Once Brutus has joined the conspirators, can he turn back?
Brutus's defining character traits are his nobility and integrity. He is portrayed as an extremely honorable man who is initially conflicted about joining the conspirators and assassinating Julius Caesar. Despite his positive character traits, Brutus is rather naive, and Cassius easily manipulates him into believing that Julius Caesar is a threat to the Roman Republic. After extensive deliberation, Brutus decides to join the conspirators and assassinate Julius Caesar to prevent him from disbanding the Senate and ruling as a ruthless tyrant.
In act two, scene one, the conspirators arrive at Brutus's home, and Brutus immediately takes a leading role. Brutus demonstrates his resolve by refusing to take an oath, which emphasizes his firm belief in the plot to murder Caesar. Brutus tells the other conspirators,
No, not an oath. If not the face of men,
The sufferance of our souls, the time’s abuse—
If these be motives weak, break off betimes,
And every man hence to his idle bed.
So let high-sighted tyranny range on
Till each man drop by lottery. But if these—
As I am sure they do—bear fire enough
To kindle cowards and to steel with valor
The melting spirits of women, then, countrymen,
What need we any spur but our own cause
To prick us to redress? What other bond
Than secret Romans that have spoke the word
And will not palter? And what other oath
Than honesty to honesty engaged,
That this shall be, or we will fall for it?
Brutus's strong words reveal that he will never back out of the assassination plot and is determined to follow through with the murder. Unlike the other conspirators, Brutus's intentions are noble, and he genuinely believes that he is protecting the Roman populace by assassinating a potential tyrant. Considering Brutus's nobility, honorable personality, and strong words to his fellow conspirators, Brutus is unwilling to turn back on his decision to assassinate Caesar and will accept the consequences of their actions. If Brutus were to turn back, the senators would more than likely consider him a target and take revenge on him for foiling their plot.
Brutus does not seem to be the kind of man who would turn back after doing so much soul-searching. Conceivably he could turn back, but that would leave him in a dangerous position. He would either have to stand by and do nothing while the other conspirators went ahead with their plan to assassinate Caesar, or else he would have to turn against them and warn his good friend what the conspirators were planning. Either course would lead to bloodshed. The conspirators would go ahead and kill Casear, and they would include Antony in the purge that followed Caesar's death. Or, on the other hand, Casear would use his soldiers to kill all the conspirators that Brutus named. It would seem to be to Brutus' best interest to warn Caesar if he decided not to participate in the conspiracy, because Brutus himself could easily become one of the victims of the conspirators if they succeeded in assassinating Caesar and gaining power. They would probably want revenge against Brutus for abandoning them. They might even think he had intended to betray them whether he did or not.