He conducted numerous experiments in telepathy and was interested in apparitional experiences. The two volumes consist of 701 cases of alleged spontaneous apparitional communications. Fun starts as the fantasy element appears in the form of their "apparitional" alter egos. Doyle returned the favor by guesting on "Mr. Sardonicus" on Blitzkid's "Apparitional" album. Apparitional experiences also have implications for the philosophy of perception. In the 1880s, the Society investigated apparitional experiences and hallucinations in the sane.