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", ie they can be included in a story without much explanation, because readers are all 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
- Androids
- Cyborgs and Cybernetics
- Robots
- Apocalypses or world wide disasters
- See also Post-apocalyptic science fiction
- Arcologies
- Artificial intelligence
- Clones
- Colonisation
- Cosmology
- Cryonics
- Cyberpunk
- Ecology
- 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
- Post-"Age of Scarcity" (arguments over how to distribute resources are irrelevant since anyone can have anything they reasonably want, e.g. The Culture, and the problems of excessive wealth as in 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
- Interstellar travel
- Faster than Light
- Very nearly light speed
- Ursula LeGuin's NAFAL ships, and the Twin paradox
- Much slower than Light
- Moving planets
- 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 (eg Babel 17 by Samuel R. Delany or The Languages of Pao by Jack Vance)
- Universal Translators (e.g. Babelfish)
- 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
- 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
- Enhancement of the organism
- Psi powers
- Sex (including gender roles, sexuality and procreation)
- Shapeshifting
- Simulated reality
- Sociology and sociobiology
- Superhumans
- Technology and its side effects
- Telepathy
- Teleportation
- Time travel
- Anachronism
- The Grandfather paradox -- e.g. Can someone go back in time and kill his parents before they beget the killer?
- Uplift
- Virtual reality