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Mediocrity principle

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Title: Mediocrity principle  
Author: World Heritage Encyclopedia
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Subject: Earth analog, Fermi paradox, Copernican principle, Xenoarchaeology, Search for extraterrestrial intelligence
Collection: Earth, Philosophy of Science, Principles, Search for Extraterrestrial Intelligence
Publisher: World Heritage Encyclopedia

Mediocrity principle

The mediocrity principle is the philosophical notion that "if an item is drawn at random from one of several sets or categories, it's likelier to come from the most numerous category than from any one of the less numerous categories".[1] The principle has been taken to suggest that there is nothing very unusual about the evolution of the Solar System, Earth's history, the evolution of biological complexity, human evolution, or any one nation. It is a heuristic in the vein of the Copernican principle, and is sometimes used as a philosophical statement about the place of humanity. The idea is to assume mediocrity, rather than starting with the assumption that a phenomenon is special, privileged, exceptional, or even superior.[2][3]

Consistent with the notion, astronomers reported, on 4 November 2013, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy alone, based on Kepler space mission data.[4][5] 11 billion of these estimated planets may be orbiting sun-like stars.[6] The nearest such planet may be 12 light-years away, according to the scientists.[4][5]


  • Extraterrestrial life 1
  • Other uses of the heuristic 2
  • See also 3
  • Notes 4
  • References 5
  • External links 6

Extraterrestrial life

Life on Earth is ubiquitous, but does it exist elsewhere?

The mediocrity principle suggests, given the existence of life on Earth, that life typically exists on Earth-like planets throughout the universe.[7]

Other uses of the heuristic

David Deutsch argues that the mediocrity principle is not actually correct from a physical point of view, either in reference to our part of the universe or to our species. Deutsch refers to Stephen Hawking's quote that "The human race is just a chemical scum on a moderate-sized planet, orbiting around a very average star in the outer suburb of one among a hundred billion galaxies", writing that our neighborhood in the universe is not typical (80% of the universe's matter is dark matter) and that a concentration of mass such as our solar system is an "isolated, uncommon phenomenon". He also argues with Richard Dawkins's opinion that humans, as result of natural evolution, are limited to the capabilities of our species — Deutsch responds that even though evolution did not give humans the ability to detect neutrinos, scientists can currently detect them, significantly expanding their capabilities beyond what is available as a result of evolution.[8]

See also


  1. ^ Kukla, A. (2009). Extraterrestrials: A Philosophical Perspective. Lexington Books. p. 20.  
  2. ^ Encyclopædia Britannica
  3. ^ PZ Myers explains the Mediocrity principle at
  4. ^ a b Overbye, Dennis (4 November 2013). "Far-Off Planets Like the Earth Dot the Galaxy".  
  5. ^ a b Petigura, Eric A.; Howard, Andrew W.; Marcy, Geoffrey W. (31 October 2013). "Prevalence of Earth-size planets orbiting Sun-like stars".  
  6. ^ Khan, Amina (4 November 2013). "Milky Way may host billions of Earth-size planets".  
  7. ^ Chaisson, Eric, and Steve McMillan. Astronomy: A Beginner’s Guide to the Universe [2]. Ed. Nancy Whilton. San Francisco: Pearson, 2010.
  8. ^  


External links

  • Goodwin, Gribbin, and Hendry's 1997 Hubble Parameter measurement relying on the mediocrity principle The authors call this the 'Principle of Terrestrial Mediocrity' even though the assumption they make is that the Milky Way Galaxy is typical (rather than Earth). This term was coined by Alexander Vilenkin (1995).
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