The opposite of liberal is stingy. The opposite of radical is superficial. The opposite of conservative is destructive. So I declare that I am a radi… - R. A. Lafferty

Science Fiction is a group of symptoms and not a disease,” so a medical student (failed) told me once. “It's like the old disease hydropsy that doctors treated for so long before discovering that it was only a collection of symptoms, sometimes for a heart disease, sometimes for a liver or kidney disease, or sometimes even for a septic throat.”
Well, the symptoms for Science Fiction are a prowling avidity to search out and read certain occult texts; an uneasiness or excitement that permates the whole routine of life; it's the ‘itchy ears’, as mentioned in Scripture, seeking for ‘new things’. The symptoms are usually a falcon-like hunting or questing; a series of sudden tuneful encounters; a group of euphorias and buoyancies that cry in opposite directions to be hoarded like misers' treasures and simultaneously to be shared with fellow sufferers of the symptoms; feeling that the ‘World We Live In’ is somehow masked and needs to be unmasked. These and other symptoms indicate either a strange disease or diseases, or they indicate a perpetually new kind of health.
Tracing the symptoms back to the ‘disease’ does indicate that the disease is multiple, that it has such names as Hard Science Fiction, Soft Science Fiction, High Fantasy, Low Fantasy, Non-Conforming Adventure Fiction. And sometimes it bears such non-consensus names as Biological Fiction, Ontological Fiction, Eschatological Fiction (did Teilhard, for instance, know that he was writing Eschatological Fiction?), Theological Fiction, or Psychological or Philosophical or Technological or Geological or Historical Fiction. These things and many others share the same complex of symptoms.

The ghost of some other fiction might say in truth to Science Fiction: “You're not very good, are you?” But Science Fiction can answer “Maybe not, but I'm alive and you're dead.

The New Prophets began to preach by torchlight as though the latter days had come. It was the younger Pliny, those many centuries ago, who mentioned that in times of turmoil men with beards will appear instantly, when in all Rome there had not been bearded men before the moment of strife. The younger Pliny had lived in a shaved age; he believed that the bearded men who appear suddenly are wraiths or portents, and not men at all.