One famous line from "Julius Caesar" is Caesar's remarks about Cassius when he sees him, remarks that prove prophetic:
Let me have men about me that are fat,/Sleek-headed men, and such as sleep a-nights./Yond Cassius has a lean and hungry look;/He things too much: such men are dangerous...Such men as he be never at heart's ease/Whiles they behold a greater than themselves,/And therefore are they very dangerous .(I,ii,192-210)
Indeed, Cassius does envy the power of Caesar. For, he speaks of Caesar in this manner:
Why, man, he doth bestride the narrow world/Like a Colossus, and we petty men/Walk under his huge legs and peep about/To find ourselves dishonorable graves./Men at some time are masters of their fates:/The fault, dear Brutus, is not in our stars,/But in ourselves, that we are underlings. (I,ii,135-141)
Very manipulative, Cassius flatters Brutus that he is noble and should not be under such an aged man. Then he suggests the tyranny of Caesar, an idea which sways Brutus into joining the conspirators:
And it is very much lamented, Brutus,/That you have no such mirrors as will turn/Your hidden worthiness into your eye,/That you might see your shadow. I have heart/Where many of the best respect in Rome/(Except immortal Caesar), speaking of Brutus,/And groaning underneath this age's yoke,/Have wished that noble Brutus had his eyes. (I,ii,55-65)
When Brutus asks Cassius why he holds him up, and if his point is toward the "general good,"
as I love/The name of honor more than I fear death" (I,ii,88-89)
Cassius then skewers the truth:
I know that virute to be in you, Brutus,/As well as I do know your outward favor./Well, honor is the subject of my story. (I,ii,93-95)
Act I, scene 2 is, in fact, referred to as "the seduction scene." And, as the play continues, Cassius continues to defer to decisions by Brutus, which help bring about the demise of a noble man.
The character of Cassius is well established by the end of Act I. He reveals himself to be angry, bitter, and jealous of Caesar's power in Rome. Cassius speaks of Caesar with contempt and sarcasm. In the stories he tells Brutus, he shows Caesar to be weak and unworthy of the position he now holds over them. (According to Cassius, he himself is physically stronger than Caesar.) He complains bitterly to Brutus that they are now like "petty men" in comparison to the great Caesar. Cassius also reveals himself to be secretive and manipulative. In disparaging Caesar, Cassius is acting to draw Brutus into the conspiracy to murder him. To further influence Brutus to move against Caesar, Cassius writes false letters, supposedly from the Roman people, and has them delivered to Brutus and posted in the city. Cassius knows how to play upon Brutus's sense of honor; he feels confident at the end of Act I that he will engage Brutus in the conspiracy.