What Dreams May Come in the book are derived from my wide range of reading." One of Matheson's influences was Harold W. Percival, an adherent of Theosophy, a belief system with a strong Eastern and Hindu influence. The story also shares the same theme of the ancient Greek myth Orpheus and Eurydice, in which the gifted musician makes a challenging journey to Hell to retrieve his wife. One character quotes from the writings of 18th century Christian mystic Emanuel Swedenborg. Matheson bases his descriptions of the death experience itself on studies by Elisabeth Kübler-Ross and Raymond Moody. When reading these accounts, Matheson found that
Hades Achilles, whom Odysseus conjured with a blood libation, said: Hades, as the god of the dead, was a fearsome figure to those still living; in no hurry to meet him, they were reluctant to swear oaths in his name, and averted their faces when sacrificing to him. Since to many, simply to say the word "Hades" was frightening, euphemisms were pressed into use. Since precious minerals come from under the earth (i.e., the "underworld" ruled by Hades), he was considered to have control of these as well, and as such the Greeks referred to him as Πλούτων (Greek "Plouton"; Latin