In "The Fall of the House of Usher," imagination overcoming reason is evident as the characters succumb to their fears and superstitions. Roderick Usher's heightened senses and mental instability lead him to believe in the sentient nature of his house, ultimately causing his and his sister's demise. The narrator, too, is influenced by the eerie atmosphere, showing how imagination can overpower rational thought.

The narrator in "The Fall of the House of Usher" exhibits signs of mental instability through his vivid imagination and exaggerated perceptions. He describes an "insufferable gloom" upon seeing the house, imagines it with human-like features, and experiences superstition and fear that intensify upon entering. His descriptions of events, such as the sounds from a book occurring in real life and Madeline's return from the tomb, suggest delusion. These elements indicate possible mental illness.

The crumbling house in "The Fall of the House of Usher" symbolizes the theme of insanity by mirroring the mental deterioration of its owner, Roderick Usher. The house's decaying structure, with its ancient, rotting facade and widening fissures, reflects Roderick's growing madness. As the story progresses, the house's physical collapse parallels Roderick's mental breakdown, culminating in both the literal and figurative fall of the House of Usher.

"The Fall of the House of Usher" effectively portrays paranoia through the character of Roderick Usher, whose fragile mental state deteriorates into intense paranoia. Roderick becomes hypersensitive and agitated, hearing sounds no one else notices, which exacerbates his fear. Edgar Allan Poe uses Roderick's descent into paranoia to illustrate how it can manifest physically and psychologically, suggesting that such paranoia is contagious and can affect others, as seen through the narrator's observations.

The descriptions of the valet and physician in "The House of Usher" enhance the narrator's fears by contributing to the story's eerie atmosphere. The valet's stealthy movements and the physician's fearful demeanor with "low cunning" suggest they too sense something ominous. These characterizations, along with the narrator's encounters with the Ushers, reinforce the narrator's apprehensions about the bizarre and supernatural elements pervading the mansion, heightening the overall sense of dread.