Science fiction has a number of common concepts and themes that have been reused by numerous authors. Some have become cliches, and only truly novel treatments of them gain attention, whilst others have become "part of the furniture"—they can be included in a story without much explanation because readers are already familiar with the core concept.

In alphabetical order:

• Aliens (see Aliens in fiction)
  • Alien invasion
  • Benevolent aliens
  • First contact
    • Principles of non-interference (e.g. Prime Directive)
  • Xenobiology
• Alternate History
• Androids
  • Cyborgs and Cybernetics
  • Robots
• Apocalypses or world wide disasters
  • See also Post-apocalyptic science fiction
• Arcologies
• Artificial intelligence
  • von Neumann machines
• Clones
• Colonisation
  • Terraforming
• Cosmology
  • Creation of the Universe
  • Ultimate fate of the Universe
  • Omega Point
• Cryonics
• Cyberpunk
  • Steampunk
• Detective
• Ecology
  • Symbionts
  • Science Fiction is used to raise awareness of Ecological ideas. Lends itself well to dystopian futures. Frank Herbert and Kim Stanley Robinson are known for their serious concern with ecological issues.
• Economics
  • "Age of Greater Scarcity", often in connection with ecological or post-apocalyptic themes. In such dystopias, people are poorer and have fewer resources to draw on.
  • Post-"Age of Scarcity" (arguments over how to distribute resources are irrelevant since anyone can have anything they reasonably want). Examples include:
    1. Ian M. Banks' The Culture
    2. Cory Doctorow's Down and Out in the Magic Kingdom, which uses a "reputation economy"
    3. Frederik Pohl's The Midas Plague
• Fantasy fiction
• Galactic Empire
• History
  • Alternate history
  • History repeating itself (either on long or short scales)
  • Scientific prediction of the future (e.g. psychohistory)
  • Secret history
• Horror fiction
• Language
  • Alien languages (e.g. Klingon)
  • All humans speaking one language (possibly Esperanto)
  • Current human languages evolving/splitting
  • The Sapir-Whorf Hypothesis being strongly true (e.g. Babel 17 by Samuel R. Delany or The Languages of Pao by Jack Vance)
  • Universal Translators (e.g. Babel fish)
• Military - strategy, weapons, ranks, technologies.
  • Ray guns
  • Space warfare
• Mind
  • Artificial intelligence
  • Beings of pure mentality
  • Hive minds
  • Memory removal/editing
  • Mind control
  • Mind uploading
  • Neural implants and interfacing with machinery (directly)
  • Solipsism
• Mutants
• Nanotech
• Parallel worlds or universes.
• Planets in Science Fiction
• Politics
  • Dystopias and (supposed) utopias
  • Galactic Empire
  • Interstellar federation of planets
  • Totalitarianism vs. Libertarianism
  • World government
  • Workable anarchism
• Post-apocalyptic science fiction and new societies that develop after the event
  • There is a space based civilization variant of this theme. This plot device allows writers to write soft science fiction while accounting for the lack of technological advancement and thus similarity to the present day.
• Posthumanism
  • Enhancement of the organism
    • Body modification, including genetic modification
    • Cyborgs
• Psi powers and psychic phenomenon
  • Clairvoyance
  • Telepathy
  • Telekinesis
• Sex (including gender roles, polygamy, sexuality and procreation)
• Shapeshifting
• Simulated reality
• Sociology and sociobiology
  • return to feudalism
  • hive-like eusocial societies
  • future caste systems
• Space Exploration
  • Interstellar travel
    • Faster than Light
      • Hyperspace
      • Warp drives
      • Wormholes
  • Very nearly light speed
    • Ursula LeGuin's NAFAL ships, and the Twin paradox
  • Much slower than Light
    • Generation ship
    • Sleeper ship
  • Moving planets
  • Space stations
  • Colonization of Other Planets, moons, asteroids.
    • Terraforming
• Superhumans
• Technology and its side effects
  • Nanotechnology
  • Singularity
• Telepathy
• Teleportation
• Time travel
  • Alternate history: time travel can be used as a plot device to explore parallel universes. While alternative history has its own category (see above), it often occurs in time travel stories as well.
  • Anachronism
  • The Grandfather paradox -- e.g. Can someone go back in time and kill his parents before they beget the killer?
• Uplift
• Virtual reality

External Links

• http://vesuvius.jsc.nasa.gov/er/seh/scifi.html
• http://www.jessesword.com/SF/sf_citations.shtml
• http://www.itsf.org/resources/keywords.php
• http://www.cs.colorado.edu/~main/sfthemes.html
• If You Like This, Then You'll Like That (0.5Meg) (http://www.magicdragon.com/UltimateSF/thisthat.html)