J.G. Ballard, intro to French 1973 edition of Crash:
"The kind of imagination that now manifests itself in science fiction is not something new. Homer, Shakespeare, and Milton all invented new worlds to comment on this one. The split of science fiction into a separate and somewhat disreputable genre is a recent development. It is connected with the near disappearance of dramatic and philosophical poetry and the slow shrinking of the traditional novel as it concerns itself more and more exclusively with the nuances of human relationships. Among those areas neglected by the traditional novel are, above all, the dynamics of human societies (the traditional novel tends to depict society as static), and man's place in the universe. However crudely or naively, science fiction at least attempts to place a philosophical and metaphysical frame around the most important events within our lives and consciousness.
In the past we have always assumed that the external world around us has represented reality, however confusing or uncertain, and that the inner world of our minds, its dreams, hopes, ambitions, represented the realm of fantasy and the imagination. These roles, too, it seems to me, have been reversed. The most prudent and effective method of dealing with the world around us is to assume that it is a complete fiction -- conversely, the one small node of reality left to us is inside our own heads. Freud's classic distinction between the latent and manifest content of the dream, between the apparent and the real, now needs to be applied to the external world of so-called reality.
I feel myself that the writer's role, his authority and license to act, has changed radically. I feel that, in a sense, the writer knows nothing any longer. He has no moral stance. He offers the reader the contents of his own head, he offers a set of options and imaginative alternatives. His role is that of the scientist, whether on safari or in his laboratory, faced with a completely unknown terrain or subject. All he can do is to devise hypotheses and test them against the facts."
William Gibson, 2007 (via Ballardian):
"Well, I thought that writing about the world today as I perceive it would probably be more challenging, in the real sense of science fiction, than continuing just to make things up… If I’m going to write fiction set in an imaginary future now, I’m going to need a yardstick that gives me some accurate sense of how weird things are now. ‘Cause I’m going to have to go beyond that… But I don’t know if I’ll be able to do it again. I don’t know if I’ll be able to make up an imaginary future in the same way. In the ’80s and ’90s, as strange as it may seem to say this, we had such luxury of stability. Things weren’t changing quite so quickly in the ’80s and ’90s. And when things are changing too quickly, as one of the characters in Pattern Recognition says, you don’t have any place to stand from which to imagine a very elaborate future."Lukacs, attacking Bloch's support for the Expressionist and Surrealist modernist avant-gardes, on "the anticipatory function of ideology" (from "Realism in the Balance," 1938):
"To remain within the sphere of literature, we need only remind ourselves of what Paul Lafargue has to say about Marx's evaluation of Balzac: 'Balzac was not just the chronicler of his own society, he was also the creator of prophetic figures who were still embryonic under Louis Philippe and who only emerged fully grown after his death, under Napoleon III.' But is this Marxian view still valid in the present? Of course it is. Such 'prophetic figures,' however, are to be found exclusively in the works of the important realists.
There is nothing mysterious or paradoxical about any of this -- it is the very essence of all authentic realism of any importance. Since such realism must be concerned with the creation of types (this has always been the case, from Don Quixote down to Oblomov and the realists of our own time), the realist must seek out the lasting features in people, in their relations with each other and in the situations in which they have to act; he must focus on those elements which endure over long periods and which constitute the objective human tendencies of society and indeed of mankind as a whole.
Such writers form the authentic ideological avant-garde since they depict the vital, but not immediately obvious forces at work in objective reality. They do so with such profundity and truth that the products of their imagination receive confirmation from subsequent events -- not merely in the simple sense in which a successful photograph mirrors the original, but because they express the wealth and diversity of reality, reflecting forces as yet submerged beneath the surface, which only blossom forth visibly to all at a later stage. Great realism, therefore, does not portray an immediately obvious aspect of reality but one which is permanent and objectively more significant, namely man in the whole range of his relations to the real world, above all those which outlast mere fashion. Over and above that, it captures tendencies of development that only exist incipiently and so have not yet had the opportunity to unfold their entire human and social potential. To discern and give shape to such underground trends is the great historical mission of the true literary avant-garde.
So what really matters is not the subjective belief, however sincere, that one belongs to the avant-garde and is eager to march in the forefront of literary developments. Nor is it essential to have been the first to discover some technical innovation, however dazzling. What counts is the social and human content of the avant-garde, the breadth, the profundity and the truth of the ideas that have been 'prophetically' anticipated.
In short, what is at issue here is not whether or not we deny the possibility of anticipatory movements in the superstructure. The vital questions are what was anticipated, in what manner and by whom?"
see also a discussion of (speculative) realism in philosophy here.