What is the theme for the story "Black Boy" by Richard Wright?

In a nutshell, the novel's theme is the individual's struggle to survive in an atmosphere of prejudice and intolerance, and to understand the forces that create the environment in which he lives. 

Richard Wright grew up on a Mississippi plantation during the period between the two world wars.  "Black Boy" is an autobiographical work, in which Wright describes his early years and examines the effect the mindset of the Jim Crow South had on himself and those around him.  He discovers that both racism and tolerance are entities that must be reconciled within individuals both black and white, and that although the primary manifestation of prejudice in his life is racial, it can concern intelligence and religion as well.  As a man of color, Wright is the object of an all-pervasive racial prejudice, but even as he fights to deal with the inequities that surround him, he understands also that within his own mind he must guard against developing prejudicial attitudes towards those who are not as intelligent as he is.  Wright must come to terms with religious prejudice as well, within his own family.

Through his lifelong struggle to understand the nature of his society's attitudes and individual responses to those attitudes, especially, but not only, as they concern intolerance and acceptance, Wright discovers a sense of self, and his worth as an individual and as a writer.