What were Brutus's and Cassius's motives for killing Caesar?

Cassius appears to envy Julius Caesar, while Brutus is fearful for the Roman Republic. Cassius points out that Caesar has grown too powerful, though he is not more worthy than anyone else: “Brutus and Caesar: what should be in that 'Caesar'? / Why should that name be sounded more than yours?” Cassius condemns Caesar’s weakness as a human, emphasizing that he is nothing more than a man who may aspire to be dictator. Caesar describes Cassius’s ambition and jealousy: “Such men as he be never at heart's ease / Whiles they behold a greater than themselves.”

Brutus, on the other hand, cares about Caesar: “I know no personal cause to spurn at him, / But for the general.” However, he worries about how power will corrupt Caesar and believes it necessary to nip his aspirations in the bud. At Caesar’s funeral, Brutus emphasizes how much he loved and mourns for Caesar: “Not that I loved Caesar less, but that I loved Rome more.” He slew Caesar for his ambition, which he considered a threat to Rome. As far as Brutus is concerned, a monarchy would make them all slaves.

Both Cassius and Brutus worried about Caesar’s growing popularity. Caesar was a proud and strong-willed man, so their fears were very valid. Their conflicting motives result in some irreconcilable contradictions in their coup, which ultimately falls to Mark Antony and Octavius Caesar. Octavius would usher in the Roman Empire, the exact fate Brutus was hoping to avoid.