For the Elizabethan, there is a hierarchy to the world:
- Spiritual Class
- Man (+ Understanding)
- Sensitive Class (Existence + life+feeling: hearing, touch, memory, and movement)
- Vegetative Class (Existence + life)
- Inanimate Class (Existence)
Man possesses all the possibilities of the Earthly Existence as he forms a microcosm for the macrocosm of the Universe. Thus, the inanimate class nourishes the vegetative class that nourishes the animal class, and so on. In other words, the bottom of one class is related to the top of another class.
With each element at a certain level having a correspondence to another level, when one level is upset, then all levels are disturbed. And, Elizabethans recognize that the happenings of the earthly world affect the world of spirits and the spiritual. In Shakespeare's Julius Caesar, Caesar, who has ignored the words of the soothsayer, and who has become sick with epilepsy, has made the heavens disturbed; for this reason there is thunder and lightning:
Nor heaven nor earth have been at peace tonight:
Thrice hath Calpurnia in her sleep cried out
"Help, ho! They murder Caesar!" Who's within? (2.2.1-3)
Cassius, with his "lean and hungry look" has denied this link of man with the other elements of the universe:
The fault, dear Brutus, is not in our stars,
But in ourselves, that we are underlings. (1.2.145-146)
When Casca reports all the cosmic disturbances that he has observed, animals and fire, and declares that they are "prodigies" and "portentous things," the Elizabethan understands that Man is between Matter and Nature, and his behavior can disturb the order of things. As he tries to reconcile the beast within him, he causes conflict, a conflict that is often represented by thunder and lightning.
As is the case in many works of literature, Shakespeare natural occurrences such as thunder and lightning to predict or precede bad things--in this case, Caesar's murder. To understand the significance of the thunder and lightning in Acts 1 and 2, is important for readers to understand the role that natural occurrances/disasters and the supernatural played in the Elizabethan period.
As Brutus considers participating in the conspiracy in Act 1 and ultimately decides to join in Act 2, thunder and lightning are accompanied by many supernatural occurrences. Aside from the storm, Casca reports that he has observed a men on fire in the streets, a lion walking around the capital and not paying attention to any of the people in its path, and an owl (traditionally a bird only seen at night) shrieking during the middle of the day. Casca believes, as the Elizabethan audience would, that those are "portentous things/ Unto the climate that they point upon."
Though these occurrences can be interpreted in different ways, they ultimately foreshadow the murder of Caesar and the chaos that ensues as a result.