Cassius is the one behind the conspiracy. He is jealous of Caesar's rise to power, especially since Caesar is physically weaker than Cassius. Cassius explains to Brutus that several times he had to save Caesar's life. Cassius uses the "good of Rome" as his reasoning behind bringing other Senators and leaders together to kill Caesar. He knows that Brutus has more influence due to Brutus's unwavering loyalty to Rome, which is why he needs Brutus to help led the conspiracy.