The future depicted in a good SF story ought to be in fact possible, or at least plausible. That means that the writer should be able to convince the reader (and himself) that the wonders he is describing really can come true... and that gets tricky when you take a good, hard look at the world around you.
Frederik PohlI did that for 40 years or more. I never had any writer's block. I got up in the morning, sat down at the typewriter - now, computer - lit up a cigarette.
Frederik PohlIn terms of stories I would buy for a science fiction magazine, if they take place in the future, that might do it.
Frederik PohlAdvertising reaches out to touch the fantasy part of people's lives. And you know, most people's fantasies are pretty sad.
Frederik Pohl