Iago does not immediately suggest Desdemona’s death. He first ensures that Othello is convinced of her guilt. At the beginning of the scene, Iago tells Othello that it is not a crime for a woman to be naked with a man if nothing happens. He also states that if he were to give his wife a handkerchief, she would be able to do with it as she wished. These reminders of Desdemona’s supposed unfaithfulness arouse Othello’s anger. After Iago finally admits that Cassio has told him he has lain with Desdemona, Othello is already blind with rage and jealousy.
In order to further goad Othello, Iago convinces Othello to hide explaining that he will ask Cassio to describe his relationship with Desdemona. Iago instructs Othello to observe Cassio’s face during the conversation. In reality Iago recounts his experience with a prostitute named Bianca. Cassio is so amused by his story that he laughs hysterically. Othello, who is already irrational at this point, imagines that he is hearing more than he actually is. When Cassio talks about about Bianca hanging on his neck and pulling at him, Othello says, “Now he tells how she plucked him to y chamber” (4. 1. 141).
Later on in the scene, Bianca appears, and argues with Cassio. Iago uses this in his favor by convincing Othello that Cassio has given Desdemona’s handkerchief to Bianca, a prositute. Othello asks, “How shall I murder him, Iago? ” (4. 1. 170). When Iago attempts to equate both Cassio and Desdemona to trash, Othello can think only of killing Cassio, but not his beautiful and loving wife. Sarcastically, Iago says to Othello, “If you are so fond over her iniquity, give her patent to offend; for, if it touch not you, it comes near nobody” (4. 1. 197-199).
Threatened with emotional isolation, Othello responds as Iago wants him to and says, “I will chop her into messes. Cuckold me! ” (4. 1. 200). Iago first discredits Desdemona by supposedly offering proof of her infidelities to Othello. Iago then angers Othello by framing Cassio, making it appear as though Cassio is laughing about his trysts with Desdemona. Othello is so enraged that he decides Cassio must die, but he cannot bring himself to kill Desdemona. Finally, Iago threatens Othello with emotional isolation. Othello finally concedes and states that Desdemona must die.