Themes
The themes of this novella are very clear:one (the fragility of people's dreams) is indicated in the title.The other themes are friendship,and its opposite,loneliness.
The fagility of dreams
The novella's title comes from a poem,To a Mouse (on turning her up in her nest with the plough) by the Scots poet Robert Burns (1759-1796):
“The best-laid plans of mice and men
Gang aft agley (=often go wrong).
And leave us naught but grief and pain
For promised joy.”
Burns shows how the plans of men are no more secure than those of the mouse,and this is the point of Steinbeck's title.The source of the characters' dreams is their discontent with their present.Steinbeck shows how poor their lifestyle is:they have few possessions,fewer comforts,no chance of marriage or family life and no place of their own.