From the very beginning of the book Othello, the reader gets a strong demonstration of just how present jealousy is. The reader is also shown in time that many of these jealousies are misplaced. These misplaced jealousies are the thematic centers of the play. They are shown to the reader many times throughout the story in various forms. They appear in the form of sexual jealousies as shown by both Iago and Othello. They also appear in the form of professional jealousy as shown again by Iago. These jealousies, most of which are misplaced, are ultimately the means to an end for many of the lead characters in the story. However, Othello's jealousy is completely unfounded and he is the subject of manipulation.
The jealousy that the reader views from Othello is that of Cassio and his wife Desdemona. Believing in falsified information provided by Iago, Othello believes that Desdemona is having an affair with his officer, Cassio. Many small coincidences and twisted information further reinforces this strong belief. For instance, Iago plants the handkerchief that Othello gave to Desdemona in Cassio's room, knowing that it would somehow get back to Othello that Cassio had the scarf, making Othello believe that Desdemona gave the scarf to Cassio. Also, Cassio and Desdemona are good friends and meet periodically throughout the story. One of these times however, Othello and Iago are approaching and Cassio sneaks away, letting Iago plant the idea in Othello's head that Desdemona and Cassio are meeting secretly to have an affair. These either coincidental or falsified events lead to the murder of both Desdemona and Cassio (both of which Othello acted in some way upon), and Othello's suicide, all of which were orchestrated by Iago despite testimonies provided by both Desdemona, his sworn wife, and Emila, Desdemona's attendant and close friend, Othello continues to believe Iago seemingly out of pure emotional blindness.