Alienation in Edgar Allan Poe's work.The black cat", "the purloined letter", "the fall of the house of usher", "william wilson" and "the gold bug".

In all of the stories you have mentioned, a main character
is alienated by his madness or intelligence.

In "The Black
Cat," "William Wilson" and "The Fall of the House of Usher," the main characters are
alienated by their madness.  In "The Purloined Letter" and "The Gold Bug," the main
characters are alienated from others by their superior
intellect.

Alienation is a common
theme in Poe's work for several reasons.  First, Poe knows
alienation because of his personal life: he was alienated from parents, then from his
adopted family, and ultimately, from his wife, who died so
young.

Alienation also seems a
necessary component for the author in order to build either suspense or the presence of
madness (or both) into Poe's stories so that there are no witnesses and/or no "voices of
reason" to sway the evil or dark intent, or predilection to madness, that so many of
Poe's characters experience.

It is interesting to note the
irony of alienation for Poe: it haunted his waking moments and made
his life a misery, however it is also what drove his creative genius, and "flavored" so
many stories that remain Poe's greatest bequest to the literary
world.