Mort argues that one of the difficulties facing Christian science fiction authors who endorse Creationism—especially those writing "hard" science fiction—is reconciling the limits placed on the author in exploring science within a Creationist framework. This is made even more problematic when one considers that the notion of "the future as divinely ordered" limits the author's ability to speculate on what that future may be. For example, the first of these difficulties has been identified by Pierce as a problem with some of R. A. Lafferty's work, who "is uncomfortable with the idea of even biological evolution"; while Tom Doyle notes the predictability of the Christian apocalyptic novel, due, he argues, to the genre following "a particular interpretation of biblical prophecy".