Throughout The Souls of Black Folk, W. E. B. Du Bois uses numerous literary devices. Among those he most commonly employs are metaphor, simile, idiom, and rhetorical question.
Du Bois frequently uses metaphors, including extended metaphors or conceits. A metaphor is a direct comparison between two unlike things for effect. One important extended metaphor in the work is the “veil.” The "veil" means the African Americans' separation from white-dominated society which they cannot fully participate in, although they can see it.
The Negro is a sort of seventh son, born with a veil, and gifted with second-sight in this American world.
Two metaphors in one sentence are “bleaching” for emulating white culture and “a flood” for the overwhelming amount and speed of that culture’s domination:
He would not bleach his Negro soul in a flood of white Americanism.
A simile is a comparison between unlike things using “like” or “as.” Du Bois employs a simile comparing the occasionally recognized contributions of black men to stars.
The powers of single black men flash here and there like falling stars.
An allusion is a reference to a person, a place, a thing, or an event from real life or literature. Dubois often alludes to events in American history. One example is his mention of white people bringing up “Mechanicsville,” which was a Virginia battle site in the Civil War: “I fought at Mechanicsville.” Du Bois thereby invokes the larger context of the war and white attitudes toward black people.
Another allusion is to the black eighteenth-century Haitian revolutionary leader, Toussaint L’Ouverture, whom Du Bois mentions as someone whom whites disdain:
the all-pervading desire to inculcate disdain for everything black, from Toussaint to the devil.
An idiom is a common expression in which the conventional meaning is different from the literal meaning. An example is using “Greek” to mean something that is unfamiliar or not understood.
[T]he knowledge which would teach the white world was Greek to his own flesh and blood.
A rhetorical question is one to which the answer is already known or which provokes the listener or reader to think about the subject. He uses a series of rhetorical questions in one passage about the impact of the right to vote guaranteed by the Fifteenth Amendment.
Had not votes made war and emancipated millions? Had not votes enfranchised the freedmen? Was anything impossible to a power that had done all this?