Cassius successfully persuades Brutus into joining the conspirators by appealing to his honorable character and portraying Julius Caesar as an ambitious, undeserving politician, who will eventually disband the Senate and rule Rome as a ruthless tyrant. In act 1, scene 2, Cassius recognizes that Brutus is concerned about Caesar's growing popularity and calls attention to his feelings. Cassius then mentions that many Romans wish that Brutus would intervene in government issues and recognize the threat of impending tyranny. Cassius then shifts Brutus's attention to Caesar's flaws and tells a story about the time he saved Caesar from drowning in the Tiber River. He proclaims that Caesar is a flawed mortal like everyone else and recalls a time when Caesar suffered an epileptic seizure. After Cassius focuses on Caesar's obvious flaws, he proceeds to describe Caesar's confident, arrogant personality by telling Brutus,
Why, man, he doth bestride the narrow world Like a Colossus, and we petty men Walk under his huge legs and peep about To find ourselves dishonorable graves. Men at some time are masters of their fates. The fault, dear Brutus, is not in our stars But in ourselves, that we are underlings (Shakespeare, 1.2.136–143).
Cassius's words are moving and depict Caesar as a domineering, arrogant man, who believes he is inherently superior. He also depicts Rome as full of passive, cowardly men, who are afraid to challenge Caesar and will not rise up against the future tyrant. Cassius then reminds Brutus of his noble, valiant ancestor by saying,
Now is it Rome indeed, and room enough, When there is in it but one only man. Oh, you and I have heard our fathers say, There was a Brutus once that would have brooked Th' eternal devil to keep his state in Rome As easily as a king (Shakespeare, 1.2.157–163).
After Cassius's moving words, Brutus responds by promising to think about his valid argument and entertains the idea of joining the conspirators. Brutus proceeds to tell Cassius,
Brutus had rather be a villager Than to repute himself a son of Rome Under these hard conditions as this time Is like to lay upon us (Shakespeare, 1.2.173–176).
In addition to portraying Caesar as an ambitious tyrant and calling attention to his obvious flaws, Cassius also forges letters from concerned citizens encouraging Brutus to intervene and preserve the Republic.