How does Edgar Allan Poe's "The Black Cat" reveal an unreliable narrator?

The
narrator of the story "" can certainly be considered unreliable due to his alcoholism
and his account of his sudden and drastic change in character. Formerly, the narrator had been
known as an uniquely kind and compassionate man, particularly toward animals. However, as the
narrator admits, his warm heart slowly turned cold and cruel over the years as he sank deeper
and deeper into alcoholism. As the narrator becomes crueler, he seems to be unable to fully
control his impulses or understand where his violent and ill-mannered behaviors stem from. The
narrator does not appear to understand his own thought processes or actions. This lack of
understanding of his own cognitive functioning does not instill confidence that he is a reliable
narrator.

Throughout the story, the narrator becomes more and more unhinged
and violent as he becomes tormented by his hideous act against the cat, Pluto, whom he viciously
attacked and then killed by hanging. As the story progresses,...