Loneliness: The isolation and loneliness of the characters are a recurring theme throughout the book. In chapter 5, we see how Curley's wife is feeling lonely and isolated on the ranch, leading her to seek out the company of other men.
Gender inequality: The female characters in the book are depicted as powerless and marginalized. Curley's wife, for example, is not given a name and is often referred to as Curley's possession. This reflects the patriarchal society of the time.
Racism: Although not directly discussed in this chapter, the book is set in a time and place where racism was rampant. The only African American character, Crooks, is isolated and segregated from the rest of the workers due to his race.
Discrimination: The characters in the book are discriminated against based on their physical or mental capabilities. Lennie, for example, is often referred to as "crazy" and is constantly being underestimated and mistreated by others.
Lack of opportunity: The characters in the book are portrayed as having limited opportunities and choices. They are stuck in dead-end jobs with no prospects of advancement or a better life. This is exemplified by the fact that George and Lennie are constantly moving from job to job without making any real progress towards their dream of owning a farm.