Iago claims he hates Othello because Othello passed him over for a promotion, instead choosing Cassio. However, Iago then says he hates Othello because of a rumor that Othello slept with Iago's wife. Iago decides to ruin Othello's life because of this suspicion alone. Iago's plan is to manipulate Othello's trusting nature by making him believe his wife Desdemona is having an affair with Cassio, stoking the flames of jealousy within Othello.