William Shakespeare’s play explores jealousy as a dangerous but all-too-common human emotion, which in this case has devastating consequences. The main character who suffers throughout the play from severe jealousy is Othello. However, jealousy is also what motivates Iago; because he understands the emotion so well, he also understands how to fan the flames and turn a spark of jealousy into a raging fire.
Iago is the prime mover of the play, a kind of master puppeteer who obsessively manipulates all the other characters. His jealousy is both professional and personal, as well as fueled by racism. He is jealous of Cassio for getting the promotion he thinks was owed to him and because he thinks Cassio slept with his wife, Emilia. Because Othello, in his newly elevated position, was the one who chose Cassio, Iago determines to destroy him. Using his personal insights into jealousy, he twists and turns every word and gesture into something else until Othello cannot tell truth from lies. Iago builds on Othello’s insecurity about Desdemona’s love to make him doubt her fidelity. Once Othello believes that she could be unfaithful, it is a short step to being certain that she has already done so. Once he crosses that line, he cannot recover his trust in her, leading to the tragic ending with their deaths.