What principles govern the choices Cassius and Brutus make in Julius Caesar?

This is a difficult question, because it concerns internal motivations. It is even difficult to judge our own motivations. However, we can surmise. Let me focus on Brutus. When it comes to Brutus, we must look at past Roman history. When we do this, we read of another Brutus that acted on behalf of the Roman people. When Tarquinius Superbus was the king of Rome, some Roman believed that they must get rid of the corrupt king. What they wanted was a government that was more equal and protected the people. This was the beginning of the Republic.

When we come to Caesar, we read of another Brutus. This Brutus was probably motivated by duty, a love for the Republic, a sense of honor that stemmed from the other Brutus. When he realized that Caesar stepped the boundaries of the Republic, he wanted to reestablish the Republic, like his noble ancestor.