"O, beware, my lord, of Jealousy. It is the green-eyed monster." (Act 3, scene 3, 167-68) were Iago's words to Othello. This warning turns out not only to be for Othello, but also for Roderigo and for Iago.
Jealousy is being used as a catalyst to cause relationship problems when the trusted Iago rots Othello's mind by telling him that he is being betrayed by Desdemona and Cassio. Iago tells Othello lies to create a whirlpool of jealous emotions in his head. He tells Othello untrue stories of a romantic situation between Desdemona and Cassio, "In sleep I heard him say, "Sweet Desdemona, Let us be wary, let us hide our loves"." (Act 3, scene 3, 420-21). In telling him these lies, Othello grows more and more aggressive in his relationship with Desdemona, "Excellent wretch! Perdition catch my soul. But I do love thee! And when I love thee not, Chaos is come again." (Act 3, scene 3, 90-92). Othello's jealousy is the catalyst for the inescapable end he sees for his relationship with Desdemona. .
It was originally Iago's evil-minded goal to make Othello jealous of Cassio, as he suspected Othello of sleeping with his wife, Emilia. However, it was due to Iago's cruel manipulation of Othello that made him jealous of Cassio and allowed him to believe that Cassio had slept with his wife, Desdemona. Sexual jealousy is vital in Othello no more than when Roderigo was jealous of Desdemona. "Faith, I have heard too much, for your words and performances are no kin together." (Act 4, scene 2, 181-82). Iago deceived yet another character, Roderigo, into paying him to try and get "beautiful, sweet" Desdemona close to him. However, as all the other characters eventually found out, Iago's intentions were for nobody's pleasure other than his own. This created mixed feeling of jealousy and mistrust between the characters. All of the above situations were caused by the powerful and irrational act of sexual jealousy that caused a mountain of tension between characters.
