How do the weaknesses of both Cassio and Roderigo aid Iago's cause and contribute to Othello's tragedy? .
In Shakespeare's Othello, Iago, the villain and instigator of trouble in this play, employs manipulation and deceit to gradually gain power over Cassio and Roderigo, which in turn helps him carry out revenge on Othello, and ultimately leads to Othello's tragedy. .
The main weakness of both Cassio and Roderigo, which proves to be the leading factor in the unfortunate conclusion of Othello, is gullibility. .
Manipulation is a very powerful tactic used in this play by Iago to achieve his goals, one of which he uses almost to perfection. This tactic proves to be extremely effective in persuading Cassio and Roderigo's into indirectly accomplishing Iago's objectives, mostly due to their high tendency to believe everything Iago tells them. .
The fist instance wherein Iago cunningly manipulates one of these characters, which in turn spontaneously triggers a series of events is when he convinces Roderigo to pursue Desdemona even though she is married to Othello, leading him to start a fight with Cassio. Although it is clear to the reader that that Desdemona has no knowledge of Roderigo's mere existence, his gullibility leads him to believe Iago's cleverly delivered lies of how she will soon leave the Moor and finally notice him even when the facts prove otherwise. This pattern continues on throughout the play, ultimately resulting in Roderigo's murder as he attempts to kill Cassio in one final hope to win Desdemona's heart, once again prompted by Iago's manipulative lies. .
Cassio, very much like Roderigo is a very trusting and gullible person, and succumbs numerous times to Iago's deception. Iago even manages to get Cassio drunk at one point, contrary to Cassio's attempts to thwart it, through the use of persuasion and manipulation, resulting in Cassio's demotion from lieutenant. Following this, under the guise of friendship, Iago advises Cassio to ask Desdemona to help him sway Othello towards getting his job reinstated, which results in Cassio's pursuit of Desdemona's help behind Othello's back.