[Updated 12th December 2005]"So Fuck?"
There are many definitions of SF. They are all right… for someone. They are all wrong... for someone. The definitions below are taken from this online list
. Some of them are, I think, paraphrases rather than quotations, but they'll do.
"What SF writers write is SF."
-- Orson Scott Card
"If this appears that I am arguing for a deconstruction of our ideas of generic norms, returning us to a primal chaos of fictive forms in which all fictive forms are equally privileged; if this appears that I am arguing for the dismantling of the concept itself, ‘science fiction,’ as more a barrier than an aid to reading; if this seems as if I am saying that all fiction worth examining is, one way or another, science fiction; it is because that is what I am doing."
-- Frank McConnell
"Science Fiction is what we point to when we say 'science fiction'."
-- Damon Knight
I've never found the existing definitions of Science Fiction terribly convincing, I have to admit, and I've never found them terribly useful. In most respects SF has always struck me as an arbitrary lumping together of diverse works for the sole reason of marketing. For many readers, writers, editors and agents, I think, this is in fact the working (in)definition. It's what can be sold as Science Fiction. SF is short for "So Fuck?"
Likewise, Fantasy can be defined, if one so wishes, as whatever can be sold as Fantasy. These are simply marketing categories, characterising the literary products in no way, shape or form; they're circular definitions which can't really be argued with for that reason, but which, also for that reason, don't exactly serve a purpose, other than the obvious commercial one.
So, since I've been thinking about this the last week or so, I'm going to advance a few more conflicting definitions which do actually attempt to characterise the type of fiction which gets called Science Fiction and/or Fantasy. Rather than use the marketing labels, however, and risk the assumption that I'm talking, with any of these definitions, about some singular, coherent "genre" which these variant definitions could or could not, should or should not, be applied to, I'm going to make up a new label for every type of definition. Cause it's fun. For ease of reference, all of these will abbreviate to SF, but the point is to examine the multiplicity of features, not to end up in pointless bickering over which of these features are required or forbidden if some work is to be called SF. Each of these SFs is to be considered a quite distinct SF, its own SF, an SF which may not be yours and may not be mine, but which probably belongs to someone out there.
Here's one SF:"Scientific Fancy"
In its weaker form the content-based type of definition of this SF simply requires the presence of an element of vaguely plausible scientific speculation, extrapolated out into background, plot, etc. This speculation need not be the focus of reader attention, and may serve as little more than a superficial justification for the Romantic story structures. This SF is simply Fantasy with the fanciful element rationalised in terms of science or technology.
"By ‘scientifiction’… I mean the Jules Verne, H.G. Wells, and Edgar Allan Poe type of story -- a charming romance intermingled with scientific fact and prophetic vision."
-- Hugo Gernsback
"The best definition of science fiction is that it consists of stories in which one or more definitely scientific notion or theory or actual discovery is extrapolated, played with, embroidered on, in a non-logical, or fictional sense, and thus carried beyond the realm of the immediately possible in an effort to see how much fun the author and reader can have exploring the imaginary outer reaches of a given idea’s potentialities."
-- Groff Conklin
"A simplified definition would be that the author of a ‘straight’ science fiction story proceeds from (or alleges to proceed from) known facts, developed in a credible way, whereas the author of a fantasy story starts with an idea and builds a world around it. The question of whether a certain story of imagination is a fantasy or a science fiction work would depend upon the device the author uses to explain his projected or unreal world. If he uses the gimmick or device of saying: ‘This is a logical or probable assumption based upon known science, which is going to develop from known science or from investigations of areas not yet quite explored but suspected,’ then one could call it science fiction. But if he asks the reader to suspend his disbelief simply because of the fun of it, in other words, just to say: ‘Here is a fairy tale I’m going to tell you,’ then it is fantasy. It could actually be the same story."
-- Sam J. Lundwall
"Science fiction is a branch of fantasy identifiable by the fact that it eases the ‘willing suspension of disbelief’ on the part of its readers by utilizing an atmosphere of science credibility for its imaginative speculations in physical science, space, time, social science and philosophy."
-- Sam Moskowitz
Although Lundwall's definition sets up SF (with explanation) in opposition to Fantasy (with no explanation), I include it here because he focuses more on the fact of explanation than on the rigour of it, just as Moskowitz focuses on the "atmosphere of science credibility" and Conklin on the sense of play. The caveat of "areas not yet quite explored" also provides the backdoor by which metaphysics and magic (e.g. FTL or ESP) can sneak into SF, with a wave of the hand and a mutter of "hyperspace" or "untapped human potential". Working by this type of definition , the writer may play fast and loose with even the laws of physics; as long as the reader comes along for the ride then it's still seen as SF -- Scientific Fancy, that is.
This is not to assume that the writer will
play fast and loose with the laws of physics. The approach can be quite systematic.
"Fantasy is the literature of believing in a world greater than the one that meets the eye, and letting your imagination take you in unlimited directions. Science fiction is the literature of presenting a world that can be systematically extrapolated from elements of our own reality."
-- Vera Nazarian
It is more that the science serves in the main to extrapolate the environment -- low-level details of technological artefacts included -- in which the story takes place, rather than being, by definition, the subject of the story."Scientistic Fiction"
In its stronger form the content-based type of definition specifically turns the whole focus of the story on science in terms of character, background and plot, not only regarding the scientific speculation as essential but requiring its centrality and expecting a degree of rigour in its treatment.
"[Science fiction] is fiction about the future of science and scientists."
-- Isaac Asimov
"Science fiction is the branch of literature that deals with the effects of change on people in the real world as it can be projected into the past, the future, or to distant places. It often concerns itself with scientific or technological change, and it usually involves matters whose importance is greater than the individual or the community; often the civilization or the race itself is in danger."
-- James Gunn
"Fiction in which new and futuristic scientific developments propel the plot."
-- Harper Handbook of Literature
"Realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method."
-- Robert Heinlein
If this were all then one would simply classify this SF as particularly rationalist Scientific Fancy; but in its most extreme form this SF actually does something quite distinct, precluding the presence of any element in the story which breaches scientific orthodoxy.
Magic is something of a sticking point for many SF writers, so much so that many include it in their definition of SF. Where Scientific Fancy is predicated on the inclusion of a certain element, this type of definition is predicated also on the exclusion of another element, usually referred to as "magic".
"To be science fiction, not fantasy, an honest effort at prophetic extrapolation of the known must be made. Ghosts can enter science fiction, if they’re logically explained, but not if they are simply the ghosts of fantasy. Prophetic extrapolation can derive from a number of different sources, and apply in a number of fields. Sociology, psychology, and para-psychology are, today, not true sciences; therefore, instead of forecasting future results of application of sociological science of today, we must forecast the development of a science of sociology. From there the story can take off."
-- John W. Campbell
"The term can be applied only to a story in which wherein removal of its scientific content would invalidate the narrative."
-- Theodore Sturgeon
"It is the premise of science fiction that anything shown shall in principle be interpretable empirically and rationally. In science fiction there can be no inexplicable marvels, no transcendence, no devils or demons--and the patterns of occurrence must be verisimilar."
-- Stanislaw Lem
This type of definition has to be at its very narrowest (as where Campbell rejects sociology and pyschology) in order to cover all the strictures that identify Hard SF; but even when applied widely and loosely enough to include the "soft sciences", this type of definition remains qualitatively different from Scientific Fancy in its exclusion of the inexplicable. The deep-rooted Scientism of this type of definition involves a rejection of the metaphysical and magical ideas allowed by Scientific Fancy. Many of the novels of Philip K. Dick could not, for example, be classified as Scientistic Fiction."Soul Fiction"
Definitions of SF are not all predicated on the presence or absence of a certain type of content, however. Another type of definition based on effect or process treats SF as the mythology of the Modern Age, as the form of fiction which renders physical forces, events and agencies with the same import and to the same purpose as the pre-industrial religious literature rendered metaphysical forces, events and agencies.
"Science fiction is the prophetic… the apocalyptic literature of our particular and culminating epoch of crisis."
-- Gerald Heard
"[Science fiction] is the myth-making principle of human nature today."
-- Lester Del Rey
"Science fiction is the myth of machine civilization, which, in its utopian extrapolation, it tends to glorify."
-- Mark R. Hillegas
"Science fiction frequently tries to imagine what life would be like on a plane as far above us as we are above savagery; its setting is often of a kind that appears to us technologically miraculous. It is thus a mode of romance with a strong tendency to myth."
-- Northrup Frye
"In this kind of story the pseudo-scientific apparatus is to be taken simply as a ‘machine’ in the sense which that word bore for the Neo-Classical critics. The most superficial appearance of plausibility--the merest sop to our critical intellect--will do. I am inclined to think that frankly supernatural methods are best. I took a hero once to Mars in a space-ship, but when I knew better I had angels convey him to Venus. Nor need the strange worlds, when we get there, be at all strictly tied to scientific probabilities. It is their wonder, or beauty, or suggestiveness that matter."
-- C. S. Lewis
Assuming that portrayals of metaphysical or of physical forces, events and agencies can both have contemporary relevance and mythopoeic import, by this definition there is little coherent distinction between works which achieve the required effect with an iconography of science and those which achieve it using an iconography of magic. Only the degree to which one iconography is contemporary and the other obsolete might differentiate the effect and therefore, by extension, the process."Scientific Fabulation"
There is of course an SF which does differentiate the process in this way. This next type of process-based definition envisions our scientific culture as a source of metaphor and meaning. This is not dissimilar to the previous SFs and could be considered, in some respects, the process by which Scientific Fancy is made to function also as Soul Fiction, by taking one or more scientific fancies as metaphoric conceits and extending them through the body of the story or novel.
"Science fiction is a form of fantastic fiction which exploits the imaginative perspectives of modern science."
-- David Pringle
"Science fiction is not fiction about science, but fiction which endeavors to find the meaning in science and in the scientific technology we are constructing."
-- Judith Merrill
"In fact, one good working definition of science fiction may be the literature which, growing with science and technology, evaluates it and relates it meaningfully to the rest of human existence."
-- H. Bruce Franklin
"Science fiction, then, commonly uses techniques both from the realistic and the fantastic traditions of narrative to tell a story of which a referent, implicit or explicit, is the mind-set, the content, or the mythos of science and technology.
"In his Strategies of Fantasy, Brian Attebery shows how science fiction uses science as its ‘megatext.’ The nourishing medium, the origin of the imagery, the motive of the narrative, is to be found in the contents, assumptions, and world view of modern science and technology. ‘Science [writes Attebery] surrounds, supports, and judges SF in much the same way the Bible grounds Christian devotional poetry.’"
-- Ursula K. LeGuin
"[A] fictional exploration of human situations made perceptible by the implications of recent science. Its favourite themes involve the impact of developments or revelations derived from the human or physical sciences upon the people who must live with those revelations or developments."
-- Robert Scholes
"Science fiction is the search for a definition of man and his status in the universe which will stand in our advanced but confused state of knowledge (science), and is characteristically cast in the Gothic or post-Gothic mould."
-- Brian Aldiss
There is still no explicit exclusion of the metaphysical in this SF, but in its focus on the relationship between science and humanity it is arguable that this SF is more likely to treat any metaphysical forces, events or agencies it might utilise as either open to rational explication or of secondary import. This would be true by definition; just as the investigation and explication of the conceit is what defines the process as fabulation, the source and nature of the main conceit(s) is what defines the process as scientific. With many of the works of Philip K. Dick however, we might argue that the major fabulation is focused on the metaphysical but the context of scientific fabulation it is embedded within is sufficient to classify the work as SF... by this definition."Slightly Fucked"
Alternatively, where the major focus is on the metaphysical one may well say, if not entirely seriously, that the metaphysical speculation is the definitive feature, that (one) SF is basically embedded in the context of science, taking its literary language from the technological culture it developed within, but appropriating that heritage and metaphorising it into more abstract ideas.
"Science fiction is the bratty kid resulting from the marriage between Metaphysics
. The child was born out of wedlock, however, and was put up for adoption–to be raised by a radio tinker and amateur rocketry enthusiast who happened to live in an abandoned nuclear powerplant."
-- Alan De Niro
This SF could be seen as a more intellectual relative of Soul Fiction, concerned with developing modern metaphysics rather than modern mythology, or as a more mystical relative of Scientific Fancy, accepting metaphysics as a valid domain for speculation. Since this type of definition is largely context-based, a definition which positions this SF in relation to other modes of discourse rather than identifying key features of content, process or effect, and since the coinage of "Slightly Fucked" has been advanced (we might also suggest "Stoner Fiction" as a less intelligent sibling of this SF -- c.f. the works of the Wachowsky Bros), we include it here as distinct definitional approach."Strictured Fantasy"
All of these types of definitions can be thought of as placing different limitations on the nature of the fancy and its relationship to the story. Within the structural limitations of Scientific Fabulation the fancy is developed through the fabric of the story or novel. Within the symbolic limitations of Scientific Fancy, Scientistic Fiction and Scientific Fabulation, the fancy is (definitely maybe) sourced from the domain of science. In a wider sense then all these SFs can be considered as forms of Strictured Fantasy. It is simply that the particular strictures vary depending on what type of SF you happen to be writing.
"Science fiction is not predictive; it is descriptive. All fiction is metaphor. Science fiction is metaphor. What sets it apart from older forms of fiction seems to be its use of new metaphors, drawn from certain great dominants of our contemporary life--science, all the sciences and technology, and the relativistic and the historical outlook, among them. Space travel is one of those metaphors, so is an alternative society, an alternative biology; the future is another. The future, in fiction, is a metaphor."
-- Ursula K. LeGuin
But everything, in fiction, can be a metaphor, and if new metaphors can be and are drawn from the historical outlook, then we should, I think, allow this particular definition of Strictured Fantasy to stand alone, as a form of fantastic fiction which requires only a level of structural and/or symbolic restraint sufficient to distinguish it from otherwise freeform fantastic fiction. This SF is, then, the SF of Dick's The Man In The High Castle and of other alternate history novels. It's the SF of Mieville's Perdido Street Station and of other "alternate society" or "alternate biology" novels (to coin even more new terms). It might even be the SF of Zelazny's Roadmarks or Silverberg's The Book of Skulls; given that I've heard both of those books described as SF, I can only suggest such a wide-ranging generalised definition as a way to plausibly justify that description."Symbolic Formulation"
In another type of SF, we must note -- a type related more closely to the Soul Fiction outlined above as defined mainly by affect rather than content -- both structural and symbolic limitations are not systematic, as with the other SFs, but are rather, I would suggest, mainly if not entirely conventional. This type of SF is, it would seem, derived from the previous types through a process of copying and conventionalisation. It is recognised as SF by these conventions, sold as SF on the basis of these conventions and bought as SF for these conventions. This SF is identified by the the tropes of character, background and other such trappings, and by the plot-structures which these tropes are fitted into like symbols in a formula. This Symbolic Formulation is, sadly, the form that many who do not read deeply within the field are most familiar with.
"Science fiction will always offer easier alternatives. Science fiction will always be slanted, by definition, to taking its readers out of the world. Only weak people, however -- pat Freudianism and the great cult psychology movements of the seventies have taught us -- want out of the world. Strong people want in. Strong people want to, must deal with life as it is presented. Science fiction is a literature for the weak, the defenseless, the handicapped and the scorned. Panacea and pap."
-- Barry Malzburg
"Nine tenths of science fiction is crud. Of course, nine tenths of everything is crud."
-- Theodore Sturgeon
To talk of this Symbolic Formulation as distinct from any other equivalent genre is misleading. Functionally speaking, the formulas of one genre can be utilised with the symbols of another, and vice versa. Symbols may even be mixed and matched in order to simulate originality by offering an unexpected hybrid form. As a process this SF could be considered as failed Soul Food, striving for the archetypal resonance of myth but achieving only the stereotypal hollowness of pulp.
One might, however, argue that as a process the definition of this SF does not specify failure. Nor does it specify the exclusion of other SFnal content, effects or processes as parallel and related activities within a single text. Many works of this SF, we might argue, utilising the most familiar tropes and the most formulaic plots, may nevertheless function simultaneously on other levels by also applying the features which characterise the other SFs. Symbolic Formulation is only derivative hackwork in the absence of any real creative activity."Strange Fiction"
The last definition of SF is one in which it's simply a subset of fantastic fiction in the vaguest terms, with no real distinction made.
"A work belongs in the genre of science fiction if its narrative world is at least somewhat different from our own, and if that difference is apparent against the background of an organized body of knowledge."
-- Eric S. Rabkin
"We talk a lot about science fiction as extrapolation, but in fact most science fiction does not extrapolate seriously. Instead it takes a willful, often whimsical, leap into a world spun out of the fantasy of the author."
-- H. Bruce Franklin
"Science fiction represents the modern heresy and the cutting edge of speculative imagination as it grapples with Mysterious Time -- linear or non-linear time."
-- Frank Herbert
"[T]he idea that a magazine like Astounding, or Analog as it's now called, has anything to do with the sciences is ludicrous. You have only to pick up a journal like Nature, say, or any scientific journal, and you can see that science belongs in a completely different world."
-- J.G. Ballard
In the recent blogosphere debate over SF and Fantasy I came across a few definitions put forward for Fantasy which were about as grandiose and all-encompassing as you can get. I've heard the argument before. All fiction is made up, it goes; therefore, all fiction is fantasy. A quick look at the dictionary.com entry for "fantastic", I would argue, establishes very quickly that this is playing fast and loose with the concepts of "fiction" and "fantasy":
1 -- Quaint or strange in form, conception, or appearance.
a. Unrestrainedly fanciful; extravagant: fantastic hopes
b. Bizarre, as in form or appearance; strange: fantastic attire; fantastic behavior
c. Based on or existing only in fantasy; unreal: fantastic ideas about her own superiority
d. Wonderful or superb; remarkable: a fantastic trip to Europe
Not all fiction is strange. Strangeness is a feature of only a subset of fiction, a type of fiction which involves something extraordinary. Look at the words scattered through that definition -- quaint; fanciful; extravagant; bizarre; unreal; wonderful; remarkable. This is not a description of fiction in general. But it might well be a definition of SF. Or rather of one SF -- Strange Fiction.
"Science fiction is the literature of cognitive estrangement."
-- Darko Suvin
"A representation which estranges is one which allows us to recognize its subject, but at the same time make it seem unfamiliar."
-- Bertolt Brecht
"[Science fiction is] a new way of reading, a new way of making texts make sense--collectively producing a new set of codes. [SF writers invented the genre] by writing new kinds of sentences and embedding them in contexts in which those sentences were readable."
-- Samuel R. Delany
Elsewhere, in his essay, "About Five Thousand Seven Hundred And Fifty Words", Delany outlines a continuous correction process involved in reading a simple sentence:The red sun was high, the blue low.
Being Delany, he does this at great length and in the most fascinating way. Starting the essay with a proposition that it is meaningless to talk of style in opposition to content -- that it is all, in fact, form -- that meaning is best considered as a thread of memory we follow from word to word through a text -- he gives us a reconstruction of the reader's path through this particular sentence, leading us eventually into a discussion of the role of subjunctivity in relation to genre.
"[W]hat distinguishes science fiction from other kinds of fiction is a peculiar compromise between scientific truth and untruth. Samuel Delany has analyzed this compromise in terms of the SF text’s subjunctivity ("About 5,750 Words". What he means by this term is the degree to which every statement in the fiction describes a hypothetical condition: something that is not happening, has not happened, could not have happened in the past (unlike realistic fiction), but might happen, given the proper changes in society and scientific knowledge. Another word for subjunctivity might be ‘ifness,’ the condition of being contingent.
"What SF is contingent upon is change that does not violate the reader’s understanding of scientifically defined reality, which is not to say that we necessarily accept any statement in the text as scientifically valid. Rather, we accept reference within SF as allusions to science, broadly conceived of as a field of endeavor, a way of mapping the universe, and a way of speaking about the universe and the attempt to comprehend it."
-- Brian Ateberry
"Suppose a series of words is presented to us as a piece of reportage. A blanket indicative tension informs the whole series: this happened
. That is the particular level of subjunctivity at which journalism takes place... The subjunctivity level for a series of words labeled naturalistic fiction is defined by: could have happened
.... Fantasy takes the subjunctivity of naturalistic fiction and throws it into reverse. At the appearance of elves, witches, or magic in a non-metaphorical position, or at some correction of image too bizarre to be explained by other than the super-natural, the level of subjunctivity becomes: could not have happened
-- Samuel R. Delany
So when a strange, fanciful, fantastic image appears in a story or novel, Delany says, we're kicked out of the naturalistic subjunctivity -- this could have happened
-- and into another -- this could not have happened
. Delany distinguishes this from the subjunctivity of speculative fiction:
"[W]hen spaceships, ray guns, or more accurately any correction of images that indicates the future appears in a series of words and marks it as s-f, the subjunctivity level is changed once more: These objects, these convolutions of objects into situations and events, are blanketly defined by: have not happened
-- Samuel R. Delany
One of the most interesting things about Delany's essay is that Delany thereby places both naturalistic and fantastic fiction as subsets of his SF, the subjunctivities of events which "have not happened (but could)" or "have not happened (and could not)". He says this explicitly about naturalistic fiction in the notes to the essay. He doesn't actually say the same about fantastic fiction, but the way I read it, this is surely a ramification of his idea.
But I'm not talking about Delany's SF here -- speculative fiction -- but about Strange Fiction, which is defined not by one or other subjunctivity but rather by the challenge itself. The subjunctivity of this SF is undecided, conflicted. Here's a sentence, modelled on Delany's own:The crescent sun was high, the moon low.
When a strange, fanciful, fantastic image appears in a story or novel, I would argue, we can not immediately rule out the possibility of an explanation emerging later in the text. There is a moment of subjunctive indefinition here which is, I think, essential to our understanding of how all Strange Fiction works. In reading a sentence such as the one above, when we read "The crescent sun" we are faced with an impossibility which requires interrogation. Does the sun only appear
to be a crescent, the sun being in partial eclipse perhaps? Is the crescent sun an image
rather than an actuality, a symbol on a flag perhaps? When we read further, to "The crescent sun was high," the question becomes more pressing. Is the writer using the symbol on the flag to represent the flag itself? Or is this to be read literally? When the moon appears we might abandon the idea of the flag, our reading corrected by the parallel of sun and moon, so that we decide: yes, this is a description of the sky. Any moment now we're going to get stars in a darkened sky, the shadow covering the earth, and so on. But we still have a moment of interrogation to go through:The crescent sun was high, the moon
... was what? Eclipsing it? Obscuring it? Hiding it? With the last word, "low" this resolves into impossibility. We're asked to accept that the moon is not, in fact, eclipsing the sun but is, in fact, in another place entirely. In the sky? In the real world, our world, where this is a physical impossibility?
We might say that, at this point, the subjunctivity flips, becomes that of fantastic fiction: this could not happen
. But I think what we actually have is subjunctive indefinition, indecision -- neither "this could happen" nor "this could not happen", not a statement but a challenge: could this happen?
I think this tension of subjunctivities is actually the dominant mode of SF, the characteristic feature.
Later in the story or novel in which that sentence appears we might be offered a resolution. The hero removes his VR goggles and we realise this is speculative fiction. Or he wakes up in bed and we realise this is naturalistic fiction. Or he meets an elf and we realise this is fantastic fiction. But SF is defined, I would argue, more by the moments of indecision than by the moments of decision.
All fiction requires the suspension of disbelief. Strange Fiction is that which actively challenges that suspension of disbelief, throwing at the reader images, situations, which are dissonant with our knowledge of what Wallace Stevens calls "things as they are". In some respects the differentiation of Strange Fiction into Science Fiction, Fantasy and Horror may simply be a matter of how we respond to those situations. Do we understand them? Do we desire them? Do we fear them? In our moments of subjunctive indecision, other questions are fired off by that basic question of "could this happen". With curiosity we ask ourselves: how, when, where could this happen? With fear and desire we ask ourselves: would this, could this, should this (not) happen?
None of these are mutually exclusive. And these are the defining questions of Strange Fiction, of wish-fulfillment dreams and dread-filled nightmares, plausible or implausible. Possibility is irrelevant. We know these novum (as Suvin refers to the fantastic ideas which instigate his "cognitive estrangement") are not
possible to us, not here and now. But we have already suspended our disbelief. We are willing to accept temporarily, in reading any work of fiction, that these are events which are happening now in the constructed elsewhere of our imagination, events which are happening in simulation. With naturalistic fiction there is seldom any question that these events have not happened but could have -- elsewhere, elsewhen, in an alternate history that is simply so close to our own it's all but indistiguishable. With Strange Fiction, though, that elsewhere or elsewhen, as we reconstruct it in the reading, is rendered so different from our own by the novum which the writer employs that it is, quite literally, incredible. The sense of wonder or horror which permeates SF -- all the SFs -- is based on the exploitation of our incredulous response to these novum and of our desire and/or fear -- in our state of suspended disbelief -- that they might somehow be made real. To that extent, SF is driven not by credibility, scientific or otherwise, but by incredibility.
That's my SF, anyway. Yours may be one of the others, or something else entirely.