When you ask someone whether they have ever seen a ghost, you are asking them whether they believe in the inexplicable. Some people are more accustomed to the idea than others: In different folklores, throughout history, ghosts appear as omens and lost spirits; they signify regret, pain, open endings. Then there are the ghosts that haunt not a culture, but a person.
Still, the idea that the spirit of a dead person or animal could return to the land of the living was present as far back as the ancient world, according to Morton, the author of Ghosts. The 19th century ushered in a cultural obsession with spiritualism. Ghosts peppered Victorian literature, and séances soared in popularity. The supernatural rituals, in which participants called upon the spirits of their deceased loved ones and others, challenged the idea that the living couldn't communicate with the dead, said Morton.
The author experienced strange knocking sounds at night in his Los Angeles apartment, leading him to fear for his safety and suspect supernatural involvement.