Not only does Christianity acknowledge the existence of the spirit world, even great saints sometimes experience encounters with “ghosts.” One such saint was John Bosco (1815 – 1888). While a young man, Bosco made an agreement with his friend Comollo that whichever of them died first would give the other some sign as to the state of his soul. As it happened, Comollo’s death came first, on April 2, 1839. The next evening, following the funeral of his friend, Bosco sat sleepless on his bed in the dorm room he shared with twenty other seminarians. At this point, we take up the story in Bosco’s own words:
“Midnight struck and I then heard a dull rolling sound from the end of the passage, which grew ever more clear, loud and deep, the nearer it came. It sounded as though a heavy dray were being drawn by many horses, like a railway train, almost like the discharge of a cannon…While the noise came nearer the dormitory, the walls, ceiling and floor of the passage re-echoed and trembled behind it…The students in the dormitory awoke, but none of them spoke…Then the door opened violently of its own accord without anybody seeing anything except a dim light of changing colour that seemed to control the sound…Then a voice was clearly heard, ‘Bosco, Bosco, Bosco, I am saved.’… The seminarists leapt out of bed and fled without knowing where to go. Some gathered in a corner of the dormitory and sought to inspire each other with courage, others crowded around the prefect, Don Giuseppe Fiorito di Rivolo; thus they passed the night and waited anxiously for the coming of day. All had heard the noise and some of them the voice without gathering the meaning of the words. I sat upon my bed and told my comrades that they had no cause for alarm. I had clearly understood the words; they were ‘I am saved.’ Some had also understood them clearly as I had done, and for a long time afterwards there was no other subject of conversation in the seminary.”
 As quoted in: Abbot Alois Wiesinger, Occult Phenomena in the Light of Theology (London: Burns and Oates, 1957) 228-229.