Iago feels that he was passed over for a promotion to lieutenant and resents Cassio, the new lieutenant. He also harbors a potential grudge against Othello, who promoted Cassio. Iago explains to Roderigo that Cassio was appointed despite the fact that three important Venetians had asked Othello to promote Iago. Iago states “I know my price, I am worth no worse a place” (1. 1. 11), which shows that he felt that he deserved the promotion.
He resents that he has fought alongside Othello several times in battle, yet Cassio a mere “counter-caster”(1. 1. 31), who has never served in battle, was made lieutenant. He holds Othello responsible for his being passed over, and mocks Othello’s race and character. Iago’s conduct reveals his malicious nature. His statement “I am not what I am” (1. 1. 65) summarizes the deceitfulness of his character. Iago suggests to the heartbroken Roderigo that he “Call up her father, / Rouse him: make after him, poison his delight, / Proclaim him in the streets” (1. 1. 67-69). This shows Iago’s vindictive nature.
He suggests that Roderigo not only disturb Barbantio in the middle of the night, but that he publicly announce that Desdemona has eloped, thus subjecting Barbantio and his family to shame. While calling out to Barbantio, Iago remains in the dark and does not reveal his identity. Here, as in the rest of the play, Iago acts an instigator, hidden in the shadows, yet still managing to manipulate those around him. In speaking to Barbantio, Iago insults him, and describes the relationship of Desdemona in derogatory and pornographic terms.
After doing his best to make Barbantio panic, Iago returns to Othello and pretends to be loyal. However, he instructs Roderigo to tell Barbantio exactly where Desdemona and Othello can be found. Iago’s conduct reveals his ability to control others, while they remain unaware of his influence. This is shown by the fact that he uses Roderigo to anger Barbantio, whom he uses to destroy Othello. At this point, Barbantio and Othello are oblivious to Iago’s devious nature. Iago callously betrays Othello but pretends to be loyal to him.