A handy short definition of almost all science fiction might read: realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method.
Robert A. HeinleinDeath is the lot of us all, and the only way that the human race has ever conquered death is by treating it with contempt. By living every golden minute as if one had all Eternity.
Robert A. HeinleinOn two subjects the overwhelming majority of people regarded their own opinions as Absolute Truth, and sincerely believed that anyone who disagreed with them was immoral, outrageous, sinful, sacrilegious, offensive, intolerable, stupid, illogical, treasonable, actionable, against the public interest, ridiculous, and obscene. The two subjects were (of course) sex and religion.
Robert A. Heinlein