys yell when they're mad an'--I'll be in the way kid laugh when they're hungry an' they know supper's ready....See? God, I'm talkin' like Casy....Seems like I can see him sometimes."
After they part, Ma does not cry, for there is hope.