As a whole, is Gaines' work concerned with the character and society, human nature and values, or the nature of our existence?
I don't think that Gaines' work is forcing a choice between the three options. It seems to me that Gaines' work is concerned with all three realities. The scope and thematic nature of the text is one in which these issues all are relevant to its understanding.
James is developed in both the trials he must face as an individual and his relationship to society. James "becoming a man" and what that entails encompasses both individual and social realms. The element of what it means to have values and the composition of one's human nature is relevant as James seeks to understand the reality of a segregated South, a world in which Civil Rights for people of color is not evident. The reaction one has to such a condition is of vital importance to the narrative, and is one in which James' understanding of human nature and the values to which one ascribes are relevant. In listening to the discussion in the doctor's office, with different points of view being articulated, James seeks to understand and define his own sense of human nature and the values that can be used to define such a nature. The ending in which his mother affirms to him what it means to "be a man" is not only an answer to the complex and thorny issue of how one defines their human nature and values in a world of segregation, but also helps to define the nature of one's existence. The question that James does not necessarily articulate, but completely experiences is whether or not the nature of one's existence is an identity in which one takes the form of the world around them or seeks to define themselves in a transcendent manner from it. James struggles to understand or to grasp the complex implications of such a profound question. The nature of one's existence lies at the heart of such a discourse. James' mother realizes this and seeks to assist James in developing the nature of his existence as to transcend what is around him. The end lesson of "becoming a man" is an idea that suggests that the nature of one's existence is something that can transcend what is around the individual and move them into a realm of what can be and what should be. In this, the work addresses all three issues in a complex and convergent manner.