“The fascination of what’s difficult,” said Chalk. “It spins the world on its bearings.” — Robert Silverberg

She shuttled between impish girlhood and neurotic womanhood.

Of course, Chalk had little need for further money. It had motivated him once, but not now. Nor did the acquisition of greater power please him much. Despite the customary theories, Chalk had attained sufficient power so that he was willing to stop expanding if only he could be sure of holding what he had. No, it was something else, something inner, that governed his decisions now. When the love of money and the love of power are both sated, the love of love remains.

I have come to prefer something looser, a rough sort of definition which says simply that science fiction attempts to portray that which does not exist, a speculative reality, but endeavors to explore the consequences of such a speculation in a rigorous, systematic, and scientifically plausible way.