From the play’s beginning, Iago expresses his hatred for Othello and continues to give reasons for it. Firstly, Iago is angered by Othello’s act of promoting Cassio to the lieutenant position when he is more deserving of the promotion. This is the only reason Iago shares openly with other characters.
Secondly, rumors about Othello sleeping with Iago’s wife, Emilia, cause Iago so much pain that he seeks revenge. Although this is not discussed with the characters, Iago swears to take the rumors as true and harm Othello for the betrayal. For this suspected betrayal, Iago is determined to get even with Othello by cheating with the general’s wife.
Iago’s feelings are not justified in both cases because Othello has the right to choose a lieutenant as he pleases, and sleeping with Emilia is a mere suspicion. He argues that he has more battle experience and hence, he is a better soldier than Cassio.
In addition, some other people had recommended Iago as the best candidate for the lieutenant position. However, Iago sends the men to speak highly of him before Othello. The accusation of Othello sleeping with Iago’s wife is only a suspicion as Iago himself says that he has no evidence. Without any proof, Iago is not justified in believing the cheating claims.
Since the reasons for Iago’s hatred cannot be justified, his revenge is not warranted. Without any evidence of cheating and jealousy, Iago planned a revenge mission that led to the deaths of many people. Although orchestrating the plan without being discovered shows, he was a better soldier than Cassio, his failure to become rational taints his character as a leader.
His bitterness towards Othello and other characters deprives him of any humanity, making him as ruthless as an animal, as he eventually kills even his own wife. Overall, the extent of his vengeance mission is not proportionate with any of the reasons he gives to other characters and the audience through his soliloquies.