Reading my way through the stories on the preliminary Nebula ballot, I was struck with a thought. Although I enjoy a variety of SF subgenres -- humor (Connie Willis), sociological extrapolation (Bruce Sterling), metafiction (John Kessel, sometimes), space opera, hard SF, soft SF, high-viscosity SF (in Mike Flynn's wonderful term) -- what I really want from my SF is not so much hard science as hard humanism.
Hard SF works to supply scientific extrapolation that is believable within the parameters of what we think we know about how the universe actually functions. Hard SF is concerned with how things work. What I want is fiction whose characters are believable within the parameters of what we think we know about how human beings actually function. I want SF concerned with how human behavior works.
And very often, I don't find it. Characters are too sketchy to be believable. Or they behave in ways that may be required by the plot but don't ring true to me. They are too good or too villainous or too competent or too all-knowing or too heroic or too stoic. Nobody is any of these things all the time, and so characters who are, don't seem real to me and thus violate the tenets of Hard Humanism. On the other hand, writers whose characters are both consistent enough to be identifiable AND complex enough to have varying moods and behaviors, sometimes admirable and sometimes not, running on their own quirky individualism -- such characters can, for me, carry even the most recycled plot. Ursula LeGuin, for one, is superb at such characters. Shevek! Estraven! Owen Pugh! Yoss!
LeGuin is not, of course, the only writer who can create such multi-dimensional characters. So can some of the writers I mentioned above, which is why I like to read them. Such "hard humanism" wrters are worth any number of attacking aliens, intricate robots, or FTL starships.
To me, anyway.