As in all his history plays, Shakespeare has the recurring motif of the Elizabethan "unified theory" that is termed the Chain of Being. In this theory, a semi-divine monarch is at the head of an odering of human life, both physical and psychological. Therefore, to an Elizabethan, chaos meant
the cosmic anarchy before creation and the wholesale dissolution that would result if the pressure of Providence relaxed and allowed the law of nature to cease functioning.
So connected are the supernatural and the earthly happenings that the order which prevails in the cosmos, or heavens, is duplicated on earth. This theme, then, can be the thesis of an essay on the role of the supernatural in Julius Caesar. As the Roman Emperor, Julius Caesar was also the divine representative on earth; thus, any treasonous act against him is foreshadowed and accompanied by bizarre supernatural happenings. These supernatural events are, in fact, the driving force of the plot (the fates of the characters) and the psychological states of the characters along with the imagery that shapes their speeches since the assassination of Caesar disrupts the Chain of Being and effects the chaos that follows.
As a demonstration of this relationship of the divine with the earthly, in Act I, Scene 3, Casca and Cicero encounter each other on a Roman street where a terrible storm is brewing. Casca remarks,
Either there is a civil strife in heaven,
Or else the world, too saucy with the gods,
Incenses them to send destruction. (1.3.11-13)
And, he goes on to describe the "wonderful" bizarre and terrifying sights he has observed.
So, in organizing the essay, these chaotic events and irregularities in the thinking of the main characters and the unusual imagery of their speeches can be used to support the thesis that as a result of disturbing the Chain of Being, the fates of the characters and the plot of the drama are determined.
(See the link below that explains the Elizabethan Chain of Being for further explication)