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". 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.

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

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 the Solar System is an "isolated, uncommon phenomenon". He also argues with Richard Dawkins' 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.

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