George’s account is evidently oft-repeated as Lennie joins in and echoes parts of it back to him, like a child repeating lines from a favourite story. Not only does this emphasise how child-like Lennie is, it also highlights the most important theme of the book: loneliness.
George and Lennie are shown to have something special because they have each other. In their line of work, men don’t trust each other much, and people tend to keep to themselves so that they only have themselves to worry about. At first George expresses annoyance that he has to look after Lennie. Now he changes his mind, declaring that what he and Lennie have is better because they will always have someone who cares about them, someone to look out for them, and someone to talk to. They will not have to put up with the loneliness that drives others to madness or despair. By having each other, and working together, they can also build a dream for their future based on co-operation. This theme will be picked up again and again throughout the book.