Clarke's three laws
- When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
- The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
- Any sufficiently advanced technology is indistinguishable from magic.
The first Clarke's Law was proposed by Arthur C. Clarke in the essay "Hazards of Prophecy: The Failure of Imagination", in Profiles of the Future (1962).
The second law is offered as a simple observation in the same essay. Status as Clarke's Second Law was conferred by others. In a 1973 revision of his compendium of essays, Profiles of the Future, Clarke acknowledged the Second Law and proposed the Third. "As three laws were good enough for Newton, I have modestly decided to stop there".
The Third Law is the best known and most widely cited. Also appearing in Clarke's Essay "Hazards of Prophecy: The Failure of Imagination". It may be an echo of a statement in a 1942 story by Leigh Brackett: "Witchcraft to the ignorant, .... Simple science to the learned". Even earlier examples of this sentiment may be found in Wild Talents by author Charles Fort where he makes the statement: "...a performance that may some day be considered understandable, but that, in these primitive times, so transcends what is said to be the known that it is what I mean by magic."
Invoking his own Third Law, Clarke postulates advanced technologies without resorting to flawed engineering concepts or explanations grounded in incorrect science or engineering, or taking cues from trends in research and engineering. Powers of any future superintelligence would otherwise seem astonishing. One of the characters in Ben Bova's novel Orion and King Arthur credits the saying to "a very wise man.".
In novels (The City and the Stars) and short stories ("The Sentinel" upon which 2001: A Space Odyssey was based), Clarke presents ultra-advanced technologies. In Against the Fall of Night, the human race regressed after a full billion years of civilization, and faces remnants of past glories such as roadways. Physical possibilities are inexplicable from their perspective.
See also 
- List of eponymous laws
- Finagle's law
- First contact (anthropology)
- Futures studies
- Niven's laws
- Search for extraterrestrial intelligence
- Shermer's last law
- Sturgeon's Law
- Three Laws of Robotics
- "'Hazards of Prophecy: The Failure of Imagination'" in the collection Profiles of the Future: An Enquiry into the Limits of the Possible (1962, rev. 1973), pp. 14, 21, 36.
- "The Sorcerer of Rhiannon", Astounding February 1942, p. 39.
- Orion and King Arthur. Tor Tom Doherty. 2012. p. 224. ISBN 9780765330178.