Involuntary isolation is a central theme of John Steinbeck's Of Mice and Men. Most of the characters are isolated for a specific reason and long for companionship. As George repeatedly tells Lennie, they are different because they "have each other." The idea of loyal companionship between the migrant workers is so foreign during the 1930s that Curley and his father, the Boss, are perplexed and bothered by George and Lennie traveling around together. Listed below are several examples of other characters' struggle with loneliness.
1. Candy--The old handyman is isolated because of his physical handicap and age. He feels useless and relies upon his aged dog for companionship. When Carlson shoots Candy's dog, Candy jumps at the idea of putting all of his savings into George and Lennie's ranch dream simply because he needs human fellowship.
2. Curley's Wife--As Curley's Wife prowls the ranch, others misinterpret her motives. She simply longs for someone to talk to. Ultimately, her desperate search for fellowship leads her to Lennie, and though she knows that he is not really listening to most of what she says, she longs so badly for companionship, that she continues talking to him anyway.
3. Crooks--Crooks is an outcast because of his race. Separated from the other men's living quarters, he passes time by reading. He, like Curley's Wife, settles for talking to Lennie because Lennie is the first person in years who will pay attention to him and listen to him. In the end, Crooks decides that his desire for human contact is not worth the struggle that he would have to go through to obtain it.
4. George--Even though George often loses his temper with Lennie, he will never leave Lennie behind, because he values the companionship which Lennie provides. Similarly, George's willingness to open up to Slim about his and Lennie's past problems demonstrates his need for real conversation.
Steinbeck creates all of his isolated characters to illustrate the basic necessity in all humans for fellowship and human attention. The manner in which the characters go about their quest for attention drives the plot in Of Mice and Men.