In Shakespeare's Hamlet, in Act One, scene one, Horatio mentions several reasons why the ghost might appear; these reasons reflect the beliefs of the Elizabethan society when Shakespeare was writing his plays.
The first reason Horatio supplies is the idea that there has been a disruption in the universe: that somehow the balance of power has been changed.
But, in the gross and scope of my opinion,
This bodes some strange eruption to our state. (lines 81-82)
This is also a theme present in Macbeth, for the same reason: when a king is killed and another man, not chosen by God takes the throne, other elements of the universe are out of balance. In Hamlet, Old Hamlet has been murdered and Claudius has taken his place. The Elizabethans believed that a leader was made king (or queen) by divine right: chosen by God. Divine right means:
that a monarch is subject to no earthly authority, deriving his right to rule directly from the will of God.
Claudius is certainly not a divine right monarch.
Horatio also mentions the supernatural events in Rome, just before Caesar was assassinated—graves were opened and bodies still enshrouded, screamed. Comets shot out from the sun, with blood-red tails. And the ability to see the moon in the heavens was almost obliterated.
In the most high and palmy state of Rome,
A little ere the mightiest Julius fell,
The graves stood tenantless, and the sheeted dead
Did squeak and gibber in the Roman streets; (130)
As stars with trains of fire and dews of blood,
Disasters in the sun; and the moist star,
Upon whose influence Neptune's empire stands
Was sick almost to doomsday with eclipse. (I.i.127-134)
Other warnings and predictions, Horatio states, have been delivered in Denmark now as well.
None of this information would have seemed unusual to an Elizabethan audience, as they believed in witches, fairies, ghosts, demons and additional other-worldly creatures.
When the ghost re-enters the scene, Horatio is determined to speak to it, despite the potential danger. He urges the ghost to stay and to talk to him, if the ghost has "any sound, or use of voice." In continuing to urge the ghost to converse with him, Horatio says this:
If there be any good thing to be done,
That may to thee do ease and grace to me,
Speak to me:
If thou art privy to thy country's fate,
Which, happily, foreknowing may avoid,
Or if thou hast uphoarded in thy life
Extorted treasure in the womb of earth,
For which, they say, you spirits oft walk in death,
Speak of it: stay, and speak!
In his words to the ghost, Horatio thus indicates three reasons he believes the ghost might be appearing:
- To seek assistance in easing its own suffering by asking the living to perform some good deed or kindness;
- To warn about some danger to the ghost's country so that it can be averted;
- To seek some treasure acquired through dishonorable means that the ghost had buried in the earth while still living.
As it happens, Horatio is close to the truth. Old Hamlet's ghost seeks justice since Claudius had murdered him, and the ghost seeks to remove Claudius as the country's king since he has stolen the throne. The ghost cannot rest until these wrongs have been righted.