What is a major theme of the novel Of Mice and Men?
One major theme is the gap between idealism and reality. The two protagonists want to escape their migrant worker life and build a farm together, but they are unable to fight against the uncaring oppression of reality, which makes no concessions. Throughout the book, they attempt to live in harmony with others so they can save money and build towards their dream, but continually run into the greed and dishonesty of other people. Lennie, the mentally-disabled friend of George, continues to cling to his dream even after tragedy strikes, since he is forgetful and cannot associate past events with present events:
"...Go on, George! Tell about what we're gonna have in the garden and about the rabbits in the cages and about the rain in the winter and the stove, and how thick the cream is on the milk like you can hardly cut it. Tell about that, George."
"Why'n't you do it yourself? You know all of it."
(Steinbeck, Of Mice and Men, Google Books)
Their failure comes not from their own ineptitude, but from their persistence in trying to trust people, and especially George's attempt to have Lennie grow up and be trusted alone. However, the manipulations of other people leads Lennie into committing harm without intent, and George knows that he will be found guilty and hanged. George's final act in the story is one of mercy, and is one that hammers the final nail into his dream of a small farm.
Another significant theme of Steinbeck's novella is the importance of the fraternity of men as a defense against the social conditions in which they live. The power structure of capitalism and its failure places the common man of the Depression era represented by George, Lennie, and the other "bindle stiffs" in one of defenselessness against the "bosses" represented by Curley.
With the union of men there is strength against social forces. George and Lennie remind each other that they have their friendship as a defense--"I got you, and you got me"--and they share a dream for the future. Together they will save their money and buy a farm and gain their independence from a failing system. When Candy joins in with their dream, there is an even better chance that their dream will come true.
"....With us it ain't like that. We got a future. We got somebody to talk to that gives a damn about us."
Steinbeck's political message and theme is that the individual can overcome his defenselessness against oppression through union, a fraternity of men. He came to this conclusion after examining the plight of the migrant workers of California whose social condition he chose to structure his narrative, states critic Kevin Attell.