Final answer:
The narrator's obsession with the eye in 'The Tell-Tale Heart' is caused by a combination of factors including its perceived evil, the narrator's guilt, and his growing madness.
Step-by-step explanation:
In 'The Tell-Tale Heart', the narrator's obsession with the eye is caused by a combination of factors including the eye's perceived evil and the narrator's growing madness. The eye represents the narrator's guilt and conscience, and he becomes fixated on it as a symbol of his own wrongdoing. The narrator's obsession with the eye intensifies as his mental state deteriorates, eventually leading him to commit a heinous act to rid himself of the eye.