Final answer:
The narrator of 'The Tell-Tale Heart' is an unreliable narrator, likely insisting on their sanity to try to counteract their clear signs of madness and to convince the reader and themselves of their rationality.
Step-by-step explanation:
The narrator of 'The Tell-Tale Heart' is an example of an unreliable narrator. This concept refers to a narrator whose credibility has been seriously compromised, often due to mental illness, bias, or deliberate deception. This is visible in the narrator's insistence on their own sanity, despite exhibiting signs of madness such as an obsession with an old man's eye and premeditated murder. The repetition of the claim not to be mad seems to be an attempt to persuade both themselves and the reader of their sanity, likely driven by their own awareness of their irrational actions and thoughts.
In literature, an unreliable narrator can compel readers to question the truth of the story being told. When reading from the first-person point of view, we must look for evidence to support or contradict the narrator's perspective. This approach encourages critical thinking and a deeper engagement with the text's themes and characters.