examine how the motif of ambition is developed. For this thesis you can use Marc Antony's remark in his funeral oration as a motivator:  "Ambition should be made of sterner stuff."  For, this line is ironic since Brutus, and especially Cassius who is so ambitious are not of the "sternest stuff" and are defeated by Antony and Octavius.  Your thesis, then, can state that it is for his ambition that Brutus believes Caesar dangerous, but the conspirators prove to be even more ambitious and it is this ambition that is also their demise.

Click on the site below for ideas on themes of this play.

Or, perhaps you wish to analyze a character. There has always been great debate on who is the tragic character in this play.  But, many feel Brutus is, and you can glean some good ideas from the site below on this opinion.  So, for your thesis  you can state that Brutus is the tragic hero in "Julius Caesar" because he is of noble stature and has noble ideals, but he makes a tragic mistake for which he pays tragic consequences.

You will need to think through the character of Brutus, and in particular his motives for wanting to depose Caesar. There are many different ways of viewing his character, but one valid approach is to explore the way that Brutus is actually tremendously naive. He has lofty motives for deposing Caesar, but his innocence and naivety makes him easy prey for the flattering tongue of Cassius. He is used by the plotters to gain credibility for their less-than-noble actions yet he remains unaware of the way that he is being used. He believes all the while that he himself is trying to do what is right for Rome, but we as the audience cannot help seeing another more questionable agenda at work. Brutus, like Caesar before him, is prone to the same power-hungry tendencies of anyone given such unlimited control and might. Thus a good thesis statement might be:

Brutus is the tragic hero of this play because of his naivety and innocence, both in regard to other people and himself.

This would allow you to explore the differing approaches I have outlined above and will make for an interesting essay. Good luck!

You could focus on the irony and contradiction in Brutus’s character and fate. Cassius steers Brutus into conspiring to assassinate Julius Caesar, who would not suspect Brutus’s involvement: “Caesar doth bear me hard; but he loves Brutus.” Cassius sees that Brutus can be manipulated both in spite of and because of his nobility. He flatters Brutus and appeals to his sense of equality. For his ideals, Brutus justifies murdering his closest friend, harming both himself and others: “I slew my best lover for the good of Rome.” He cares about people enough to kill one.

Another contradiction is that Brutus is a natural leader who does not believe any one person should rule. In spite of Caesar’s death being Cassius’s brainchild, Brutus often takes control of the situation. He contradicts and undermines Cassius multiple times in front of other conspirators. Brutus addresses the senators in his house and describes at length the moral reasons for Caesar’s death. When Decius and Cassius suggest killing Mark Antony as well, Brutus shuts them down: “Our course will seem too bloody.” Later, Brutus grants Antony permission to speak at Caesar’s funeral, without consulting the other conspirators. Cassius argues that “the people may be moved / By that which he will utter,” but Brutus is not persuaded.

This reveals yet another irony in Brutus’s nature and actions. His leniency leads to civil war. Brutus allows Antony to live and even speak to the public, two decisions that seal the conspirators’ fates. The crowd turns on them, and Antony and Octavius wage war against Brutus and Cassius. Brutus’s honor leads him to commit murder, but it also prevents him from fully carrying out the coup. In the end, Brutus’s whole purpose is thwarted: he killed Caesar to prevent Rome from transforming from a republic into a monarchy, but, after Brutus dies, Octavius Caesar will turn Rome into an empire that would last for centuries.

A good quotation with which to start your paper on Brutus as the tragic hero of William Shakespeare's 'Julius Caesar' is with Marc Anthony's epitaph: 'This was the noblest Roman of them all.' Of the conspirators, only Brutus acted out of unmixed philosophical ideals. What makes this such a tragic circumstance is that Brutus and Caesar genuinely cared for one another, but Brutus felt that because Caesar would be a good tyrant, he would cause tyranny to become firmly entrenched in Rome, and thus, paradoxically, Brutus murdered Caesar because of his good qualities. This opening quotation allows you to move on to discuss the nobility of Brutus, one of the major themes of the play.

A thesis statement is a sentence expressing the central claim of your paper. The problem here is not that you are struggling to formulate a thesis "statement" but rather that you haven't yet developed a thesis to be stated. A thesis is a point that you are arguing. Since Brutus is widely acknowledged to be the tragic hero of Julius Caesar, it does not need to be argued; you should look for a thesis which would either need to be supported or which which illuminate some new aspect of the play for a reader. 

The reason the Brutus is widely acknowledge to be the hero of the play is twofold. First, there is no one else who fits the role. Caesar dies early, Mark Antony and Octavian are the antagonists, and Cassius is a morally dubious character. 

Brutus himself has the standard characteristics of the tragic hero as described in Aristotle's Poetics. He is of noble background and character, he has moral stature, and he is engaged in actions of a certain greatness or seriousness. His major flaw is that he does not realize the duplicity of others readily and is perhaps too wedded to an uncompromising ideology, not realizing that Caesar's death would fail to restore the Republic. Because of his strength of moral character, we feel fear and pity at his downfall.

A possible thesis about Brutus might be that "the way that Brutus' participation in assassination of Caesar leads to his replacement by an even more authoritarian dictator shows that an ethical system focused on desired outcomes leads to morally questionable acts with unintended consequences."

For a character to be considered a tragic hero he must possesses several qualities--he must be a person in a noble position (Brutus is a highly respected Senator from a famous Roman family); he must fall from that noble position (obviously, Brutus experiences the ultimate downfall); he must have a tragic flaw which results in his downfall (think about what personality trait Brutus possesses that leads to his death at the end of the play); and he must experience a tragic realization (this normally occurs right before the tragic hero's death; so think about Brutus realizes before he chooses to die).

Keeping those characteristics in mind for your body paragraphs, your thesis should discuss Brutus's high position and his downfall. Consider his noble goals (regarding killing Caesar) and what ultimately ends up happening to those goals.