How does Montresor justify what he is about to do to Fortunato? What is left uncertain in his explanation

How does Montresor justify what he is about to do to Fortunato?

Answer: Fortunato has 'injured' Montresor in the past and deserves to be punished.

Explanation:

The Cask of Amontillado is a short story, written by Edgar Alan Poe.

In the story, Montresor seeks revenge on his friend, Fortunato, as he has 'injured' Montresor in the past:

"The thousand injuries of Fortunato I had borne as I best could, but when he ventured upon insult, I vowed revenge. You, who know so well the nature of my soul, will not suppose, however, that I gave utterance to a threat."

Montresor believes that Fortunato deserves to be punished for what he did. He chooses not to discuss this issue openly with Fortunato - instead, he lures him into the catacombs of his home. He invites him to try a special type of wine, but buries him alive.

Montresor also justifies his actions when he states that by insulting him, Fortunato actually insulted the whole Montresor family. It is now Montresor's duty to protect the honor of his family.

What is left uncertain in his explanation?

Answer: Montresor never explains how exactly Fortunato insulted him.

Explanation:

Montresor insists that Fortunato insulted him, but never actually explains what he did. This makes Montresor quite unreliable and treacherous, especially if we consider the method he chose in his revenge. Even if Fortunato did something horrible to him, it is questionable whether he deserves to die such a terrible death. Montresor's refusal to deal with the problem in a civilized manner and reveal the whole story makes us doubt his sanity.