Taxonomy of the Fallacy of Overgenerality


As this is the 25th Anniversary of "Thriller" and, Mr. [Michael] Jackson’s worldwide sales have to date exceeded over 750 million units, Mr. Jackson is being recognised for his phenomenal, record-breaking achievements.

Source: Raymone K. Bain, Letter, King of Pop, 10/31/2006

Fact 1: Michael Jackson is the third biggest-selling pop act of all time, after The Beatles and Elvis Presley, with album sales of 750 million.

Source: "Twelve Facts about Michael Jackson", BBC News, 6/26/2009



There are two types of overgenerality:

  1. Overly-General Concepts: No concept is inherently overly general, but in a particular context of use it may be. For instance, if you were asked to aid in a search, it wouldn't be helpful to be told to look for a "thing". In this context, "thing" is an overly-general concept, since it won't help you to identify the lost object. Overly-general concepts are often used by politicians as a way to avoid commitment to particular policies, which is a type of "doublespeak".
  2. Overly-Broad Generalizations: To generalize is to draw a general conclusion from some evidence. To overgeneralize is to draw an overly-general conclusion that is unwarranted by the evidence. For instance, if I have seen only one swan and it was white, "all swans are white" would be an overgeneralization. Specifically, it would be an instance of the subfallacy of Hasty Generalization.


Overgenerality should not be confused with either vagueness or abstractness:

  • Vagueness: Concepts which are imprecise because of overgenerality are often called "vague". However, overgenerality and vagueness are two different types of imprecision. A concept is vague when there are borderline cases of its application, whereas an overly-general concept may not be vague. Similarly, a vague concept need not be overly general; for instance, the concept of "chair" is vague, because there are borderline cases such as beanbag chairs and barstools, but it is not an overly-general concept for the object upon which I sit―"furniture", in contrast, probably would be overly general.
  • Abstractness: Abstraction is a very different concept from overgenerality. Abstract objects are nonphysical objects that lack spatial or temporal locations. For instance, numbers are abstract objects: you can't touch a number, nor point to where it's located, nor give its date of origin. There are general concepts for both abstract and physical objects. "Number" is a general concept for a type of abstract object, whereas "chair" is a general concept for a type of physical object.

    Highly general concepts may be confused with abstractions because the physical objects that we experience are always instances of highly specific concepts. For instance, we never see just an "animal", we see a cat or a dog or a member of some other species. This may lead us to think that "animal" is an abstract concept, but animals are physical objects with a location, come into existence at a particular time, and leave it at a later one.

    Another difference between generality and abstraction is that the former is a comparative notion, whereas the latter is not. Some concepts are more general than others: for instance, "mammal" is a more general concept than "cat", but a more specific concept than "animal". In contrast, a concept is either an abstraction or it isn't; no concept is more abstract than another.

Analysis of the Example:

Bain, who was at the time of this letter a publicist for Michael Jackson, was overly general in describing Jackson's supposed sales of 750 million "units". What is a "unit": a record, a song, or some combination of the two? A number of news organizations, including the BBC, apparently thought that a "unit" was an album, and reported it as a "fact" that Jackson had sold 750 million albums. Thus, Bain's over-general characterization of Jackson's sales led some news organizations to draw an unwarranted conclusion.

Source: Carl Bialik, "Spun: The Off-the-Wall Accounting of Record Sales", The Numbers Guy, 7/15/2009