"For Samuel R. Delany, Jr., speculative fiction, as he preferred to call the genre, is radically different from standard fiction for reasons ranging from syntactic variation to thematic vistas to authorial function (Science447-51). Joanna Russ agrees with Delany’s assessment. She notes that futurist fiction is highly didactic, and for any didactic work to be understood by its reader-critics, they must grasp its constitutive principles. Thus, Russ maintains, as science generates new paradigms, the vast majority of contemporary literary critics who lack a sufficient scientific understanding cannot credibly assay speculative fiction (556-67). Although Russ’ polemic can be applied to futurist fiction generally, it is most directly relevant to hard SF. Hard SF valorizes the central tenet that scientific plausibility must constitute the guiding framework for the story. Although John W. Campbell promulgated its tenets in the 1930s, hard SF would not become a distinct FFF subgenre until the late 1950s ormid-1960s. Some critics see the establishment of hard SF as a conservative reaction to the New Wave literary movement, which embraced extra-scientific influences."