Harper Lee is showing the concept of duality or double consciousness that African Americans experience in navigating two separate cultures—a white one and a black one. W. E. B. Dubois writes about the two roles blacks play in his famous book, The Souls of Black Folk. He states that blacks often act one way in white society and a different way in black society. He calls it having “two souls . . . two warring ideals in one dark body.” For Scout, she sees this duality show itself in the way Calpurnia speaks. At the Finch’s, Calpurnia speaks proper English in order to “fit in” to white society. With the black community, she is free to use dialect and slang to communicate with her culture. It’s a shock for Scout, for she has only seen one side of Calpurnia until she visits Calpurnia’s church.
This double consciousness is still something blacks are aware of even today and it causes them to change things like speech when interacting with two different cultures. It is enormous pressure to switch between the two, so one is not ostracized by either community. Dubois says that it is “strength that alone keeps it from being torn asunder.” Here Dubois states that it is only by strength that the souls of blacks are not torn apart by this double consciousness. The pressure is how to psychologically survive when you are expected to be two different people depending on where you are and who you talk to.