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Themediocrity principle is thephilosophical notion that "if an item is drawn at random from one of several sets or categories, it's more likely 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 theevolution of the Solar System,Earth's history, theevolution of biological complexity,human evolution, or any onenation. It is aheuristic in the vein of theCopernican 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 evensuperior.[2][3]
David Bates ascribed the mediocrity principle toSebastian von Hoerner,[4][5] who as early as 1961 wrote the following:[6][notes 1]
Because we have no knowledge whatsoever about other civilizations, we have to rely completely on assumptions. The one basic assumption we want to make can be formulated in a general way:
- Anything seemingly unique and peculiar to us is actually one out of many and is probably average.
The mediocrity principle suggests, given the existence of life on Earth, that shouldlife exist elsewhere in theuniverse, it will typically exist onEarth-like planets.[7]
The mediocrity principle was implicitly applied during the 17th century, when astronomers attempted to measure the distance between distantstars and theEarth. By assuming that theSun was just an average star, and that some stars seemed brighter simply because they were closer to us, they were able to estimate how far these stars were from the Earth. Although this method was flawed due to the differences among stars, it gave astronomers at that time a rough idea of how far the stars were from the Earth. For example,James Gregory,Isaac Newton andChristiaan Huygens were able to estimate the distance betweenSirius and the Earth through this method.[8]
The mediocrity principle is in contrast with theanthropic principle, which asserts that the presence of an intelligent observer (humans) limits the circumstances to bounds under which intelligent life can be observed to exist, no matterhow improbable.[9] Both stand in contrast to thefine-tuning hypothesis, which asserts that the natural conditions for intelligent life are implausibly rare.
The mediocrity principle implies that Earth-like environments are necessarily common, based in part on the evidence ofany happening at all, whereas the anthropic principle suggests that no assertion can be made about the probability of intelligent life based on a sample set of one (self-described) example, who are necessarily capable of making such an assertion about themselves.
It is also possible to handle the Mediocrity Principle as a statistical problem, a case of a singledata point statistics, also present in theGerman tank problem.
The mediocrity principle can also be used to estimate the futurelife expectancy of presently observable objects, and is especially useful when no harddata is available.Richard Gott extended the mediocrity principle to argue that if there is nothing special about observing an object in the present moment (Tnow), then one can expect the present moment to occur randomly between the start (Tstart) and the end (Tend) of the observed object's longevity. Therefore, the total longevity of an observable object can be expected (with 50% confidence) to lie in theinterval 1/3 ⋅ Tstart < Tnow < 3 ⋅ Tend. This estimation technique was derived after a 1969 visit to theBerlin Wall, which was constructed eight years earlier. Gott reasoned that there was nothing special about the timing of his visit, so the above equation (with T = 8) estimates that the Berlin Wall would be likely to last for at least 2.67 years but no longer than 24 years. (The Berlin Wall fell 20 years later, in 1989.)
Longevity estimation reflects themaxim "old things tend to last and new things tend to disappear." Most applications of longevity estimation use a 95% confidence interval, which decreases the precision of the estimate by drastically increasing the interval of estimation. One useful estimation made on this confidence interval is the survival ofHomo sapiens, which is thought to have emerged around 200,000 years ago. If there is nothing special about our observation ofspecies now, in the 21st century, then longevity estimation (with T = 200,000 and a confidence interval of 95%) yields a projected timespan of between 5,100 and 7.8 million years during which the human species will be extant.
Some other projected lifespans (with 95% confidence) includeindustrial technology (estimated to last somewhere between 7 years and 10,000 years), theinternet (between 7 months and 975 years), andWikipedia (between 6 months and 772 years).Jim Holt analyzed longevity estimation and concluded that our understanding ofhumor andnumber will survive for at least one million years. Humans share these traits with other species, which implies we share these traits with somecommon ancestor that lived millions of years ago.
David Deutsch argues that the mediocrity principle is incorrect from a physical point of view, in reference either to humanity's part of the universe or to its species. Deutsch refers toStephen Hawking's quote: "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 hundredbillion galaxies". Deutsch wrote that Earth's neighborhood in the universe is not typical (80% of the universe's matter isdark matter) and that a concentration of mass such as the Solar System is an "isolated, uncommon phenomenon". He also disagrees withRichard Dawkins, who considers that humans, because of natural evolution, are limited to the capabilities of their species. Deutsch responds that even though evolution did not give humans the ability to detectneutrinos, scientists can currently detect them, which significantly expands their capabilities beyond what is available as a result of evolution.[10][clarification needed]
