The omens, dreams and supernatural events in Julius Caesar foreshadow future things in the play using certain events. The first omen showing that something is not right is the agitation of the commoners and the tribunes that stop them from celebrating the victory of Caesar over Pompey. The common cobbler seems to trick the tribunes with puns, "a mender of bad soles". This is furthered by Caesar's distrust of Cassius early on in the play, "Cassius has a lean and hungry look... such men are dangerous..." Caesar's observation was swept to the side and Cassius became the man who set the conspiracy in motion, which led to Caesar's death. The audience might have thought that if Caesar had acted on this thought, Cassius would not have been a part of Caesar’s death. The fact that Caesar describes Cassius as "hungry" shows that Caesar knows about Cassius' drive to be better.
This incident is copied when Brutus decides that Antony is not bad after Caesar has been murdered. It seems ironic that both the people that Caesar, and Brutus were told not to worry about were responsible for their death. These events foreshadow more tragedy to come as they show you that you should trust your instincts.
These omens that were not looked after, contribute to the play the theme of fate vs. free will, which gets someone to consider what 'may have been'. The supernatural, again helps to foreshadow events, like when Cinna the poet has his dream, "I dreamt to-night that I did feast with Caesar...” however unimportant this dream may seem, quickly after, Cinna was killed because he had the same name as the conspirator Cinna and he was possibly going to be with Caesar as they were both killed. This dream shows how the supernatural was important in Shakespeare’s time, because it played a big role in