Final answer:
Cassius writes fake letters from commoners to manipulate Brutus into joining the conspiracy to overthrow Caesar, playing on Brutus's sense of duty and desire to protect the Roman Republic. By creating the illusion that the commoners are against Caesar, Cassius tries to convince Brutus that killing Caesar is necessary for the greater good of Rome.
Step-by-step explanation:
In the play Julius Caesar, Cassius writes fake letters from commoners to convince Brutus to join the conspiracy to overthrow Caesar. He does this to manipulate Brutus into thinking that the people are against Caesar and that it is necessary to remove him from power for the greater good of Rome.
By fabricating letters from the commoners, Cassius plays on Brutus's sense of duty and desire to protect the well-being of the Roman Republic. Cassius knows that Brutus values the opinion of the people and believes in their support, so he creates the illusion that the commoners are calling for Caesar's downfall.
This manipulative tactic is meant to sway Brutus's decision and make him believe that killing Caesar is not only justified but also necessary to preserve liberty and prevent Caesar from becoming a tyrant.