A thesis statement is a claim one can prove or disprove using evidence from the text. An argumentative essay cannot simply be a summary of a plot but must make a specific claim.

"The Black Cat" by Edgar Allan Poe is a story written in the first person by an unreliable narrator. Although the narrator claims to have been driven mad by the cat, he is not trustworthy and overestimates his own mental stability. Poe provides readers with several clues to how readers should view the narrator's mental state.

In the first paragraph, the narrator states, "I neither expect nor solicit belief," and his very insistence that he is not mad but that the events themselves are horrifying suggests paranoia and lack of self awareness. Readers are signaled to see the story, therefore, as a portrait of madness and understand external events as reflections of the narrator's own madness.

The narrator confesses to being "intemperate", a term that can indicate not only state of mind but also alcoholism. He confesses to mistreating even his beloved Pluto. As he is wracked by guilt and descends further into alcoholism, his fantasies about a perfectly ordinary and innocent cat become increasingly bizarre. His comment that the cat "exasperated me to madness" is not evidence that a cat purring and rubbing against his legs was something that would drive a mentally healthy person to madness but rather evidence of his own deranged state of mind.