The 'Over-Soul' is prevelent throughout The Grapes of Wrath. It occurs right off the bat of the book at first when Tom meets the trucker. He is carrying a "No Riders" sticker on his truck. Tom is able to talk him into letting him get a ride by saying, "Sure-I seen it. But sometimes a guy'll be a good guy even if some rich bastard makes him carry a sticker" (Page 11). When the trucker let's him ride despite not being alowed to, it is symbolic of the Over-Soul. The fact that the trucker let him ride represents that all people are on the same level and should help eachother because we are all connected.
When the Joads meet up with the Wilsons, the oversoul is being displayed once again. The Wilsons give the Joads a tent for Grampa Joad to rest in and blanket so he can stay comfortable. In return, Al fixes the Wilson's car. By working together, they achieve mutual benefits. This is the theory of Karl Marx: The Communist Manifesto. This is the main concept of the oversoul. By working together everyone will prosper; but if one breaks off and goes alone he will be in a constant struggle. This also relates to Ecclesiastes....
"Two are better than one, because they have a good reward for their toil. For if they fall, one will lift up his fellow; but woe to him who is alone and falls and has not another to lift him up. Again, if two lie together, they are one; how can one be warm alone? And though a man might prevail against one who is alone, two will withstand him. A threefold cord is not quickly broken."
A threefold cord is not quickly broken. When the Joads and Wilsons work together, they form a multi-fold cord and that makes them stronger.
Oversoul.....stay as one, everyone lives...break from the oversoul...your fate is none but toil.