Cassius: Then, Brutus, I have much mistook your passion,
By means whereof this breast of mine hath buried,
Thoughts of great value, worthy cogitations.
Tell me, good Brutus, can you see your face?

So, as it shows, Cassius is the speaker in this quotation. He is speaking to Brutus about Caesar while Caesar is going through the town. Cassius is bothered that everyone in the town is treating Caesar like he is so great, because no one ever treated the other ruler, Pompey the same way. Cassius' AMBITION in this conversation between himself and Brutus is to turn Brutus against Caesar. As the conversation goes on Cassius finds that it may not be hard to do.
In the quotation above, we imagine Cassius speaking in very dulcet yet persuasive tones. He first begins talking well of Caesar, but slips in the little subliminal message that he does not like him. As the two continue their conversation, they almost begin the formation of their plot to overthrow the dictator. Cassius practically convinces Brutus to hate Caesar even more than he already does. --Macdog1