'Double consciousness' is a phrase coined by prominent scholar and African American rights activist W.E.B. Du Bois. It is the principle subject of his book The Souls of Black Folk, and one of the ideas by which he is best remembered.
Du Bois wrote that this phenomenon results from a sort of twoness in African American identify comprised of their own cultural identity as well as the often contemptuous perspective of the dominant culture in which they live. In the discussion of civil rights Du Bois believed that equality could not be about sameness, because in the context of double consciousness this would amount to assimilation. Thus, from the first few pages of The Souls Of Black Folk, he proposes to investigate "the spiritual world" of the African American as a second-class citizen, and how that affects any journey towards actualized moral equality.
What is particularly important about Du Bois' concept is that he is arguing at least partly against the position on African American rights represented primarily by Booker T. Washington. Washington advocated an extreme assimilation program, wherein he advised blacks to agree to vocational schooling in low-level industrialized education and reconcile with whites in general and the South in specific. Du Bois, thinking from a philosophical perspective rather than a practical one, considered this view to be completely contradictory. If the goal is equality, then one cannot submit to unequal conditions, even as means to an end. He says that his only aim is to "make it possible for a man to be both Negro and an American, without being cursed and spit upon by his fellows, without having the doors of Opportunity shut roughly in his face." Du Bois' goal is immediate realization of an equal Negro presence in politics, community, and professional life; not as an assimilated American, but as an African American in American society. This is the reconciliation of the 'double-consciousness.'