Many superstitions of the Elizabethan Age date back to much earlier times, including the Age of the Roman Empire. Thus, the inclusion of omens and dreams in Shakespeare's Julius Caesar is of great significance both to the audience and to the play itself. Throughout the play, there are soothsayers, dreams, ghosts, and personal interpretations of the stars that greatly affect the characters.
Caesar, of course, ignores all supernatural warnings and signs for fear that the Roman people think him weak. He refuses to listen to the soothsayer who cautions him against the Ides of March; he ignores his wife's entreaties to not attend the Senate because she has had a most portentous dream. The storm of the previous night moves him not. All these signs he ignores lest his role as leader be questioned; yet, ironically, he is easily swayed by Decius's interpretations of these omens and dreams that he should, indeed, go to the Senate.
And, it is this vacillation between disbelief and belief that threads the play Julius Caesar. For instance, in "the seduction scene" of Act I, Cassius tells Brutus,
The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings. I,ii,140-141)
But later, in Act V, he tells Messala that he once "held Epicurus strong," meaning he does not believe, as Epicurus did, that the gods interest themselves in men's affairs. but, now, Brutus says, "...I change my mind" (V,i,78-79). Cassius tells Messala of an omen that presaged death.
Likewise, Brutus vacillates between belief and disbelief in omens and other superstitions. For, in Act I, he is convinced by Cassius's statement that destiny lies in the hands of each man. Later, he ignores the portents of the suicide of his wife Portia; however, he talks to Cassius of destiny regarding their forthcoming battle in Philippi:
There is a tide in the affairs of men
Which, taken at the flood, leads on to fortune;
Omitted, all the voyage of their life
Is bound in shallows and in miseries.
On such a full sea are we now afloat,
And we must take the current when it serves,
Or lose our ventures. (IV,iii, 244-250)
And, directly after this speech, Brutus encounters the ghost of Caesar, telling it,
That mak'st my blood cold, and my hair to stare?
Speak to me what thou art. ...
Ill spirit, I would hold more talk with thee. (IV,iii,315-317)
But when Cassius tells Brutus that "the affairs of men rests still incertain" after having witnessed the omen of the eagles, Brutus rejects such ideas saying,
But I do find it cowardly and vile,
For fear of what might fall, so to prevent
The time of life, arming myself with patience
To stay the providence of some high powers
That govern us below. (V,iii,112-116)
These words, indeed, echo those of Caesar before he goes to the Senate. Is it, then, the ghost of Caesar which has made Brutus say these words--"thy [Brutus's] evil spirit"--or himself?
Certainly, from the opening festival of Lupercal in which infertile women hope to change their condition during this superstitious holiday, to the words of the soothsayer that presage the tragedy of Julius Caesar, superstition, along with its acceptance and rejection, is a powerful force in Shakespeare's classic play. But, perhaps like modern man, the Romans manipulated their superstitions to fit their own inner desires, fears, and motives, underscoring the statement of William Jennings Bryant:
Destiny is not a matter of chance, but of choice. It is not a thing to be waited for; it is a thing to be achieved.
And, so it is true, as Cassius says, that "the fault is not in the stars, but in ourselves."