In the novel Of Mice and Men , by John Steinbeck, the theme of "power" is illustrated through the characters of the story by showing how limited, or not, some people are in the quest of reaching their ultimate dream.
Basically, Steinbeck tells us that every single man in the farm is literally powerless. This is evident in that none of the men seem to be able to leave the farm and start a new life for themselves, not even Slim with all his good qualities.
Contrastingly, Steinbeck awards the "powers" in the story to Curley's father, to Curley, and to Curley's wife. Their power, however, does not come from the characters' own abilities and strength: The only way they can exert power over the field hands is through harassment, abuse, or through work. Other than that, we find that Curley and his wife are equally powerless to make anything in their lives better.
Although money seems to be the most powerful element of the story (since all the men seem to need a lot of it), the real power the farm hands wish to have is the power to become free: From hunger, from the farm, from the hard work, from isolation, and from injustice. Power is a force that has shut down inside of each of them, making them unable to produce any change in their lives. Therefore, although Steinbeck is clear in that the injustices of society make it harder for the typical man to attain the American Dream, the story is clear that these men were basically trapped in an unhappy place, learning to survive day by day.