The Importance of the Ghost in Hamlet
The stage presence of a ghost would have been familiar to an Elizabethan audience and so the appearance of the Ghost in 'Hamlet' carries some messages which are general - almost as though the ghost was a familiar symbol which evoked certain thoughts merely by being present. The Ghost in 'Hamlet' has a more specific role than that given to ghosts in general, however; it has a crucial part to play in the development of the plot. Thirdly, the interaction between the Ghost and Hamlet raises difficult questions regarding duty and free will, and as the trigger for much of the protagonist's anguished philosophising the ghost plays a key but problematic role as Hamlet's true adversary.
There are certain points to be made which are about ghosts in general. To a superstitious Elizabethan audience a ghost would be less improbable than it seems to a sceptical modern audience, but it would signify that something is wrong with the natural order. In Act I scene i the characters indicate that they believe this; the rational Horatio observes that "This bodes some strange eruption to our state"; Marcellus says that "Something is rotten in the state of Denmark". Even before the arrival of the Ghost the scene is tense - the first words ("Who's there?") are terse and nervy and even Francisco (whom we never see again and so perhaps represents the unseen population of Denmark) admits that he is "sick at heart". The presence of the Ghost, then, adds to this sense that something is deeply wrong - like many such superstitious entities (Horatio refers to other omens that preceded the death of Julius Caesar: the allusion to which makes the audience yet more uncertain of what is to happen) the mere presence of the Ghost is a potent symbol in stage notation.
The Ghost also plays an important role in the plot, however, and is not merely an atmospheric device. Initially the audience is presented only with the impending conflict with Norway as a source of these omens - when Horatio proposes that the preparation for war and a danger to the state might be the cause of the Ghost's presence, Bernardo agrees - "I think it may be no other but e'en so". It is not until the Ghost speaks to Hamlet in scene v that a more feasible source of the wrong in nature is proposed - that the old king was "sleeping, by a brother's hand / Of life, of crown, of queen at once dispatched". We as an audience cannot be sure that this is true (as Hamlet himself says later, "The spirit that I have seen / May be a devil") but it echoes Hamlet's anger and grief at his mother's swift remarriage as expressed in Act I scene ii and seems horrendously plausible. In terms of the Ghost's role in Hamlet the actual truth of his words are irrelevant; his principle plot importance is his exhortation to revenge -
"If thou didst ever thy dear father love...
Revenge his foul and most unnatural murder".
Hamlet's response is...