Interestingly, Le Guin's story, "The Ones Who Walk Away from Omelas" is subtitled "Variations on a Theme by Williams James." James, the older brother of psychologist and author Henry James, proposed the theory of pragmatism. This belief states that a person's thoughts should guide his or her actions, and that truth is a consequence of a person's beliefs. Her story takes this theory to its moral consequences (enotes).
With this theory of pragmatism in mind, the reader is advised by the "intrusive narrator" that
Happiness is based on a just discrimination of what is necessary, what is neither necessary nor destructive, and what is destructive....One thing I know there is none of in Omelas is guilt.
Those who remain in Omelas "perceive the terrible justice of reality, and...accept it." They are those who are willing to sacrifice the misery of one or a few for the contentment of the majority. But, those who walk away cannot accept this condition. Therefore, happiness is an individual determination. This is why the narrator suggests that the reader add whatever he/she feels will make for the utopian situation, be it orgies, temples, central heating, subway train, washing machines, etc.
If, then, happiness is "the just discrimination of what is necessary," there is no guilt for those who accept the necessity of the scapegoat. Only moral indignation makes the others leave. Le Guin writes,
To exchange all the goodness and grace of every life in Omelas for that single, small improvement: to throw away the happiness of thousands for the chance of the happiness of one: that would be to let guilt within the walls indeed.
Along with the theme of Guilt, the theme of Victim/Victimization is apparent as the miserable child is made the scapegoat so that the people in Omelas may be happy. The absence of explanation for the necessity of a scapegoat certainly adds to the moral conflict of those who leave Omelas. In addition, there is the question of how one can know happiness without having experienced sorrow, its emotional complement. Perhaps this is why
they seem to know where they are going, the ones who walk away from Omelas.