Invisibility,
As evinced by the novel's title, invisibility is a primary theme in Invisible Man, and it functions on several levels. The protagonist struggles to be seen as an individual by others in the novel. He is continually identified by his grouping, whether it be as a black man, a southerner, or a member of the Brotherhood.
This theme is brought forth in the prologue because the protagonist is living underground, invisible to the world, and even to the Monopolated Power and Light Company from whom he uses free electricity to light his room. He also recounts an encounter in which he bumps into a white man in an alley and the man calls him a "nigger". They scuffle and exchange harsh words but the protagonist concludes that the man did not truly see him. He was invisible to him.
The protagonist goes through many instances in the novel where he is being treated as though he is invisible and told who he is by others. To most of the people he encounters in the novel, he isn't a person but a representation. He ultimately experiments with this invisibility when he disguises himself for protection against Ras. He is mistaken for Rinehart, a figure with multiple identities. The protagonist notes that Rinehart has made the most out of his invisibility and that might be an option for his own life.
The novel ends with the protagonist going underground and literally out of sight.
Blindness
Blindness is another theme that dominates the novel. Almost every character that the protagonist encounters has some degree of blindness whether it be literal blindness or blind allegiance to ideology. And in some instances, the protagonist literally and figuratively experiences blindness. The first and perhaps most significant example of this is at the beginning of the novel when the young black men are being made to fight in the Battle Royal while blindfolded. This type of fighting (young black men blindly fighting against one another under the direction of whites) foreshadows the protagonist's strained relationship with Brother Wrestrum at the end and their public feuding in the presence of white members of the Brotherhood.
Also, blindness is present in those who have a position of leadership and/or authority. Homer A. Barbee, a minister from Chicago, IL, delivers the Founder's Day sermon and describes in vivid detail the founder's life and death. However, the protagonist realizes that Barbee is actually blind and perhaps is relating these events from a perspective of dramatizing history and not presenting the true picture. This is also true for Jack, a prominent leader of the Brotherhood. The protagonist learns at the end of the novel that Jack wears a glass eye and is thus limited in vision.
Struggle for Self-Definition
The protagonist attributes his invisibility largely to his inability to define himself outside of the influence of others. Almost everyone he encounters attempts to tell him who he is and how he should conduct himself.
At the college, Dr. Bledsoe tells the narrator that he should smile and lie to please whites. In New York City, he encounters Mary who places her hope for the future on him and those of her generation. She expresses, to the point of pressure, that he needs to be someone who goes on to do great things. Certainly, the Brotherhood attempts to redefine him by giving him a new name and identity and by having him go through intense instruction to ensure that he adopts the organisations' philosophies.
Ultimately, the protagonist has to go underground in order to define himself.
