The Theme of Madness in Edgar Allan Poe's The Black Cat

In "The Black Cat," the narrator was aware that his thoughts and actions were transforming into a downward spiral. He was aware of his increased irritability, his disregard of the feelings of others, and the unreasonable violent actions he carried out towards his wife. He was even aware that his favorite pet and playmate, Pluto, was falling victim to the ill-effects brought by alcoholism onto the narrator. However, for reasons that remain inscrutable to the reader, he continues his descent into moral degeneration. Is he affected with "perverseness"? Is it a result of the alcohol? Does he not know what he is doing?