Lapham's Quarterly, “a magazine of history and ideas,” for March 13, 2010, has a piece, “Kurt Vonnegut at the Blackboard,” where the writer gives a lesson in creative writing. Dealing with Hamlet’s soliloquy with the ghost of his father, Vonnegut (1922-2007) adds:
To this day we don’t know if that ghost was really Hamlet’s father. If you have messed around with Ouija boards, you know there are malicious spirits floating around, liable to tell you anything, and you shouldn’t believe them. Madame Blavatsky, who knew more about the spirit world than anybody else, said you are a fool to take any apparition seriously, because they are often malicious and they are frequently the souls of people who were murdered, were suicides, or were terribly cheated in life in one way or another, and they are out for revenge.
“Lapham's Quarterly is published by the American Agora Foundation, Inc., a not-for-profit foundation dedicated to fostering interest in, and developing an acquaintance with, history.” The rest of the article can be read here.