What a beautiful and terrible line that is!
To move more directly to your question, in this quotation Poe is addressing the way that humans rebel against thing. You might think of Adam and Eve in the Garden of Eden. They did the one thing that they were forbidden to do, and that's what created human life as we know it.
Since the narrator in this story first blinds a cat, then becomes an alcoholic, then kills his wife, this statement works to justify and cleanse his actions. Instead of being horrific, these actions are explained as being the essence of humanity. At the same time, they create irony. Do we accept this statement, which would indicate the narrator did these things on purpose, or do we accept the statements in the moment, which say he did them by accident?