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Here are themes in John Steinbeck's "Of Mice and Men":
- Brotherhood of man - As a socialist Steinbeck felt that man needed man. The strength of the many against the oppressive few was strong in many of Steinbeck's novels.
- Alienation - Crooks says life in no good without a companion to turn to. The characters are helpless by their isolation. Yet, in their alienation from one another some seek to destroy the other such as Curley who is belligerent.
- Idealism George and Lennie cling to their dream repeating it like a mantra. Because the lonely idealize friendship, they wish for untarnished happiness.
- Racism - Crooks, the black stable hand, is isolated and made to live in the barn away from the others. Because of this isolation, he is anxious and mistrustful.
- Class Separation - With Curley as the son of the ranch owner, all the men are distrustful of him; he is unwelcome in the ranch house.
- Mental Disability - Lennie, disabled mentally, is misjudged by Curley. His attempts to live in the world of the other men causes him tragic results. If he were to live after killing Curley's wife, he would be tried as a normal man and incarcerated. This situation would be one that Lennie would not understand, and he would be destroyed mentally by it. Knowing this fact is why George commits his "mercy killing."
- Loyalty - George is absolutely loyal to Lennie, having promised Lennie's aunt that he would look out for him. The reward of this loyalty is the loving devotion and friendship of Lennie.
- Misogynism - The men are all distrustful of women such as Curley's wife who, in her visits to the ranch house, causes conflict among the men. Her enticing sexuality causes men to behave in way they would not among themselves. Of course, she brings about the destruction of Lennie and, therefore, the dream.
- Freedom - The dream of George and Lennie represents a better life, a life with the freedom of working for themselves, not someone else who can hire and fire people.
- Predatory Powers of Man - Candy's dog is symbolic of this theme. Having outlived his purpose, he is killed. Candy, who is disabled and old, fears the same end for himself, as well.