Brutus is the most complex of the characters in this play. He is proud of his reputation for honor and nobleness, but he is not always practical, and is often naive. He is the only major character in the play intensely committed to fashioning his behavior to fit a strict moral and ethical code, but he take actions that are unconsciously hypocritical. One of the significant themes that Shakespeare uses to enrich the complexity of Brutus involves his attempt to ritualize the assassination of Caesar. He cannot justify, to his own satisfaction, the murder of a man who is a friend and who has not excessively misused the powers of his office. Consequently, thinking of the assassination in terms of a quasi-religious ritual instead of cold-blooded murder makes it more acceptable to him. Unfortunately for him, he consistently misjudges the people and the citizens of Rome; he believes that they will be willing to consider the assassination in abstract terms.
Brutus is guided in all things by his concepts of honor. He speaks of them often to Cassius, and he is greatly disturbed when events force him to act in a manner inconsistent with them. Consider his anguish when he drinks a toast with Caesar while wearing a false face to hide his complicity in the conspiracy. Ironically, his widely reputed honor is what causes Cassius to make an all-out effort to bring him into an enterprise of debatable moral respectability. Brutus' reputation is so great that it will act to convince others who are as yet undecided to join.
Brutus' concentration on honorable and noble behavior also leads him into assuming a naive view of the world. He is unable to see through the roles being played by Cassius, Casca, and Antony. He does not recognize the bogus letters as having been sent by Cassius, although they contain sentiments and diction that would warn a more perceptive man. He underestimates Antony as an opponent, and he loses control over the discussion at the Capitol following the assassination by meeting Antony's requests too readily. Brutus as a naive thinker is most clearly revealed in the scene in the Forum. He presents his reasons for the assassination, and he leaves believing that he has satisfied the Roman citizens with his reasoned oration. He does not realize that his speech has only moved the mob emotionally; it has not prodded them to make reasoned assessments of what the conspirators have done.
Brutus is endowed with qualities that could make him a successful private man but that limit him severely, even fatally, when he endeavors to compete in public life with those who do not choose to act with the same ethical and moral considerations. In his scene with Portia, Brutus shows that he has already become alienated with his once happy home life because of his concentration on his "enterprise," which will eventually cause him to lose everything except the belief that he has acted honorably and nobly. In the tent at Sardis, after learning of Portia's death and believing that Cassius is bringing discredit on the republican cause, Brutus becomes most isolated. His private life is destroyed, and he also has difficulty avoiding the taint of dishonor in his public life.
Brutus makes moral decisions slowly, and he is continually at war with himself even after he has decided on a course of action. He has been thinking about the problem that Caesar represents to Roman liberty for an unspecified time when the play opens. After Cassius raises the subject and asks for Brutus' commitment, he requests time to think the matter over, and a month later, speaking alone in his orchard, he reveals that he has since thought of little else. He has trouble arriving at a decision whether to participate in the assassination, he expresses contradictory attitudes towards the conspiracy, he attempts to "purify" the murder through ritual, and he condemns Cassius' money-raising practices while asking for a share. His final words, "Caesar, now be still: / I kill'd not thee with half so good a will," are almost a supplication for an end to his mental torture.
On the other hand, Brutus characteristically makes decisions that are essential to his and Cassius' success with much less forethought, and after he's committed to a plan, he does not waiver. He quickly takes command of the conspiracy and makes crucial decisions regarding Cicero and Antony. He does not, however, make adequate plans to solidify republican control of government following the assassination, and he too readily agrees to allow Antony to speak.
Brutus' character is made even more complex by his unconscious hypocrisy. He has conflicting attitudes toward the conspiracy, but he becomes more favorable following his becoming a member of the plot against Caesar. He attacks Cassius for raising money dishonestly, yet he demands a portion. Nevertheless, at the end, Brutus is a man who nobly accepts his fate. He dismisses the ghost of Caesar at Sardis. He chooses personal honor over a strict adherence to an abstract philosophy. He reacts calmly and reasonably to Cassius' death, as he had earlier in a moment of crisis when Popilius revealed that the conspiracy was no longer secret. In his last moments, he has the satisfaction of being certain in his own mind that he has been faithful to the principles embodying the honor and nobility on which he has placed so much value throughout his life.