Art (and, as a part of it, also literature) is frequently seen as a substitute for religion, a perspective that dates back to the Romantic era. The article takes a look at the possible reasons, using the Perceval/Parzival/Parsifal material as an example. It argues that the difference between a text accepted as religious truth and a fictional literary text can not be found in the texts themselves, but depends on the function assigned to them by social resp. theological authority. The closeness of literature and religion is, it can be supposed, largely due to using the same media. Despite the fact that transcendent topics seem to further interchange, content is secondary to function. In differentiated modern societies due to the absence of central dogmatic authority literary motives can serve as a basis for religious cult. The Grail-Movement that draws on different strands of the Parzival tradition, but especially on Richard Wagner's Parsifal, serves to demonstrate this.