Each of the three phases of science fiction I have outlined can be roughly correlated with a set of contemporary philosophical or metaphysical assumptions. Each set of contemporary assumptions constitutes an ideology or Weltanschauung exerting a gravitational pull on the fiction that comes under its influence. In this sense, prophetic science fiction belongs with Positivism and scientific materialism; science fiction as myth implies either neoChristianity or a pragmatic cultural relativism drawing on psychoanalytical and anthropological insights; while science fiction as metaphor tends to imply a post-structuralist 'conventionalism' or 'anti-foundationalism' denying or downgrading the referential aspects of fiction. In this view, statements no longer have a truth content, so that it would be absurd to judge imagined futures by their potential correspondence with any 'real' future. Prophetic sf is a propaganda device which is meaningful only in relation to the discursive present in which it arises.

Admittedly, it...