Character Role Analysis
Cassius isn't a traditional guide or mentor, as he doesn't teach Brutus anything. Instead, he's important because he's the one who moves Brutus's thoughts – which may have already been tending toward taking down Caesar – to the point of action. In that sense, Cassius guides Brutus to realize what he really wants. Interestingly, Cassius tries to persuade Brutus by stoking his ambition, but Brutus isn't flattered or moved by any such tomfoolery – he decides to kill Caesar only when he thinks Caesar is getting too ambitious.