In his essay "Souls of Black Folk," DuBois tells the story of his first realization that his race made him different from the white children at school, and realized that he was "shut out from their world by a vast veil." Later in the essay he says that the real dilemma of the black american is a feeling of double-consciousness, the need to be both American and black, and the "longing to attain self-conscious manhood, to merge his double self into a better and truer self" without losing either of his cultural backgrounds. He feels that people have to stay in touch with their roots because each race has its own story- its own part in history that cannot be articulated by another race.
In his short story "The Comet," DuBois creates a situation- perhaps what he believes to be the only situation- in which the black character, Jim, is released from the veil that society has put on him. In the story, Jim and a young white woman find themselves as equals, simply because everyone else is dead. DuBois story assumes that the only way a relationship between a black man and a white women would work is if they were literally the last two people on earth. In "The Comet," Jim is also released from his obligation to teach the world about his culture, his blackness, because his status as the last living man surpasses his role as a black man.
At the end of the short story, when it is discovered that there are still other living people, Jim immediately resumes his former role as a black man, a person at the bottom of society. This shows that whatever he and the woman learned in their time together was not lasting. It would take more than this to make a change.