Sturgeon's law (or Sturgeon's revelation) is an adage that states that "ninety percent of everything is crap." The adage was coined by Theodore Sturgeon, an American science fiction author and critic. The adage was inspired by Sturgeon's observation that while science fiction was often derided for its low quality by critics, the majority of examples of works in other fields could equally be seen to be of low quality, and science fiction was thus no different in that regard from other art.
The first written reference to the adage is in the September 1957 issue of Venture:
And on that hangs Sturgeon’s revelation. It came to him that [science fiction] is indeed ninety-percent crud, but that also—Eureka!—ninety-percent of everything is crud. All things—cars, books, cheeses, hairstyles, people and pins are, to the expert and discerning eye, crud, except for the acceptable tithe which we each happen to like.
The adage appears again in the March 1958 issue of Venture, where Sturgeon wrote:
It is in this vein that I repeat Sturgeon's Revelation, which was wrung out of me after twenty years of wearying defense of science fiction against attacks of people who used the worst examples of the field for ammunition, and whose conclusion was that ninety percent of s f is crud. The Revelation: Ninety percent of everything is crud. Corollary 1: The existence of immense quantities of trash in science fiction is admitted and it is regrettable; but it is no more unnatural than the existence of trash anywhere. Corollary 2: The best science fiction is as good as the best fiction in any field.
According to Philip Klass (William Tenn), Sturgeon made this remark circa 1951, at a talk at New York University attended by Tenn. The statement was subsequently included in a talk Sturgeon gave at a 1953 Labor Day weekend session of the World Science Fiction Convention in Philadelphia.
In 2013, philosopher Daniel Dennett championed Sturgeon's law as one of his seven tools for critical thinking. "90% of everything is crap. That is true, whether you are talking about physics, chemistry, evolutionary psychology, sociology, medicine—you name it—rock music, country western. 90% of everything is crap." Its re-introduction to a modern audience received a positive reception, according to Dennett.
The original Sturgeon's law
Sturgeon deemed Sturgeon's law to mean "nothing is always absolutely so" in the story "The Claustrophile" in a 1956 issue of Galaxy. The second adage, variously rendered as "ninety percent of everything is crud" or "ninety percent of everything is crap", was known as "Sturgeon's Revelation", formulated as such in his book review column for Venture in 1957. However, almost all modern uses of the term Sturgeon's law refer to the second, including the definition listed in the Oxford English Dictionary.