in act three scene three discuss the ways in which iago cleverly sows his poisonous seeds of doubt in othellos mind throughout this scene

Desdemona decides that she wants to advocate for Cassio. She tells Emilia so, and that she believes Cassio is a good person, and has been wronged in this case; she pledges to do everything she can to persuade her husband to reinstate Cassio. Cassio speaks with her briefly, but leaves just as Othello enters because he does not wish for a confrontation. Iago seizes on this opportunity to play on Othello's insecurities, and make Cassio's exit seem guilty and incriminating. Othello then speaks to Desdemona, and Desdemona expresses her concern for Cassio; she is persistent in his suit, which Othello is not too pleased about. Othello says he will humor her, and the subject is dropped for a while.

Iago then plays on Othello's insecurities about Desdemona, and gets Othello to believe, through insinuation, that there is something going on between Desdemona and Cassio. Othello seizes on this, and Iago works at building up his suspicions. Soon, Othello begins to doubt his wife, as Iago lets his insinuations gain the force of an accusation against her. Othello begins to voice his insecurities when it comes to Desdemona, and himself as well.

Desdemona drops the handkerchief that Othello gave her on their honeymoon; Emilia takes it and gives it to Iago, who decides to use the handkerchief as the key prop in his bitter play. Othello re-enters, and tells Iago that he now doubts his wife; Othello demands "ocular proof" of Desdemona's dishonesty, so Iago makes up stories about Cassio talking in his sleep, and says that Cassio has the handkerchief that Othello gave to Desdemona. Iago knows how important this handkerchief is to Othello; it was his first gift to Desdemona, and was given to him by his mother.