For Montresor, revenge is a perfectly logical way to deal with someone who has wronged him in some way. Montresor claims that Fortunato has dealt with a thousand injuries at the hands of Fortunato, but he never details these injuries. He adds that an insult is the last straw and this inspires him to swear revenge against Fortunato. Again, he does not say just what this insult is. Whatever the injuries and the insult were, Montresor is determined to "not only punish but punish with impunity." Montresor also says that the avenger (person seeking revenge) should make himself known to his enemy:
It (a wrong) is equally unredressed when the avenger fails to make himself felt as such to him who has done the wrong.
Montresor is proud and arrogant. He is self-centered and therefore wants Fortunato to know that he (Montresor) is the one punishing him. Montresor considers himself as judge and jury. He justifies his torture of Fortunato based upon the vague notions of "injuries" and an "insult." Montresor believes it is his right to punish Fortunato. This suggests that Montresor is a an elitist. He thinks his high social status gives him the right to avenge anyone who wrongs him. The fact that he goes to such lengths to punish Fortunato also shows that he is immoral, maybe even a psychopath. To an immoral, elitist, psychopath, revenge (even murder) is logical and acceptable.