Cassius is the first to praise him, saying that, "many of the best respect in Rome" (Act 1, Scene 2, Line 59) also think highly of him. Casca also praises Brutus and so does Antony.
Brutus is an idealist and believes that other men have the same high principles as himself. He is descended from patriots and he is often reminded of the Lucius Janius Brutus who drove Tarquin from Rome and helped to found the first republic. Brutus's motives for joining the conspiracy are totally pure and he intends to maintain this purity in everything. He feels that to swear an oath of allegiance between the conspirators, would, "stain/ The even virtue of our enterprise" (Act 2, Scene1, Lines 132-33), casting a shadow of doubt both on the cause and on the men. .
Brutus will not agree that Antony should be killed along with Caesar because this would turn what he seems as ritual sacrifice into bloody butchery. Cassius argues against Brutus here, and also when Antony asks permission to address the citizens at Caesar's funeral. On both occasions, Brutus's idealism is strong and Cassius is overruled; events prove Cassius to have been right both times. The contrast between idealist Brutus and the realist Cassius is clearly shown through their quarrel about money.
The trouble with idealism is that it can so easily blind those who posses it. Brutus is blinded. The conspiracy might have succeeded if Antony, as well as Caesar had died on the Ides of March. All might still have been well for the murderers if Antony had not been allowed to stir the citizens to mutiny with his funeral speech. The biggest mistake that Brutus makes is that Caesar has to die.
When he thinks to himself in the garden, it becomes clear that Brutus is deceiving himself. Unable to find fault with Caesar's conduct, Brutus resorts to a generalization, which says that ambitious men, scorn those beneath them. In this way, Brutus argues that Caesar is a tyrant and therefore must be killed.
