If I were to use the theme of loneliness as part of a thesis statement for Of Mice and Men, could you give some examples of how to do that?
For a thesis on the theme of loneliness in Of Mice and Men you may want to attach the theme to specific characters who best exhibit loneliness in the novel. Curley's wife, Crooks and Candy each seem like prime candidates for an essay on loneliness in Of Mice and Men.
A thesis statement could look like this: Of Mice and Men is a novel, in part, about friendship, yet the story is peopled with figures of isolation and loneliness like, Candy, Crooks and Curley's wife.
I would find some aspect of loneliness that is unique. There are many different types of loneliness, and that would be an interesting thesis. You can compare and contrast how Lennie's loneliness is different from George's and from Curley's wife. Then explain each example.
Loneliness is a major theme in Of Mice and Men, so the topic itself is fine for a thesis, but remember a thesis is supposed to make a claim or argument, so consider carefully what you want to say about it.
Here are some examples of loneliness along with some ideas to get you started on the actual thesis statement:
1) Lennie and George have no real home, being migrant workers. They work the season, then move on, so they have no family, no community, not ties except each other.
2) Candy is a senior citizen with a physical handicap, and even though we get the sense he has been at the ranch for some time, he has few ties or friends either, and tells Lennie and George later in the story that he has no family, no kids. He is alone in most senses of the word.
3) Curley's Wife is in an unhappy marriage, and more or less trapped on the farm. She seeks the male company of many of the workers simply for someone to talk to, and since Curley himself is such an abusive jerk.
As for a thesis, consider how just about every character is lonely in some way, and how this was common during the Great Depression the story takes place in. You can argue that Steinbeck reinforces the frightening, lonely and troubled times of the Depression by reinforcing the loneliness of the characters. Also try to think of another argument of your own to include in a thesis based on these or other examples. Post again if you want a critique of your final thesis.