It is his flaw - he trusts too easily. When he must choose between Desdemona's honesty and Iago's alleged honesty, he cries, "If she be false, O, then Heaven mocks itself! I"ll not believe it." (3.3.278-279) He does need to believe in his wife, as he needs to trust Iago too. He needs to believe in his friend, Iago, who has served him well: "O brave Iago, honest and just, that hast such noble sense." (5.1.31-32) Because of his need to trust and his deep unrealistic love for Desdemona, Othello is easily swayed by Iago's lies on Desdemona. This finally leads to Othello's loss of reason. He is infected so deeply by Iago's poison, he feels it is his duty to destroy his new bride or "else she"ll betray more men." (5.2.6) He deceives himself and is doomed to face the consequences of his actions. Our antagonist, Iago, also becomes responsible for his actions in the end. Iago acts on revenge against Othello, simply because he is overlooked for a promotion in Othello's army. Like Othello, Iago is well liked and trusted. He reinforces his honesty and loyalty to Othello and conceals his disappointment and plans for revenge. Jealousy overwhelms Iago. He is very persuasive with his words. For example, in Act 3, Scene 3, Iago makes Othello imagine Desdemona "topped" (398) by the young Cassio. His language is savage and brutal throughout the play. Iago, however, does not realize the immensity of the situation and in the process kills his wife, Emilia, and is promised rightful punishment in the end.
This tragedy begins with Iago, a soldier in the Venetian army, and Roderigo, a former suitor of Brabantio's daughter Desdemona arguing in the streets of Venice over Desdemona's marriage with the Moor, Othello. Iago loathes Othello, because Othello passed him up for a promotion. The promotion went to a soldier, Cassio, who learned from books and had no field experience. And so the conflict begins and Iago starts a plan for revenge.