Before the Ghost of Hamlet’s father ever appears on stage, Horatio and the guards give a detailed description of the recently deceased King Hamlet, painting him as a good and courageous ruler. They are afraid of his specter, but their fear is due to the supernatural element rather than the man himself. They debate if it is in fact the King’s soul at all and not something darker trying to manipulate Hamlet. If it is the King, they take the appearance of the Ghost as a sign that the former King’s soul is in a state of unrest. When the Ghost does appear on stage, he is fully armed and armored, which Hamlet interprets as a further sign that his father’s soul is prepared to do battle.
True to Horatio’s account of the King’s personality, the Ghost is pragmatic and specific about how he delivers his message of revenge. He speaks only to Hamlet and makes sure to get his son alone before they converse. He begins by asking Hamlet to pay careful attention to his message and confirm his identity as the spirit of Hamlet’s father. The Ghost impresses on Hamlet the gravity of what happened to him and entreats Hamlet to seek revenge for his death. After Hamlet agrees, he plainly tells Hamlet that Claudius poisoned him to take his wife and throne.
After all the relevant information is on the table, however, the Ghost starts to reveal an emotional and performative tendency that is plainly echoed and amplified in his son Hamlet. The Ghost has the restraint to communicate the essentials of his request for vengeance first, but clearly he still possesses a very human sense of personal pain at his brother’s betrayal. His instruction for Hamlet to enact revenge on Claudius is in service of political justice to protect the crown, but it is also just as much about personal justice. While Hamlet seems primarily concerned with the latter motive, the Ghost is keenly aware of both purposes.
This kingly sense of justice motivates the Ghost to appear to Hamlet one final time after Hamlet accidentally kills Polonius and subsequently becomes enraged at Gertrude. By this point, the Ghost is either too weak to make himself known to Gertrude, or chooses not to, but he feels it necessary to intercede and remind Hamlet what his goal is. The Ghost wants only for Hamlet to kill Claudius. Although he previously expressed anger toward Gertrude, he wants Hamlet and Gertrude to reconcile. Hamlet struggles with his task of proper revenge, but the Ghost has a clear and constant desire for justice.
Although the Ghost incites the play’s plot, he may not be the King at all. Horatio and the guards agree that the Ghost looks exactly like Hamlet’s father, and Hamlet strongly considers that the Ghost is telling him the truth. Claudius eventually confirms that he did in fact kill the King, as the Ghost said, so that much the audience knows to be true. However, Hamlet is the only character to ever talk with the Ghost, and Gertrude cannot even see it. Hamlet himself wonders if the Ghost is a devil trying to trick him. Ultimately, the text leaves the true identity of the Ghost ambiguous. It could be Hamlet’s father, but it could also be something more sinister and mysterious meant to cause strife in Denmark.