Christian science fiction is a subgenre of both Christian literature and science fiction, in which there are strong Christian themes, or which are written from a Christian point of view. These themes may be subtle, expressed by way of analogy, or more explicit. Major influences include early science fiction authors such as C. S. Lewis, while more recent figures include Stephen Lawhead. The term is not usually applied to works simply because most or all of the characters are Christian, or simply because the author is Christian. Influences While earlier works such as Victor Rousseau's The Messiah of the Cylinder (1917) are regarded as part of the Christian science fiction subgenre, John Mort argues that the most influential Christian science fiction author was C. S. Lewis, a "prolific writer who wrote works of Christian science fiction and theology for the average person." In When World Views Collide: A Study in Imagination and Evolution, John J. Pierce presents the argument that Lewis was partially writing in response to what Lewis saw as "Wellsianity"—an "anthropocentric evolutionary mythology"—which he came to view as both false and blasphemous, condemning H. G. Wells' world view through works such as Out of the Silent Planet. While the extent to which Lewis' influence varies, Mort points in particular to Madeleine L'Engle's A Wrinkle in Time as a Christian science fiction work which, as he puts it, cannot be read "without being reminded of Lewis' Narnia stories." (Of course, Narnia was fantasy rather than science fiction, but Mort is noting the similarities in style and execution of the story.) Other early authors identified by Mort as being influences upon the development of Christian science fiction include J. R. R. Tolkien, George MacDonald and Charles Williams. (Although, again, these writers worked in fantasy, their influence on Christian science fiction is clear, Mort argues.) Notable authors C. S. Lewis, whose The Space Trilogy is regarded as one of the most influential works in the subgenre. Stephen Lawhead, although he is better known for his fantasy novels than his science fiction works. Madeleine L'Engle, especially in regard to her novel A Wrinkle in Time and its sequels, first published in 1962. Walker Percy with his Christian science fiction work Love in the Ruins. Kathy Tyers author of the Firebird series. Gene Wolfe, author of e.g. The Book of the New Sun, who is noted for the strong influence of his Catholic