Some of the main themes used in Act 1 Scene 2

Another theme in this act is also they way people are easily swayed. The public of Rome is very fickle and can change their minds quickly and often, also the way flavius and marallus view the crowd how they can pay homage to a tyranny.

Sure, there is the power of speech. The hordes of people are cheering Caesar. The power of oratory in mesmerising the crowd is at play here. Also the simple mindedness of the masses and their ease to be manipulated is important as well. The theme of loyalty vs duty can be seen as well. Brutus is at war with himself over what to do about Caesar's rising power. Treachery is also at play here for the little meeting between the conspirators takes place.