Brutus is an honorable, noble character. He and Cassius are talking. Brutus claims that he fears Caesar would crown himself king. Cassius jumps at this opportunity to try and convince Brutus to join a conspiracy to kill Caesar. Brutus listens but is careful or hesitant to join the conspiracy. Brutus loves Caesar and considers him his friend.
Brutus is honorable in that he chooses to protect Rome from Caesar's ambition. Brutus is clearly torn between killing Caesar his friend and protecting Rome. Brutus is honorable because he loves Rome more than he loves himself or Caesar:
It is not an easy task for Brutus to commit to, but he detemines that Caesar must die. Night after night, Brutus spends awake, contemplating whether he should kill Caesar or not.
Ultimately, Brutus puts his own tender feelings for Caesar aside and joins the conspiracy in killing Caesar. Brutus is so honorable that the people seem to trust him in that he has done the right thing in killing Caesar. A citizen silences the people to hear what the noble Brutus has to say:
The noble Brutus is on the platform. Silence!
Then Brutus in all his honor eloquently explains why he had to kill Caesar:
Romans, countrymen, and friends! Listen to my cause, and be
silent, so you can hear. Believe me based on my honor, and have
respect for my honor, so you can believe. Judge me in your
wisdom, and wake up your senses, so you can be a better judge.
If there is anyone in this assembly, any dear friend of Caesar's, to
him I say that Brutus' love to Caesar was no less than his love. If
then that friend demands why Brutus rose against Caesar, this is
my answer,—Not that I loved Caesar less, but that I loved Rome.
Brutus is honorable in his honesty. He continues to explain that Caesar had to die for his ambition:
As Caesar loved me, I
weep for him; as he was fortunate, I rejoice at it; as he was
valiant, I honor him; but, as he was ambitious, I killed him.
There are tears for his love; joy for his fortune; honor for his
valor, and death for his ambition.
Then Brutus in all of his honor agrees to allow Mark Antony to speak. Antony turns on Brutus and stirs the people into a rage against the honorable Brutus.
Brutus has to flee for his very life. He dies in battle. He falls on his own sword. Mark Antony sums up the extent of Brutus' honor in his final words upon finding Brutus' dead body:
This was the noblest Roman of them all.
All the conspirators, except him,
Did that they did out of jealousy of great Caesar;
Only he, in a general-honest thought
And common good to all, made one of them.
His life was gentle, and the elements
So mixed in him that Nature might stand up
And say to all the world, "This was a man!"
Even Octavius honors Brutus by treating his bones with the utmost respect:
According to his virtue, let’s treat him
With all respect and rites of burial.
His bones tonight shall lie inside my tent,
Most like a soldier, ordered honorably.
Brutus lived and died an honorable man as is noted by even his enemy.