From my point of view, medieval people did believe in ghosts due to different circumstances, especially religious issues. The period of Middle Ages is considered as the time of great upheaval and pestilence. So the majority of medieval people were fearful, uneducated and very superstitious. They believed in different myths and magic things of any kind.The stories about ghosts in medieval England were connected to the Catholic idea of Purgatory. It implied that those souls who did not go directly to Heaven or Hell stayed and wandered among people and even at times interacted with them. Medieval people worried about their dead family members or relatives and tried to help by doing different religious rites which would reduce their time in Purgatory. I think that Hamlet's father can be considered as that kind of soul. In the play he is referred as “Ghost” but his name is also Hamlet. He appears as a real spirit for the purpose to tell Hamlet the truth and ask to avenge his own death. The most important fact here is that Hamlet is not the only one who is able to see the ghost but Marcellus, Bernardo and Horatio as well.