In Joaquim Machado de Assis’s novel, the titular protagonist Dom Casmurro (a nickname for Bento) is looking back on his life. When we meet him, he is a lonely old man who seems intent on not just telling his life’s story but vindicating a number of difficult decisions he made.
Over the course of the novel, the reader comes to see that Bento suffered from the flaw of hubris—excessive pride. Unable to move past his narrow-mindedness and jealousy, he either alienated himself from others or drove them away. His inability to let go of his jealousy over his wife’s supposed infidelity (and with his best friend!) destroys his entire world, but he lives on in self-imposed suffering. While it is specifically his jealousy that ruins everything, that jealousy is only a reflection of the fundamental sin of pride that renders him unable to admit that he is wrong.
The author has Bento tell his own story in order to emphasize the numerous flaws in his argument, which will be clearly visible to the reader. We gradually see that the utter absence of self-confidence and self-love rendered Bento unable to believe that the lovely Capitú, his heart’s desire, would prefer him over his friend Escobar. Rather than properly mourn his friend’s death, Bento uses his funeral as an occasion to further his suspicions of his wife for expressing grief. The greatest damage results from his ongoing obsession in believing that Escobar, not himself, is the father of his son, Ezekiel.