In this study, Arthur Schopenhauer attempts, in a very careful way, an approach to the phenomenon of the appearance of spirits and ghosts, which he connects with other related phenomena, such as prophetic dreams, hypnosis, sleepwalking, prophetic visions, divination, magic, etc. Without the usual prejudices with which such topics are often approached, the great philosopher wonders about the possibility of the existence of such phenomena, while simultaneously trying to seek the often indistinguishable boundaries between their real appearance and their creation by the imagination of humans. His answer, based on philosophical metaphysical foundations, is that yes, such phenomena can exist, but under strict conditions...