In Julius Caesar, the crowd rules the city, at least once it turns into a mob.
The crowd is featured from the first scene of the play, when commoners are celebrating Caesar's return from a victory over another Roman general, Pompey, in a civil war. This opening scene is used for exposition. The crowd's love for Caesar is established, as well as the fact that some do not like Caesar being favored by the Roman people.
The most important crowd scene occurs in Act 3.2, though, when Antony delivers his vital speech. Antony manages to convince the crowd that Caesar was not ambitious and should not have been assassinated. He motivates the crowd to riot and to go after the conspirators. They do, and another civil war is on.
The crowd turned into a mob controls the city. Antony manipulates the crowd's fickle nature, and its actions change the course of the play.
In Shakespeare's Julius Caesar, the reactions of the crowd--mob rule--are what lend meaning first to the speeches of Cassius, Brutus, and then to that of Marc Antony, thus propelling the action of the play. For instance, in Act I, Scene Two, in what has come to be known as "the seduction scene," Cassius seeks to persuade Brutus that Caesar is power-hungry. He tells Brutus that when Caesar triumphantly entered the streets of Rome after having defeated Pompey, Marc Antony offered him a crown--a "coronet":
Then he offered it to him again; then he put it by again; but to my thinking, he was very loath to lay his fingers off it. And he offered it the third time. He put it the third time by; and still as he refused it, the rabblement hooted, and clapped their chopt hands, and threw up their sweaty nightcaps, and uttered such a deal of stinking breath because Caesar refused the crown....(I,ii,239-246)
Here Cassius makes reference to the crowd to impress upon Brutus the power lust of Caesar, as well as to illustrate how Marc Antony can manipulate a crowd. In fact, this scene foreshadows the future manipulation of the Roman crowd by Antony in Act III. That Cassius understands this weakness of the Romans in the meek acceptance of the appearances of things is exhibited in his statement to Brutus in Act I:
The Romans now/Have thews and limbs like to their ancestors;/But woe the while! Our fathers' minds are dead,/And we are governed with out mothers'Spirits;/ Our yoke and sufferance show us womanish. I,ii,80-84)
Then, in Act III, after Brutus and the other conspirators assassinate Caesar, Brutus prepares to speak to the crowd, Antony approaches and asks permission to also address them. Against the wise advice of Cassius who understands mob mentality, Brutus gives his permission provided Antony not blame the conspirators and he is allowed to speak first. As Brutus speaks to the Romans, he places his faith in the logical reasons he provides for Caesar's death:
Believe me for mine honor, and have respect to mine honor, that you may believe. Censure me in your wisdom, and awake your senses, that you may the better judge....(III,ii,14-20)
Brutus then addresses the crowd and asks any to speak "for him have I offended. I pause for a reply" (III,ii,33-34) The crowd is positively persuaded and reply "None, Brutus, none!" (III,ii,35)
However, with Marc Antony enters with Caesar's body and shows the crowd where all the daggers have gone, the "womanish" crowd is emotionally swayed. With rhetorical devices such as repetition and tone of voice, and irony, along with the reading of Caesar's will as an example of his altruism, Antony persuades the crowd that Caesar was senselessly murdered:
They were villains, murderers!
O piteous spectacle!
O noble Caesar!
O most bloody sight!
We will be revenged!
Revenge! About! Seek! Burn! Fire! Kill! Slay! Let not a traitor live! (III,ii,199-206)
Clearly, emotional appeals sway the crowd more than rational ones. An ensuing civil war begins as a result of the persuasive arguments of Marc Antony who in the first act proves that he knows how "to work the crowd" to his advantage. This crowd, then, in effect, initiates the demise of Brutus and Cassius and the triumph of Antony, Octavian, and Lepidus, the second triumvirate.