Science fiction is based upon a belief that the world is changing, that the way we live is changing, and that humanity will adjust to it, or will adjust change to humanity, or will perish.
For writers science fiction always has had two major appeals: its relevance and its freedom. It has been relevant because of its concern for contemporary issues: atomic weapons and their control, space travel, the machine and its im-pact upon man and upon society, aliens, pollution, social inventions such as advertising and television, robots, computers, overpopulation, and those eternal problems of communication, prejudice, intolerance, and injustice. The writer who wishes to deal with many of these problems will find himself writing science fiction or something resembling it.
James Gunn (1975). Alternate Worlds: The Illustrated History of Science Fiction. New Jersey: Prentice-Hall.