Of Mice and Men takes its title from a famous lyric by the Scottish poet Robert Burns (1759 - 1796). Burns's poem "To a Mouse" contains the lines, "The best laid plans of mice and men / Often go awry." Nearly all of the main characters Of Mice and Men harbor dreams and plans that never come true. Most notably, George, Lennie, and Candy share a doomed dream of buying their own farm and living off the land. George often laments the life he could have had as a freewheeling bachelor, free of the burden of caring for Lennie. "[I]f I was alone I could live so easy," he says. Lennie has his own private dream of living in a cave with his own rabbits, while Curley's wife often regrets her missed chance to become a Hollywood actress. In the end, the novel's main theme is that people must learn to reconcile their dreams with reality, to accept that everyone's best laid plans often perish. These plans "go awry" not because the characters in the novella give up on them, but because forces beyond their control destroy them. In the bleak economic outlook of the Great Depression, during which the novel was written and set, coming to terms with dreams broken by out-of-control economic forces became a reality nearly everyone in America faced.
The American Dream is written into the Declaration of Independence: "life, liberty, and the pursuit of happiness." Lennie and George's dream of owning a farm and living off the "fatta the lan" symbolizes this dream. Of Mice and Men shows that for poor migrant workers during the Depression, the American Dream became an illusion and a trap. All the ranch hands in Of Mice and Men dream of life, liberty, and happiness, but none ever gets it. As Crooks says when he hears of Lennie's dream to own his own farm, "Nobody ever gets to heaven, and nobody gets no land."
At the same time, while the dream may never be realized, Of Mice and Men suggests that in order for life to be full and meaningful, it must contain dreams. George and Lennie never achieve their dream, but the dream holds their remarkable friendship together. Their dream is real because it's real in their imaginations. The dream keeps Lennie happy and stops George from becoming "mean" and lonely like most ranch hands. The dream gives them life, even if life never allows them to achieve their dreams.
Of Mice and Men explores the dynamics of male friendship. When Lennie asks George to tell him why they're not like other ranchers, George explains that they're different because they have each other. Usually ranchers have no family, no friends, and, therefore, no future. George and Lennie's friendship strikes the other ranch workers as odd: their dependence on each other makes the boss and Curley suspicious; and Slim observes that ranch workers rarely travel together because they're scared of each other. Although most of the men in the novel are entirely alone, they all crave true companionship. As Crooks, perhaps the novel's most solitary character because of his black skin, puts it, "A guy needs somebody—to be near him."
Though many characters in Of Mice and Men long for friendship and compassion, they live in fear of each other. As Carlson's unsentimental shooting of Candy's dog makes clear, in the Great Depression the useless, old, or weak were inevitably destroyed as the strong and useful fought for survival. Everyone on the ranch constantly tries to look strong, especially if they feel weak. The fear of the weak being overrun by the strong explains why Curley likes to fight larger men, why Crooks tells Lennie that George is going to abandon him, and why Curley's wife threatens to have Crooks lynched. Each character tries to appear strong by asserting power over another. The fear of the strong also explains why most of the other characters in Of Mice and Men can't comprehend Lennie and George's friendship. A human relationship devoid of power dynamics simply makes no sense to the other characters, all of whom assume they're in a fight for survival.
There are two different visions of women in Of Mice and Men: the male characters' view of women, and the novel's view of women. The men tend to view women with scorn and fear, dismissing women as dangerous sexual temptresses. Women are often referred to as "tarts," a derogatory word for women that means "tramp." Lennie and George have a mutual friend in prison "on account of a tart," and their own troubles result twice from the enticing allure of a woman—the woman in Weed, and Curley's wife. Yet although Curley's wife plays into her role as sexy temptress, Of Mice and Men presents her, at least partly, as a victim. She craves the attention of the men because she's desperately lonely, and flaunts her power over the men because she herself feels weak. Similarly, the novella's portrayal of Aunt Clara as a vision of wholesome femininity from a more innocent age contrasts with the male characters' consistently negative view of women.