Julius Caesar

Do you feel that the supernatural elements in the play "Julius Caesar" were additions by Shakespeare or were they real?

The answer is neither -- they were legends found in his sources. Shakespeare's information for most of Julius Caesar came from the Roman historian Plutarch, through the English translation by Thomas North (published 1579). The Romans believed very strongly in supernatural occurences and signs, and so it would have been extremely unusual for a career as important as Caesar's to have lacked these.

For instance, in Act I scene 3, Casca speaks of men walking up and down the street all aflame, night birds seen during the day, and the augurs failing to find a heart inside their sacrificial animal before Caesar's murder. Shakespeare lifts all these details directly from the account of Plutarch, with the order of the omens and even much of the wording the same. Another example is Caesar's famous exchange with the soothsayer about the Ides of March.

However, Shakespeare sometimes modified or supplemented the accounts of supernatural events for his own dramatic purposes. An example here is when Calpurnia, Caesar's wife, asks him not to go to the Senate that day because she has dreamed he was murdered. In Plutarch, Calpurnia simply dreams of murder; in Shakespeare, the incident is elaborated in a way that allows both a negative and a positive reading to be made of the omen (Act II, scene 2). Another example is the ghost that appears to Brutus -- in Plutarch, it is never explicitly identified as Caesar's, but only as Brutus' "evil genius."