There are very real differences between science fiction and realistic fiction, between horror and fantasy, between romance and mystery. Differences in writing them, in reading them, in criticizing them. Vive les différences! They're what gives each genre its singular flavor and savor, its particular interest for the reader--and the writer.

It is a real wilderness, and those who go there should not feel too safe.

Dragons are more dangerous, and a good deal commoner, than bears. Fantasy is nearer to poetry, to mysticism, and to insanity than naturalistic fiction is. It is a real wilderness, and those who go there should not feel too safe.

Sci-fi uses the images that sf - starting with H.G. Wells - made familiar: space travel, aliens, galactic wars and federations, time machines, et cetera, taking them literally, not caring if they are possible or even plausible. It has no interest in or relation to real science or technology. It's fantasy in space suits. Spectacle. Wizards with lasers. Kids with ray guns. I've written both, but I have to say I respect science fiction enough that I wince when people call it sci-fi.