In Shakespeare' Julius Caesar the theme of "honor and reputation" speaks to how a man is perceived by his peers at that time. These characteristics were important as they defined a man's value: to lose one's honor in many societies would cause one to take his life. (This was common with samurai warriors committing seppuku.)
The first comes from Cassius. He believes that he has been dishonored and, therefore, that his reputation suffers—not honored as one of Caesar's inner-circle as he thinks he should be. His jealousy is what drives Cassius to see Caesar dead. Whereas Brutus fears Caesar will lead to Rome's destruction, Cassius has no such noble concerns. In Act One, scene two, Cassius describes a swimming contest when Cassius saved Caesar's life.
For once, upon a raw and gusty day,
The troubled Tiber chafing with her shores,
Caesar said to me, “Darest thou, Cassius, now
Leap in with me into this angry flood
And swim to yonder point?” Upon the word,
Accoutred as I was, I plunged in
And bade him follow. So indeed he did.
The torrent roar'd, and we did buffet it...
[Then] Caesar cried, “Help me, Cassius, or I sink!”
I, as Aeneas our great ancestor
Did from the flames of Troy upon his shoulder
The old Anchises bear, so from the waves of Tiber
Did I the tired Caesar. (106-113, 117-121)
However, Cassius has been shown no regard for this service, and he greatly resents Caesar. Cassius complains that he is treated like "a wretched creature" that must bow to Caesar like everyone else. He has not been honored, and his reputation has not improved because Caesar has ignored the event.
And this man
Is now become a god, and Cassius is
A wretched creature, and must bend his body
If Caesar carelessly but nod on him. (121-124)
In Act One, scene two, we learn that honor means more to Brutus than anything else:
For let the gods so speed me as I love
The name of honor more than I fear death. (94-95)
Cassius will use Brutus' sense of honor to get him to agree to kill Caesar.
I know that virtue to be in you, Brutus,
As well as I do know your outward favor. (96-97)
Another incident where honor and reputation are important is after the conspirators assassinate Caesar. Antony approaches Brutus and the others and makes a show of shaking hands with them, rather than openly condemning them. He wants to address the crowds at Caesar's funeral. Brutus agrees, but only if Antony does not cast Brutus and the others in an unfavorable light—for Brutus believes he has saved Rome in killing this man who wanted to be the king—a dictator. Antony outwardly agrees.
Mark Antony, here, take you Caesar's body.
You shall not in your funeral speech blame us,
But speak all good you can devise of Caesar,
And say you do't by our permission,
Else shall you not have any hand at all
About his funeral. (III.i.263-268)
Brutus has no desire that his honor be besmirched. He has acted out of love for Rome and wants to be able to defend his actions before the people. If the people reject him, his reputation will be destroyed, and they may well kill him. At first the people honor him for Caesar's death. However, Antony, a powerful orator who artfully employs "reverse psychology," is able to turn the crowds away from their support of Caesar's murderers. This will eventually lead to civil war.