Final answer:
Othello's seizure in Act IV is driven by a combination of factors, including visual evidence, a forged letter, false confession, and catching someone lying.
Step-by-step explanation:
Othello's seizure in Act IV is driven by multiple factors:
Seeing Cassio with the handkerchief: Othello sees Cassio with the handkerchief that was a symbol of Desdemona's love for him. This visual evidence triggers his jealousy and anger.
Finding a forged letter: Iago plants a forged letter, supposedly written by Desdemona, which implicates her in an affair with Cassio. This further fuels Othello's suspicions and leads him to doubt Desdemona's loyalty.
Iago's false confession: Iago tells Othello that Cassio has confessed to sleeping with Desdemona. This revelation pushes Othello to the brink of madness, as he believes his wife has betrayed him.
Catching Emilia lying: Othello confronts Emilia, Desdemona's maid and Iago's wife, about the handkerchief. Emilia lies, claiming that she found the handkerchief and gave it to Iago. This lie adds to Othello's growing anger and mistrust.