Of Mice and Men/Themes
Weakness and Human Nature 
Throughout the story we come across weakness in characters. These characters prey upon those weaker than themselves as part of their human nature. Examples of this include Curley's wife's threat to the crippled Crooks: 'you keep your place then, Nigger. I could have you strung up on a tree so easy it ain't even funny.'; Crooks' taunting of Lennie, zeroing in on his most sensitive fears: that George will abandon him to pursue the 'swell time' he says he could have without Lennie in his life; and that Lennie's dream of a life with George and the rabbits is never going to happen. It is these malicious attacks of the weak, upon the weak that support the claim that the most strong, hurtful and soul destroying forms of oppression are born of weakness.
Loneliness and Isolation 
Isolation is shown in many ways. For one the towns name Soledad when translated it means Isolation. Despite living together communally as a small group with similar needs, the ranch workers do not form meaningful friendships of any lasting significance. They are timid and reluctant to initiate or recognize social contact. They move from ranch to ranch like wandering nomads in constant search for work. The opportunity to create relationships becomes lost in the drive to promote basic survival.
Curley's Wife is also very lonely. She is married, well-off and surrounded by people - yet she is depressed and lonely, lacking female friends to share her interests. She lacks any human contact and conversation as she said that not even Curley talks to her much.
Other lonely characters include Crooks, who is relegated to an inferior social status by others not of his race, and Candy, whose age and physical disability place him outside the circle of acceptance of the society he interacts within on a restricted level.
George and Lennie are the exception to this: at the beginning of the novel George talks about how they are different to other ranch-workers; as Lennie puts it "cos I got you an' you got me."
The ranch itself is a desolate and isolated area, separated by many miles from any town or city. Its isolation is dramatized by the absence of any means of transportation connecting it to the next town ten miles distant. It can be reached by infrequent visitors such as George and Lennie who come to it by means of a dusty, untended dirt road that is barren of directional signs.
Unfulfilled Dreams 
George and Lennie's dream is to have their own little place in the country, able to do what they want when they want and have nobody ordering them around. Candy eventually joins in this dream, offering to pay for most of it, and Crooks also fleetingly wishes to join but bows out, from fear and the realization that his dream will never come true.
Curley's wife also has dreams, dreams of becoming an actress and going to Hollywood. Her dream is also not possible and she ends up married to Curley and feeling utterly miserable and alone. Curley's wife also wants someone to talk to and companionship, as she is lonely on the ranch and has no one to talk to so flirts with the workers.
The theme that I will examine first is loneliness, All the characters are extremely lonely and unhappy with their lives (except Slim, who is the only character that seems to be confident and happy with his life), and none of them can escape this unhappiness Because of the period the novel is set in, it is obvious that the men are a mobile workforce and never have the chance to lay down roots. To study the technique of loneliness in “Of Mice and Men”, we will study loneliness in Crooks, Candy and Curley's wife.
Crooks is a black man that experiences isolation because in that time black people were looked at and treated differently from white people. The quote "A guy goes nuts if he ain't got nobody. Don't matter no difference who the guy is, longs he with you. I tell ya a guy gets too lonely an he gets sick" was his means of finding a personal connection to Lennie. Like Lennie, Crooks has a 'relationship' with loneliness. Crooks is rejected from every group of people and cannot socially interact with others, just like Lennie who can’t socially interact properly because of his mental-disability. "Cause I'm black. They play cards in there, but I can't play because I'm Black. They say I stink. Well I tell you, you all stink to me!" Crooks is lonely because he is black; others treat him unfairly because he is different from them given that he is black. Crooks isn’t allowed to play games with white people such as card games. He is treated unfairly and acts the same way towards the white people who have treated him differently. Even if all people are miserable when they are lonely, the consequences of friendship can be even worse. When one of the members of a friendship is removed, it causes misery and pain; when Candy lost his dog, he kept thinking about him, and felt terrible because he kept thinking that he should have shot his dog himself, and looks for friendship elsewhere. When George had to shoot Lennie, he felt terrible, because he had just shot his best friend, his lifetime companion, his only friend in the world. Because of this, he has to live the rest of his life, in guilt, alone and knowing that he killed his only friend.
Candy, like Crooks is also different from everyone else because his age and physical disability make him different from the rest of the men on the ranch, but he always tries to talk and play games with them as much as he can. Candy’s best friend in the world, is his dog, which he cannot even talk to. However, when his dog dies, he has to look for a different friendship. He hopes that these friends can be George and Lennie. Because of his age and disability, he feels as if he is useless “They’ll call me purty soon”. Candy thinks that nobody wants to be friends with him because of this disability. Eventually, he tries to find friendship by trying to join the dream of George and Lennie. Candy offered his help to become a part of George and Lennie's friendship and dream, this is one of Candy's attempts to find a place in the world by making himself useful to someone, by doing the things he could do to show that he is in fact useful and could bring a lot in the dream as well and the friendship “I could cook and tend the chickens and hoe the garden some” “you’ll let me hoe in the garden…An’ I’ll wash the dishes an’ little chicken stuff like that”. After Candy lost his dog, he felt much more lonely than he was before. The dog was something that Candy had owned and shared his life with. Candy and his dog had the same relationship that George and Lennie had shared for so many years.
Curley's Wife's loneliness has a different reason for being lonely; her husband causes it. Even though Curley's wife is mentioned quite a lot, nobody asks what her name is. Nobody wants to talk her because people are afraid of Curley; he is jealous and would start a fight with anyone who tried to talk to her. She does not like Curley, and he doesn’t talk to her at all because of it, and there's no one in her life she can share her feelings with, and longs for a good friend. She dresses the way she does, to gain the attention of the ranchers and to help her loneliness. Doing this gives her a feeling of relief and makes her feel wanted so she can share her Thoughts and memory’s with, she notices that Lennie finds her “purty” and tries to talk to him and get close to him a few times. She also makes sure that Lennie is listening to her when she speaks "You listenin'?", since she is not used to talking to anyone, she wants to be sure that what she is saying is being heard. Her death could be thought of as a negative thing, but as a positive thing as well because it ended her loneliness; being the only woman in the ranch and having married a man like Curley. But now that she is dead, she will not have to worry about being lonely ever again.