As has already been noted, fantastic literature developed....

“ As has already been noted, fantastic literature developed at precisely the moment when genuine belief in the supernatural was on the wane, and when the sources provided by folklore could safely be used as literary material. It is almost a necessity, for the writer as well as for the reader of fantastic literature, that he or she should not believe in the literal truth of the beings and objects described, although the preferred mode of literary expression is a naive realism. Authors of fantastic literature are, with a few exceptions, not out to convert, but to set down a narrative story endowed with the consistency and conviction of inner reality only during the time of the reading: a game, sometimes a highly serious game, with anxiety and fright, horror and terror. ”

Franz Rottensteiner

From : The Fantasy Book: An Illustrated History From Dracula To Tolkien