Scholes's definitions of "fabulation" and "structural fabulation" below. Some definitions of sub-types of science fiction are included, too; for example see David Ketterer's definition of "philosophically oriented science fiction". In addition, some definitions are included that define, for example, a science fiction story, rather than science fiction itself, since these also illuminate an underlying definition of science fiction.
The Encyclopedia of Science Fiction, edited by John Clute and Peter Nicholls, contains an extensive discussion of the problem of definition, under the heading "Definitions of SF". The authors regard Darko Suvin's definition as having been most useful in catalysing academic debate, though they consider disagreements to be inevitable as science fiction is not homogeneous. Suvin's cited definition, dating from 1972, is: "a literary genre whose necessary and sufficient conditions arefuture world, though its bias is undoubtedly realistic. Rather, this is the sort of SF that most appeals to scientists themselves—and is often written by them. The typical 'hard' SF writer looks for new and unfamiliar scientific theories and discoveries which could provide the occasion for a story, and, at its more didactic extreme, the story is only a framework for introducing the scientific concept to the reader."[23]
―. 1980. "In 'space opera' (the analogy is with the Western 'horse opera' rather than the 'soap opera') the reverse [Parrinder is referring to his definition of "hard sf"] is true; a melodramatic adventure-fantasy involving stock themes and settings is evolved on the flimsiest scientific basis."[23]
David Pringle. 1985. "Science fiction is a form of fantastic fiction which exploits the imaginative perspectives