Fortinbras has another significance to the play. The first scene presages an important thematic thread in Hamlet, that the passing of the torch from old to young inevitably carries the duty of the young to live up to their elders' expectations. A son must obey a father's instruction, no matter how unreasonable the directive might seem — even if the directive necessitates murder, war, or mayhem. In Scene 1, Horatio explains that, because Young Fortinbras is bent on avenging his father's defeat at Old King Hamlet's hand, all of Denmark prepares for war. A single covenant inexorably propels the events of the play and is the medieval truth that rules Hamlet's life.
Horatio's fear of the Ghost mirrors the prevailing attitude toward witches and ghosts among Elizabethans and Jacobeans. Shakespeare's contemporaries believed in ghosts and closely linked apparitions with their religious fears of the devil's power and hell's dominion on earth. Like witches, ghosts were believed to be agents of an afterlife; unlike witches, however, they were not universally dreaded. While witches always represent the devil, ghosts might actually represent the spirit of God. A ghost could represent angel or devil to the Shakespearean sensibility.
According to the religious precepts of the time, anyone seeing a ghost must identify the ghost's purpose and form. A ghost could be: (1) a hallucination, which was dangerously apt to be engendered by the devil, (2) a restless spirit returned to perform a deed left undone in life, (3) a specter seen as a prediction or warning sent as a gift from God, (4) a spirit returned from beyond the grave by divine permission, or (5) a devil disguised as a dead person. Characters in Hamlet test each of these possibilities within the course of the play.
